Method and apparatus for film-formation, mineralization, fixation, separation and recovery of heavy metal ions

Abstract

The present invention relates to the technical field of heavy metal ion-containing acidic wastewater treatment, and provides a method and apparatus for film-formation, mineralization, fixation, separation and recovery of heavy metal ions. The method comprises the following steps: mixing composite mineral particles and heavy metal acidic wastewater, carrying out a first hydration reaction under a standing condition, and using the obtained colloidal liquid film to carry out adsorption-precipitation-crystallization on heavy metal ions in the heavy metal acidic wastewater to obtain particles with mineralized films on the outer layers, wherein there is a spacing between each particle and the mineralized film on the outer layer; and separating the mineralized films on the outer layers from the particles, and then respectively recovering the mineralized films and the particles. A preparation method for the composite mineral particles comprises the following steps: mixing sodium carbonate / sodium silicate, bentonite, carbide slag and water, carrying out a second hydration reaction, and then sequentially carrying out granulation, aging and dehydration condensation to obtain the composite mineral particles, the particle sizes of the bentonite and the carbide slag being independently less than or equal to 74 μm. According to the present invention, film-formation, mineralization, fixation, separation and recovery of heavy metal ions, and the treatment of waste by waste can be achieved.

Description

A method and device for the fixed separation and recovery of heavy metal ions by film-forming mineralization

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 17, 2023, with application number 202310878015.7 and invention name “A method and device for fixed separation and recovery of heavy metal ions by film-forming mineralization”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The invention relates to the technical field of treatment of acidic wastewater containing heavy metal ions, and in particular to a method and device for film-forming mineralization, fixation, separation and recovery of heavy metal ions. Background Art

[0003] With the rapid development of industry, the large-scale exploitation of mineral resources has led to increasingly prominent environmental pollution problems. Metal sulfide mines, in particular, generate large quantities of acidic wastewater containing heavy metal ions during the mining, beneficiation, and smelting processes, as well as in open-air waste ore dumps and tailings dams. This heavy metal acidic wastewater is characterized by large volumes, strong acidity (pH 2-5), high heavy metal ion concentrations (ranging from tens to hundreds of milligrams per liter), complex composition (containing a variety of heavy metals such as iron, manganese, zinc, copper, lead, cadmium, and chromium), high toxicity, wide-ranging pollution, long duration, and severe hazards. The discharge of wastewater containing valuable heavy metals, in particular, can waste mineral resources. Discharge of this heavy metal acidic wastewater without timely and proper collection and treatment can ultimately lead to heavy metal contamination of surface water, soil, crops, and groundwater. Once this non-point source pollution occurs, it is extremely difficult to control. Therefore, effective treatment of this heavy metal acidic wastewater is urgent and urgent.

[0004] At present, the main treatment methods for heavy metal acidic wastewater include neutralization, chemical precipitation, electrolytic deposition, extraction, ion exchange, membrane separation, adsorption, wetland and microbial methods, etc. However, there are still problems such as low treatment efficiency, large amount of sediment (hazardous waste), difficulty in mud-water separation, small adsorbent capacity, high cost, no energy saving, complex operation and difficulty in fixing and recovering heavy metal ions. In particular, the valuable metals in the wastewater are precious mineral resources but have not been effectively mineralized, fixed and recycled.

[0005] Therefore, how to treat heavy metal acidic wastewater and realize the resource utilization of industrial solid waste calcium carbide slag, turning waste into treasure, treating waste with waste, simultaneous treatment of wastewater and waste slag, and mineralization, fixed recovery and circular economy of valuable metal resources in wastewater have become technical problems that need to be solved urgently in this field.

[0006] Summary of the Invention

[0007] The object of the present invention is to provide a method and apparatus for the fixed separation and recovery of heavy metal ions by film-forming mineralization. The method provided by the present invention can achieve the fixed recovery of heavy metal ions by film-forming mineralization and the purification of heavy metal acidic wastewater, and can also realize the resource utilization of industrial solid waste calcium carbide slag, turning waste into treasure, treating waste with waste, and simultaneously treating wastewater and waste slag, as well as the fixed recovery of valuable metal resources in wastewater by mineralization and circular economy.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for the fixed separation and recovery of heavy metal ions by film-forming mineralization, comprising the following steps:

[0010] The composite mineral particles and heavy metal acidic wastewater are mixed, and a first hydration reaction is carried out under static conditions. The obtained colloidal liquid film adsorbs, precipitates, and crystallizes heavy metal ions in the heavy metal acidic wastewater to obtain particles having a mineralized film on the outer layer; the particles having the mineralized film on the outer layer have a distance between the mineralized film and the particles;

[0011] Separating the particles with the mineralized membrane on the outer layer to obtain the mineralized membrane and the particles, and then recovering them separately;

[0012] The preparation method of the composite mineral particles comprises the following steps:

[0013] Sodium carbonate / sodium silicate, bentonite, carbide slag and water are mixed, subjected to a second hydration reaction, and then granulated, aged and dehydrated to obtain composite mineral particles.

[0014] The particle sizes of the bentonite and carbide slag are independently ≤74 μm.

[0015] Preferably, the usage ratio of the composite mineral particles to heavy metal acidic wastewater is 0.1-2.5 g:1 L.

[0016] Preferably, the mass ratio of the bentonite to the carbide slag is (15.5-57.5): (40-80);

[0017] The mass of the sodium carbonate / sodium silicate accounts for 2.5-4.5% of the total mass of the sodium carbonate / sodium silicate, bentonite and carbide slag.

[0018] Preferably, the chemical composition of the bentonite comprises, by mass percentage, SiO2: 65-80%, Al2O3: 11-17%, Na2O: 3.0-6.0%, CaO: 2.0-3.5%, MgO: 2.0-5.0%, Fe2O3: 1.6-4.0%, TiO2: 0.04-0.20%, K2O: 0.1-1.2% and impurities: 0.10-2.16%;

[0019] The chemical composition of the carbide slag includes: CaO: 86.7-94.5%, SiO2: 2.0-6.5%, Al2O3: 0.5-3.0%, Na2O: 0.5-2.5%, Fe2O3: 0.2-1.5%, MgO: 0.10-0.22%, TiO2: 0.01-0.08% and impurities: 1.0-1.72%.

[0020] Preferably, the mixing of sodium carbonate / sodium silicate, bentonite, carbide slag and water comprises first mixing the sodium carbonate / sodium silicate, bentonite and carbide slag uniformly and then adding water for second mixing;

[0021] The mass ratio of the total mass of the sodium carbonate / sodium silicate, bentonite and carbide slag to water is 1:(0.5-0.9).

[0022] Preferably, the particle size of the product obtained by the granulation is 2 to 7 mm.

[0023] Preferably, the aging temperature is 10-35° C., and the aging time is 2-12 hours.

[0024] Preferably, the dehydration condensation is drying under natural conditions for 24 to 48 hours;

[0025] Or the dehydration condensation temperature is 150-450° C., and the dehydration condensation time is 0.6-1.5 h.

