A gradient adsorption type aluminum material chemical polishing and washing water depth aluminum removal process and system

Abstract

This invention belongs to the field of industrial hazardous waste resource utilization technology, and discloses a gradient adsorption type aluminum removal process and system for deep aluminum removal from aluminum-containing washing water, which solves the problem of cation exchange resin being affected by H+ in high acid and high aluminum environments in existing technologies. + Competitive adsorption leads to low aluminum removal rates and short resin lifespan. This invention addresses this issue by employing a layered filling structure in the cation exchange resin tank, consisting of an upper layer of ordinary hydrogen-form strongly acidic cation exchange resin and a lower layer of phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cation exchange resin. This allows the upper resin to adsorb most of the free Al. 3+ The lower-layer bifunctional resin utilizes phosphonic acid groups to react with Al 3+ Highly selective complexation adsorption for deep removal of residual Al 3+ This invention improves the total aluminum ion removal rate, extends the resin's service life, and reduces the consumption of sulfuric acid regenerator. It can be widely applied to the resource recovery of acidic and metal ion-containing waste liquids such as aluminum chemical polishing waste liquid and steel pickling waste liquid.

Description

Technical Field

[0001] This invention relates to the field of industrial hazardous waste resource utilization technology, and in particular to a deep aluminum removal process and system in the acid recovery process of aluminum washing water. Background Technology

[0002] Chemical polishing of aluminum alloys is a key process in aluminum surface treatment, which generates a large amount of wastewater containing phosphoric acid, sulfuric acid, and high concentrations of aluminum ions (chemical polishing wash water). This wastewater has a high acid concentration, is highly corrosive, and contains heavy metals, and is classified as a national hazardous waste (HW17). Currently, the resource-based treatment of chemical polishing wash water mainly adopts an integrated process of diffusion dialysis and ion exchange, in which cation exchange resin is the core unit for achieving deep separation of acid and aluminum ions and recovering phosphorus resources.

[0003] In existing technologies, cation exchange units are generally filled with a single, common hydrogen-form strong acid cation exchange resin. For example, patent CN116621402B discloses a near-zero emission recovery method for phosphorus-containing polishing waste acid, which uses hydrogen-form cation exchange resin to adsorb and remove aluminum ions. However, this technology has the following fatal flaws: 1. Severe competitive adsorption of hydrogen ions: The high-alumina residue produced after diffusion dialysis of the chemical polishing water still contains a large amount of sulfuric acid, and the H+ ions released from the sulfuric acid dissociate into hydrogen ions... + Will with Al 3+ The competing sulfonic acid adsorption sites on the resin result in low aluminum removal rate and excessively high aluminum ion content in the recovered acid, making it unsuitable for direct reuse in the chemical polishing process.

[0004] 2. Short resin lifespan: To improve the aluminum removal rate, it is necessary to significantly increase the amount of resin used or increase the concentration of regenerated sulfuric acid. This not only increases operating costs but also accelerates the swelling and aging of the resin. The average lifespan of the resin is only 6-8 months.

[0005] 3. Difficulty in treating regenerated waste liquid: High-concentration regenerated sulfuric acid will desorb a large amount of aluminum ions, forming high-acid and high-alumina regenerated waste liquid, which will result in a large load on subsequent acid retardation equipment and low sulfuric acid recovery efficiency.

[0006] To address the aforementioned problems, those skilled in the art have attempted to use modified cationic resins, such as introducing phosphonic acid functional groups to enhance the resistance to Al. 3+ The adsorption selectivity is good. However, single phosphonic acid-based resins have problems such as low adsorption capacity and high price. If all resins are used, the treatment cost will increase significantly, making industrial application difficult. Therefore, developing a deep aluminum removal process that can ensure high aluminum removal rate, reduce cost, and extend resin life has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a gradient adsorption-based deep aluminum removal process and system for aluminum-based polishing water. This system utilizes layered filling of different types of cation exchange resins to construct a gradient adsorption system, thus solving the problem of H+ removal in high-acid, high-alumina environments. + The problem of low aluminum removal rate and short resin life caused by competitive adsorption.

