Process for preparing polyaluminum chloride by eluting aluminum-absorbing resin and regeneration method of aluminum-absorbing resin

Abstract

The invention relates to a process for preparing polyaluminum chloride by eluting aluminum-absorbing resin and a regeneration method of the aluminum-absorbing resin, and the process comprises the following steps: step 1, first-stage elution: pumping hydrochloric acid into a resin tank to obtain high-aluminum eluted liquid; step 2, second-stage elution: continuously pumping hydrochloric acid into the resin tank to obtain low-aluminum eluted liquid; 3, pure water washing: washing out residual hydrochloric acid of resin in the resin tank by using pure water to obtain diluted hydrochloric acid, and enabling the diluted hydrochloric acid to flow into a diluted hydrochloric acid barrel; 4, membrane recovery of acid: respectively pumping the high-aluminum eluted liquid obtained in the step 1 and the diluted hydrochloric acid obtained in the step 3 into membrane recovery equipment to obtain pure hydrochloric acid and an aluminum chloride solution; 5, evaporation and concentration: pumping the aluminum chloride solution obtained in the step 4 into low-temperature evaporation equipment for evaporation and concentration to obtain a concentrated aluminum chloride solution; and 6, curing: adjusting the pH value of the concentrated aluminum chloride solution obtained in the step 5 to a preset value, and stirring to react for a period of time to obtain the polyaluminum chloride solution.

Description

Technical Field

[0001] This invention relates to the field of chemical treatment technology, specifically to a process for preparing polyaluminum chloride by eluting aluminum-absorbing resin and a method for regenerating aluminum-absorbing resin. Background Technology

[0002] Resin adsorption technology can effectively adsorb aluminum from waste acid in aluminum polishing, improving phosphoric acid recovery and aluminum removal rates. After resin adsorption reaches saturation, sulfuric acid or hydrochloric acid is typically used for elution. The eluted liquid mainly consists of aluminum sulfate or aluminum chloride, which can be used as raw materials for aluminum sulfate and polyaluminum chloride flocculants. A drawback of resin adsorption technology is that the elution process consumes large amounts of acid and water, generating a large amount of wastewater, which is 6 to 10 times the volume of the resin. In traditional processes, for example, 0.5 tons of 30% hydrochloric acid are consumed per ton of PAC, resulting in 8 to 10 cubic meters of wastewater. 3 The aluminum loss rate is greater than 15%. If it is discharged directly into the wastewater treatment plant, it will not only cause the loss of acid and aluminum ions, but also generate a large amount of wastewater, increasing the treatment pressure of the wastewater treatment plant and increasing the consumption of pure water. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a process for preparing polyaluminum chloride by eluting aluminum-absorbing resin and a method for regenerating the aluminum-absorbing resin, aiming to solve the problems of consuming large amounts of acid and water, generating large amounts of wastewater, and causing the loss of acid and aluminum ions during the elution process.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A process for preparing polyaluminum chloride by eluting aluminum-absorbing resin includes the following steps:

[0006] Step 1 is a single-stage elution: hydrochloric acid is pumped into the resin tank to obtain a high-alumina eluent;

[0007] Step 2 is a two-stage elution: continue pumping hydrochloric acid into the resin tank to obtain a low-aluminum eluent;

[0008] Step 3 is a pure water wash: Use pure water to wash out the residual hydrochloric acid in the resin tank, and obtain dilute hydrochloric acid, which flows into the dilute hydrochloric acid tank.

[0009] Step 4 is membrane recovery acid: The high-alumina eluent obtained in step 1 and the dilute hydrochloric acid obtained in step 3 are pumped into the membrane recovery equipment to obtain pure hydrochloric acid and aluminum chloride solution respectively;

[0010] Step 5 is evaporation and concentration: the aluminum chloride solution obtained in step 4 is pumped into a low-temperature evaporation device for evaporation and concentration to obtain a concentrated aluminum chloride solution;

[0011] Step 6 is maturation: Adjust the pH of the concentrated aluminum chloride solution obtained in step 5 to the preset value, and stir the reaction for a period of time to obtain polyaluminum chloride solution.