[0026] Preferably, the mineralized membrane is recovered as a raw material or a finished product; and the particles are recovered as an adsorbent.

[0027] The present invention also provides a device for the fixed separation and recovery of heavy metal ions by film-forming mineralization, comprising a lower plate and an upper plate arranged in a stacked manner;

[0028] The upper plate is provided with a through hole.

[0029] The present invention provides a method for the fixed separation and recovery of film-forming mineralization of heavy metal ions, comprising the following steps: mixing composite mineral particles and heavy metal acidic wastewater, performing a first hydration reaction under static conditions, and using the obtained colloidal liquid film to adsorb-precipitate-crystallize heavy metal ions in the heavy metal acidic wastewater to obtain particles with a mineralized film on the outer layer; there is a distance between the mineralized film and the particles in the particles with the mineralized film on the outer layer; separating the particles with the mineralized film on the outer layer to obtain the mineralized film and particles, and then recovering them separately; the preparation method of the composite mineral particles comprises the following steps: mixing sodium carbonate / sodium silicate, bentonite, carbide slag and water, performing a second hydration reaction, and then sequentially performing granulation, aging and dehydration condensation to obtain composite mineral particles; the particle sizes of the bentonite and carbide slag are independently ≤74μm. The method for the fixed separation and recovery of heavy metal ions by film-forming mineralization provided by the present invention regulates the particle size of bentonite and carbide slag, mixes them with sodium carbonate / sodium silicate, and generates a hydration reaction under the action of water to form hydrated calcium silicate (CSH) gel, etc., thereby improving the cohesiveness and mechanical strength of the particles; the particles obtained after the hydration reaction and granulation are aged to make the hydration reaction in the particles more complete, and the water in the hydrated calcium silicate (CSH) gel is dried and dehydrated by dehydration condensation to condense the particles; when the composite mineral particles after dehydration and condensation are placed in water during use, they absorb water, generate a hydration reaction, generate hydrated calcium silicate (CSH) gel again, release Ca(OH)2, and simultaneously release heat and expand, so that a temperature difference and composition change occur locally in the same solution around the particles to form an interface layer The system interface energy tends to shrink to a minimum, so the interface is spherical, and because the local concentration of slightly soluble Ca(OH)2 is large and the solubility is lower at high temperature, a Ca(OH)2 colloidal structure is generated to form a skeleton distributed on the spherical interface and a thicker water film is adsorbed on the surface to form a colloidal liquid film. The negatively charged colloidal liquid film rich in Ca(OH)2 adsorbs heavy metal cations to generate heavy metal hydroxide precipitates as the initial crystal nuclei to induce crystallization, and generates heavy metal basic sulfate crystals under acidic conditions. Through the continuous adsorption-precipitation-crystallization self-growth mineralization synergistic effect, a mineralized film mainly containing heavy metal basic sulfate crystals is finally generated. By separating the mineralized film and particles and recovering them separately, the fixed mineralization recovery of heavy metal ions and the recovery of particles are realized. Experimental results show that the method for the fixed separation and recovery of heavy metal ions by film-forming mineralization provided by the present invention can treat acidic wastewater with an initial pH value of 2 to 6 and a heavy metal ion concentration of 50 to 500 mg / L. The effluent pH reaches 6 to 9, the heavy metal removal rate reaches 95 to 100%, which can meet the emission standards, the mineralized film recovery amount reaches 200 to 2000 mg / g, the purity of heavy metals in the mineralized film reaches more than 50%, the purity of the mineralized film crystals reaches more than 90%, and the valuable metal mineralization fixed recovery effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a flow chart of the process for preparing composite mineral particles according to the present invention;

[0031] FIG2 is a schematic diagram of the composite mineral particles forming a mineralized film according to the present invention;

[0032] FIG3 shows the composite mineral particles obtained in Example 1 of the present invention spontaneously forming a colloidal liquid film and the heavy metal Cu 2+ Film-forming mineralization effect diagram;

[0033] FIG4 shows the composite mineral particles obtained in Example 2 of the present invention spontaneously forming a colloidal liquid film and the heavy metal Zn 2+ Film-forming mineralization effect diagram;

[0034] FIG5 is a photograph of bentonite, a raw material of the present invention;

[0035] FIG6 is a photograph of carbide slag, a raw material of the present invention;

[0036] FIG7 is a photograph of composite mineral particles prepared in Example 3 of the present invention;

[0037] FIG8 is an XRD diffraction pattern of bentonite and carbide slag as raw materials of the present invention;

[0038] FIG9 is a schematic diagram of a heavy metal ion film-forming mineralization fixed separation and recovery device according to the present invention;

[0039] FIG10 is a graph showing the composite mineral particles obtained in Example 3 of the present invention for treating heavy metal Cu 2+ The effect of mineralization membrane formed after acidic wastewater;

[0040] FIG11 is a diagram of the composite mineral particles obtained in Example 3 of the present invention for treating heavy metal Cu 2+ XRD diffraction pattern of mineralized film formed after acidic wastewater;

[0041] FIG12 is a graph showing the composite mineral particles obtained in Example 3 of the present invention for treating heavy metal Cu 2+ SEM photos of mineralized films formed after acidic wastewater treatment;

[0042] FIG13 is a graph showing the composite mineral particles obtained in Example 3 of the present invention for treating heavy metal Cu 2+ EDS image of mineralized film formed after acidic wastewater;

[0043] Figure 14 shows the composite mineral particles prepared in Comparative Example 2 containing Cu 2+ Wastewater effect diagram. DETAILED DESCRIPTION

[0044] The present invention provides a method for the fixed separation and recovery of heavy metal ions by film-forming mineralization, comprising the following steps:

[0045] The composite mineral particles and heavy metal acidic wastewater are mixed, and a first hydration reaction is carried out under static conditions. The obtained colloidal liquid film adsorbs, precipitates, and crystallizes heavy metal ions in the heavy metal acidic wastewater to obtain particles having a mineralized film on the outer layer; the particles having the mineralized film on the outer layer have a distance between the mineralized film and the particles;

[0046] Separating the particles with the mineralized membrane on the outer layer to obtain the mineralized membrane and the particles, and then recovering them separately;

[0047] The preparation method of the composite mineral particles comprises the following steps:

[0048] Sodium carbonate / sodium silicate, bentonite, carbide slag and water are mixed, subjected to a second hydration reaction, and then granulated, aged and dehydrated to obtain composite mineral particles.

[0049] The particle sizes of the bentonite and carbide slag are independently ≤74 μm.

[0050] The present invention mixes composite mineral particles and heavy metal acidic wastewater, performs a first hydration reaction under static conditions, and uses the obtained colloidal liquid film to adsorb-precipitate-crystallize heavy metal ions in the heavy metal acidic wastewater to obtain particles with a mineralized film on the outer layer.

[0051] In the present invention, the heavy metal acidic wastewater is preferably heavy metal acidic wastewater with an initial pH of 2 to 6 and a heavy metal ion concentration of 50 to 500 mg / L; the present invention limits the heavy metal acidic wastewater to the above types so as to maximize the film-forming mineralization performance of the composite particles.

