| 摘要 |
PROBLEM TO BE SOLVED: To develop a process for separately recovering phosphorus and aluminum from various kinds of incineration ash, which are formed from solid waste, sewage sludge, etc., and each of which contains large amounts of phosphorus, aluminum, etc., and to effectively utilize the incineration ash. SOLUTION: This process comprises: adding sulfuric acid to various kinds of incineration ash to elute phosphorus and aluminum; then adding various alkalis such as sodium bicarbonate and/or calcium carbonate, to the resulting eluate to recover phosphorus as aluminum phosphate; again adding sulfuric acid to the recovered aluminum phosphate to dissolve the aluminum phosphate into the sulfuric acid; adding ammonium sulfate to the sulfuric acid solution and cooling the resulting solution, to crystallize and separate the aluminum component as aluminum ammonium sulfate from the solution; thereafter, adding alkalis such as sodium hydroxide, sodium carbonate and/or aqueous ammonia, to the remaining solution to adjust the pH of the solution to 4, to remove residual aluminum as aluminum phosphate; further adding alkalis such as sodium hydroxide, sodium carbonate and/or aqueous ammonia to the resulting solution, to adjust the pH of the solution to 8-9, to remove heavy metals, concurrently to convert the remaining phosphoric acid component into various phosphates and to crystallize, separate and recover the phosphates.
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