Process method for recovering chromium and aluminum by comprehensively utilizing waste aluminum residues

[0024] Example 1

[0025] A process method for comprehensively utilizing aluminum mud waste to recover chromium and aluminum. The specific steps are as follows:

[0026] (1) Preliminary chromium removal by beating and washing

[0027] According to the ratio of aluminum mud mass (g): water volume (ml) of 1:3, the aluminum mud is mixed with water, heated to 65° C. and kept warm, and stirred for 145 minutes at a rotation speed of 200 r/min. Centrifuge is used for solid-liquid separation, and the supernatant and sediment are collected separately, and the supernatant is returned to the chromium salt production process for recycling, and the sediment is used for further chromium removal.

[0028] (2) Electrodialysis to remove chromium

[0029] ① Design of electrodialysis device

[0030] The main body of the electrodialysis device is a rectangular parallelepiped water tank made of organic glass. The water tank is divided into three independent spaces: a cathode chamber, an intermediate chamber, and an anode chamber with anion and cation exchange membranes in the middle of the tank. Add a stirring device to the middle chamber, and then use a DC power supply, two graphite electrodes and a wire to connect the cathode chamber and anode chamber of the electrolytic cell in series.

[0031] ②The sediment obtained in step (1), that is, the aluminum sludge after preliminary chromium removal, is uniformly mixed according to the ratio of the mass (g) of the aluminum sludge to the volume (ml) of water (ml) of 1:7, and then added to The middle chamber of the electrolytic cell is used as the raw material for electrodialysis. Prepare 0.5mol/L sodium sulfate solution and add them to the cathode chamber and anode chamber at both ends of the electrolytic cell as the working medium. Put the electrolytic cell into a water bath heating tank, heat it to 35°C and keep it warm. Turn on the stirring device, keep the speed of the stirring device at 90r/min, turn on the power supply, and electrolyze for 7 hours under the condition of 50V voltage stabilization. After the electrolysis is completed, turn off the power supply and the stirring device, and collect the liquid in the cathode, anode and intermediate chambers respectively. The liquid in the anode and cathode chambers is sodium chromate solution, which is returned to the chromium salt production process for recycling. The aluminum mud mixed solution in the middle chamber is centrifuged by a centrifuge, and the supernatant and the sediment are collected separately. The supernatant is returned to the sodium dichromate production process for recycling, and the sediment is the aluminum mud with complete chromium removal, and the hexavalent chromium content in the aluminum mud is 1%.

[0032] (3) Alkaline leaching to extract sodium aluminate leaching solution

[0033] After the completion of steps (2)-②, the mass of sediment collected in step (2)-② is the mass of aluminum sludge after chromium removal (g): the mass of sodium sulfide (g): the concentration of 200g/L The ratio of the volume (ml) of the NaOH solution is 76:1:300. The aluminum mud and sodium sulfide are added to the sodium hydroxide solution, heated to 100°C, and reacted for 3h at a rotation speed of 90r/min. After the reaction is over, let it stand and cool to normal temperature, and then filter to collect filter cake and filtrate. The filter cake is chromium slag with high chromium content, which is returned to the chromium salt roaster for recycling. The collected filtrate is the sodium aluminate leachate, which is used to prepare alumina.

[0034] (4) Preparation of alumina

[0035] ① Take the sodium aluminate leaching solution in step (3), and add the sodium pyrophosphate to the leaching solution at a ratio of 160:1 according to the volume of the leaching solution (ml): the mass (g) of sodium pyrophosphate, and heat it to At 70°C and heat preservation, at a rotation speed of 90r/min, CO2 gas was introduced at a rate of 15ml/s·L of the leachate to react until the pH was 10.8.

[0036] ② Filter the reaction solution, and collect the filter cake and filtrate respectively. The collected filtrate is stored for electrolysis to prepare sodium bicarbonate and sodium hydroxide. The filter cake is the aluminum hydroxide product. According to the ratio of filter cake mass (g): concentration of 12% NaOH solution volume (ml) to 1:4, the filter cake is added to the lye to dissolve for 1 hour, and then filter , Collect the filter cake and filtrate separately.

[0037] ③The filter cake collected according to steps (4)-② is the main chromium-containing material, and it is returned to the chromium salt roaster for recycling; the collected filtrate is repeated twice according to the steps (4)-① and (4)-② to obtain The filter cake is the final Al(OH) 3. The aluminum hydroxide is calcined at a high temperature of 300° C. for 3 hours to obtain an aluminum oxide product with a purity of 98.8%.

[0038] Example 2

[0039] A process method for comprehensively utilizing aluminum mud waste to recover chromium and aluminum is the same as implementation case 1, in which:

[0040] In step (1), the ratio of the mass (g) of the aluminum mud: the volume (ml) of the water is 1:2, heat to 60°C and keep it warm, and stir for 90 minutes at a rotation speed of 180r/min.