[0008] To achieve the above objectives, the present invention provides a gradient adsorption-based deep aluminum removal process for aluminum-removing washing water, comprising the following steps: S1. Pretreatment: The aluminum polishing water is passed through an ultrafiltration device and a diffusion dialysis device in sequence to remove suspended solids, colloids and some free acid to obtain high-alumina residual liquid; S2. Gradient adsorption for aluminum removal: The high-alumina residue obtained in step S1 is passed into a layered cation exchange resin tank, sequentially passing through an upper layer of ordinary hydrogen-form strong acidic cation exchange resin and a lower layer of phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cation exchange resin. The upper resin adsorbs most of the free Al. 3+ The lower layer of bifunctional resin deeply adsorbs residual Al 3+ The purified acid solution was obtained; S3. Resin regeneration: When the resin is saturated with adsorption, it is first pre-regenerated with dilute sulfuric acid to remove the loosely adsorbed aluminum ions on the resin surface, and then the main regeneration is carried out with concentrated sulfuric acid to desorb the adsorbed aluminum ions and obtain aluminum sulfate mixture. S4. Regenerated acid recovery: The aluminum sulfate mixture obtained in step S3 is passed into an acid retardation device to recover the free sulfuric acid therein, which is then reused in the main regeneration process and / or pre-regeneration process in step S3.

[0009] Furthermore, in step S2, the volume ratio of the upper ordinary hydrogen-form strong acid cation exchange resin to the lower bifunctional composite hydrogen-form cation exchange resin is (2-4):1. The high-alumina residue after diffusion dialysis of the chemical polishing water has a high aluminum concentration, requiring the upper ordinary hydrogen-form resin to handle 85%~90% of the coarse aluminum ion removal. Sufficient volume is necessary to withstand the high load and prevent breakthrough. In the high-acid system, H... + They will compete for resin sites; the upper, large-volume ordinary resin will first remove the high-concentration Al. 3+ Extensive removal significantly reduces the aluminum concentration in the lower-level feed solution, allowing the high selectivity of the phosphonic acid groups in the bifunctional resin to be fully utilized, completely avoiding H+. + Interference. (2-4): 1 can make the adsorption saturation cycles of the two resin layers basically synchronized, avoiding premature failure of the lower layer or long-term idleness of the upper layer, thus extending the overall service life of the resin and reducing the frequency of replacement and operating costs. Furthermore, the volume ratio of the upper ordinary hydrogen-form strong acid cation exchange resin to the lower bifunctional composite hydrogen-form cation exchange resin is 3:1.

[0010] Furthermore, the ordinary hydrogen-form strong acid cation exchange resin is a styrene-based strong acid cation exchange resin with a particle size of 0.315-1.25 mm.

[0011] Furthermore, the preparation method of the phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cation exchange resin is as follows: using styrene-divinylbenzene copolymer as the backbone, chloromethyl groups are first introduced through a chloromethylation reaction, and then reacted sequentially with triethyl phosphite and concentrated sulfuric acid to simultaneously graft phosphonic acid and sulfonic acid functional groups onto the resin backbone; in the phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cation exchange resin, the molar ratio of phosphonic acid groups to sulfonic acid groups is (1-2):1. The phosphonic acid group is Al 3+ Dedicated complexing groups, for Al 3+ The complexation constant is much higher than that of H + It can completely resist the H+ of the sulfuric acid system. + While competing with single phosphonic acid resins, these resins suffer from low exchange capacity and slow adsorption rates. Sulfonic acid resins, on the other hand, offer advantages such as high exchange capacity and rapid adsorption mass transfer, enabling the rapid adsorption of low concentrations of residual Al. 3+ However, it is susceptible to H + Interference. A molar ratio controlled at 1-2:1 ensures sufficient selectivity from the phosphonic acid groups while retaining the high capacity and rapid rate of the sulfonic acid groups, allowing the resin to simultaneously meet the dual requirements of deep aluminum removal and high-efficiency treatment. In the highly acidic environment of the wash water, H... + Concentration much higher than Al 3+ If the molar ratio of phosphonic acid groups to sulfonic acid groups is less than 1:1, there are too many sulfonic acid groups and insufficient phosphonic acid groups, resulting in weak overall anti-competitive ability of the resin. + They will still compete for adsorption sites, reducing the aluminum removal rate and making deep aluminum removal impossible. If the molar ratio of phosphonic acid groups to sulfonic acid groups is greater than 2:1, with too many phosphonic acid groups and too few sulfonic acid groups, the total exchange capacity of the resin will decrease significantly, the adsorption rate will slow down, aluminum ions will easily penetrate, and the resin will not be able to operate stably.

