Partial replacement of rock phosphate by sewage sludge ash ...
Partial amounts of rock phosphate and sewage sludge ash were mixed and digested with concentrated sulfuric acid (95%) related to the P concentration of the original substrates as indicated in Tab. 1, resulting in six superphosphate preparations [SP(0–100)]. SP(0) corresponds to a superphosphate preparation made solely based on RP with 0% SSA ...