[0052] In the present invention, the method for preparing the composite mineral particles comprises the following steps:

[0053] Sodium carbonate / sodium silicate, bentonite, carbide slag and water are mixed, subjected to a second hydration reaction, and then granulated, aged and dehydrated and condensed in sequence to obtain composite mineral particles.

[0054] In the present invention, the particle sizes of the bentonite and carbide slag are independently ≤74 μm. Limiting the particle sizes of the bentonite and carbide slag to the aforementioned range facilitates subsequent hydration reactions, further promoting the formation of colloidal liquid films by the composite particles in acidic wastewater, and the formation of film-forming mineralization to immobilize and recover heavy metal ions. If the particle sizes of the bentonite and carbide slag exceed the aforementioned range, the prepared composite particles will be unable to form film-forming mineralization to immobilize and recover heavy metal ions in acidic wastewater.

[0055] In the present invention, when the particle sizes of the bentonite and carbide slag do not meet the above requirements, the bentonite and carbide slag are preferably pretreated separately; the pretreatment preferably includes drying, grinding, and screening in sequence. The present invention does not particularly limit the drying, grinding, and screening operations; commonly used operations by those skilled in the art can be used to ensure that the particle sizes of the bentonite and carbide slag meet ≤74 μm.

[0056] In the present invention, the bentonite and carbide slag are preferably dried before use; the drying is preferably performed in an oven; the drying temperature is preferably 100-110°C, more preferably 105°C; and the drying time is preferably 2-4 hours. The present invention has no particular requirements for the type of oven; ovens commonly used by those skilled in the art can be used. By limiting the drying temperature and time within the above ranges, the bentonite and carbide slag can be fully dried.

[0057] In the present invention, the chemical composition of the bentonite preferably includes, by mass percentage, the following: SiO2: 65-80%, Al2O3: 11-17%, Na2O: 3.0-6.0%, CaO: 2.0-3.5%, MgO: 2.0-5.0%, Fe2O3: 1.6-4.0%, TiO2: 0.04-0.20%, K2O: 0.1-1.2% and impurities: 0.10-2.16%, and more preferably includes: SiO2: 73.33%, Al2O3: 13.55%, Na2O: 4.25%, CaO: 2.24%, MgO: 3.59%, Fe2O3: 2.26%, TiO2: 0.12%, K2O: 0.50% and impurities: 0.16%. The present invention limits the chemical composition of bentonite to the above range, which is more conducive to the subsequent film formation of composite particles and further fixation and recovery of heavy metal ions.

[0058] In the present invention, the chemical composition of the carbide slag preferably includes, by mass percentage, the following: CaO: 86.7-94.5%, SiO2: 2.0-6.5%, Al2O3: 0.5-3.0%, Na2O: 0.5-2.5%, Fe2O3: 0.2-1.5%, MgO: 0.10-0.22%, TiO2: 0.01-0.08%, and impurities: 1.0-1.72%, and more preferably includes: CaO: 93.65%, SiO2: 2.97%, Al2O3: 0.82%, Na2O: 0.71%, Fe2O3: 0.22%, MgO: 0.15%, TiO2: 0.06%, and impurities: 1.42%. The present invention limits the chemical composition of the carbide slag to the above range, which is more conducive to the subsequent film formation of composite particles and further fixation and recovery of heavy metal ions.

[0059] In the present invention, the mass ratio of bentonite to carbide slag is preferably (15.5-57.5):(40-80), more preferably (16-30):(60-80), and further preferably (16-26.5):(70-80). Limiting the mass ratio of bentonite to carbide slag to the above range can improve the composite particles' ability to form a film, mineralize, fix, and recover heavy metal ions.

[0060] In the present invention, the mass of the sodium carbonate / sodium silicate is preferably 2.5-4.5% of the total mass of the sodium carbonate / sodium silicate, bentonite, and carbide slag, more preferably 3.7-4.2%, and even more preferably 4%. The present invention limits the amount of sodium carbonate / sodium silicate added to the above range to fully stimulate the hydration reaction without wasting raw materials, thereby saving resources.

[0061] In the present invention, the mass ratio of the total mass of the sodium carbonate / sodium silicate, bentonite and carbide slag to water is preferably 1:(0.5-0.9), more preferably 1:(0.7-0.9). In the present invention, limiting the mass ratio of the total mass of the sodium carbonate / sodium silicate, bentonite and carbide slag to water to the above range can facilitate the hydration reaction.

[0062] In the present invention, the mixing is preferably a first mixing of sodium carbonate / sodium silicate, bentonite and carbide slag followed by a second mixing by adding water. The present invention has no particular restrictions on the specific operation of the first mixing, and can uniformly mix sodium carbonate / sodium silicate, bentonite and carbide slag. The present invention limits the mixing of sodium carbonate / sodium silicate, bentonite and carbide slag with water to the above order, which can facilitate the carrying out of the hydration reaction.

[0063] In the present invention, the mixing of the sodium carbonate / sodium silicate, bentonite and carbide slag is preferably carried out in a mechanical stirrer. The present invention does not particularly limit the model of the mechanical stirrer, and a model well known to those skilled in the art can be used. The present invention does not particularly limit the mixing temperature and time of the sodium carbonate / sodium silicate, bentonite and carbide slag, as long as the sodium carbonate / sodium silicate, bentonite and carbide slag can be uniformly mixed.

[0064] In the present invention, the second mixing is preferably performed in a mechanical stirrer; the second mixing time is preferably 10 to 20 minutes, more preferably 15 minutes. The present invention does not particularly limit the type of mechanical stirrer; any type familiar to those skilled in the art can be used. The second mixing can further enhance the hydration reaction.

[0065] The present invention mixes bentonite, carbide slag and an activator, and a hydration reaction occurs under the action of water to form a large amount of calcium silicate hydrate (CSH) gel, which can not only improve the cohesiveness and mechanical strength of the particles, but also facilitate the subsequent dehydration condensation of the composite particles to form a large amount of amorphous calcium silicate 3CaO·SiO2 or 2CaO·SiO2, thereby facilitating the first hydration reaction with the water sample. The specific reaction in the second hydration reaction process is shown in the following formula: Na2CO3+Ca(OH)2=2NaOH+CaCO3↓ 2NaOH+SiO2=Na2SiO3+H2O Na2SiO3+Ca(OH)2+nH2O=2NaOH+CaSiO3·nH2O(CSH).

[0066] In the present invention, the particle size of the product obtained by granulation is preferably 2 to 7 mm, more preferably 2 to 5 mm. The present invention does not specifically limit the process parameters for granulation; parameters familiar to those skilled in the art may be used to achieve a particle size that meets the requirements. Limiting the particle size of the granulation product to the aforementioned range can enhance the composite particles' ability to form, mineralize, fix, and recover heavy metal ions. In the present invention, granulation is preferably performed in a forming granulator.

[0067] In the present invention, the aging temperature is preferably 10-35°C, and the aging time is preferably 2-12 hours. Setting the aging temperature within this range allows for a more complete hydration reaction. The aging process allows the composite particles to form a colloidal liquid film, which can then be mineralized and fixed to recover heavy metal ions under acidic conditions.