[0012] Furthermore, the molar ratio of the phosphonic acid group to the sulfonic acid group is 1.5:1.

[0013] Furthermore, in step S2, the inlet flow rate of the high-alumina residual liquid is controlled at 1-3 BV / h, and the adsorption temperature is controlled at 25-40℃.

[0014] Furthermore, in step S3, the concentration of dilute sulfuric acid used for pre-regeneration is 8-12%, the flow rate is 2-4 BV / h, and the dosage is 2-3 BV; the concentration of concentrated sulfuric acid used for main regeneration is 22-26%, the flow rate is 1-2 BV / h, and the dosage is 3-4 BV.

[0015] The present invention also provides a gradient adsorption-based deep aluminum removal system for implementing the above-mentioned process, comprising an ultrafiltration device, a diffusion dialysis device, a cation exchange resin tank, and an acid retardation device connected in sequence. The cation exchange resin tank is filled from top to bottom with a common hydrogen-form strong acid cation resin layer and a phosphonic acid-sulfonic acid bifunctional complex hydrogen-form cation resin layer. The top of the cation exchange resin tank is provided with an inlet and a regenerator inlet, and the bottom is provided with an outlet and a regeneration waste liquid outlet.

[0016] The beneficial effects of this invention are: This invention employs a gradient adsorption structure with an upper layer of ordinary hydrogen-form resin for coarse dealumination and a lower layer of phosphonic acid-sulfonic acid bifunctional resin for fine dealumination. Most of the Al is adsorbed by the upper ordinary resin. 3+ The lower-layer bifunctional resin utilizes phosphonic acid groups to react with Al 3+ Highly selective deep adsorption completely solves the H... + The problem of competitive adsorption was addressed, and the total aluminum ion removal rate was improved. The phosphonic acid groups in the bifunctional composite resin effectively controlled the adsorption of Al ions. 3+ The complexation adsorption constant is much higher than that of H + Combined with a gradient layering design, the lower resin layer treats only low-concentration aluminum liquid, fundamentally avoiding the H+ ions in the sulfuric acid system. + Competitive adsorption sites ensure stable and deep aluminum removal under high-acid conditions. The purified acid solution can be directly reused in the chemical polishing process. This invention uses a layered filling structure to allow most aluminum ions to be adsorbed by the upper layer of inexpensive ordinary resin, while the lower layer of expensive bifunctional resin only treats low concentrations of aluminum ions, significantly reducing the load on the bifunctional resin. At the same time, the stepwise regeneration process reduces the corrosion of the resin by high-concentration sulfuric acid, extending the overall service life of the resin by 60%. Attached Figure Description

[0017] Figure 1 This is a flow chart of the gradient adsorption-based aluminum removal process for deep aluminum removal by polishing water according to the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] Example 1

[0020] This embodiment provides a gradient adsorption-based deep aluminum removal process for aluminum materials through polishing and washing. The specific steps are as follows: 1. Pretreatment: Take aluminum polishing water with a specific gravity of 1.36 g / mL, a phosphoric acid concentration of 32.18 wt%, a sulfuric acid concentration of 13.71 wt%, and an aluminum ion concentration of 18 g / L. Filter the water through an acid-resistant hollow fiber ultrafiltration membrane with a filtration accuracy of 0.05 μm to remove suspended solids and colloids, obtaining ultrafiltration filtrate. Pass the ultrafiltration filtrate into a diffusion dialysis device using a homogeneous anion exchange membrane. The flow rate ratio of waste acid to pure water is 1:2 to recover most of the free acid, obtaining a high-alumina residual liquid with a phosphoric acid concentration of 14.31 wt%, a sulfuric acid concentration of 2.95 wt%, and an aluminum ion concentration of 15 g / L.

[0021] 2. Gradient adsorption for aluminum removal: The high-alumina residue is passed into a cation exchange resin tank. The upper layer of the resin tank is filled with 3L of ordinary hydrogen-form strong acid cation exchange resin (styrene-based, particle size 0.315-1.25mm), and the lower layer is filled with 1L of phosphonic acid-sulfonic acid bifunctional complex hydrogen-form cation exchange resin. The influent flow rate is 2 BV / h, and the adsorption temperature is 30℃, resulting in purified acid solution.