[0041] In steps (2)-②, the sediment obtained in step (1), that is, the aluminum sludge after preliminary chromium removal, is based on the ratio of the mass (g) of the aluminum sludge to the volume (ml) of water (ml) as 1:5 After being mixed evenly, it is added to the middle chamber of the electrolytic cell as the raw material for electrodialysis. A 0.1mol/L sodium sulfate solution was prepared and added to the cathode chamber and anode chamber at both ends of the electrolytic cell as the working medium. Put the electrolytic cell into a water bath heating tank, heat it to 30°C and keep it warm. Turn on the stirring device, keep the speed of the stirring device at 60r/min, turn on the power supply, and electrolyze for 6h under the condition of 40V voltage stabilization. The aluminum mud mixed solution in the middle chamber is centrifuged by a centrifuge, and the supernatant and the sediment are collected separately. The supernatant is returned to the sodium dichromate production process for recycling, and the sediment is the aluminum mud with complete chromium removal, and the hexavalent chromium content in the aluminum mud is 0.5%.

[0042] In step (3), the ratio of the mass of aluminum mud after chromium removal (g): the mass of sodium sulfide (g): the volume (ml) of the NaOH solution with a concentration of 100g/L is 76:1:227. Add aluminum mud and sodium sulfide to the sodium hydroxide solution, heat to 90°C, and react for 2h at a rotation speed of 60r/min.

[0043] In step (4)-①, the ratio of the volume (ml) of the leaching solution: the mass (g) of sodium pyrophosphate is 100:1, and it is heated to 60°C and kept at a temperature of 10ml/s at a speed of 60r/min. ·The speed of L leaching solution is fed with CO2 gas for reaction until the PH is 10.5 and it stops.

[0044] In steps (4)-②, the quality of the filter cake (g): the volume of the 10% NaOH solution (ml) is 1:3, the filter cake is added to the lye to dissolve for 1 hour, and the filter cake and filtrate are collected separately .

[0045] In steps (4)-③, the aluminum hydroxide is calcined at a high temperature of 300° C. for 3 hours to obtain an aluminum oxide product with a purity of 98.6%.

[0046] Example 3

[0047] A process method for comprehensively utilizing aluminum mud waste to recover chromium and aluminum is the same as implementation case 1, in which:

[0048] In step (1), the ratio of the mass (g) of the aluminum mud: the volume (ml) of the water is 1:5, heat to 70° C. and keep it warm, and stir for 180 min at a rotation speed of 240 r/min.

[0049] In steps (2)-②, the sediment obtained in step (1), that is, the aluminum sludge after preliminary chromium removal, is based on the ratio of the mass of aluminum sludge (g) to the volume of water (ml) as 1:8 After being mixed evenly, it is added to the middle chamber of the electrolytic cell as the raw material for electrodialysis. A 1mol/L sodium sulfate solution was prepared and added to the cathode chamber and anode chamber at both ends of the electrolytic cell as the working medium. Put the electrolytic cell into a water bath heating tank, heat it to 40°C and keep it warm. Turn on the stirring device, keep the speed of the stirring device at 120r/min, switch on the power supply, and electrolyze for 8h under the condition of 60V voltage stabilization. The aluminum mud mixed solution in the middle chamber is centrifuged by a centrifuge, and the supernatant and the sediment are collected separately. The supernatant is returned to the sodium dichromate production process for recycling, and the sediment is the aluminum mud with complete chromium removal, and the hexavalent chromium content in the aluminum mud is 0.8%.

[0050] In step (3), the ratio of the mass of aluminum sludge after chromium removal (g): the mass of sodium sulfide (g): the volume (ml) of the NaOH solution with a concentration of 300g/L is 76:1:454. Add aluminum mud and sodium sulfide to the sodium hydroxide solution, heat to 105°C, and react for 5 hours at a speed of 120r/min.

[0051] In step (4)-①, the ratio of the volume (ml) of the leaching solution: the mass (g) of sodium pyrophosphate is 200:1, and it is heated to 80°C and kept at a temperature of 20ml/s at a speed of 120r/min. · The speed of L leaching solution is fed with CO2 gas for reaction until the PH is 11 and it stops.

[0052] In steps (4)-②, the quality of the filter cake (g): the volume of the 10% NaOH solution (ml) is 1:5. After adding the filter cake to the lye to dissolve for 2 hours, collect the filter cake and the filtrate separately .

[0053] In steps (4)-③, the aluminum hydroxide is calcined at a high temperature of 300° C. for 3 hours to obtain an aluminum oxide product with a purity of 98.9%.