Cu-Ca / PB adsorbent and application thereof in removal of fluoride and bivalent sulfide in aluminum industrial production process

Abstract

The invention relates to a Cu-Ca / PB adsorbent and application of the Cu-Ca / PB adsorbent in removal of fluorides and bivalent sulfides in an aluminum industrial production process, and belongs to the technical field of resource recycling and utilization and environmental protection. A substrate of the adsorbent is pseudo-boehmite gel, an organic carbon skeleton is carboxymethyl cellulose, calcium ions are doped in the substrate pseudo-boehmite gel, and copper ions are loaded on the surface of the adsorbent. The Cu-Ca / PB adsorbent and F <-> and S < 2-> in the solution are subjected to chemical adsorption, and F <-> is solidified in pseudo-boehmite sol in the form of CaF2 and AlF3 to be precipitated, so that efficient recovery of F <-> in the solution is realized; according to the present invention, the S < 2-> is cured in the pseudo-boehmite sol in the form of CuS and CaS so as to precipitate, such that the S < 2-> in the solution can be efficiently recovered, such that the Cu-Ca / PB adsorbent has the high removal efficiency on the F <-> and the S < 2-> so as to be suitable for the adsorption of the S < 2-> in the aluminum industry high-sulfur bauxite leaching liquid and the adsorption of the F <-> in the aluminum ash water leaching liquid, and the Cu-Ca / PB adsorbent has characteristics of short preparation process, low cost, high adsorption efficiency, and easy industrial production. The process is environment-friendly, and the like.

Description

Technical Field

[0001] The present invention relates to a Cu-Ca / PB adsorbent and its application in removing fluoride and divalent sulfide during the production process of the aluminum industry, belonging to the technical fields of resource recycling and environmental protection. Background Art

[0002] Sulfur in bauxite mainly exists in the form of pyrite (FeS2), which will react during the high-temperature digestion process. First, it enters the solution in the form of S 2- , and then S 2- is gradually oxidized to S2O3 2- , SO3 2- and SO4 2- . The sulfide reacts with caustic alkali and sodium aluminate solution, increasing the alkali consumption. S 2- in the solution reacts with iron salt to form sodium hydroxy thioferrate, increasing the iron content in the solution. S2O3 2- oxidizes metallic iron in an alkaline environment, causing serious corrosion of steel equipment; more iron enters the alumina seeding process, making the iron content in the alumina product exceed the standard; sulfur and its complexes will accelerate the corrosion rate of steel equipment, heat exchange pipe pipelines of the evaporator group, and filter machine screens; when Na2SO4 accumulates to a certain amount in the production process, it precipitates as a double salt, sodium carbonate alum, Na2CO3·2Na2SO4, under certain conditions. The double salt forms scale in the mother liquor evaporator and digester, reducing the heat transfer coefficient of the equipment and increasing production energy consumption.

[0003] The leaching toxicity of secondary aluminum ash mainly comes from fluoride ions. Fluorine elements mainly exist in Na3AlF6, CaF2, and K2(NaAlF6). Currently, the main method for removing fluoride ions from aluminum ash is through water leaching. The fluoride ions will enter the leaching solution and exist in ionic form. After the reaction is completed, solid-liquid separation is carried out. The pH can be adjusted with acid, other additives, etc. Finally, after impurity removal, centrifugation, dehydration, and drying, cryolite is obtained. If the leaching solution of secondary aluminum ash is not properly treated, it will lead to excessive release and diffusion of fluoride, thereby damaging the ecological environment and endangering life safety. In addition, there are also methods for recovering fluorine, such as adding sulfuric acid and alumina to be treated into aluminum fluoride at high temperature; or adding silicon and calcium compounds to solidify fluorine. The above processes have mature experience and applications at home and abroad, but the disadvantages are also obvious, such as large investment, high energy consumption, long process flow, high price of auxiliary materials, and difficult process control.