[0022] The preparation method of the phosphonic acid-sulfonic acid bifunctional complex hydrogen-form cationic resin is as follows: 100 g (dry weight) of styrene-divinylbenzene copolymer white spheres (crosslinking degree 8%, particle size 0.45-0.80 mm) were added, along with 500 mL of chloromethyl ether and 1.5 g of anhydrous zinc chloride. The mixture was stirred at 40 °C for 12 hours to carry out the chloromethylation reaction. After the reaction was completed, the resin was washed successively with methanol and deionized water until neutral, filtered, and dried to obtain the chloromethylated resin. The measured chlorine content was 4.2 mmol / g.

[0023] Take 50g of the above chloromethylated resin, add 200mL of triethyl phosphite and 150mL of nitrobenzene, and stir at 130℃ for 16 hours. After the reaction is complete, cool, filter, and wash successively with methanol and deionized water to obtain phosphonate resin.

[0024] The above-mentioned phosphonate resin was added to 300 mL of concentrated sulfuric acid (98 wt%) and stirred at 110 °C for 8 hours, during which sulfonation and phosphonate hydrolysis reactions occurred simultaneously. After the reaction was completed, the mixture was slowly cooled, diluted with deionized water, washed until neutral, then converted to the sodium form with 5% sodium hydroxide solution, and finally regenerated to the hydrogen form with 5% dilute hydrochloric acid. The mixture was then washed with deionized water until neutral, yielding a bifunctional composite hydrogen-form cationic resin with a phosphonate to sulfonic acid molar ratio of 1.5:1. Elemental analysis and titration determined that the phosphonate content was 1.50 mmol / g, the sulfonic acid content was 1.00 mmol / g, and the molar ratio was 1.5:1.

[0025] 3. Resin regeneration: When the resin is saturated and the aluminum ion concentration in the effluent is ≥0.1g / L, it is first pre-regenerated with 10% dilute sulfuric acid at a flow rate of 3BV / h and a dosage of 2.5BV; then it is mainly regenerated with 24% sulfuric acid at a flow rate of 1.5BV / h and a dosage of 3.5BV to obtain an aluminum sulfate mixture.

[0026] 4. Regenerated acid recovery: The aluminum sulfate mixture is passed into the acid-blocking low bed equipment to recover the free sulfuric acid. After adjusting the concentration to 24%, it is reused in the resin regeneration process.

[0027] Example 2

[0028] The difference between this embodiment and Embodiment 1 is that the volume ratio of the upper ordinary resin to the lower bifunctional resin in the cation exchange resin tank is 2:1, that is, the upper layer is filled with 2.67L of ordinary resin and the lower layer is filled with 1.33L of bifunctional resin; the inlet flow rate of the high-alumina residual liquid is 1.5BV / h.

[0029] Example 3

[0030] The difference between this embodiment and Embodiment 1 is that the volume ratio of the upper ordinary resin to the lower bifunctional resin in the cation exchange resin tank is 4:1, that is, the upper layer is filled with 3.2L of ordinary resin and the lower layer is filled with 0.8L of bifunctional resin; the concentration of pre-regenerated dilute sulfuric acid is 8% and the concentration of main regeneration sulfuric acid is 22%.

[0031] Comparative Example 1 This comparative example uses a single resin filling method from the prior art. The cation exchange resin tank is filled with 4L of ordinary hydrogen-form strong acid cation resin, and the remaining process parameters are exactly the same as in Example 1.

[0032] Comparative Example 2 This comparative example uses a single bifunctional resin filling method. The cation exchange resin tank is completely filled with 4L of phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cation resin, and the remaining process parameters are exactly the same as those in Example 1.

[0033] Comparative Example 3 The difference from Example 1 is that 100g of styrene-divinylbenzene copolymer white balls (crosslinking degree 8%, particle size 0.45-0.80mm) were chloromethylated according to the method in Example 1 to obtain a chloromethylated resin with a chlorine content of 4.2mmol / g.

[0034] Take 50g of the above chloromethylated resin, add 100mL of triethyl phosphite and 150mL of nitrobenzene (the amount of triethyl phosphite is 50% of that in Example 1), and stir at 130°C for 16 hours. The post-reaction treatment is the same as in Example 1, to obtain a partially phosphonate-modified resin (the remaining chloromethyl group is unreacted).

