PREPARATION METHOD CHROMIC ACID USING CR6+ CONTAINING WASTE SOLUTION

摘要

PURPOSE: A method for preparing chromic acid more economically is provided, which uses the Cr¬6+ containing waster solution. CONSTITUTION: A method comprises the steps of filtering the Cr¬6+ containing waste solution to remove insoluble impurities; adding an oxidizing agent to the solution to oxidize Fe¬2+ contained in the waste solution to Fe¬3+; adding NaOH to the solution to control the pH to be 3-5, thereby to generate the sludge of Fe3+; filtering the solution to remove the sludge; adding H2SO4 to control the pH to be 1-2; adding a reducing agent to the solution to reduce Cr¬6+ contained in the solution to Cr¬3+; adding NaOH to the solution to control the pH to be 7-11, thereby to generate Cr(OH)3 sludge; washing, filtering and drying the Cr(OH)3 sludge; and adding the equal equivalent of oxygenated water to the Cr(OH)3 sludge based on the amount of Cr(OH)3. Preferably the oxidizing agent is hydrogen peroxide or air, and the reducing agent is NaHSO3, Na2S2O5 or SO2 gas.