[0004] During the water leaching process of aluminum ash, fluorine-containing compounds are often produced; and during the digestion process of bauxite, sulfur-containing compounds are often produced, which not only have a negative impact on the aluminum ash recovery and bauxite digestion processes, reducing the aluminum ash recovery efficiency and quality, and the sulfide corrodes the equipment and affects the alumina quality, but also the emissions of high-concentration fluorine and sulfide will cause serious land and water pollution to the ecological environment, greatly increasing the production cost and recovery efficiency. Therefore, for the efficient recovery of the above F - 、S 2- , there is currently no suitable and effective treatment method. SUMMARY OF THE INVENTION

[0005] Aiming at the problem that it is difficult to recover fluoride in the aluminum ash water leaching solution and divalent sulfide in the bauxite digestion solution, the present invention proposes a Cu-Ca / PB adsorbent and its application in removing fluoride and divalent sulfide in the aluminum industry production process. The substrate of the adsorbent is pseudo-boehmite gel, the organic carbon skeleton is carboxymethyl cellulose, calcium ions are doped in the substrate pseudo-boehmite gel, and copper ions are loaded on the surface of the adsorbent. The Cu-Ca / PB adsorbent performs chemical adsorption with F - 、S 2- in the solution. F - is solidified in the pseudo-boehmite sol in the form of CaF2 and AlF3 and precipitated, realizing the efficient recovery of F - in the solution; S 2- is solidified in the pseudo-boehmite sol in the form of CuS and CaS and precipitated, realizing the efficient recovery of S 2- in the solution.

[0006] A Cu-Ca / PB adsorbent, the substrate of the adsorbent is pseudo-boehmite gel, the organic carbon skeleton is carboxymethyl cellulose, calcium ions are doped in the substrate pseudo-boehmite gel, and copper ions are loaded on the surface of the adsorbent; The preparation method of the Cu-Ca / PB adsorbent is as follows: (1) Add pseudo-boehmite to the acid solution for peptization treatment to obtain pseudo-boehmite gel; (2) Add calcium salt to the pseudo-boehmite gel and stir to dissolve to obtain a calcium-doped pseudo-boehmite gel substrate; (3) Add the organic carbon skeleton carboxymethyl cellulose to the calcium-doped pseudo-boehmite gel substrate and stir evenly to obtain a flocculent gel. The flocculent gel is dried and crushed to obtain a carrier powder; (4) Add the carrier powder to the copper ammonia solution and impregnate for 10-30 min, dry and grind to obtain the Cu-Ca / PB adsorbent.

[0007] Preferably, the acid solution in step (1) is one or more of concentrated hydrochloric acid, concentrated nitric acid, concentrated sulfuric acid, perchloric acid, and hydroiodic acid.

[0008] Preferably, in the acid solution of step (1), the concentration of H + is 12 - 16 mol / L, and the solid-liquid ratio of pseudo-boehmite to the acid solution is 6 - 10 g:mL.

[0009] Preferably, in step (2), the calcium salt is one or more of CaCl2, CaO, Ca(OH)2, Ca(NO3)3, calcium dihydrogen phosphate, calcium bicarbonate, and calcium bisulfate, and the molar ratio of Ca in the calcium salt to Al in the pseudo-boehmite is 1:1 - 3.

[0010] Preferably, in step (3), the mass ratio of pseudo-boehmite to the organic carbon framework carboxymethyl cellulose is 1 - 5:1.

[0011] Preferably, in step (4), the molar ratio of Cu in the copper ammonia solution to Al in the pseudo-boehmite is 1:1 - 3.

[0012] Application of the Cu-Ca / PB adsorbent in removing fluoride and divalent sulfide during the production process of the aluminum industry.

[0013] Preferably, the concentration of the fluoride is 10 - 100 mg / L, and the concentration of the divalent sulfide is 10 - 100 mg / L.

[0014] The beneficial effects of the present invention are as follows: (1) The present invention has high adsorption performance for low-concentration F - , S 2- , and the solidified fluorine and sulfide will not decompose and can be stabilized in the precipitate, which is convenient for subsequent separation and collection; (2) The Cu-Ca / PB adsorbent of the present invention has a high removal efficiency for low-concentration F - , S 2- , and is applicable to the adsorption of S 2- in the digestion solution of high-sulfur bauxite in the aluminum industry and the adsorption of F - in the water leaching solution of aluminum ash; (3) The preparation process of the Cu-Ca / PB adsorbent of the present invention is short, the cost is low, the adsorption efficiency is high, and the process is environmentally friendly. Specific embodiments

[0015] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the content described.

