ELECTRODIALYTIC METALS REMOVAL AND FORMATION OF WATER SOLUBLE PHOSPHATE FROM ACIDIC EXTRACT OF SEWAGE SLUDGE INCINERATED ASH

Abstract

 Firstly, the metals removal from acidic extract of sewage sludge incinerated ash was investigated using an electrodialyzer. Through the elecrtodialysis at a pH of 0.5 during 10 hours, about 90% of Al, Zn and Cu in the extract were removed, while 60% of P was retained in the extract. Secondly, the extract after the electrodialysis was neutralized with 28% ammonia water and was dried at 45°C. The water soluble phosphorus content of the dried sample was about 90%. The composition of the dried sample met the quality criteria required for the chemical fertilizer. The analyses of the dried powder sample with the XRD and FESEM-EDX showed that the dried sample would be mainly composed of (NH₄)₂SO₄, (NH₄)H₂PO₄ and P₂O₅. These findings suggest that the dried sample recovered from acidic extract of the sewage sludge ash could be recycled as a raw material of fast acting fertilizers.