[0068] In the present invention, the granulated product is preferably covered with a plastic sheet during the aging process. The present invention can avoid water loss during the aging process by covering, thereby ensuring the amount of water required for the hydration reaction.

[0069] In the present invention, the dehydration condensation is preferably dried under natural conditions for 24 to 48 hours; or the temperature of the dehydration condensation is preferably 150 to 450°C, more preferably 220 to 450°C; and the time of the dehydration condensation is preferably 0.6 to 1.5 hours. The present invention sets the temperature and time of the dehydration condensation within the above ranges, which can fully dry and dehydrate the composite particles, facilitating the subsequent film-forming mineralization and fixed recovery of heavy metal ions in acidic wastewater. Through dehydration condensation, the present invention can cause the composite particles to undergo a hydration reaction in acidic wastewater to form a colloidal liquid film, which forms a film-forming mineralization and fixed recovery of heavy metal ions.

[0070] When the dehydration condensation temperature is 150-450°C, the product after the dehydration condensation is preferably subjected to a cooling treatment; the cooling treatment is preferably natural cooling. The cooling treatment of the present invention can facilitate the preservation of the composite particles.

[0071] In an embodiment of the present invention, as shown in FIG1 , the process flow for preparing the composite mineral particles is as follows:

[0072] The bentonite and carbide slag are dried, ground, sieved and dried in sequence, and then weighed, stirred and mixed with sodium carbonate / sodium silicate in proportion. Water is then added in proportion and stirred evenly to cause a hydration reaction. Thereafter, granulation, covering with plastic cloth to keep moist, aging, natural drying or baking are carried out in sequence, and finally natural cooling is carried out to obtain composite mineral particles.

[0073] In the present invention, the ratio of the composite mineral particles to heavy metal acidic wastewater is preferably 0.1-2.5 g:1 L, and more preferably 0.5-1.5 g:1 L. Limiting the ratio of the composite mineral particles to heavy metal acidic wastewater to the above range allows for better film-forming mineralization and fixation of heavy metal ions in the wastewater.

[0074] In the present invention, the first hydration reaction is preferably that when the composite mineral particles are mixed with wastewater, they absorb water and undergo a hydration reaction to generate hydrated calcium silicate (CSH) gel, and release Ca(OH)2 while releasing heat and expanding, so that a temperature difference and composition change occur locally in the same solution around the particles to form an interface layer. The system interface energy tends to shrink to a minimum, so the interface is spherical. Moreover, since the local concentration of slightly soluble Ca(OH)2 is large and its solubility is lower at high temperature, the generated Ca(OH)2 colloidal structure forms a skeleton distributed on the spherical interface and a thicker water film is adsorbed on the surface to form a negatively charged colloidal liquid film rich in Ca(OH)2.

[0075] The present invention performs the first hydration reaction under static conditions, which is conducive to forming a colloidal liquid film under stable conditions, and is conducive to crystallization self-growth on the surface of the colloidal liquid film to form a mineralized film, and facilitates the separation and recovery of particles and the mineralized film after subsequent reactions.

[0076] In the present invention, the adsorption process is preferably a process in which a negatively charged colloidal liquid film rich in Ca(OH)2 adsorbs heavy metal ions to generate heavy metal hydroxide precipitates. The hydroxide precipitates serve as initial nuclei to induce crystallization and generate heavy metal basic sulfate crystals under acidic conditions. The adsorption-precipitation-crystallization process of heavy metal ions continues to self-grow into mineralization, ultimately forming a mineralized film primarily containing heavy metal basic sulfate crystals. The present invention achieves film-forming mineralization and fixation of heavy metal ions through the synergistic action of adsorption-precipitation-nucleation-induced crystallization self-growth mineralization.

[0077] In the present invention, in the particles having a mineralized film on the outer layer, there is a distance between the mineralized film and the particles.

[0078] After obtaining the particles with the mineralized membrane on the outer layer, the present invention separates the particles with the mineralized membrane on the outer layer to obtain the mineralized membrane and the particles, and then recovers them separately.

[0079] In the present invention, the particles are preferably composite mineral particles having a loose porous structure after releasing Ca(OH)2 through a single hydration reaction.

[0080] In the present invention, the mineralized film is preferably recovered as a raw material or finished product; the particles are preferably recovered as an adsorbent. The present invention achieves zero waste discharge, a green and environmentally friendly process, and a circular economy by separately recovering the mineralized film and particles.

[0081] In the present invention, the mineralized film is preferably recovered as a raw material or finished product, more preferably as a raw material for heavy metal salts, a raw material for heavy metal oxides, a raw material for smelting heavy metals, a broad-spectrum inorganic heavy metal salt protective algaecide, a trace element fertilizer, a flocculant or a pigment.

[0082] In the present invention, the particles are preferably dried and recovered as an adsorbent; the adsorbent is preferably used to adsorb heavy metal ions in low-concentration heavy metal acidic wastewater.

[0083] In the present invention, when the adsorbent reaches saturation in adsorbing heavy metal ions in low-concentration heavy metal acidic wastewater, the present invention preferably recovers the saturated adsorbent as a metal mineral resource after drying.

[0084] In the present invention, the drying is preferably carried out under natural conditions for 24 to 48 hours or at high temperature; the high-temperature drying is preferably carried out in an oven; the temperature of the high-temperature drying is preferably 105°C, and the high-temperature drying time is preferably 1 to 2 hours. The present invention does not particularly limit the type of oven; ovens commonly used in the art can be used. Limiting the drying temperature and time to the above ranges allows the recovered composite mineral particles to be fully dried.

[0085] The present invention collects and dries the particles, then uses them as an adsorbent to adsorb heavy metal ions until they are saturated with the heavy metal ions. The adsorbent is then recovered as a metal mineral resource. This invention utilizes the increased porosity and specific surface area of ​​the particles obtained after the hydration reaction, making them more suitable for use as an adsorbent and easy to recycle. This method eliminates waste, is environmentally friendly, and contributes to a circular economy.

[0086] The method for the fixed separation and recovery of heavy metal ions by film-forming mineralization provided by the present invention comprises the following steps: regulating the particle size of bentonite and carbide slag, mixing them with sodium carbonate / sodium silicate, and causing a hydration reaction under the action of water to form hydrated calcium silicate (CSH) gel, etc., thereby improving the cohesiveness and mechanical strength of the particles; aging the particles obtained after the hydration reaction and granulation to make the hydration reaction in the particles more complete, and drying the water in the hydrated calcium silicate (CSH) gel by dehydration condensation to condense the particles; when the composite mineral particles after dehydration condensation are placed in water during use, they absorb water, undergo a hydration reaction, and regenerate the hydrated calcium silicate (CSH) gel, releasing Ca (OH)2 simultaneously releases heat and expands, causing a local temperature difference and composition change in the wastewater around the particles to form a spherical interface layer rich in Ca(OH)2 colloidal structure, and adsorbs a thicker water film to form the initial colloidal liquid film. The negatively charged colloidal liquid film rich in Ca(OH)2 adsorbs heavy metal cations to generate metal hydroxide precipitates, which serve as initial nucleation-induced crystallization and form heavy metal basic sulfate crystals under acidic conditions. Through the continuous adsorption-precipitation-crystallization self-growth synergistic effect, a mineralized film mainly containing heavy metal basic sulfate crystals is finally generated. By separating the mineralized film from the particles, the fixed mineralization and recovery of heavy metal ions is achieved.