[0035] The above-mentioned phosphonate esterified resin was added to 300 mL of concentrated sulfuric acid (98%) and stirred at 120 °C for 12 hours (increasing the reaction temperature and extending the reaction time promotes the introduction of more sulfonic acid groups). The post-reaction treatment was the same as in Example 1. Finally, the molar ratio of phosphonate groups to sulfonic acid groups in the phosphonate-sulfonic acid bifunctional complex hydrogen-form cation resin was determined to be 1:3 by elemental analysis and titration.

[0036] Comparative Example 4 The difference from Example 1 is that 100g of styrene-divinylbenzene copolymer white balls (crosslinking degree 8%, particle size 0.45-0.80mm) were chloromethylated according to the method of Example 1 to obtain a chloromethylated resin with a chlorine content of 4.2mmol / g.

[0037] Take 50g of the above chloromethylated resin, add 300mL of triethyl phosphite and 150mL of nitrobenzene (the amount of triethyl phosphite is 1.5 times that of Example 1), and stir at 130°C for 20 hours (extending the reaction time to convert more chloromethyl groups into phosphonates). The post-reaction treatment is the same as in Example 1 to obtain a highly phosphonate-modified resin.

[0038] The above-mentioned high phosphonate esterified resin was added to 300 mL of concentrated sulfuric acid (98%) and stirred at 100 °C for 4 hours (reducing the reaction temperature and shortening the time to reduce the introduction of sulfonic acid groups). The post-reaction treatment was the same as in Example 1. Finally, by elemental analysis and titration, the molar ratio of phosphonate groups to sulfonic acid groups in the phosphonate-sulfonic acid bifunctional complex hydrogen-form cation resin was determined to be 4:1.

[0039] I. Experimental Detection Indicators This experiment tested six core indicators: total aluminum ion removal rate, resin equilibrium adsorption capacity, sulfuric acid consumption per ton of water, resin lifespan, aluminum ion content in effluent, and resin regeneration efficiency.

[0040] Example and Comparative Experimental Data

[0041] The experimental data above show that the aluminum removal rate in Examples 1-3 is ≥98%, which is much higher than the 85.30% of the single ordinary resin in Comparative Example 1; it is comparable to the aluminum removal effect of the single bifunctional resin in Comparative Example 2, but solves the problem of excessive cost in Comparative Example 2. This indicates that the gradient filling structure of the present invention, which combines coarse removal in the upper layer with fine removal in the lower layer, completely solves the problem of H +Competitive adsorption problem, achieving deep aluminum removal. Example 1 showed a resin adsorption capacity of 118 mg / g, significantly higher than Comparative Example 1 and Comparative Example 2; sulfuric acid consumption per ton of water was much lower than all comparative examples, resulting in a significant reduction in total resin cost. This demonstrates that a volume ratio of the upper ordinary resin to the lower bifunctional resin in the cation exchange resin tank within the range of (2-4):1 allows the upper ordinary resin to handle 85%-90% of the aluminum load, while the lower bifunctional resin only treats residual aluminum, resulting in a reasonable load matching. The resin lifespan of Example 1 was extended by 60% compared to Comparative Example 1 and by 18% compared to Comparative Example 2. This shows that a volume ratio of (2-4):1 synchronizes the saturation cycles of the two resin layers, preventing overload aging of the lower high-cost resin and extending the overall lifespan. Example 1 achieved the best performance in aluminum removal rate, adsorption capacity, acid consumption, and lifespan, representing the optimal ratio for industrial production. Furthermore, the aluminum removal rate in Example 1 was 98.97%; in Comparative Example 3, the removal rate plummeted to 92.10%, indicating that excessive sulfonic acid groups led to H+ oxidative stress. + Competitive sites and deep aluminum removal failure indicate that a phosphonic acid group ratio ≥1 is a necessary condition for resisting competitive adsorption in high-acid environments. Example 1 showed an adsorption capacity of 118 mg / g; Comparative Example 4 showed a main capacity reduced to 73 mg / g, with a slower adsorption rate and easier penetration, indicating that a sulfonic acid group ratio ≥0.5 is key to ensuring high resin capacity and fast mass transfer. A phosphonic acid to sulfonic acid group molar ratio of (1-2):1 in the bifunctional composite hydrogen-type cation exchange resin can balance selectivity and capacity. Furthermore, we can see that Example 1 had a regeneration efficiency of 98.6%; Comparative Examples 3 and 4 both had regeneration efficiencies <90%, indicating that too few phosphonic acid groups result in poor interference resistance, while too many lead to excessively strong complex bonds and difficulty in regeneration. A phosphonic acid to sulfonic acid group molar ratio of (1-2):1 allows the resin to be completely regenerated under 24% sulfuric acid, reducing acid consumption and extending its lifespan.

