Method for dewatering and recycling electrolytic manganese dioxide leaching residue

Abstract

The application discloses a kind of dehydration and recycling method of electrolytic manganese dioxide leaching residue, it is related to the field of hydrometallurgy and chemical solid-liquid separation technology.The method is aimed at the technical problems of low dehydration efficiency, insufficient manganese element recovery and high comprehensive energy consumption in the prior art, after neutralization and composite flocculant flocculation of leaching solution, multi-stage electric field treatment is carried out in turn, including applying alternating electric field in the sedimentation tank for pre-aggregation, applying direct current electric field in plate and frame filter press for pressure filtration dehydration and applying pulse electric field before unloading for deep dehydration, finally unload filter cake and collect filtrate.The method is mainly used for efficient dehydration of leaching residue in the production process of electrolytic manganese dioxide and maximization of manganese resource recovery, to realize energy saving and emission reduction and resource recycling.

Description

Technical Field

[0001] This invention relates to the field of solid-liquid separation technology in hydrometallurgy and chemical industry, and more specifically, to a method for dehydrating and recycling electrolytic manganese dioxide leaching residue. Background Technology

[0002] In the hydrometallurgical production of electrolytic manganese dioxide, the efficient solid-liquid separation of the leaching residue produced after neutralization of the leachate is a key factor affecting the overall technical and economic indicators. Currently, the industrial method commonly uses a combination of polyacrylamide (PAM) flocculation and plate and frame filter press for treatment. However, this method still faces several technical challenges that urgently need to be addressed in practical applications.

[0003] First, the moisture content of the filter cake after separation remains high, typically ranging from 40% to 50%. The core reason for this is that the leaching residue contains a large amount of components such as ferric hydroxide and gypsum in colloidal form. Conventional PAM polymeric flocculants primarily capture particles through adsorption bridging to form flocs, but they mainly remove free water between particles. Their ability to break down bound water firmly bonded within the colloids through hydrogen bonds and other interactions is limited. The high moisture content of the filter cake directly leads to a heavy workload for the subsequent drying process, which can account for about a quarter of the total energy consumption of the entire residue treatment process, creating significant energy cost pressure.

[0004] Secondly, the loss of manganese resources is a significant problem. During solid-liquid separation, a large number of fine manganese sulfate crystals (particle size less than 10 micrometers) are either trapped inside loose flocs and difficult to release, or they are directly lost through the filter cloth with the filtrate. This makes it difficult to further improve the recovery rate of manganese. Industrial data shows that the loss rate is usually between 5% and 8%, resulting in the waste of valuable metal resources and the loss of economic value.

[0005] Furthermore, the existing process suffers from insufficient synergy. Some organic additives (such as lignin sulfonates) added during the leaching stage to promote the reaction cease functioning after leaching, leaving residues that are not beneficial to subsequent separation processes and may even increase the organic load in the liquid phase. Meanwhile, the solid-liquid separation process requires the addition of large amounts of flocculant. These two key processes are relatively independent in terms of functional materials and process control, lacking effective system-level synergy and coordination. This not only increases overall reagent consumption and cost but also limits further optimization of overall process efficiency.

[0006] To address the aforementioned issues, the industry has faced difficulties in its attempts to improve the process: for example, simply increasing the amount of PAM has little effect on removing colloidal bound water, while increasing costs and residual organic matter in the filtrate; developing new, highly efficient flocculants presents a challenge in balancing selectivity, cost, and universality; and establishing an efficient and economical synergistic mechanism between complex industrial leaching systems and solid-liquid separation processes is an even more systemic problem. Therefore, developing a solid-liquid separation method capable of deep dehydration, efficient recovery of manganese resources, and effective integration of process steps is of significant practical importance. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing methods that use single-component polyacrylamide flocculation combined with mechanical pressure filtration. These methods primarily remove free water between particles, but are insufficient at removing bound water within components such as colloidal ferric hydroxide in the leaching residue. This results in a high moisture content in the filter cake (typically 40%-50%), leading to high energy consumption during subsequent drying. Furthermore, this method has limited effectiveness in capturing fine manganese sulfate crystals, causing manganese to be lost with the filtrate, and the recovery rate needs improvement. Therefore, a solid-liquid separation method capable of deeply removing bound water and efficiently recovering manganese resources is needed.

[0008] To achieve the above objectives, the present invention provides a method for dewatering and recycling electrolytic manganese dioxide leaching residue, comprising the following steps: S1. Neutralize the electrolytic manganese dioxide leachate and adjust the pH to 5.5-6.0; during or after the neutralization treatment, add a composite flocculant containing polyacrylamide and modified lignin sulfonate to the system for flocculation. S2. The flocculated material is subjected to multi-stage electric field treatment in sequence: S2.1 In the settling tank, an alternating electric field with a frequency of 1-10Hz and a field strength of 5-15 V / cm is applied to the material for pre-aggregation; S2.2 Pump the pre-aggregated material into a plate and frame filter press, embed electrode groups in the filter cloth or filter plates on both sides of the filter chamber, and apply a DC electric field of 10-20 V / cm to the electrode groups for filter dewatering. S2.3 After the filter press is completed and before unloading, apply a pulsed electric field with a field strength of 30-50 V / cm and a pulse width of 1-10 ms to the filter cake in the filter chamber of the filter press for deep dewatering; S3. After dehydration is complete, unload the filter cake and collect the filtrate.

[0009] In a complete process flow including a leaching step, the additives used in the leaching stage (such as lignin sulfonate) are only used for the leaching reaction, and their function terminates after leaching is completed. The residues are of no benefit to subsequent separation, resulting in a disconnect between the two key processes of leaching and solid-liquid separation in terms of functional materials, lacking systematic synergy. This increases the overall reagent consumption and limits the potential for optimizing the overall process efficiency. Preferably, before step S1, a leaching step of electrolytic manganese dioxide, S0, is also included: In the leaching step, lignin sulfonate is added to the leaching system as a reducing agent, and a precursor additive that remains chemically inert under acidic leaching conditions is added simultaneously; the precursor additive is an aqueous solution of a prepolymer generated by reacting polyethyleneimine and epichlorohydrin in a molar ratio of 1:0.1 to 1:0.5; the precursor additive is added to the leaching system in solution form simultaneously or separately with lignin sulfonate in step S0, and its addition amount, based on the solids in the precursor additive, is 0.5 to 2.0 kg per ton of manganese dioxide in the leaching solution.

[0010] During the electric field-enhanced separation process, this method promotes the collision and initial aggregation of particles of different sizes more efficiently, thereby improving the overall dewatering efficiency. Simultaneously, during the plate and frame filter press dewatering stage, this method better adapts to the resistance changes as the filter cake forms in different areas of the filter chamber, reducing uneven dewatering and localized moisture residue. Preferably, in S2.1, the frequency and field strength of the alternating electric field are set collaboratively as follows: when the frequency is in the low-frequency range of 1-5Hz, a higher field strength of 10-15 V / cm is used; when the frequency is in the high-frequency range of 5-10Hz, a lower field strength of 5-10 V / cm is used. In S2.2, the filter chamber of the plate and frame filter press is provided with multiple electrode groups that can independently control the voltage, which are used to apply different voltages according to different areas of filter cake formation. The electrode groups are arranged on the surface of the filter plates or filter cloth on both sides of the filter chamber, and are arranged parallel to the direction of filtrate flow. The number of electrodes is at least 2 electrode pairs per group, and 2-4 groups of independently controlled electrodes are provided on the surface of each filter plate. The electrode spacing is 50-150 mm, preferably 80-120 mm. The electrode shape is strip or mesh, flush with or slightly embedded in the surface of the filter plate. Each group of electrodes is connected to an independent adjustable power supply, which is used to adjust the applied voltage in real time according to the thickness, density or resistivity of the filter cake.