[0087] The present invention also provides a device for the fixed separation and recovery of heavy metal ions by film-forming mineralization, comprising a lower plate and an upper plate arranged in a stacked manner;

[0088] The upper plate is provided with a through hole.

[0089] In the present invention, the upper plate is provided with through-holes; the diameter of the through-holes is preferably 2-3 mm larger than the length of the composite mineral particles, the center-to-center distance between two adjacent through-holes is preferably 2-4 times the diameter of the through-holes, and the depth of the through-holes is preferably 1-2 mm. In the present invention, limiting the through-hole parameters on the upper plate to the above ranges can further facilitate the growth of the mineralized film on the upper plate and the subsequent separation and recovery of the particles and the mineralized film.

[0090] In the present invention, the edge of the lower plate is preferably provided with a vertical clip. The vertical clip provided on the lower plate can fix the upper plate and the lower plate together, ensuring that the upper plate and the lower plate do not slide during the heavy metal ion film mineralization process, thereby facilitating the formation of a mineralized film on the outer layer of the composite mineral particles.

[0091] In the present invention, the length of the vertical card is preferably 5 cm, the width is preferably 1 cm, and the height is preferably 5 mm greater than the sum of the thicknesses of the upper and lower plates. The present invention has no special requirements for the number of vertical card plates, as long as they can ensure that the upper and lower plates can be firmly fixed during use and that the upper and lower plates do not slide. The present invention provides vertical card plates on the lower plate to fix the upper and lower plates together, ensuring that the upper and lower plates do not slide during the heavy metal ion film mineralization process, which is conducive to the formation of a mineralized film on the outer layer of the composite mineral particles.

[0092] The present invention sets the vertical card plate to the above-mentioned size, which can fix the upper plate and the lower plate during the heavy metal ion film mineralization process, avoid sliding of the upper plate and the lower plate, and is more conducive to the growth of the mineralized film. After the heavy metal ion film mineralization process is completed, it can facilitate the separation of the upper plate and the lower plate, which is beneficial to the separation and recovery of composite mineral particles and mineralized film.

[0093] In the present invention, the material of the upper plate, lower plate and vertical card plate is preferably an organic plastic template. The present invention can prevent the device from being corroded in acidic wastewater by setting the upper plate, lower plate and vertical card plate to the above materials.

[0094] When the device described in the present invention is used to carry out the fixed separation and recovery of heavy metal ion film-forming mineralization, the composite mineral particles are evenly dispersed on the device for the fixed separation and recovery of heavy metal ion film-forming mineralization, and the device is placed in heavy metal acidic wastewater; under static conditions, the composite mineral particles undergo a first hydration reaction to form a colloidal liquid film on the upper plate around the composite mineral particles; through the adsorption-precipitation-crystallization self-growth of heavy metal ions, a mineralized film is formed on the upper plate outside the particles; after the heavy metal ion film-forming mineralization is completed, the purified heavy metal acidic wastewater is discharged, and the upper plate with the mineralized film is taken out, the mineralized film remains on the upper plate, and the particles remain on the lower plate, completing the separation of the mineralized film and the particles, and then the mineralized film on the upper plate is gently scraped off to make it fall off and be collected and recycled, and the particles left on the lower plate are collected and dried as by-products for recovery. The present invention can better separate the mineralized film from the particles through this device, so that the mineralized film and the particles can be recycled separately.

[0095] In an embodiment of the present invention, as shown in FIG9 , the device for fixed separation and recovery of heavy metal ions by film-forming mineralization includes a lower plate, an upper plate, and a vertical card plate for fixing the lower plate and the upper plate.

[0096] The present invention can better separate particles with mineralized membranes on the outer layer by using the device for fixed separation and recovery of heavy metal ions as shown in Figure 9, thereby improving the recovery efficiency and the recovery rate of heavy metals in heavy metal wastewater.

[0097] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0098] Example 1

[0099] A method for the fixed separation and recovery of heavy metal ions by film-forming mineralization comprises the following steps:

[0100] 0.5 g of composite mineral particles were evenly dispersed on the device for the fixed separation and recovery of heavy metal ions, and the device was placed in a 1 L liquid with an initial pH of 5.0 and heavy metal ion Cu 2+ In acidic wastewater containing heavy metals at a concentration of 500 mg / L, the wastewater is controlled to undergo a first hydration reaction under static conditions to obtain a colloidal liquid film. The heavy metal ions are then subjected to adsorption-precipitation-crystallization. Through the synergistic effect of adsorption-precipitation-crystallization self-growth mineralization, particles with a mineralized film on the outer layer are obtained. In the particles with the mineralized film on the outer layer, there is a distance between the mineralized film and the particles.

[0101] The preparation method of the composite mineral particles comprises the following steps:

[0102] Bentonite and carbide slag are dried in an oven at 105°C for 3 hours and then uniformly mixed with sodium carbonate in a mechanical stirrer. Water is then added and mixed for 15 minutes to carry out a second hydration reaction. Then, a granulator is used to make particles with a diameter of 2 mm and a length of 3 mm. The granulated particles are covered with plastic cloth and aged at 20°C for 10 hours. Then, they are dried under natural conditions for 24 hours for dehydration condensation to obtain composite mineral particles; the particle sizes of the bentonite and carbide slag are independently ≤74 μm; the mass ratio of the bentonite and carbide slag is 16.0:80; the mass of the sodium carbonate accounts for 4.0% of the total mass of the bentonite, carbide slag and sodium carbonate; the total mass of the sodium carbonate, bentonite and carbide slag is equal to or less than 1% of the total mass of the bentonite, carbide slag and sodium carbonate. The mass ratio of water is 1:0.9; the chemical composition of the bentonite is as follows by mass percentage: CaO: 2.24%, SiO2: 73.33%, Al2O3: 13.55%, Na2O: 4.25%, Fe2O3: 2.26%, MgO: 3.59%, TiO2: 0.12%, K2O: 0.50%, impurities: 0.16%; the chemical composition of the carbide slag is as follows by mass percentage: CaO: 93.65%, SiO2: 2.97%, Al2O3: 0.82%, Na2O: 0.71%, Fe2O3: 0.22%, MgO: 0.15%, TiO2: 0.06%, impurities: 1.42%;

[0103] The device for the fixed separation and recovery of heavy metal ions by film-forming mineralization comprises a lower plate and an upper plate arranged in a stacked manner;

[0104] The upper plate is provided with a through hole;

[0105] The edge of the lower plate is provided with a vertical card plate, and the upper plate and the lower plate are fixed together by the vertical card plate;

[0106] The diameter of the through-holes in the upper plate is 6 mm and the depth is 1 mm. The diameter of the through-holes is 2 mm larger than the length of the composite mineral particles, and the distance between two adjacent through-holes is 4 times the diameter of the through-holes. The length of the upright card is 5 cm, the width is 1 cm, and the height is 5 mm larger than the sum of the thicknesses of the upper and lower plates.