[0042] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A gradient adsorption-based deep aluminum removal process for aluminum-based polishing and washing, characterized in that, Includes the following steps: S1. Pretreatment: The aluminum polishing water is passed through an ultrafiltration device and a diffusion dialysis device in sequence to remove suspended solids, colloids and some free acid to obtain high-alumina residual liquid; S2. Gradient adsorption for aluminum removal: The high-alumina residue obtained in step S1 is passed into a layered cation exchange resin tank, sequentially passing through an upper layer of ordinary hydrogen-form strong acidic cation exchange resin and a lower layer of phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cation exchange resin. The upper resin adsorbs most of the free Al. 3+ The lower layer of bifunctional resin deeply adsorbs residual Al 3+ The purified acid solution was obtained; S3. Resin regeneration: When the resin is saturated with adsorption, it is first pre-regenerated with dilute sulfuric acid to remove the loosely adsorbed aluminum ions on the resin surface, and then the main regeneration is carried out with concentrated sulfuric acid to desorb the adsorbed aluminum ions and obtain aluminum sulfate mixture. S4. Regenerated acid recovery: The aluminum sulfate mixture obtained in step S3 is passed into an acid retardation device to recover the free sulfuric acid therein, which is then reused in the main regeneration process and / or pre-regeneration process in step S3.

2. The gradient adsorption type aluminum polishing and washing deep aluminum removal process according to claim 1, characterized in that, In step S2, the volume ratio of the upper ordinary hydrogen-form strong acid cation exchange resin to the lower bifunctional composite hydrogen-form cation exchange resin is (2-4):

1.

3. The gradient adsorption type aluminum removal process for aluminum-based polishing and washing according to claim 2, characterized in that, The volume ratio of the upper ordinary hydrogen-form strong acid cation exchange resin to the lower bifunctional complex hydrogen-form cation exchange resin is 3:

1.

4. The gradient adsorption type aluminum polishing and washing deep aluminum removal process according to claim 1, characterized in that, The common hydrogen-form strong acid cation exchange resin is a styrene-based strong acid cation exchange resin with a particle size of 0.315-1.25 mm.

5. The gradient adsorption type aluminum polishing and washing deep aluminum removal process according to claim 1, characterized in that, In the phosphonic acid-sulfonic acid bifunctional composite hydrogen-form cationic resin, the molar ratio of phosphonic acid groups to sulfonic acid groups is (1-2):

1.

6. The gradient adsorption type aluminum polishing and washing deep aluminum removal process according to claim 5, characterized in that, The molar ratio of phosphonic acid groups to sulfonic acid groups is 1.5:

1.

7. The gradient adsorption type aluminum polishing and deep aluminum removal process according to claim 1, characterized in that, In step S2, the inlet flow rate of the high-alumina residual liquid is controlled at 1-3 BV / h, and the adsorption temperature is controlled at 25-40℃.

8. The gradient adsorption type aluminum polishing and washing deep aluminum removal process according to claim 1, characterized in that, In step S3, the concentration of dilute sulfuric acid used for pre-regeneration is 8-12%, the flow rate is 2-4 BV / h, and the dosage is 2-3 BV; the concentration of concentrated sulfuric acid used for main regeneration is 22-26%, the flow rate is 1-2 BV / h, and the dosage is 3-4 BV.

9. A gradient adsorption-based deep aluminum removal system for implementing the process described in any one of claims 1-8, characterized in that, The device includes an ultrafiltration unit, a diffusion dialysis unit, a cation exchange resin tank, and an acid retardation unit connected in sequence. The cation exchange resin tank is filled from top to bottom with a common hydrogen-form strong acid cation exchange resin layer and a phosphonic acid-sulfonic acid bifunctional complex hydrogen-form cation exchange resin layer. The top of the cation exchange resin tank is provided with an inlet and a regenerator inlet, and the bottom is provided with an outlet and a regeneration waste liquid outlet.

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