[0012] Furthermore, the elution step in step 1 specifically includes:

[0013] Step 1.1: Prepare 5%–10% hydrochloric acid;

[0014] Step 1.2: Pump hydrochloric acid into the resin tank from bottom to top at a flow rate of 2-4 BV / h. The liquid flowing out from the top of the resin tank directly enters the high-alumina eluent storage tank to obtain the high-alumina eluent.

[0015] Step 1.3: When the aluminum content in the liquid flowing out from the top of the resin tank is <10g / L, switch the valve to allow the liquid to flow into the low-aluminum elution liquid storage tank.

[0016] Furthermore, the two-stage elution in step 2 specifically includes:

[0017] Step 2.1: Pump hydrochloric acid at a flow rate of 2-4 BV / h to continue eluting the resin, and let the liquid flow out from the top of the resin tank into the low-aluminum elution liquid storage tank.

[0018] Step 2.2: Stop feeding when the aluminum content in the liquid flowing from the top of the resin tank is <0.2g / L;

[0019] Step 2.3: Use air to blow off the residual hydrochloric acid in the resin tank from top to bottom, and the resulting liquid flows into the low-aluminum elution liquid storage tank.

[0020] Furthermore, the pure water washing in step 3 specifically includes:

[0021] Step 3.1: Pump pure water into the resin tank from bottom to top at a flow rate of 3-5 BV / h. The liquid flowing out from the top of the resin tank directly enters the dilute hydrochloric acid tank to obtain dilute hydrochloric acid.

[0022] Step 3.2: Stop feeding when the chlorine content in the wash water flowing from the top of the resin tank is <100mg / L;

[0023] Step 3.3: Use air to blow away the residual wash water in the resin tank from top to bottom and put it into the dilute hydrochloric acid tank.

[0024] Furthermore, step 4, the membrane recovery of acid, specifically includes:

[0025] Step 4.1: Pump the high-alumina eluent obtained in Step 1 and the dilute hydrochloric acid obtained in Step 3 into the membrane recovery equipment at a flow rate of 1:2 to 2:1 respectively;

[0026] Step 4.2: Adjust the flow rates of the high-alumina elution solution and dilute hydrochloric acid to obtain aluminum chloride solution and pure hydrochloric acid;

[0027] Step 4.3: Stop feeding when the recovery rate of pure hydrochloric acid decreases by 5% to 10%;

[0028] Step 4.4: Use pure water to wash away residual acid in the membrane recovery equipment at a flow rate ≤5 times that of hydrochloric acid until the pH of the effluent is close to neutral;

[0029] Step 4.5: Prepare a 1%–3% alkaline solution and pump it into the membrane recovery equipment at the hydrochloric acid elution flow rate. The alkali feed rate should be 5–10 L / m³. 2 Stop adding alkali when the time is right;

[0030] Step 4.6: Elute the membrane recovery equipment with pure water at a flow rate ≤5 times that of hydrochloric acid until the pH of the effluent is <7, then stop the water intake.

[0031] Furthermore, the rinsing water from steps 4.4 and 4.6 is reused for the pure water rinsing in step 3.

[0032] Furthermore, step 5, evaporation and concentration, specifically includes:

[0033] Step 5.1: Pump the aluminum chloride solution obtained in step 4 into a low-temperature evaporation device and evaporate and concentrate it at 30-40°C to obtain a concentrated solution. The condensate generated during the evaporation process is reused for pure water washing in step 3 or membrane cleaning in step 4.

[0034] Step 5.2: When the effective aluminum content in the concentrate, calculated as alumina, is ≥8%, the concentrated aluminum chloride solution is discharged.