[0107] After obtaining particles with a mineralized film on the outer layer, the purified heavy metal acidic wastewater is discharged, and the upper plate with the mineralized film is taken out, the mineralized film remains on the upper plate, and the particles remain on the lower plate, completing the separation of the mineralized film and the particles. The mineralized film on the upper plate is then gently scraped off to make it fall off and be collected for recycling. The particles left on the lower plate are collected as by-products, naturally dried for 48 hours, and then recycled. The recycled particles can be recycled as adsorbents for adsorbing heavy metal ions. After the recycled particles are saturated with heavy metal ions, they can continue to be recycled as metal mineral resources, realizing a waste-free, green, and circular economy.

[0108] The pH of the effluent of heavy metal acid wastewater treated by the method for the fixed separation and recovery of heavy metal ions provided by the present invention can reach 6.8, and the effluent Cu 2+ It can reach 1mg / L, meeting the emission standards, the heavy metal removal rate reaches 99.8%, the mineralized film recovery volume reaches 998mg / g, the heavy metal purity in the mineralized film reaches 52%, the mineralized film crystal purity reaches more than 90%, and the valuable metal film mineralization fixed recovery effect is good.

[0109] Example 2

[0110] A method for the fixed separation and recovery of heavy metal ions by film-forming mineralization comprises the following steps:

[0111] 1g of composite mineral particles were evenly dispersed on the device for the fixed separation and recovery of heavy metal ions, and the device was placed in a 1L tank with an initial pH of 3.2 and heavy metal ion Zn 2+ In acidic wastewater containing heavy metals at a concentration of 300 mg / L, the wastewater is controlled to undergo a first hydration reaction under static conditions to obtain a colloidal liquid film. The heavy metal ions are then subjected to adsorption-precipitation-crystallization. Through the synergistic effect of adsorption-precipitation-crystallization self-growth mineralization, particles with a mineralized film on the outer layer are obtained. In the particles with the mineralized film on the outer layer, there is a distance between the mineralized film and the particles.

[0112] The preparation method of the composite mineral particles comprises the following steps:

[0113] The bentonite and carbide slag are dried in an oven at 105°C for 3 hours and then uniformly mixed with sodium silicate in a mechanical stirrer. Water is then added and mixed for 15 minutes to carry out a second hydration reaction. Then, a granulator is used to make particles with a diameter of 2 mm and a length of 3 mm. The granulated particles are covered with plastic cloth and aged at 20°C for 10 hours. Then, they are baked at 220°C for 1.0 hour for dehydration condensation, and then naturally cooled to obtain composite mineral particles; the particle size of the bentonite and carbide slag is independently ≤74μm; the mass ratio of the bentonite and carbide slag is 16.5:80; the mass of the sodium silicate accounts for 3.5% of the total mass of the sodium silicate, bentonite and carbide slag; the sodium silicate, bentonite and carbide slag are The mass ratio of the total mass of the bentonite to water is 1:0.8; the chemical composition of the bentonite is as follows by mass percentage: CaO: 2.24%, SiO2: 73.33%, Al2O3: 13.55%, Na2O: 4.25%, Fe2O3: 2.26%, MgO: 3.59%, TiO2: 0.12%, K2O: 0.50%, impurities: 0.16%; the chemical composition of the carbide slag is as follows by mass percentage: CaO: 93.65%, SiO2: 2.97%, Al2O3: 0.82%, Na2O: 0.71%, Fe2O3: 0.22%, MgO: 0.15%, TiO2: 0.06%, impurities: 1.42%;

[0114] The device for film-forming mineralization, fixation, separation and recovery of heavy metal ions comprises a lower plate and an upper plate arranged in a stacked manner;

[0115] The upper plate is provided with a through hole;

[0116] The edge of the lower plate is provided with a vertical card plate, and the upper plate and the lower plate are fixed together by the vertical card plate;

[0117] The diameter of the through hole in the upper plate is 5 mm and the depth is 1 mm. The diameter of the through hole is 2 mm larger than the length of the composite mineral particles, and the center distance between two adjacent through holes is 3 times the diameter of the through hole. The length of the vertical card is 5 cm, the width is 1 cm, and the height is 5 mm larger than the sum of the thickness of the upper plate and the lower plate.

[0118] After obtaining particles with a mineralized film on the outer layer, the purified heavy metal acidic wastewater is discharged, and the upper plate with the mineralized film is taken out, the mineralized film remains on the upper plate, and the particles remain on the lower plate, completing the separation of the mineralized film and the particles. The mineralized film on the upper plate is then gently scraped off to make it fall off and be collected for recycling. The particles left on the lower plate are collected as by-products, naturally dried for 48 hours, and then recycled. The recycled particles can be recycled as adsorbents for adsorbing heavy metal ions. After the recycled particles are saturated with heavy metal ions, they can continue to be recycled as metal mineral resources, realizing a waste-free, green, and circular economy.

[0119] The pH of the effluent of heavy metal acid wastewater treated by the method for the fixed separation and recovery of heavy metal ions provided by the present invention can reach 6.7, and the effluent Zn 2+ It can reach 1.0 mg / L, meeting the emission standards, the heavy metal removal rate reaches 99.7%, the mineralized film recovery volume reaches 299 mg / g, the heavy metal purity in the mineralized film reaches 50%, the mineralized film crystal purity reaches more than 90%, and the valuable metal film mineralization fixed recovery effect is good.

[0120] Example 3

[0121] A method for the fixed separation and recovery of heavy metal ions by film-forming mineralization comprises the following steps:

[0122] 1g of composite mineral particles were evenly dispersed on the device for the fixed separation and recovery of heavy metal ions, and the device was placed in a 1L liquid with an initial pH of 3.2 and heavy metal ion Cu 2+ In acidic wastewater containing heavy metals at a concentration of 300 mg / L, the wastewater is controlled to undergo a first hydration reaction under static conditions to obtain a colloidal liquid film. The heavy metal ions are then subjected to adsorption-precipitation-crystallization. Through the synergistic effect of adsorption-precipitation-crystallization self-growth mineralization, particles with a mineralized film on the outer layer are obtained. In the particles with the mineralized film on the outer layer, there is a distance between the mineralized film and the particles.

