Selective acidic elution of Ca from sewage sludge ash for phosphorus recovery under pH control

Phosphorus (P) is recovered from sewage sludge ash (SSA) by selective HCl elution of Ca. Leaching and rearrangement of P were very fast and the amounts of leaching and recombination of P depend strongly on pH. pH control at 4.0 obtained selective elution ratio (Ca(%)/P(%)) of 20 by recombination of P to Al in SSA residue while it was 5.6 without pH control. XRD and element mass balance showed that Ca-P in the raw SSA was converted to Al-P complex during the acid pretreatment. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.