[0035] Furthermore, the ripening process in step 6 specifically includes:

[0036] Step 6.1: Adjust the pH of the concentrated aluminum chloride solution obtained in Step 5 to 3-5 using calcium aluminate, sodium hydroxide, or aluminum hydroxide, and stir the reaction for 0.5-1 h;

[0037] Step 6.2: Filter out excess residue;

[0038] Step 6.3: Stir the reaction at a speed not exceeding 100 r / min between 20 and 30°C for 12 to 48 hours to obtain a polyaluminum chloride solution.

[0039] A method for regenerating aluminum-absorbing resin includes the following steps:

[0040] a) Pre-elution: Hydrochloric acid elution is completed by the elution step as described in any one of claims 1 to 3;

[0041] b) Salt regeneration: Pump a 5-8% NaCl solution from bottom to top into the resin tank at a flow rate of 1-2 BV / h.

[0042] c) Endpoint control: Stop the influent when the pH of the effluent rises to 5-6;

[0043] d) Water washing transformation: Rinse with pure water at a flow rate of 2-3 BV / h until the effluent Cl- < 50 mg / L;

[0044] e) Air purging: Blow off residual liquid from top to bottom with compressed air at a pressure of 0.2 to 0.4 MPa.

[0045] The beneficial effects of the process for preparing polyaluminum chloride from aluminum-absorbing resin and the method for regenerating aluminum-absorbing resin described in this invention are as follows:

[0046] The process involves a first-stage elution yielding a high-alumina eluent, a second-stage elution yielding a low-alumina eluent, and washing with pure water to obtain dilute hydrochloric acid. This staged elution method enables the tiered utilization of aluminum resources. The high-alumina eluent and dilute hydrochloric acid are directly used in PAC synthesis, improving aluminum recovery. A membrane recovery system simultaneously processes the high-alumina eluent and dilute hydrochloric acid, converting waste acid into reusable hydrochloric acid + pure AlCl solution, thus improving hydrochloric acid reuse. The increased aluminum recovery and hydrochloric acid reuse rates reduce acid and aluminum ion losses, while also decreasing wastewater volume. Furthermore, the use of low-temperature evaporation equipment avoids Al... 3 + Hydrolysis, while saving energy compared to traditional processes that use evaporation at 80-100℃. Attached Figure Description

[0047] Figure 1 This is a flowchart of the process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to an embodiment of the present invention. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0049] like Figure 1 As shown, this invention discloses a process for preparing polyaluminum chloride by eluting aluminum-absorbing resin, comprising the following steps:

[0050] Step 1 is a single-stage elution: hydrochloric acid is pumped into the resin tank to obtain a high-alumina eluent;

[0051] Step 2 is a two-stage elution: continue pumping hydrochloric acid into the resin tank to obtain a low-aluminum eluent;

[0052] Step 3 is a pure water wash: Use pure water to wash out the residual hydrochloric acid in the resin tank, and obtain dilute hydrochloric acid, which flows into the dilute hydrochloric acid tank.

[0053] Step 4 is membrane recovery acid: The high-alumina eluent obtained in step 1 and the dilute hydrochloric acid obtained in step 3 are pumped into the membrane recovery equipment to obtain pure hydrochloric acid and aluminum chloride solution respectively;

[0054] Step 5 is evaporation and concentration: the aluminum chloride solution obtained in step 4 is pumped into a low-temperature evaporation device for evaporation and concentration to obtain a concentrated aluminum chloride solution;

[0055] Step 6 is maturation: Adjust the pH of the concentrated aluminum chloride solution obtained in step 5 to the preset value, and stir the reaction for a period of time to obtain polyaluminum chloride solution.

[0056] The process involves a first-stage elution yielding a high-alumina eluent, a second-stage elution yielding a low-alumina eluent, and washing with pure water to obtain dilute hydrochloric acid. This staged elution method enables the tiered utilization of aluminum resources. The high-alumina eluent and dilute hydrochloric acid are directly used in PAC synthesis, improving the aluminum recovery rate. A membrane recovery system simultaneously processes the high-alumina eluent and dilute hydrochloric acid, converting waste acid into a recycled hydrochloric acid + pure AlCl3 solution, thus improving the hydrochloric acid reuse rate. Due to the increased aluminum recovery and hydrochloric acid reuse rates, the loss of acid and aluminum ions is reduced, as is the amount of wastewater. Furthermore, the use of low-temperature evaporation equipment avoids Al... 3+ Hydrolysis, while also saving energy compared to traditional evaporation at 80-100℃.