[0016] Example 1: A Cu-Ca / PB adsorbent, the substrate of the adsorbent is pseudo-boehmite gel, the organic carbon framework is carboxymethyl cellulose, calcium ions are doped in the substrate pseudo-boehmite gel, and copper ions are loaded on the surface of the adsorbent; The preparation method of the Cu-Ca / PB adsorbent is as follows: (1) Boehmite is added to concentrated hydrochloric acid for peptization treatment to obtain a boehmite gel; the concentration of H in the concentrated hydrochloric acid solution is + 12 mol / L, and the solid-liquid ratio of boehmite to the acid solution is 7:1 (g:mL); (2) A calcium salt (CaCl2) is added to the boehmite gel and stirred until dissolved to obtain a calcium-doped boehmite gel substrate; the molar ratio of Ca in the calcium salt (CaCl2) to Al in boehmite is 1:1; (3) Organic carbon framework carboxymethyl cellulose is added to the calcium-doped boehmite gel substrate and stirred evenly to obtain a flocculent gel. The flocculent gel is dried at 60 °C and pulverized to obtain a carrier powder; the mass ratio of boehmite to organic carbon framework carboxymethyl cellulose is 2:1; (4) The carrier powder is added to a copper ammonia solution with a concentration of 0.8 mol / L and impregnated for 10 min, then dried at 100 °C and ground to obtain the Cu-Ca / PB adsorbent; the molar ratio of Cu in the copper ammonia solution to Al in boehmite is 1:1; 4 g of the Cu-Ca / PB adsorbent is added to 100 mL of a sodium aluminate solution (pH value is 4, containing 30 mg / L of F - ) during the production of alumina from high-sulfur bauxite for adsorption for 120 min, and samples are taken at 10 min, 20 min, 40 min, 60 min, 90 min, and 120 min to measure the concentration of F in the sodium aluminate solution, which are - 26.577 mg / L, 8.506 mg / L, 6.062 mg / L, 5.377 mg / L, 4.632 mg / L, 4.595 mg / L, and 4.182 mg / L respectively; Therefore, the adsorption removal rate of the Cu-Ca / PB adsorbent in this example for F in the sodium aluminate solution reaches - 83.015% in 120 min.

[0017] Example 2: A Cu-Ca / PB adsorbent, the substrate of the adsorbent is a boehmite gel, the organic carbon framework is carboxymethyl cellulose, calcium ions are doped in the substrate boehmite gel, and copper ions are loaded on the surface of the adsorbent; The preparation method of the Cu-Ca / PB adsorbent is as follows: (1) Boehmite is added to concentrated hydrochloric acid for peptization treatment to obtain a boehmite gel; the concentration of the acid solution, concentrated hydrochloric acid, is + 37% by mass fraction, and the solid-liquid ratio of boehmite to the acid solution is 8:1 (g:mL); (2) Add calcium salt (CaCl2) to the pseudo-boehmite gel and stir to dissolve to obtain a calcium-doped pseudo-boehmite gel substrate; the molar ratio of Ca in the calcium salt (CaCl2) to Al in the pseudo-boehmite is 1:2; (3) Add organic carbon framework carboxymethyl cellulose to the calcium-doped pseudo-boehmite gel substrate and stir evenly to obtain a flocculent gel. The flocculent gel is dried at 70 °C and pulverized to obtain a carrier powder; the mass ratio of the pseudo-boehmite to the organic carbon framework carboxymethyl cellulose is 3:1; (4) Add the carrier powder to a copper ammonia solution with a concentration of 0.8 mol / L and impregnate for 20 min, then dry at 90 °C and grind to obtain a Cu-Ca / PB adsorbent; the molar ratio of Cu in the copper ammonia solution to Al in the pseudo-boehmite is 1:2; Add 2 g, 3 g, 4 g, 5 g, and 6 g of the Cu-Ca / PB adsorbent to the sodium aluminate solution (pH value is 6, containing 30 mg / L of F - ) in the production of alumina from high-sulfur bauxite for 120 min of adsorption, and sample and measure the concentration of F in the sodium aluminate solution - ; When adding 2 g, 3 g, 4 g, 5 g, and 6 g of the Cu-Ca / PB adsorbent respectively, the concentrations of F - in the sodium aluminate solution are 6.847 mg / L, 5.045 mg / L, 4.315 mg / L, 4.745 mg / L, and 2.453 mg / L respectively, and the removal rates of F - are 75.609%, 81.369%, 83.015%, 82.247%, and 91.824% respectively.