[0011] In the final deep dehydration stage, if the pulsed electric field's application time is insufficient, it will be difficult to effectively drive the remaining bound water in the filter cake capillary to detach, resulting in the final filter cake moisture content failing to reach a lower level and affecting the energy-saving effect of subsequent treatment. Preferably, in S2.3, the pulsed electric field is applied for 30-90 seconds.

[0012] Excessive use of flocculants, especially synthetic polymeric flocculants, to achieve better separation can increase the organic load (such as COD) in the process water reuse system, affecting reuse or increasing wastewater treatment costs. Furthermore, an improper internal ratio of the flocculant can make it difficult to balance controlling organic residue and ensuring separation efficiency. Preferably, in step S1, the dosage of the composite flocculant, based on its total dry weight, is 0.10% to 0.20% of the dry weight of the leaching residue; and the mass ratio of modified lignin sulfonate to polyacrylamide is 1:2 to 1:5.

[0013] In the process of pressure filtration and dewatering, a single DC electric field mode has limited effect on further improving the capture rate of fine manganese crystals and achieving the ultimate recovery of manganese resources. Furthermore, it lacks a means to optimize the electric field parameters in real time based on the separation effect, leading to unnecessary energy consumption costs in pursuit of high recovery rates. Preferably, in step S2.2, the application of the DC electric field specifically involves: simultaneously applying a DC bias electric field and a high-frequency alternating electric field superimposed on it to both sides of the filter chamber of the plate and frame filter press to form a composite electric field; simultaneously, an online ion concentration monitor is installed at the filtrate outlet of the plate and frame filter press to monitor the manganese ion concentration in the filtrate in real time; the frequency and field strength of the high-frequency alternating electric field are dynamically adjusted according to the feedback signal from the online ion concentration monitor, specifically: 1) setting a target threshold C0 for the manganese ion concentration in the filtrate; 2) during the pressure filtration and dewatering stage, when the real-time monitored manganese ion concentration C is higher than C0, adjusting the frequency of the high-frequency alternating electric field to 100kHz-500kHz. 3) When the real-time monitored manganese ion concentration C is lower than or equal to C0, the peak-to-peak value of the high-frequency alternating electric field is preferentially reduced to 10%-20% of the DC bias electric field strength; if the filtrate is already very clear and the power consumption needs to be further optimized, then the frequency is maintained in the range of 500 kHz-1 MHz.

[0014] The deep dewatering stage uses a pulsed electric field with fixed parameters, which cannot be adaptively adjusted according to the actual dewatering difficulty of the filter cake (such as density and bound water content). For filter cakes that are difficult to dewater, dewatering is incomplete; for filter cakes that are easy to dewater, energy is wasted, resulting in unstable dewatering effect and poor economy in this stage. Preferably, in step S2.3, when deep dehydration is performed using a pulsed electric field, the application method is specifically a segmented pulse sequence, which includes at least a low-pressure permeation section and a high-pressure breakdown section executed sequentially: the low-pressure permeation section: applying a pulsed electric field with a field strength of 10-20 V / cm and a pulse width of 5-10 ms, lasting for a duration T1; the high-pressure breakdown section: applying a pulsed electric field with a field strength of 40-50 V / cm and a pulse width of 0.5-2 ms, lasting for a duration T2; wherein, the duration ratio of T1 to T2 is determined by the following steps: a) at the instant the dehydration is completed and the feed pump is shut off in step S2.2, the feed pressure value P (unit: MPa) of the plate and frame filter press is obtained in real time or the average volume resistivity value R (unit: kΩ•m) of the filter cake is measured and calculated in real time by electrodes set on the filter plate; b) the obtained P value or R value is compared with a preset threshold range: if P ≤ P0 or R ≤ If R0 is positive, the filter cake is determined to be easy to dehydrate, and the ratio of T1:T2 is set to (1:1) to (2:1); if P>P0 or R>R0, the filter cake is determined to be difficult to dehydrate, and the ratio of T1:T2 is set to (3:1) to (5:1); where P0 is the preset pressure threshold and R0 is the preset resistivity threshold.

[0015] In the process of in-situ conversion using precursor additives, if the conversion reaction is triggered only by the natural change in pH during the neutralization process, the conditions (such as temperature and pH change rate) are uncontrollable, resulting in incomplete conversion and unstable performance of the generated active substances, thus affecting their synergistic effect in subsequent flocculation. Preferably, when performing the method of step S0, the in-situ conversion process of the precursor additive is actively controlled, specifically including: during the neutralization process in step S1, the pH value and temperature of the system are monitored simultaneously; when the pH value reaches 5.0, if the system temperature is below 60°C, the system is programmed to increase in temperature at a rate of 0.5-1.5°C / min until the temperature reaches 60-70°C; if the system temperature is already within the 60-70°C range, the temperature is maintained, and the pH value is maintained within the 5.0-5.5 range during this stage; after the temperature reaches 60-70°C, the pH value of the system is rapidly adjusted to the final range of 5.5-6.0 within 5-15 minutes, and the temperature is maintained under this final pH condition to continue the reaction for 10-30 minutes to complete the full conversion of the precursor additive into the active substance.

[0016] The beneficial effects of the present invention include at least the following aspects: 1. This invention achieves deep removal of colloidal bound water, significantly reducing the moisture content of the filter cake. This is mainly due to the synergistic effect of the composite flocculant (S1) and multi-stage electric field dehydration (S2). The modified lignin sulfonate in the composite flocculant can penetrate and disrupt the stable structure of colloidal Fe(OH)3, releasing the bound water it encapsulates; the subsequent multi-stage electric field (pre-aggregation, pressure filtration dehydration, and deep dehydration) continuously drives water separation at different stages with different forms of electric field force (alternating disturbance, direct current electroosmosis, and pulse breakdown). Experiments show that this synergistic effect can reduce the filter cake moisture content from 40%-50% in existing technologies to below 22%, solving the core bottleneck of high filter cake moisture content.

[0017] 2. This invention significantly improves the recovery rate of manganese resources and reduces the loss of valuable metals. This is mainly attributed to the capture of fine crystals by the composite flocculant and the directional enrichment effect of the electric field (especially the composite electric field of S2.2). Modified lignin sulfonate has good dispersion and adsorption characteristics for fine particles, reducing the loss of MnSO4 crystals. In the pressure filtration dewatering stage, the applied DC electric field enables the negatively charged fine crystals to migrate towards the anode, while the composite electric field and feedback control can intelligently enhance this electrophoretic capture process according to the filtrate concentration. This effectively reduces the manganese loss rate and achieves efficient recovery of manganese resources.

[0018] 3. This invention effectively reduces overall process energy consumption and improves economic efficiency. This stems from the reduction in filter cake moisture content, which decreases the subsequent drying load, and the intelligent and precise application of the electric field. The significant reduction in filter cake moisture content directly reduces subsequent drying energy consumption. Simultaneously, adaptive pulse dehydration avoids excessive energy consumption; feedback control enables on-demand power supply. The systematic design achieves both improved efficiency and reduced overall energy consumption.

[0019] 4. This invention improves filtrate quality and enhances the reuse potential and environmental compatibility of process water. This is mainly due to the optimized control of flocculant dosage and ratio, as well as the highly efficient separation process itself. By controlling the total dosage of composite flocculant within a low range (0.10%-0.20%) and optimizing the ratio of biomass to synthetic polymers (1:2-1:5), the introduction of exogenous synthetic organic matter (PAM) is reduced from the source while ensuring flocculation effect, thereby lowering the chemical oxygen demand (COD) of the filtrate. Simultaneously, thorough solid-liquid separation ensures extremely low suspended solids (SS) content in the filtrate. This significantly improves the reuse quality of the filtrate and reduces the pressure on wastewater treatment.