[0057] Furthermore, the elution step in step 1 specifically includes:

[0058] Step 1.1: Prepare 5%–10% hydrochloric acid;

[0059] Step 1.2: Pump hydrochloric acid into the resin tank from bottom to top at a flow rate of 2-4 BV / h. The liquid flowing out from the top of the resin tank directly enters the high-alumina eluent storage tank to obtain the high-alumina eluent.

[0060] Step 1.3: When the aluminum content in the liquid flowing out from the top of the resin tank is <10g / L, switch the valve to allow the liquid to flow into the low-aluminum elution liquid storage tank.

[0061] The switching point is set at an aluminum content of <10g / L in the feed solution to ensure the concentration of the eluent after high-aluminum elution (Al). 3+ (≥40g / L) accurately separates high-aluminum components, meeting the purity requirements of PAC raw materials. Hydrochloric acid is pumped into the resin tank from bottom to top at a flow rate of 2-4 BV / h, which avoids short-circuiting of the resin bed and improves elution efficiency.

[0062] Furthermore, the two-stage elution in step 2 specifically includes:

[0063] Step 2.1: Pump hydrochloric acid at a flow rate of 2-4 BV / h to continue eluting the resin, and let the liquid flow out from the top of the resin tank into the low-aluminum elution liquid storage tank.

[0064] Step 2.2: Stop feeding when the aluminum content in the liquid flowing from the top of the resin tank is <0.2g / L;

[0065] Step 2.3: Use air to blow off the residual hydrochloric acid in the resin tank from top to bottom, and the resulting liquid flows into the low-aluminum elution liquid storage tank.

[0066] The feeding is stopped when the aluminum content in the feed solution is <0.2g / L. At this point, the residual aluminum rate in the resin is <0.5%, and the adsorption capacity recovery rate is >99%. This allows for the extraction of residual aluminum from the resin with minimal hydrochloric acid, reducing the amount of hydrochloric acid consumed. At the same time, air is blown off from top to bottom, reducing the amount of residual hydrochloric acid in the tank, reducing acid residue in the resin tank, and reducing the burden on subsequent water washing.

[0067] Furthermore, the pure water washing in step 3 specifically includes:

[0068] Step 3.1: Pump pure water into the resin tank from bottom to top at a flow rate of 3-5 BV / h. The liquid flowing out from the top of the resin tank directly enters the dilute hydrochloric acid tank to obtain dilute hydrochloric acid.

[0069] Step 3.2: Stop feeding when the chlorine content in the wash water flowing from the top of the resin tank is <100mg / L;

[0070] Step 3.3: Use air to blow away the residual wash water in the resin tank from top to bottom and put it into the dilute hydrochloric acid tank.

[0071] Compared to traditional processes where wastewater volume is 6 to 10 times the resin volume, this application uses a chlorine content of <100 mg / L in the wash water as the feed termination point, precisely controlling the washing volume and reducing wastewater volume to 3 to 4 times the resin volume. Dilute hydrochloric acid with a Cl- concentration of 3 to 8 g / L is collected for membrane recovery, avoiding increased energy consumption due to acid dilution.