[0018] Example 3: A Cu-Ca / PB adsorbent, the substrate of the adsorbent is pseudo-boehmite gel, the organic carbon framework is carboxymethyl cellulose, calcium ions are doped in the substrate pseudo-boehmite gel, and copper ions are loaded on the surface of the adsorbent; The preparation method of the Cu-Ca / PB adsorbent is specifically as follows: (1) Add pseudo-boehmite to concentrated nitric acid for peptization treatment to obtain pseudo-boehmite gel; the concentration of H + in the acid solution concentrated nitric acid is 68% by mass fraction, and the solid-liquid ratio of pseudo-boehmite to the acid solution is g:mL = 9:1; (2) Add calcium salt (CaCl2) to the pseudo-boehmite gel and stir to dissolve to obtain a calcium-doped pseudo-boehmite gel substrate; the molar ratio of Ca in the calcium salt (CaCl2) to Al in the pseudo-boehmite is 1:3; (3) Add the organic carbon framework carboxymethyl cellulose to the calcium-doped pseudoboehmite gel substrate and stir evenly to obtain a flocculent gel. The flocculent gel is dried at 80 °C and pulverized to obtain a carrier powder; the mass ratio of the pseudoboehmite to the organic carbon framework carboxymethyl cellulose is 4:1; (4) Add the carrier powder to a copper ammonia solution with a concentration of mol / L and impregnate for 15 min, then dry at 70 °C and grind to obtain a Cu-Ca / PB adsorbent; the molar ratio of Cu in the copper ammonia solution to Al in the pseudoboehmite is 1:3; Add 4 g of the Cu-Ca / PB adsorbent to 100 mL of sodium aluminate solution (pH values are 4, 5, 6, 7, 8, 9 respectively) during the production of alumina from high-sulfur bauxite, containing 30 mg / L of F - ) and adsorb for 120 min, and sample and measure the concentration of F in the sodium aluminate solution - When the pH values of the sodium aluminate solution are 4, 5, 6, 7, 8, 9 respectively, the concentrations of F in the sodium aluminate solution - are 3.538 mg / L, 2.319 mg / L, 2.774 mg / L, 4.212 mg / L, 4.548 mg / L respectively, and the removal rates of F - are 86.773%, 91.071%, 89.021%, 84.259%, 84.321%, 82.928% respectively.

[0019] Example 4: A Cu-Ca / PB adsorbent, the substrate of the adsorbent is pseudoboehmite gel, the organic carbon framework is carboxymethyl cellulose, calcium ions are doped in the substrate pseudoboehmite gel, and copper ions are loaded on the surface of the adsorbent; The preparation method of the Cu-Ca / PB adsorbent is as follows: (1) Add pseudoboehmite to concentrated nitric acid for peptization treatment to obtain pseudoboehmite gel; the concentration of H + in the concentrated nitric acid is 68% by mass fraction, and the solid-liquid ratio of pseudoboehmite to acid solution is g:mL = 10:1; (2) Add calcium salt (CaCl2) to the pseudoboehmite gel and stir to dissolve to obtain a calcium-doped pseudoboehmite gel substrate; the molar ratio of Ca in the calcium salt (CaCl2) to Al in the pseudoboehmite is 1:4; (3) Add the organic carbon framework carboxymethyl cellulose to the calcium-doped pseudoboehmite gel substrate and stir evenly to obtain a flocculent gel. The flocculent gel is dried at 90 °C and pulverized to obtain a carrier powder; the mass ratio of the pseudoboehmite to the organic carbon framework carboxymethyl cellulose is 5:1; (4)The carrier powder was added to a cuprammonium solution with a concentration of mol / L and impregnated for 25 min, then dried at 80 °C and ground to obtain the Cu-Ca / PB adsorbent; the molar ratio of Cu in the cuprammonium solution to Al in pseudo-boehmite was 1:4; 4 g of the Cu-Ca / PB adsorbent was added to 100 mL of the purified aluminum ash residue water-leaching solution (pH value was 5, containing S with a concentration of 28.76 mg / L) 2- and adsorbed for 120 min. Samples were taken and measured for the concentration of S in the sodium aluminate solution at 10 min, 20 min, 40 min, 60 min, 90 min, and 120 min respectively. 2- The concentrations were 15.89 mg / L, 11.43 mg / L, 11.19 mg / L, 11.17 mg / L, 11.17 mg / L, and 11.16 mg / L respectively; Therefore, the adsorption removal rate of S in the purified aluminum ash residue water-leaching solution by the Cu-Ca / PB adsorbent in this example reached 61.242% in 120 min. 2-