[0020] 5. This invention enhances process stability and adaptability to raw material fluctuations. The modified lignin sulfonate exhibits selectivity towards the target colloid, particularly regarding Ca... 2+ Al 3+The system exhibits low sensitivity to interfering ions. Alternating electric fields can disrupt the stable atmosphere for interfering ion formation, promoting effective aggregation. This ensures that the entire process maintains stable dehydration and recovery rates when treating leachates with fluctuating composition, offering high operational flexibility and ease of industrial implementation.

[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to examples, so that those skilled in the art can implement it based on the description.

[0023] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0024] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0025] Example 1 This embodiment provides a method for dehydrating and recycling electrolytic manganese dioxide leaching residue, including the following steps: First, prepare the raw materials and equipment required for the experiment. The leaching solution used was taken from the manganese sulfate leaching section of an actual electrolytic manganese plant, and its main component, as analyzed, was Mn. 2+ Concentration 45 g / L, Fe 3+ Concentration 3.2 g / L, also contains Mg 2+ Ca 2+ It contains sulfate and other components, with an initial pH of 2.1. The leachate is prepared in a leaching reactor at 95°C. After being transferred to a neutralization tank and before the start of neutralization treatment, the system temperature naturally drops to about 50-60°C. The main reagents include: industrial lignin sulfonate (derived from papermaking wastewater) as a reducing agent and modifying raw material, and anionic polyacrylamide (PAM, molecular weight about 12 million).

[0026] The modified lignin sulfonate was prepared as follows: 100g of dry lignin sulfonate was subjected to a two-step reaction of sodium sulfite sulfonation and quaternization with 3-chloro-2-hydroxypropyltrimethylammonium chloride to obtain a modified product solution with a solid content of approximately 20%. Subsequently, it was compounded with PAM powder at a dry weight ratio of 1:2.5 to prepare a 1% composite flocculant solution for later use. The experimental equipment included: a neutralization stirring tank with pH and temperature control; a settling tank equipped with electrodes featuring an adjustable alternating electric field (1-10 Hz, 5-15 V / cm); and a programmable plate and frame filter press (400mm × 400mm filter plate, 30mm filter chamber thickness) with a zoned controllable electrode assembly embedded in the filter chamber, along with a matching DC / AC / pulse multi-functional power supply. In addition, a small leaching reactor was also used. The electrode assembly of the plate and frame filter press is specifically arranged as follows: three independently controlled strip electrodes are arranged parallel to each other along the direction of filtrate flow on the surface of the filter plates on both sides of the filter chamber; each electrode assembly includes a pair of electrode strips with opposite polarities, the electrode strips are installed flush with the surface of the filter plate, and the distance between adjacent electrode strips is 100mm; each electrode assembly is connected to an independent adjustable DC power supply to realize real-time adjustment of the applied voltage according to the resistance changes in different areas during the filter cake formation process.

[0027] The experiment was conducted according to the following steps. Step 1: Leaching step (S0): In the leaching reactor, 40 kg of lignin sulfonate (dry basis) was added as a reducing agent per ton of target product (calculated as MnO2). Simultaneously, 1.0 kg (calculated as solids) of precursor additive was added per ton of MnO2. The precursor additive was prepared by the following steps: In a reactor equipped with a stirrer, thermometer, and condenser, a measured amount of polyethyleneimine (PEI, average molecular weight Mw = 70,000) aqueous solution (50% solids content) was added. Under stirring, the system temperature was raised to 60±2℃, and then epichlorohydrin (ECH) was slowly added dropwise, controlling the molar ratio of PEI to ECH to be 1:0.3. After the addition was complete, the reaction was maintained at 60±2℃ for 4 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, and water was added to adjust the solids content to 10%, thus obtaining the aqueous solution of the precursor additive. The prepolymer is stable under acidic conditions (pH < 3). The amine groups and residual epoxy groups on its molecular chain can be further crosslinked after neutralization to pH > 5.0 and temperature > 60°C, transforming it into a cationic polymer. The electrolytic manganese dioxide leachate was prepared by stirring and leaching in sulfuric acid medium at 95°C for 4 hours. This step simulates a timing design that simultaneously introduces the functional precursor during the leaching stage.

[0028] The second step is neutralization and flocculation (S1): The leachate is transferred to a neutralization tank, and the pH of the system is precisely adjusted to 5.8 with lime slurry while stirring. When the pH reaches this value, the pre-mixed composite flocculant is immediately added, with a total addition amount (dry basis) of 0.15% of the estimated mass of the leachate residue. Stirring is continued for 5 minutes to complete flocculation.

[0029] The third step involves multi-stage electric field treatment (S2): First, the flocculated material is pumped into a settling tank, and an alternating electric field with a frequency of 3Hz and a field strength of 12 V / cm is applied for pre-aggregation (S2.1). After 15 minutes, the flocs become noticeably coarser. Next, the concentrated slurry is pumped into a plate and frame filter press, and dewatering is performed simultaneously with a 15 V / cm DC electric field (S2.2). 12V and 18V voltages are applied to the electrode components near the feed inlet and deep within the filter chamber. Filtration ends when the feed pressure reaches 0.8 MPa. Subsequently, with the filter chamber closed, a pulsed electric field with a field strength of 40V / cm and a pulse width of 5 ms is applied for 60 seconds for deep dewatering (S2.3).

[0030] Finally, perform step S3: unload the filter cake, collect all the filtrate, and weigh, sample, and perform subsequent analysis.

[0031] 1. To evaluate the effectiveness of the technical solution in this embodiment, we designed four comparative examples for parallel control experiments.

[0032] Comparative Example 1 simulates the existing general process described in the background technology: in the leaching stage, only lignin sulfonate is used as a reducing agent (the amount is the same as in Example 1), and no precursor is added; in the subsequent neutralization and flocculation, only a single anionic PAM is used in the same amount as in Example 1; no electric field is applied throughout the solid-liquid separation process, and only conventional sedimentation and mechanical plate and frame filtration are performed.

[0033] Comparative Example 2 aims to examine the individual contribution of the composite flocculant: its leaching, flocculation steps, and agent types and dosages are exactly the same as those in Example 1, but no electric field is applied throughout the solid-liquid separation process (S2.1, S2.2, S2.3).

[0034] Comparative Example 3 was used to examine the individual contribution of the multi-stage electric field technology: the leaching stage was the same as that of Comparative Example 1 (only lignin sulfonate was used), the flocculation stage used only the same amount of single PAM as in Example 1, but the solid-liquid separation process was carried out using the same multi-stage electric field treatment process as in Example 1.

[0035] Comparative Example 4 addresses the solution of the prior art CN103255291B (Application of lignin sulfonate and a reduction leaching method for pyrolusite): In accordance with the method in the patent document, lignin sulfonate is used as a reducing agent and dispersant in the leaching stage (the dosage is the same as in Example 1). After leaching, the subsequent flocculation and separation processes adopt the conventional and inherited process in this technical field after this leaching method, that is, using single PAM flocculation combined with conventional mechanical pressure filtration (without electric field assistance), thus forming a comparative solution.

[0036] The key performance indicators of each group of experiments were systematically measured and compared, and the results are summarized in the table below: Table 1 Performance indicators of each group of experiments *Note: The total energy consumption has been converted and includes the power consumption of the filter press and the estimated drying energy consumption required to dry the filter cake to the same final moisture content.

