Detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues

Patent metadata

Field	Value
Publication number	US-10619225-B2
Application number	US-201716074155-A
Country	US
Kind code	B2
Filing date	Jun 13, 2017
Priority date	Jun 30, 2016
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

A method for extracting and recycling chromium from hexavalent chromium-containing residues includes the following steps: 1) adding water to the hexavalent chromium-containing residues and mixing uniformly; 2) adding sodium sulfate, sodium chlorate and sulfuric acid to a solution obtained in step 1) and stirring sufficiently to obtain a mixed liquid; 3) treating the mixed liquid by a hydrothermal method or direct heating; 4) after the heating treatment, naturally cooling a solid-liquid mixture to room temperature for holding; 5) separating solid residues and a chromium-containing supernatant, and washing filtered residues with water and then drying; 6) precipitating the supernatant and the water used for washing the filtered residues with a precipitant CaCl2, then centrifugally washing, dewatering and drying the precipitates; and 7) recycling a chromium-containing solution for returning to a work section, or for a treatment of recycling chromium.

First claim

What is claimed:

1. A detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues, a main component of the residues is particles of calcium sulfate dihydrate which adsorb sodium chromate, characterized in that, the detoxification treatment method comprises steps as follows:
1) adding water to the hexavalent chromium-containing residues and mixing uniformly, forming a solution;
2) adding mineralizers to the solution obtained in step 1) and stirring sufficiently to obtain a mixed liquid; and the mineralizers are sodium sulfate, sodium chlorate and sulfuric acid;
3) treating the mixed liquid obtained in step 2) by a hydrothermal method or direct heating;
4) naturally cooling a solid-liquid mixture obtained in step 3) to room temperature for holding, thereby growing solid calcium sulfate crystals in the residues;
5) separating solid residues and a chromium-containing supernatant, and washing the solid residues with water and then drying;
6) precipitating the supernatant and the water used for washing the solid residues with a precipitant CaCl 2 , then centrifugally washing, dewatering and drying the precipitates; and
7) recycling a chromium-containing solution obtained in step 6) for a treatment of recycling chromium; the treatment of recycling chromium has specific steps as follows: adding a reductant to the chromium-containing solution, with hexavalent chromium in the solution being reduced to trivalent chromium, then adding a precipitant NaOH to generate precipitate of Cr(OH) 3 , and finally calcining the precipitate of Cr(OH) 3 into Cr 2 O 3 ; and the reductant is sodium sulfide or sodium bisulfite.

2. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein a w/w solid-to-liquid ratio after water is added to the hexavalent chromium-containing residues in step 1) is 1:0.5-1:10.

3. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein sodium sulfate in step 2) in the mixed liquid has a concentration of 0.1 mol/L-1 mol/L.

4. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein sodium chlorate in step 2) in the mixed liquid has a concentration of 0.1 mol/L-1 mol/L.

5. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein the mixed liquid in step 2) has a pH value of 1-5.

6. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein a temperature of the hydrothermal method or direct heating in step 3) is controlled between 50° C. and 200° C.

7. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein a time for treating the mixed liquid in step 3) is 2 to 10 hours.

8. The detoxification treatment method for extracting and recycling chromium from hexavalent chromium-containing residues according to claim 1 , wherein a time for naturally cooling the solid-liquid mixture in step 4) is 0.5 to 48 hours.

Assignees

• Univ South China Tech
• South Carolina Univ Of Technology

Inventors

• Lin Zhang
• Liu Weizhen
• Liu Xueming
• Rong Wencong

Classifications

• C22B34/32 Primary

  Obtaining chromium · CPC title

• C01G37/02

  Oxides or hydrates thereof · CPC title

• C22B7/006

  Wet processes · CPC title

• C22B7/007 Primary

  by acid leaching · CPC title

• Y02P10/234

  Cross-Sectional Technologies · mapped topic