[0072] Furthermore, step 4, the membrane recovery of acid, specifically includes:

[0073] Step 4.1: Pump the high-alumina eluent obtained in Step 1 and the dilute hydrochloric acid obtained in Step 3 into the membrane recovery equipment at a flow rate of 1:2 to 2:1 respectively;

[0074] Step 4.2: Adjust the flow rates of the high-alumina elution solution and dilute hydrochloric acid to obtain aluminum chloride solution and pure hydrochloric acid;

[0075] Step 4.3: Stop feeding when the recovery rate of pure hydrochloric acid decreases by 5% to 10%;

[0076] Step 4.4: Use pure water to wash away residual acid in the membrane recovery equipment at a flow rate ≤5 times that of hydrochloric acid until the pH of the effluent is close to neutral;

[0077] Step 4.5: Prepare a 1%–3% alkaline solution and pump it into the membrane recovery equipment at the hydrochloric acid elution flow rate. The alkali feed rate should be 5–10 L / m³. 2 Stop adding alkali when the time is right;

[0078] Step 4.6: Elute the membrane recovery equipment with pure water at a flow rate ≤5 times that of hydrochloric acid until the pH of the effluent is <7, then stop the water intake.

[0079] High-alumina liquid and dilute hydrochloric acid are fed in a ratio of 1:2 to 2:1 to maintain H2O on both sides of the membrane. + Due to the concentration difference, the acid recovery rate is increased to 90%, with no waste acid discharge. Cleaning is triggered when the recovery rate decreases by 5%–10%, with an alkaline washing flux of 5–10 L / m³. 2 Precise control extends membrane life by 3 times.

[0080] Furthermore, the rinsing water from steps 4.4 and 4.6 is reused for the pure water rinsing in step 3, thus recycling the rinsing water, improving the water circulation chain, and reducing pure water consumption.

[0081] Furthermore, step 5, evaporation and concentration, specifically includes:

[0082] Step 5.1: Pump the aluminum chloride solution obtained in step 4 into a low-temperature evaporation device and evaporate and concentrate it at 30-40°C to obtain a concentrated solution. The condensate generated during the evaporation process is reused for pure water washing in step 3 or membrane cleaning in step 4.

[0083] Step 5.2: When the effective aluminum content in the concentrate, calculated as alumina, is ≥8%, the concentrated aluminum chloride solution is discharged.

[0084] Evaporation at 30–40℃ inhibits the AlCl3→Al(OH)3 conversion, resulting in an effective aluminum retention rate >98%, while the effective aluminum retention rate of traditional processes using evaporation at 80–100℃ is only 80%. The endpoint was set at Al2O3 ≥ 8% (corresponding to Al...). 3+ The concentration is 36 g / L to ensure the activity of the ripening reaction. The reuse of condensate generated during the evaporation process improves the water circulation chain and reduces the consumption of pure water.

[0085] Furthermore, the ripening process in step 6 specifically includes:

[0086] Step 6.1: Adjust the pH of the concentrated aluminum chloride solution obtained in Step 5 to 3-5 using calcium aluminate, sodium hydroxide, or aluminum hydroxide, and stir the reaction for 0.5-1 h;

[0087] Step 6.2: Filter out excess residue;

[0088] Step 6.3: Stir the reaction at a speed not exceeding 100 r / min between 20 and 30°C for 12 to 48 hours to obtain a polyaluminum chloride solution.

[0089] Alkalization occurs in the pH range of 3 to 5, promoting [AlO4Al] 12 (OH) 24 (H2O) 12 ] 7+ (Alb) is generated, accounting for >70%. The mixture is stirred at a low temperature of 20–30℃ and a slow speed of ≤100 rpm for 12–48 hours to avoid localized over-alkalinity precipitation, thus improving basicity stability with fluctuations <5%.

[0090] Table 1 shows the comparison of various indicators between the traditional elution process and the elution process of aluminum-absorbing resin for preparing polyaluminum chloride of the present invention.

[0091] Table 1

[0092] index Traditional crafts This invention Improvement effect Hydrochloric acid consumption 0.5 tons / ton PAC 0.05 tons / ton PAC Hydrochloric acid consumption decreased Wastewater generation <![CDATA[8-10m 3 / ton PAC]]> <![CDATA[0.01m 3 / ton PAC]]> Near-zero emissions PAC basicity stability 45-60％(±15％) 65-70％(±3％) Improved stability Effective aluminum utilization rate 80-85％ 98％ Raw material loss decreased

[0093] By employing a process of graded elution → membrane aluminum separation → low-temperature process control, production costs are reduced by 42% (mainly due to acid recovery and energy saving); wastewater and waste acid are nearly discharged; and PAC flocculation performance is improved (flocculation time is shortened by 40%, and residual aluminum is reduced by 80%).