[0037] The experimental results show that, firstly, Example 1 achieved significant results: the filter cake moisture content was as low as 21.5%, which is not only far lower than the existing technology (48%) of Comparative Examples 1 and 4, but also significantly better than any single improvement scheme (Comparative Examples 2 and 3), fully achieving the technical effect of a moisture content below 22%; at the same time, the manganese recovery rate was as high as 99.3%, greatly reducing resource loss. This strongly demonstrates the decisive synergistic effect of composite flocculants and multi-stage electric field technology in breaking down colloidal structures, releasing bound water, and capturing fine crystals. Specifically, Comparative Example 2 (composite flocculant only) lacked electric field drive, resulting in insufficient dehydration and the inability to strongly enrich and capture fine crystals, leading to poor results. Comparative Example 3 (multi-stage electric field only) shows that, based on the loose flocs formed by traditional flocculants, although the electric field can enhance dehydration, its ability to release colloidal bound water is limited, and its efficiency in capturing unflocculated fine crystals is insufficient. Specifically, a comparison with Comparative Example 4 shows that even with the leaching technology of patent CN103255291B, if the subsequent solid-liquid separation follows traditional methods, the filter cake moisture content and manganese recovery rate are no different from the most common existing process (Comparative Example 1), still facing the core bottlenecks of high energy consumption and high losses. This highlights the innovative approach of this invention, which shifts the focus from the leaching reaction itself to the interfacial process and system integration of leaching and separation, and introduces a composite flocculation and multi-stage electric field enhancement throughout the process, solving key problems that existing technologies have not addressed. In terms of energy consumption and efficiency, the lower final moisture content of Example 1 significantly reduces subsequent drying energy consumption, resulting in the lowest overall energy consumption and a shorter filter press cycle, demonstrating good technical and economic efficiency.

[0038] 2. Optimization experiment of composite flocculant dosage. By precisely controlling the total dosage to 0.10% to 0.20% of the dry weight of the leaching residue, and optimizing its internal ratio (modified lignin sulfonate and polyacrylamide) within the range of 1:2 to 1:3, a significant effect of reducing environmental impact was achieved while ensuring efficient separation.

[0039] The entire experiment was conducted under the same process framework and operating conditions as Example 1, including the use of the same leachate raw materials, execution of the complete process comprising S0 to S3, and the use of identical multi-stage electric field treatment parameters (S2.1, S2.2, S2.3). The only variables were strictly controlled on the total dosage of the composite flocculant added in step S1 and its internal mass ratio.

[0040] In Example 1, after the leachate was neutralized to pH 5.8, the total amount of the added composite flocculant (on a dry basis) was 0.15% of the dry basis mass of the leachate residue, and the ratio of modified lignin sulfonate to PAM was 1:2.5.

[0041] Four comparative experiments were also conducted. Every process detail of all comparative experiments, except for the flocculant parameters, was kept consistent with Example 1, thus ensuring that any observed performance differences could be directly attributed to changes in the flocculant parameters.

[0042] Comparative Example A, with a total dosage of 0.15%, has a mixing ratio of 1:5.

[0043] Comparative Example B, with the same total dosage of 0.15%, has a ratio set at 1:1.

[0044] Comparative Example C serves as the benchmark for existing technologies, employing a common industry-standard single PAM flocculation scheme with a dosage of 0.18%.

[0045] Comparative example D was used to examine the effect of excessive total dosage (0.25%) when the ratio was 1:2.5.

[0046] After the experiment, the filter cake and filtrate of all experimental groups (Example 1 and each comparative example) were tested using the same standard method: the moisture content of the filter cake was determined by the drying loss method (drying at 105℃ to constant weight); the chemical oxygen demand (COD) of the filtrate was determined by the rapid digestion spectrophotometric method (HJ / T 399-2007); the suspended solids (SS) of the filtrate were determined by the gravimetric method (GB / T11901-1989); and the manganese recovery rate was obtained by mass balance of manganese in the filter cake and filtrate. The core data comparison is shown in the table below: Table 2 Comparison of Core Data As can be seen, firstly, the formulation of Example 1 successfully achieved the goals of efficient separation and low environmental impact. Its filter cake moisture content (21.7%) and manganese recovery rate (99.2%) remained excellent, while the COD and SS values ​​of the filtrate were at their lowest levels (285 mg / L, 32 mg / L). In Comparative Example A, with proper control of the total dosage, using a PAM ratio (1:5) resulted in a significant increase in filtrate COD to 520 mg / L. This indicates that to reduce the organic pollution load, the relative proportion of biomass components in the composite flocculant must be increased, i.e., the ratio needs to be optimized to the range of 1:2 to 1:3. The results of Comparative Example B demonstrate that excessively increasing the biomass proportion (1:1) weakens the floc skeleton strength, leading to a deterioration in solid-liquid separation, and a significant increase in both filter cake moisture content and filtrate SS. Therefore, there is an upper limit to the optimization of the formulation. Comparative Example D shows that even with the optimized 1:2.5 ratio, an excessively high total dosage (0.25%) still causes a sharp increase in filtrate COD (410 mg / L), indicating that controlling the total dosage and optimizing the ratio are both crucial and must be adjusted synergistically. Finally, compared with Comparative Example C, which represents the prior art, Example 1 demonstrates comprehensive advantages in both separation performance and environmental indicators.

[0047] 3. To verify the effectiveness of the present invention's technical solution in actual leachate composition fluctuations, especially in the presence of Al... 3+ High concentration of Ca 2+ It exhibits outstanding ability to maintain efficient and stable operation under conditions with complex interfering ions. These interfering ions can both form their own hydroxide colloids, increasing the complexity of the system, and compete with flocculants for complexation, severely interfering with the traditional single PAM flocculation process and causing significant fluctuations in separation performance.

[0048] This invention includes a comparative experiment. First, three test solutions were prepared: the base solution was a standard leachate (Fe...). 3+ 3.2 g / L); Interference solution 1 is prepared by adding Al2(SO4)3 to the base solution, so that Al 3+ The concentration reached 1.5 g / L to simulate aluminum impurity interference; interference solution 2 was prepared by adding CaO to the base solution to increase the Ca content. 2+The concentration was significantly increased to 5.0 g / L to simulate calcium ion interference caused by excessive lime neutralization or high-calcium water. For each test solution, Example 1 of this invention and Comparative Example 1 of the conventional control scheme were used for treatment without electric field assistance. In the first round of experiments, both maintained their original flocculant dosage optimized for standard leachate (0.15% composite flocculant in this invention, 0.18% single PAM in the conventional scheme), and their performance retention rate under interference conditions was directly compared. Subsequently, a dose sensitivity test was conducted: if the performance of a certain scheme decreased beyond the allowable range under interference (e.g., filter cake moisture content >25% or manganese recovery rate <98%), the flocculant dosage was gradually increased until the performance recovered to near the base solution level. The required increase in dosage was recorded to evaluate the operational flexibility of the scheme in response to fluctuations.

[0049] The core performance comparison data of the experiment are shown in the table below, where the change value refers to the change in the baseline performance of each scheme in the base fluid: Table 3 Comparison of Anti-interference Experimental Performance First, regarding performance retention, in the face of AI 3+ and Ca 2+ Despite severe interference, the solution of this invention (Example 1) exhibits extremely strong stability. The increase in filter cake moisture content was controlled within 2 percentage points (+1.4, +1.7), and the decrease in manganese recovery rate was less than 0.5 percentage points (-0.3, -0.4). In contrast, the performance of the conventional solution (Comparative Example 1) was significantly reduced, with moisture content increasing by more than 5.6 percentage points, even approaching 8 percentage points, and manganese recovery rate decreasing by more than 3 percentage points, indicating that the existing technology is highly sensitive to ion interference. Secondly, regarding dosage sensitivity, the solution of this invention maintains excellent performance without requiring additional flocculant dosage under interference conditions, demonstrating an extremely wide operating window and strong anti-interference capability. In contrast, the conventional solution requires increasing the flocculant dosage by 40% to 55% to barely restore performance to an acceptable range, which not only significantly increases reagent costs but also exacerbates the risk of residual organic matter (COD) in the filtrate. This comparative result clearly demonstrates that the synergy between the composite flocculant of this invention and multi-stage electric field pretreatment constructs a highly robust solid-liquid separation system. The selective action of its modified lignin sulfonate and the physical destabilization effect of the electric field effectively resist the interference of complex ionic environment, thereby ensuring the continuous stability and high efficiency of the production process when faced with raw material fluctuations.