[0123] The preparation method of the composite mineral particles comprises the following steps:

[0124] The bentonite and carbide slag are dried in an oven at 105°C for 3 hours and then mixed evenly with sodium carbonate in a mechanical stirrer. Water is then added and mixed for 15 minutes to carry out a second hydration reaction. Then, a granulator is used to make particles with a diameter of 2 mm and a length of 3 mm. The granulated particles are covered with plastic cloth and aged at 25°C for 6 hours. Then, they are baked at 400°C for 1.0 hour for dehydration condensation, and then naturally cooled to obtain composite mineral particles; the particle size of the bentonite and carbide slag is independently ≤74μm; the mass ratio of the bentonite and carbide slag is 25.5:70; the mass of the sodium carbonate accounts for 4.5% of the total mass of the bentonite, carbide slag and sodium carbonate; the sodium carbonate, bentonite and carbide slag are The mass ratio of the total mass to water is 1:0.7; the chemical composition of the bentonite is as follows by mass percentage: CaO: 2.24%, SiO2: 73.33%, Al2O3: 13.55%, Na2O: 4.25%, Fe2O3: 2.26%, MgO: 3.59%, TiO2: 0.12%, K2O: 0.50%, impurities: 0.16%; the chemical composition of the carbide slag is as follows by mass percentage: CaO: 93.65%, SiO2: 2.97%, Al2O3: 0.82%, Na2O: 0.71%, Fe2O3: 0.22%, MgO: 0.15%, TiO2: 0.06%, impurities: 1.42%;

[0125] The device for the fixed separation and recovery of heavy metal ions by film-forming mineralization comprises a lower plate and an upper plate arranged in a stacked manner;

[0126] The upper plate is provided with a through hole;

[0127] The edge of the lower plate is provided with a vertical card plate, and the upper plate and the lower plate are fixed together by the vertical card plate;

[0128] The diameter of the through-holes in the upper plate is 6 mm and the depth is 1 mm. The diameter of the through-holes is 3 mm larger than the length of the composite mineral particles, and the center distance between two adjacent through-holes is 3 times the diameter of the through-holes. The length of the upright card is 5 cm, the width is 1 cm, and the height is 5 mm larger than the sum of the thicknesses of the upper and lower plates.

[0129] After obtaining particles with a mineralized film on the outer layer, the purified heavy metal acidic wastewater is discharged, and the upper plate with the mineralized film is taken out, the mineralized film remains on the upper plate, and the particles remain on the lower plate, completing the separation of the mineralized film and the particles. The mineralized film on the upper plate is then gently scraped off to make it fall off and be collected for recycling. The particles left on the lower plate are collected as by-products, naturally dried for 48 hours, and then recycled. The recycled particles can be recycled as adsorbents for adsorbing heavy metal ions. After the recycled particles are saturated with heavy metal ions, they can continue to be recycled as metal mineral resources, realizing a waste-free, green, and circular economy.

[0130] The pH of the effluent of heavy metal acid wastewater treated by the method for the fixed separation and recovery of heavy metal ions provided by the present invention can reach 7.3, and the effluent Cu 2+ It can reach 0.3 mg / L, meeting the emission standards, the heavy metal removal rate reaches 99.9%, the mineralized film recovery volume reaches 299.7 mg / g, the heavy metal purity in the mineralized film reaches 55.86%, the mineralized film crystal purity reaches more than 90%, and the valuable metal film mineralization fixed recovery effect is good.

[0131] Example 4

[0132] The difference from Example 3 is that the carbide slag used is not dried and the moisture content is controlled at 50-70%. The rest of the content is consistent with Example 3.

[0133] Compared with Example 3, the use of carbide slag with a high moisture content results in the heat released by the carbide slag in the initial stage not being utilized, which is not conducive to the hydration reaction with bentonite to form hydrated calcium silicate (CSH) gel, etc.

[0134] Comparative Example 1

[0135] The difference from Example 3 is that bentonite and carbide slag are dried in a 105°C baking oven for 3 hours and then mixed with sodium carbonate in a mechanical stirrer to form compound A, compound A is extruded and crushed to form mixed particles B, and mixed particles B is directly baked at 400°C for 1.0h without aging. The remaining contents are consistent with those of Example 3.

[0136] Compared with Example 3, the crushing effect easily causes the mixed particles B to become loose and cracked, affecting the cohesiveness of the particles and preventing them from being well formed. In addition, the prepared mixed particles B are not aged, resulting in insufficient hydration reaction, and unable to form calcium silicate hydrate (CSH) gel, etc., which is not conducive to particle cohesion.

[0137] Comparative Example 2

[0138] The difference from Example 3 is that the carbide slag adopted is not dried, and the moisture content is controlled at 50-70%. Bentonite is dried in 105 ℃ of baking ovens for 3 hours and mixed with yellow soda ash in a mechanical stirrer to make compound A. Compound A is squeezed and crushed to make mixed particles B. Mixed particles B is not aged and directly cured at 400 ℃ for 1.0h. All the other contents are consistent with Example 3.

[0139] Compared with Example 3, the heat released in the early stage of carbide slag using high water content is not utilized, which is not conducive to the formation of calcium silicate hydrate (CSH) gel with bentonite generation hydration reaction, and the like. At the same time, due to the crushing effect, loose cracking occurs inside the mixed particles B, which affects the particle cohesion and can not be well formed. Moreover, the mixed particles B prepared are not aged, and the hydration reaction is insufficient, and can not form calcium silicate hydrate (CSH) gel well. Since the composite particles calcium silicate hydrate (CSH) gel is less in amount, it only forms a small amount of hydrated calcium silicate (CSH) gel after dehydration condensation. A small amount of amorphous tricalcium silicate 3CaO·SiO2 or dicalcium silicate 2CaO·SiO2 is formed. When the composite particles after dehydration condensation are put into water for use, the water absorption and hydration reaction are not obvious, the amount of hydrated calcium silicate (CSH) gel generated again is small, and local heat release and expansion cannot occur. A spherical colloidal liquid film rich in Ca(OH)2 colloidal structure cannot be formed around the particles, and no induced crystallization to form a mineral film of heavy metal basic sulfate crystals can occur. Instead, only Cu(OH)2 precipitates are generated in the water sample around the particles.

[0140] FIG2 is a schematic diagram of the formation of a mineralized film by composite mineral particles. As can be seen from FIG2 , a spherical mineralized film is formed at a certain distance around the composite mineral particles.

[0141] FIG3 shows the composite mineral particles obtained in Example 1 of the present invention spontaneously forming a colloidal liquid film and the heavy metal Cu 2+ Film mineralization effect diagram, Figure 4 shows the composite mineral particles obtained in Example 2 of the present invention spontaneously forming a colloidal liquid film and the effect of heavy metal Zn 2+ Film mineralization effect diagram, from Figure 3 and Figure 4, the formation of colloidal liquid film and the heavy metal Cu 2+ and Zn 2+ The film mineralization effect diagram shows that the prepared composite mineral particles can form colloidal liquid film in heavy metal acidic wastewater. In addition, according to Figures 3 and 4, it can be clearly seen that the colloidal liquid film mineralization fixes Cu 2+ 、Zn 2+ .

[0142] Figure 5 is a photograph of the raw material bentonite of the present invention, Figure 6 is a photograph of the raw material carbide slag of the present invention, Figure 7 is a photograph of the composite mineral particles prepared in Example 3 of the present invention, and Figure 8 is an XRD diffraction pattern of the raw materials bentonite and carbide slag of the present invention. It can be seen from Figures 5 and 6 that both the bentonite and carbide slag are powdery and fine particles, it can be seen from Figure 8 that the bentonite and carbide slag have fewer impurities, and it can be seen from Figure 7 that the prepared composite mineral particles are uniform in size and not easy to loosen.