[0020] Example 5: The Cu-Ca / PB adsorbent in this example was the same as that in Example 1; 4 g of the Cu-Ca / PB adsorbent was respectively added to 100 mL of the purified aluminum ash residue water-leaching solution (pH values were 4, 5, 6, 7, 8, 9 respectively, containing S with a concentration of 28.76 mg / L) 2- and adsorbed for 120 min. Samples were taken and measured for the concentration of S in the purified aluminum ash residue water-leaching solution. 2- When the pH values of the purified aluminum ash residue water-leaching solution were 4, 5, 6, 7, 8, 9 respectively, the concentrations of S in the purified aluminum ash residue water-leaching solution were 12.15 mg / L, 11.17 mg / L, 2.66 mg / L, 0.51 mg / L, 0.81 mg / L, and 1.59 mg / L respectively, and the removal rates of F 2- were 57.800%, 61.312%, 90.797%, 98.226%, 97.172%, and 94.471% respectively. -

[0021] Example 6: The Cu-Ca / PB adsorbent in this example was the same as that in Example 2; 2 g, 3 g, 4 g, 5 g, and 6 g of the Cu-Ca / PB adsorbent were respectively added to 100 mL of the purified aluminum ash residue water-leaching solution (pH value was 6, containing S with a concentration of 28.76 mg / L) 2- and adsorbed for 120 min. Samples were taken and measured for the concentration of S in the purified aluminum ash residue water-leaching solution; when 2 g, 3 g, 4 g, 5 g, and 6 g of the Cu-Ca / PB adsorbent were added respectively, the concentration of S in the purified aluminum ash residue water-leaching solution 2- ​2- The concentrations are 3.07 mg / L, 3.05 mg / L, 0.5 mg / L, 0.92 mg / L, and 1.09 mg / L respectively, and F - The removal rates are 89.325%, 89.395%, 98.261%, 96.801%, and 96.210% respectively.

[0022] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. A Cu-Ca / PB adsorbent, characterized in that: The base of the adsorbent is pseudo-boehmite gel, the organic carbon skeleton is carboxymethyl cellulose, the base pseudo-boehmite gel is doped with calcium ions, and the surface of the adsorbent is loaded with copper ions; The preparation method of the Cu-Ca / PB adsorbent comprises the following specific steps: (1) adding pseudo-boehmite into an acid solution for peptization treatment to obtain pseudo-boehmite gel; (2) adding calcium salt to the pseudo-boehmite gel, stirring and dissolving to obtain a calcium-doped pseudo-boehmite gel substrate; (3) adding the organic carbon skeleton carboxymethyl cellulose to the calcium-doped pseudo-boehmite gel base and stirring evenly to obtain a flocculent gel, and drying and crushing the flocculent gel to obtain a carrier powder; (4) The carrier powder is added to a copper ammonia solution and immersed for 10 to 30 minutes. After drying, the powder is ground to obtain a Cu-Ca / PB adsorbent.

2. The Cu-Ca / PB adsorbent according to claim 1, characterized in that: The acid solution in step (1) is one or more of concentrated hydrochloric acid, concentrated nitric acid, concentrated sulfuric acid, perchloric acid, and hydroiodic acid.

3. The Cu-Ca / PB adsorbent according to claim 2, characterized in that: Step (1) H in the acid solution + The concentration is 12~16mol / L, and the solid-liquid ratio of pseudo-boehmite to acid solution is 6~10:1 g:mL.

4. The Cu-Ca / PB adsorbent according to claim 1, characterized in that: The calcium salt in step (2) is one or more of CaCl2, CaO, Ca(OH)2, Ca(NO3)3, calcium dihydrogen phosphate, calcium bicarbonate, and calcium hydrogen sulfate, and the molar ratio of Ca in the calcium salt to Al in the pseudo-boehmite is 1:1-3.

5. The Cu-Ca / PB adsorbent according to claim 1, characterized in that: In step (3), the mass ratio of pseudo-boehmite to organic carbon skeleton carboxymethyl cellulose is 1-5:

1.

6. The Cu-Ca / PB adsorbent according to claim 1, characterized in that: In step (4), the molar ratio of Cu in the copper ammonia solution to Al in the pseudo-boehmite is 1:1-3.

7. Use of the Cu-Ca / PB adsorbent according to any one of claims 1 to 6 in removing fluoride and divalent sulfide in the production process of aluminum industry.