[0050] Example 2 This embodiment, based on the technical solution and experimental conditions established in Embodiment 1, introduces a DC-high frequency composite electric field and real-time feedback control based on the manganese concentration of the filtrate. Embodiment 2 is identical to Embodiment 1 in steps S0, S1, S2.1, S2.3, and S3, with the only difference being the method of applying the DC electric field and the control system in step S2.2 (plate and frame filter press dewatering).

[0051] To implement the technical solution of Example 2, the electrical control system of the plate and frame filter press is upgraded based on the equipment used in Example 1: a composite power supply capable of simultaneously outputting DC bias and high-frequency AC waveforms replaces the original pure DC power supply; simultaneously, a bypass sampling branch pipe (DN10 diameter) is installed at the outlet of the filtrate manifold of the plate and frame filter press, and an online manganese ion analyzer suitable for industrial wastewater monitoring is installed (preferably a colorimetric analyzer, as its resistance to complex matrix interference is generally better than that of ion-selective electrodes) (measurement range 1-1000 mg / L, response time <30 seconds) to ensure continuous, bubble-free sampling. A self-cleaning filter (100 μm) is installed before the sampling point to prevent particulate matter blockage. The signal output terminal of the monitor communicates in real time with the control system of the composite power supply. The analyzer has a built-in temperature sensor and pH electrode, which can automatically measure and compensate for fluctuations in the filtrate within the common range of this process (temperature 40-70℃, pH 5.0-6.5). The control system is technologically mature, highly reliable, and easy to maintain. It automatically performs a two-point calibration every 8 hours (using 50 mg / L and 500 mg / L standard manganese solutions) to ensure long-term measurement stability. If the monitoring signal is abnormal (e.g., disconnection, over-range), the system automatically switches to a fixed parameter mode to maintain the DC bias electric field and avoid production interruptions. The control system's PLC reads the manganese concentration value every 10 seconds and uses a moving average filter (30-second window) to eliminate instantaneous fluctuations. The frequency and field strength setpoint of the high-frequency electric field are calculated based on a feedback algorithm, and the power output is controlled via an analog output module or pulse width modulation (PWM). The human-machine interface displays the manganese concentration curve, electric field parameters, and alarm information in real time, supporting operator manual intervention or setting of the target threshold C0.

[0052] The specific implementation process of Example 2 is as follows: After completing steps S0, S1, and S2.1 (pre-aggregation) identical to those in Example 1, proceed to step S2.2. Pump the pre-aggregated material into the plate and frame filter press and start the filtration process. Simultaneously, activate the composite electric field and feedback control system. Setting Control Targets: Set a target threshold C0 of 50 mg / L for the manganese ion concentration in the filtrate. This threshold means that a very small amount of manganese loss is permissible, but far below the concentration corresponding to a 5-8% loss rate (approximately 2000-3000 mg / L). If the manganese concentration in the filtrate exceeds 200 mg / L, direct discharge or reuse will result in significant manganese loss (>5%). Setting C0 to 50 mg / L ensures a manganese recovery rate >99.0%, while avoiding a surge in energy consumption in pursuit of extreme recovery (e.g., <10 mg / L). If the filtrate is returned to the leaching process for recycling, the manganese concentration must be controlled within a certain range to avoid impurity accumulation. A threshold of 50 mg / L meets the circulating water quality requirements (Mn) of most plants. 2+ <100 mg / L). Existing online ion-selective electrodes (ISE) or colorimetric monitors have good measurement accuracy (±5%) and response speed (<30 s) around 50 mg / L, making them suitable for control.

[0053] A combined electric field is applied and monitoring is initiated: A DC bias electric field with a strength of 15 V / cm and a high-frequency alternating electric field with initial parameters set to 500 kHz frequency and a peak-to-peak value of 15% of the DC field strength (i.e., 2.25 V / cm) are simultaneously applied to the electrodes on both sides of the filter chamber. The pressure filtration and dewatering process begins, and the online monitoring instrument starts real-time monitoring of the manganese ion concentration C in the filtrate.

[0054] Perform dynamic feedback adjustment: In the early stage of pressure filtration, the filtrate flow rate and concentration were high, and monitoring showed that the C value rapidly rose to 200 mg / L and exceeded C0. The control system immediately triggered an adjustment command: adjusting the frequency of the high-frequency alternating electric field to 200 kHz (falling into the 100-500 kHz range), and simultaneously increasing its peak-to-peak field strength to 40% of the DC bias electric field strength (i.e., 6 V / cm).

[0055] As the pressure filtration proceeds, the filtrate becomes clear, and the manganese ion concentration C begins to decrease. When the C value drops to 50 mg / L (equal to C0), the control system adjusts again: reducing the peak-to-peak value of the high-frequency electric field to 15% of the DC field strength (i.e., 2.25 V / cm), while maintaining the frequency at 500 kHz.

[0056] In the later stages of pressure filtration, the C value stabilizes at 20 mg / L (below C0), and the control system maintains low-frequency weak field or high-frequency low field mode to save energy.

[0057] Complete the pressure filtration: Filtrate to the same endpoint pressure (0.8 MPa) as in Example 1. The subsequent S2.3 (pulse electric field deep dehydration) and S3 (discharge and collection) operations are exactly the same as in Example 1.

[0058] To evaluate the improvement effect of the technical solution in Example 2 (composite electric field + real-time feedback) compared with the basic solution (Example 1, DC electric field only), the following two comparative experiments were designed: Comparative Example 5 (Basic Scheme Comparison): The description of Comparative Example 5 clearly states that all its process parameters are the same as those of Example 1. In S2.2, only a steady-state DC electric field of 15 V / cm is applied, with no high-frequency components and no feedback control.

[0059] Comparative Example 6 (with composite electric field, without feedback control): In S2.2, the same initial composite electric field as in Example 2 (DC 15 V / cm + high frequency 500 kHz / 2.25 V / cm peak-to-peak) was applied, but this parameter was kept constant throughout the pressure filtration process without any dynamic adjustment based on the filtrate concentration. All other steps were consistent with Examples 1 and 2.

[0060] The test results of each group of experiments are compared as follows: Table 4 Comparison of experimental test results for each group Example 2 achieved a manganese recovery rate of 99.7%, a further measurable improvement compared to Comparative Example 5 (99.3%) and Comparative Example 6 (99.5%). This directly demonstrates that the introduction of a high-frequency alternating electric field, especially when a lower frequency (200 kHz) and a higher field strength (40%) are used when the manganese concentration is high, can generate a stronger dielectric force that effectively acts on the fine MnSO4 crystals, enhancing their migration and adsorption on the filter cloth (anode). This precise enhancement cannot be achieved by a single DC electric field (Comparative Example 5) or a high-frequency electric field with fixed parameters (Comparative Example 6).

[0061] Example 2 exhibited the lowest average manganese concentration in the filtrate (38 mg / L), and its power consumption in stage S2.2 (4.8 kWh / t) was significantly lower than that of Comparative Example 6 (5.2 kWh / t). This indicates that real-time feedback control is a key technology. It does not blindly apply a strong high-frequency electric field throughout the entire process, but rather strengthens the field only when the risk of manganese loss is high (C>C0), and reduces energy consumption when the risk is low (C≤C0). This dynamic strategy ensures optimal recovery while avoiding energy waste and solves the secondary problem of sacrificing energy efficiency for improved performance. In contrast, although Comparative Example 6 also has high-frequency components, its fixed parameters result in higher energy consumption in stages where strong action is not required, leading to poorer economic efficiency.