[0143] Figure 9 is a schematic diagram of the heavy metal ion film-forming mineralization fixed separation and recovery device of the present invention. It can be seen from Figure 9 that the heavy metal ion film-forming mineralization fixed separation and recovery device includes a lower plate, an upper plate and an upright card plate for fixing the lower plate and the upper plate.

[0144] FIG10 is a graph showing the composite mineral particles obtained in Example 3 of the present invention for treating heavy metal Cu 2+ Figure 11 shows the effect of the mineralization film formed after acidic wastewater. Figure 11 shows the effect of the composite mineral particles obtained in Example 3 of the present invention on the treatment of heavy metal Cu 2+ The XRD diffraction pattern of the mineralized film generated after acidic wastewater is shown in Figure 12. 2+ SEM photos of the mineralized film formed after acidic wastewater, Figure 13 is the composite mineral particles obtained in Example 3 of the present invention to treat the heavy metal Cu 2+ EDS diagrams of the mineralized film generated after acidic wastewater. It can be seen from Figures 10 to 13 that the mineralized film is finally formed around the composite mineral particles, and the mineralized film is mainly composed of lamellar basic copper sulfate crystals (Cu4SO4(OH)6·2H2O) minerals, with a purity of heavy metal copper reaching 55.86%, which is above 50%, and the purity of the heavy metal basic sulfate crystals (Cu4SO4(OH)6·2H2O) mineral crystal phase can reach more than 90%.

[0145] Figure 14 shows the composite mineral particles prepared in Comparative Example 2 containing Cu 2+ The effect diagram of wastewater, as shown in Figure 14, can be seen that the composite mineral particles prepared in Comparative Example 2 cannot form a mineralized film, but only generate Cu(OH)2 precipitation in the water sample around the particles.

[0146] The present invention provides a method for the fixed separation and recovery of heavy metal ions by film-forming mineralization. The method can treat acidic wastewater with an initial pH value of 2 to 6 and a heavy metal ion concentration of 50 to 500 mg / L. The effluent pH reaches 6 to 9, the heavy metal removal rate reaches 95 to 100%, which can meet the emission standards, the recovery amount of the mineralized film reaches 200 to 2000 mg / g, the purity of the heavy metals in the mineralized film reaches more than 50%, the purity of the mineralized film crystals reaches more than 90%, and the mineralized fixed recovery effect of the valuable metals is good. At the same time, the method can realize the resource utilization of industrial solid waste carbide slag, turning waste into treasure, treating waste with waste, synchronously treating wastewater and waste slag, and the mineralized fixed recovery and circular economy of valuable metal resources in wastewater.

[0147] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for the fixed separation and recovery of heavy metal ions by film-forming mineralization, characterized in that: The following steps are involved: The composite mineral particles and heavy metal acidic wastewater are mixed, and a first hydration reaction is performed under static conditions, and the obtained colloidal liquid film is used to adsorb, precipitate and crystallize heavy metal ions in the heavy metal acidic wastewater to obtain particles with a mineralized film on the outer layer; in the particles with the mineralized film on the outer layer, there is a distance between the mineralized film and the particles; Separating the particles with the mineralized membrane on the outer layer to obtain the mineralized membrane and the particles, and then recovering them separately; The preparation method of the composite mineral particles comprises the following steps: The sodium carbonate / sodium silicate, bentonite, carbide slag and water are mixed, and after a second hydration reaction, granulation, aging and dehydration condensation are sequentially performed to obtain composite mineral particles; The particle sizes of the bentonite and carbide slag are independently ≤74 μm.

2. The method according to claim 1, characterized in that The usage ratio of the composite mineral particles to the heavy metal acidic wastewater is 0.1-2.5 g:1L.

3. The method according to claim 1 or 2, characterized in that: The heavy metal acidic wastewater has an initial pH of 2 to 6 and a heavy metal ion concentration of 50 to 500 mg / L.

4. The method according to claim 1, characterized in that The mass ratio of the bentonite to the carbide slag is (15.5-57.5): (40-80); The mass of the sodium carbonate / sodium silicate accounts for 2.5-4.5% of the total mass of the sodium carbonate / sodium silicate, bentonite and carbide slag.

5. The method according to claim 1 or 4, characterized in that: The chemical composition of the bentonite includes, by mass percentage, SiO2: 65-80%, Al2O3: 11-17%, Na2O: 3.0-6.0%, CaO: 2.0-3.5%, MgO: 2.0-5.0%, Fe2O3: 1.6-4.0%, TiO2: 0.04-0.20%, K2O: 0.1-1.2% and impurities: 0.10-2.16%; The chemical composition of the carbide slag includes: CaO: 86.7-94.5%, SiO2: 2.0-6.5%, Al2O3: 0.5-3.0%, Na2O: 0.5-2.5%, Fe2O3: 0.2-1.5%, MgO: 0.10-0.22%, TiO2: 0.01-0.08% and impurities: 1.0-1.72%.

6. The method according to claim 1, characterized in that The mixing of sodium carbonate / sodium silicate, bentonite, carbide slag and water comprises first mixing the sodium carbonate / sodium silicate, bentonite and carbide slag uniformly and then adding water for second mixing; The mass ratio of the total mass of the sodium carbonate / sodium silicate, bentonite and carbide slag to water is 1:(0.5-0.9).

7. The method according to claim 1 or 6, characterized in that: The bentonite and carbide slag are dried before use; the drying temperature is 100-110° C., and the drying time is 2-4 hours.

8. The method according to claim 1, characterized in that The particle size of the product obtained by the granulation is 2 to 7 mm.

9. The method according to claim 1, characterized in that: The aging temperature is 10-35° C., and the aging time is 2-12 hours.

10. The method according to claim 1, characterized in that The dehydration condensation is carried out by drying under natural conditions for 24 to 48 hours; Or the dehydration condensation temperature is 150-450° C., and the dehydration condensation time is 0.6-1.5 h.

11. The method according to claim 1, characterized in that: The mineralized film is recovered as a raw material or a finished product; and the particles are recovered as an adsorbent.

12. A device for the fixed separation and recovery of heavy metal ions by film-forming mineralization, characterized in that: It includes a lower plate and an upper plate which are stacked; The upper plate is provided with a through hole.

13. The device according to claim 12, characterized in that The diameter of the through hole is 2 to 3 mm larger than the length of the composite mineral particles, the center distance between two adjacent through holes is 2 to 4 times the diameter of the through hole, and the depth of the through hole is 1 to 2 mm.

14. The device according to claim 12, characterized in that The edge of the lower plate is provided with a vertical card plate.

15. The device according to claim 14, characterized in that The length of the erected card board is 5 cm, the width is 1 cm, and the height is 5 mm greater than the sum of the thickness of the upper plate and the lower plate.

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