[0094] This invention also discloses a method for regenerating aluminum-absorbing resin, comprising the following steps:

[0095] a) Pre-elution: Complete the hydrochloric acid elution as described above;

[0096] b) Salt regeneration: Pump a 5% to 8% NaCl solution into the resin tank from bottom to top at a flow rate of 1 to 2 BV / h;

[0097] c) Endpoint control: Stop the influent when the pH of the effluent rises to 5-6;

[0098] d) Water washing transformation: Rinse with pure water at a flow rate of 2-3 BV / h until the effluent Cl- < 50 mg / L;

[0099] e) Air purging: Blow off residual liquid from top to bottom with compressed air at a pressure of 0.2 to 0.4 MPa.

[0100] Previous processes only covered the elution-PAC preparation stage, omitting resin regeneration and re-adsorption cycles, leading to a decrease in resin adsorption capacity. The new aluminum-adsorbing resin regeneration method involves elution and regeneration, extending resin lifespan. By optimizing NaCl concentration and flow rate, swelling stress damage is avoided, saving on resin replacement and outsourced regeneration costs, thus reducing production costs.

[0101] A NaCl solution concentration less than 5% will result in a resin regeneration rate of less than 90%; a NaCl solution concentration greater than 8% will cause resin shrinkage cracks. Pumping the NaCl solution into the resin tank from bottom to top at a flow rate of 1–2 BV / h is the minimum fluidization rate to prevent channeling. When the pH of the effluent rises to 5–6, it indicates that the H... + Complete displacement. Washing to the endpoint until Cl- < 50 mg / L can prevent residual Cl- from affecting the next round of aluminum adsorption.

[0102] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A process for preparing polyaluminum chloride by eluting aluminum-absorbing resin, characterized in that, Includes the following steps: Step 1 is a single-stage elution: hydrochloric acid is pumped into the resin tank to obtain a high-alumina eluent; Step 2 is a two-stage elution: continue pumping hydrochloric acid into the resin tank to obtain a low-aluminum eluent; Step 3 is a pure water wash: Use pure water to wash out the residual hydrochloric acid in the resin tank, and obtain dilute hydrochloric acid, which flows into the dilute hydrochloric acid tank. Step 4 is membrane recovery acid: The high-alumina eluent obtained in step 1 and the dilute hydrochloric acid obtained in step 3 are pumped into the membrane recovery equipment to obtain pure hydrochloric acid and aluminum chloride solution respectively; Step 5 is evaporation and concentration: the aluminum chloride solution obtained in step 4 is pumped into a low-temperature evaporation device for evaporation and concentration to obtain a concentrated aluminum chloride solution; Step 6 is maturation: Adjust the pH of the concentrated aluminum chloride solution obtained in step 5 to the preset value, and stir the reaction for a period of time to obtain polyaluminum chloride solution.

2. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 1, characterized in that, The elution process in step 1 specifically includes: Step 1.1: Prepare 5%–10% hydrochloric acid; Step 1.2: Pump hydrochloric acid into the resin tank from bottom to top at a flow rate of 2-4 BV / h. The liquid flowing out from the top of the resin tank directly enters the high-alumina eluent storage tank to obtain the high-alumina eluent. Step 1.3: When the aluminum content in the liquid flowing out from the top of the resin tank is <10g / L, switch the valve to allow the liquid to flow into the low-aluminum elution liquid storage tank.

3. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 1, characterized in that, The two-stage elution process in step 2 specifically includes: Step 2.1: Pump hydrochloric acid at a flow rate of 2-4 BV / h to continue eluting the resin, and let the liquid flow out from the top of the resin tank into the low-aluminum elution liquid storage tank. Step 2.2: Stop feeding when the aluminum content in the liquid flowing from the top of the resin tank is <0.2g / L; Step 2.3: Use air to blow off the residual hydrochloric acid in the resin tank from top to bottom, and the resulting liquid flows into the low-aluminum elution liquid storage tank.

4. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 1, characterized in that, The pure water washing in step 3 specifically includes: Step 3.1: Pump pure water into the resin tank from bottom to top at a flow rate of 3-5 BV / h. The liquid flowing out from the top of the resin tank directly enters the dilute hydrochloric acid tank to obtain dilute hydrochloric acid. Step 3.2: Stop feeding when the chlorine content in the wash water flowing from the top of the resin tank is <100mg / L; Step 3.3: Use air to blow away the residual wash water in the resin tank from top to bottom and put it into the dilute hydrochloric acid tank.

5. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 1, characterized in that, The membrane recovery of acid in step 4 specifically includes: Step 4.1: Pump the high-alumina eluent obtained in Step 1 and the dilute hydrochloric acid obtained in Step 3 into the membrane recovery equipment at a flow rate of 1:2 to 2:1 respectively; Step 4.2: Adjust the flow rates of the high-alumina elution solution and dilute hydrochloric acid to obtain aluminum chloride solution and pure hydrochloric acid; Step 4.3: Stop feeding when the recovery rate of pure hydrochloric acid decreases by 5% to 10%; Step 4.4: Use pure water to wash away residual acid in the membrane recovery equipment at a flow rate ≤5 times that of hydrochloric acid until the pH of the effluent is close to neutral; Step 4.5: Prepare a 1%–3% alkaline solution and pump it into the membrane recovery equipment at the hydrochloric acid elution flow rate. The alkali feed rate should be 5–10 L / m³. 2 Stop adding alkali when the time is right; Step 4.6: Elute the membrane recovery equipment with pure water at a flow rate ≤5 times that of hydrochloric acid until the pH of the effluent is <7, then stop the water intake.

6. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 5, characterized in that, The rinsing water from steps 4.4 and 4.6 is reused for the pure water rinsing in step 3.

7. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 1, characterized in that, Step 5, evaporation and concentration, specifically includes: Step 5.1: Pump the aluminum chloride solution obtained in step 4 into a low-temperature evaporation device and evaporate and concentrate it at 30-40°C to obtain a concentrated solution. The condensate generated during the evaporation process is reused for pure water washing in step 3 or membrane cleaning in step 4. Step 5.2: When the effective aluminum content in the concentrate, calculated as alumina, is ≥8%, the concentrated aluminum chloride solution is discharged.

8. The process for preparing polyaluminum chloride by eluting aluminum-absorbing resin according to claim 1, characterized in that, Step 6, the ripening process, specifically includes: Step 6.1: Adjust the pH of the concentrated aluminum chloride solution obtained in Step 5 to 3-5 using calcium aluminate, sodium hydroxide, or aluminum hydroxide, and stir the reaction for 0.5-1 h; Step 6.2: Filter out excess residue; Step 6.3: Stir the reaction at a speed not exceeding 100 r / min between 20 and 30°C for 12 to 48 hours to obtain a polyaluminum chloride solution.

9. A method for regenerating aluminum-absorbing resin, characterized in that, Includes the following steps: a) Pre-elution: Hydrochloric acid elution is completed by the elution step as described in any one of claims 1 to 3; b) Salt regeneration: Pump a 5-8% NaCl solution from bottom to top into the resin tank at a flow rate of 1-2 BV / h. c) Endpoint control: Stop the influent when the pH of the effluent rises to 5-6; d) Water washing transformation: Rinse with pure water at a flow rate of 2-3 BV / h until the effluent Cl- < 50 mg / L; e) Air purging: Blow off residual liquid from top to bottom with compressed air at a pressure of 0.2 to 0.4 MPa.

Images