[0062] The effect of Example 2 is the result of the synergy between the composite electric field and feedback control. Without the high-frequency component (Comparative Example 5), there is a lack of additional force on the microcrystalline material; without feedback control (Comparative Example 6), it is impossible to intelligently optimize the timing and intensity of the high-frequency component, resulting in low energy efficiency and potentially suboptimal performance.

[0063] Example 2, while maintaining the same excellent dehydration effect as Example 1 (moisture content 21.3%), pushed the manganese recovery rate to a higher level, and optimized the energy consumption structure of this step through intelligent control.

[0064] Example 3 This embodiment uses an adaptive segmented pulse sequence for deep dehydration. Embodiment 3 is completely identical to Embodiment 1 in steps S0, S1, S2.1, S2.2, and S3. The core difference lies only in the application strategy of the pulsed electric field in step S2.3 (deep dehydration), that is, changing from the fixed parameter single-mode pulse of Embodiment 1 to the use of an adaptive segmented pulse sequence based on real-time judgment of the filter cake state.

[0065] To implement the solution in Example 3, a real-time acquisition interface for the feed pressure sensor signal of the plate and frame filter press was added to the pulse power supply and control system in Example 1, and a decision logic was preset. In specific implementation, we chose to use the feed pressure value P as the judgment criterion (the filter cake resistance R can also be used, with the same principle). The preset pressure threshold P0 is set to 0.75MPa, which is an empirical value that can effectively distinguish the degree of difficulty in dewatering the filter cake.

[0066] Statistical analysis of the filtration process of hundreds of batches of leachates from different sources revealed that when the final pressure P ≤ 0.75 MPa, the filter cake porosity is high (>45%), the capillary water content is low, and it is an easily dewatered filter cake. When P > 0.75 MPa, the filter cake is dense (porosity <35%), the proportion of colloidal bound water increases significantly, and it is a difficult-to-dewater filter cake. This threshold corresponds to the inflection point of the average moisture content of the filter cake (approximately 28%), has clear engineering differentiation, and is suitable for filter chambers with a thickness of 30 mm and a filtration area of ​​1 m². 2 For plate and frame filter presses, the pressure can be proportionally adjusted for different specifications of equipment. For example, for every 10 mm increase in filter chamber thickness, P0 increases by approximately 0.1 MPa. The pressure threshold P0 is an empirical value obtained for the specific specification of plate and frame filter press (filter chamber thickness 30 mm) used in the experiment under the stated material system. For different specifications of equipment, this threshold needs to be recalibrated through a small number of process experiments.

[0067] Similarly, the filter cake volume resistivity threshold R0 can be used to replace or assist in judging the ease of dewatering. For example, a set value of R0 = 15 kΩ·m (typical value, which can be fine-tuned according to the material). The filter cake resistivity is closely related to its porosity, water content, and ion concentration. Laboratory measurements show that when the filter cake moisture content is below 30%, the resistivity increases exponentially with decreasing moisture content. The filter cake moisture content corresponding to R0 = 15 kΩ·m is approximately 27%, which is consistent with the difficult dewatering boundary judged by P0. The advantage of using the resistivity criterion is that it allows for real-time, non-destructive measurement, especially suitable for situations where the filter cake is uneven or the pressure sensor fails. A low-frequency AC signal (such as 1 kHz) is applied by a ring electrode embedded in the filter plate, and the impedance of the filter cake is measured and converted into volume resistivity.

[0068] The specific implementation process of Example 3 is as follows: After completing steps S0 to S2.2, which are identical to those in Example 1, at the instant the feed pressure reaches 0.8 MPa and the feed pump is shut off during the pressure filtration process, the control system captures the feed pressure value P = 0.80 MPa in real time. Subsequently, the system executes decision logic: comparing the P value with P0. Since P (0.80 MPa) > P0 (0.75 MPa), the system determines that the currently formed filter cake is difficult to dewater. Accordingly, the system automatically sets the parameters for the subsequent segmented pulse sequence: the duration ratio T1:T2 of the low-pressure permeation section to the high-pressure breakdown section is 4:1. Then, the segmented pulse sequence is initiated for deep dewatering (S2.3). Low-pressure permeation section: Apply a pulsed electric field with a field strength of 15 V / cm and a pulse width of 8 ms for a duration of T1=48 seconds.

[0069] High-voltage breakdown stage: Immediately afterwards, a pulsed electric field with a field strength of 45 V / cm and a pulse width of 1 ms is applied for a duration of T2 = 12 seconds.

[0070] The total duration of the entire pulse sequence was 60 seconds (equal to the total pulse duration in Example 1 to ensure fairness in the comparison). In this sequence, the longer low-pressure permeation phase was designed to allow the electric field force to fully penetrate the deep capillary structure of the filter cake, loosening the bound water; the brief high-pressure breakdown phase was designed to provide a strong driving force to completely expel the loosened water. After the pulse ended, the same S3 step as in Example 1 was performed, followed by unloading and analysis.

[0071] To evaluate the improvement of Example 3 over the fixed pulse mode (Example 1), the following two comparative examples were designed: Comparative Example 7 (Fixed Pulse Control): Example 1 itself was used as a control. In S2.3, a fixed 40 V / cm, 5 ms pulse was applied for 60 seconds without segmentation or adaptation.

[0072] Comparative Example 8 (fixed ratio segmented pulse, non-adaptive): Segmented pulses are applied in S2.3, but the ratio of T1:T2 = 1:1 (i.e., 30 seconds each) is fixed. The low pressure and high pressure parameters are the same as in Example 3, but they are not judged or adjusted according to the pressure P. This fixed mode is used for all filter cakes.

[0073] The key dehydration effects and energy consumption indicators of the three groups of experiments were compared and analyzed, and the results are shown in the table below: Table 5 Dehydration effect and energy consumption index Example 3 achieved a minimum final filter cake moisture content of 20.1%, significantly lower than 21.5% in Comparative Example 7 and 21.0% in Comparative Example 8. This demonstrates the effectiveness of the adaptive segmented pulse sequence. Under the experimental conditions (P = 0.80 MPa > P0), the system correctly identified the filter cake as difficult to dewater and implemented a long low-pressure segment scheme (4:1) emphasizing permeation. This ensured that the electric field energy was used more effectively to disrupt deep bound water, rather than prematurely applying a high field strength to the already dewatered surface layer as in fixed pulses (Comparative Example 7) or balanced segmentation (Comparative Example 8), resulting in insufficient energy utilization and inadequate removal of deep water.

[0074] The improvement in Example 3 does not come from simply increasing energy consumption. Data shows that its pulse stage power consumption (0.85 kWh / t) is at the same level as Comparative Examples 7 and 8, but its dehydration effect is better. Comparative Example 8 adopted a fixed proportion segmentation, which is slightly better than single pulse (Comparative Example 7), but because it failed to adjust the strategy according to the actual situation of the filter cake (this batch is a difficult-to-dehydrate filter cake), the effect is still not as good as the adaptive scheme of Example 3.

[0075] Example 3 shows that the lower final moisture content means a significant reduction in the amount of water that needs to be evaporated in subsequent drying processes. It is estimated that this reduction in moisture content can further reduce subsequent drying energy consumption by approximately 8-10%, thus solving the technical problem of excessive energy consumption in subsequent processing.

[0076] In summary, the experimental data clearly demonstrate that, compared to a fixed pulse dewatering mode, the adaptive segmented pulse sequence based on real-time judgment of filter cake state (feed pressure) can achieve deeper and more uniform dewatering without increasing additional energy consumption, reducing the filter cake moisture content to a lower level. This provides crucial technical support for significantly reducing subsequent drying energy consumption. This improvement reflects the value of intelligent process control and possesses significant innovative and practical benefits.

[0077] Example 4 This embodiment implements active program control over the in-situ conversion process of the precursor additive. Example 4 shares the same overall process framework as Example 1, including a leaching step (S0) and using a specific precursor additive. Its core difference from Example 1 lies in the specific execution method of step S1 (neutralization and flocculation): Example 1 only adjusts the pH to the target value (5.8), while Example 4 implements a time-sequential coordinated control program for pH and temperature to actively guide and optimize the conversion process of the precursor into the active substance.

[0078] In this invention, the polyethyleneimine-epoxychloropropane prepolymer (precursor additive) added in step S0 is designed to remain chemically inert under acidic leaching conditions, while being activated in situ during subsequent neutralization and transformed into a cationic polymer with flocculation activity. Its inert-to-active transition mechanism is as follows: During the leaching stage (in a sulfuric acid medium at a pH of approximately 2.0 and a temperature of approximately 95°C), the amine (-NH2) and imine (-NH-) groups on the prepolymer molecular chain are highly protonated, forming a positively charged ammonium salt structure (-NH3). + -NH2 + -). At this point, due to electrostatic repulsion, the molecular chains are in an extended state with a high positive charge density, making them readily react with the large number of anions (such as SO42-) in the leachate. 2- This forms ion pairs, temporarily causing it to lose its flocculation activity. At the same time, epichlorohydrin residues have an extremely low hydrolysis rate under acidic conditions, and the prepolymer structure is stable, preventing premature cross-linking or degradation, thus achieving chemical inertness.

[0079] When the leachate enters the neutralization stage (step S1), as the pH gradually increases (to 5.0-6.0), the H+ in the system... + As the concentration decreases, the protonated amine protons on the prepolymer molecular chains gradually dissociate, restoring to neutral amine groups. This process leads to two changes: the positive charge density of the molecular chains decreases, electrostatic repulsion weakens, and the molecular chains can coil and expose adsorption sites. Simultaneously, the remaining cationic groups can still adsorb onto the surface of negatively charged colloidal particles (such as Fe(OH)3 colloid), achieving charge neutralization. Under conditions where the pH rises above 5.0 and the temperature reaches 60-70℃, the active sites (such as hydroxyl groups) introduced by epichlorohydrin on the prepolymer molecular chains undergo cross-linking condensation reactions with the excess amine groups on adjacent molecular chains, forming a three-dimensional network structure, increasing the molecular weight, and significantly enhancing flocculation activity. Verification showed that at pH < 3, the prepolymer zeta potential reached as high as +30 mV, and the molecular chains stretched out; when the pH rose to 5.5-6.0 and the temperature reached 65℃, the zeta potential decreased to +5 to +10 mV, the molecular chains showed cross-linking characteristic peaks, and the flocculation activity was significantly enhanced.

[0080] The programmed temperature rise and segmented pH control used in Example 4 are precisely to optimize this transition process. By controlling the heating rate and the timing of pH jumps, the kinetics of the cross-linking reaction can be regulated, avoiding excessive cross-linking that could lead to flocculant deactivation. At the same time, it ensures that the generated active polymer has the most suitable charge density and molecular configuration, thereby producing a synergistic effect with the subsequently added composite flocculant.

[0081] The specific implementation process of Example 4 is as follows: Step S0 (leaching) is exactly the same as in Example 1: 40 kg of lignin sulfonate and 1.0 kg (solids) of polyethyleneimine-epoxychloropropane prepolymer (molar ratio 1:0.3) are added per ton of MnO2 as precursor additives, and leaching is carried out at 95°C under acidic conditions for 4 hours to obtain the leachate. After this, the crucial distinguishing step S1 is performed.

[0082] The leachate was transferred to a neutralization and stirring tank equipped with precise pH and temperature control. Lime slurry was slowly added under stirring, with the pH and temperature of the system monitored in real time. When the online pH meter detected that the system's pH reached 5.0, the system automatically activated its program control logic.

[0083] Phase 1: Programmed Temperature Increase and pH Maintenance: Upon reaching pH 5.0, the control system begins programmed temperature increase of the reaction system at a set rate of 1.0 °C / min. Simultaneously, by precisely controlling the lime slurry addition rate, the pH value of the system is dynamically maintained within a narrow range of 5.0-5.3, meeting the requirement of maintaining a pH value within the 5.0-5.5 range. This process continues until the temperature rises from approximately 55 °C (the temperature at the start of this phase) and stabilizes at 65 °C.

[0084] Phase Two: pH Jump and Maturation Reaction: Once the temperature stabilizes at 65℃, the control system changes mode and, within 10 minutes, adjusts the pH of the system to 5.8 by continuously adding lime slurry. After reaching pH 5.8, maintain this pH condition and the temperature of 65℃, and continue stirring for 20 minutes to complete the full conversion and maturation of the precursor additive.

[0085] Flocculant addition: After the in-situ conversion reaction controlled by the above procedure is completed, immediately add the same type and dosage (0.15% of the slag weight on a dry basis) of composite flocculant (modified lignin sulfonate to PAM mass ratio 1:5) as in Example 1 to the system. After stirring for 5 minutes, proceed to the subsequent S2 (multi-stage electric field treatment) and S3 steps. All operating parameters and procedures for S2 and S3 are consistent with those in Example 1.

[0086] To verify the necessity of the active control program and its resulting technical effects, the following comparative examples were designed: Comparative Example 9 (Basic Scheme Control): This comparative example used the same precursor additive as Example 4 in step S0. In step S1, no active program control was implemented; only routine operation was simulated: the leachate was neutralized to pH 5.8, and the system temperature changed naturally during the process. After reaching pH 5.8, the composite flocculant was added. All other subsequent steps (S2, S3) were the same as in Example 4.

[0087] Comparative Example 10: This comparative example simulates the conventional method. In its S0 step, only lignin sulfonate is added as a reducing agent, without any precursor additives. In the S1 step, after directly adjusting the pH to 5.8, an equal amount of commercially available cationic polyacrylamide (CPAM) and PAM composite flocculant is added (to simulate an externally added flocculant scheme) in an attempt to achieve a similar flocculation effect.

[0088] A systematic comparison was made of the experimental results of Example 4 and the two comparative examples, focusing on the impact of the differences in step S1 on the flocculation effect and the final separation index: Table 6 Flocculation effect and final separation index Example 4, through a process of pH-triggered heating-constant pH heating-rapid pH adjustment-constant temperature aging, provided a transformation kinetic pathway for precursor molecules. This directly led to a significant improvement in floc quality: the flocs were denser and stronger. This was reflected in faster settling rates (12 minutes in Example 4, 18 minutes in Comparative Example 9), signifying improved initial efficiency of solid-liquid separation. Comparative Example 9, relying solely on pH changes and natural cooling, had random transformation conditions, resulting in unsatisfactory structures and properties of the generated active substances, leading to loose flocs. Comparative Example 10, entirely dependent on external flocculants, failed to achieve in-situ, specific interaction with the leaching residue components, resulting in the worst flocculation effect.

[0089] Thanks to the high-quality flocs formed, Example 4 achieved a lower filter cake moisture content (20.8%) and a higher manganese recovery rate (99.5%) after undergoing the same multi-stage electric field dehydration. This indicates that, through active control, the flocculant active substances generated at the process source (S1) more effectively disrupted the colloidal structure and encapsulated fine particles, laying a more solid foundation for subsequent electric field dehydration and resource recovery. Comparative Example 9 showed improvement, but its effect was not as good as Example 4, proving that timing settings must be combined with active control to achieve maximum effectiveness. Comparative Example 10 showed the weakest effect, exhibiting a disconnect between the leaching and separation stages.

[0090] This embodiment addresses a secondary technical challenge inherent in the timing design: ensuring efficient and controllable precursor conversion. It proactively designs and controls this process, transforming the conversion from an uncontrollable accompanying reaction into a manageable unit operation. This avoids fluctuations in flocculation effects due to incomplete conversion or unstable product properties, thereby improving the stability and reliability of the entire process.

[0091] The effectiveness of Example 4 is attributed to the better synergy between the high-quality flocs (from the optimized S1) and the subsequent multi-stage electric field treatment (S2). The denser flocs can withstand stronger electric field forces without breaking, which is beneficial for deep dehydration; at the same time, more thorough colloidal disruption reduces bound water from the source, reducing the burden on deep dehydration in S2.3.

[0092] Experimental results show that, compared with simple pH adjustment, active programmed regulation, including programmed temperature rise and segmented pH control, can significantly optimize the performance of the generated active substances in the in-situ conversion process of precursor additives. This results in higher-quality flocs, faster settling speeds, and ultimately, better dewatering effects and resource recovery rates. This approach not only solves the problem of disconnected process steps but also provides a key guarantee for the stable and efficient operation of the entire system by improving the quality and controllability of the source process, demonstrating outstanding innovation and practical value.

[0093] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Further modifications can be readily implemented by those skilled in the art.

Claims

1. A method for dewatering and recycling electrolytic manganese dioxide leaching residue, characterized in that, Includes the following steps: S1. Neutralize the electrolytic manganese dioxide leachate and adjust the pH to 5.5-6.0; during or after the neutralization treatment, add a composite flocculant containing polyacrylamide and modified lignin sulfonate to the system for flocculation. S2. The flocculated material is subjected to multi-stage electric field treatment in sequence: S2.1 In the settling tank, an alternating electric field with a frequency of 1-10Hz and a field strength of 5-15 V / cm is applied to the material for pre-aggregation; S2.2 Pump the pre-aggregated material into a plate and frame filter press, embed electrode groups in the filter cloth or filter plates on both sides of the filter chamber, and apply a DC electric field of 10-20 V / cm to the electrode groups for filter dewatering. S2.3 After the filter press is completed and before unloading, apply a pulsed electric field with a field strength of 30-50 V / cm and a pulse width of 1-10 ms to the filter cake in the filter chamber of the filter press for deep dewatering; S3. After dehydration is complete, unload the filter cake and collect the filtrate.

2. The method according to claim 1, characterized in that, Before step S1, the process also includes step S0, the leaching step of electrolytic manganese dioxide: In the leaching step, lignin sulfonate is added to the leaching system as a reducing agent, and a precursor additive is added simultaneously; the precursor additive is an aqueous solution of a prepolymer generated by reacting polyethyleneimine and epichlorohydrin in a molar ratio of 1:0.1 to 1:0.5; the precursor additive is added to the leaching system in step S0 in solution form simultaneously or separately with lignin sulfonate, and the amount added is 0.5 to 2.0 kg per ton of manganese dioxide in the leaching solution, based on the solids in the precursor additive.

3. The method according to claim 1, characterized in that, In S2.1, the frequency and field strength of the alternating electric field are set collaboratively as follows: when the frequency is in the low-frequency range of 1-5Hz, a higher field strength of 10-15 V / cm is used; when the frequency is in the high-frequency range of 5-10Hz, a lower field strength of 5-10 V / cm is used. In S2.2, the filter chamber of the plate and frame filter press is equipped with multiple electrode groups that can independently control the voltage, which are used to apply different voltages according to different areas of filter cake formation. The electrode groups are arranged on the surface of the filter plates or filter cloth on both sides of the filter chamber, and are arranged parallel to the direction of filtrate flow. The number of electrodes is at least 2 electrode pairs per group, and each filter plate surface is equipped with 2-4 groups of independently controlled electrodes. The electrode spacing is 50-150mm. The electrode shape is strip or mesh, flush with or slightly embedded in the surface of the filter plate. Each group of electrodes is connected to an independent adjustable power supply, which is used to adjust the applied voltage in real time according to the thickness, density or resistivity of the filter cake.

4. The method according to claim 3, characterized in that, In S2.3, the duration of the pulsed electric field application is 30-90 seconds.

5. The method according to claim 1, characterized in that, In step S1, the dosage of the composite flocculant is 0.10% to 0.20% of the dry weight of the leaching residue, based on its total dry weight; and the mass ratio of modified lignin sulfonate to polyacrylamide is 1:2 to 1:

5.

6. The method according to claim 1 or 3, characterized in that, In step S2.2, the application of the DC electric field specifically involves: simultaneously applying a DC bias electric field and a high-frequency alternating electric field superimposed on it to both sides of the filter chamber of the plate and frame filter press to form a composite electric field; simultaneously, an online ion concentration monitor is installed at the filtrate outlet of the plate and frame filter press to monitor the manganese ion concentration in the filtrate in real time; the frequency and field strength of the high-frequency alternating electric field are dynamically adjusted according to the feedback signal from the online ion concentration monitor, specifically in the following manner: 1) Set the target threshold C0 for the concentration of manganese ions in the filtrate; 2) During the pressure filtration and dewatering stage, when the real-time monitored manganese ion concentration C is higher than C0, the frequency of the high-frequency alternating electric field is adjusted to the range of 100 kHz-500 kHz, and at the same time, its peak-to-peak field strength is increased to 30%-50% of the DC bias electric field strength; 3) When the real-time monitored manganese ion concentration C is lower than or equal to C0, the peak-to-peak value of the high-frequency alternating electric field is reduced to 10%-20% of the DC bias electric field strength.

7. The method according to claim 1, characterized in that, In step S2.3, when deep dehydration is performed using a pulsed electric field, the application method is specifically a segmented pulse sequence, which includes at least a low-pressure permeation section and a high-pressure breakdown section executed sequentially: the low-pressure permeation section: applying a pulsed electric field with a field strength of 10-20 V / cm and a pulse width of 5-10 ms, lasting for a duration T1; the high-pressure breakdown section: applying a pulsed electric field with a field strength of 40-50 V / cm and a pulse width of 0.5-2 ms, lasting for a duration T2; The time ratio of T1 to T2 is determined through the following steps: a) At the moment when the filter press dewatering ends in step S2.2 and the feed pump is turned off, the feed pressure value P of the plate and frame filter press is obtained in real time or the average volume resistivity value R of the filter cake is measured and calculated in real time by the electrodes set on the filter plate. b) Compare the obtained P-value or R-value with the preset threshold range: If P ≤ P0 or R ≤ R0, it is determined to be an easily dehydrated filter cake, and the ratio of T1 : T2 is set to (1-2):1; If P > P0 or R > R0, it is determined to be a filter cake that is difficult to dehydrate, and the ratio of T1 to T2 is set to (3-5):1; Wherein, P0 is the preset pressure threshold and R0 is the preset resistivity threshold.

8. The method according to claim 2, characterized in that, When performing step S0, the in-situ conversion process of the precursor additive is actively controlled, specifically including: During the neutralization process in step S1, the pH and temperature of the system are monitored simultaneously. When the pH reaches 5.0, if the system temperature is below 60°C, the system is programmed to increase in temperature at a rate of 0.5-1.5°C / min until it reaches 60-70°C. If the system temperature is already within the 60-70°C range, it is maintained at that temperature, and the pH is maintained within the 5.0-5.5 range during this stage. After the temperature reaches 60-70°C, the pH of the system is rapidly adjusted to the final range of 5.5-6.0 within 5-15 minutes, and the temperature is maintained at this final pH condition to continue the reaction for 10-30 minutes.

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