Abstract:

The purpose was to efficiently separate and utilize sulfur，magnesium and phosphorus from waste phosphorus sludge produced in the production of industrial monoammonium phosphate（MAP），while removing impurity ions.Magnesium ammonium sulfate and ammonium phosphate sulfate were prepared by acid leaching，defluorination，cooling crystallization，impurity removal and ammoniation of waste phosphorus sludge.The research showed that when the acid leach solution was defluoridated and the pH was adjusted to 0.85 by adding ammonia，the yield of crystallized magnesium ammonium sulphate by cooling could reach 62%.When the pH was adjusted to 2.6 by adding ammonia to the filtrate after cooling crystallized magnesium ammonium sulphate，the mass fraction of impurities Fe₂O₃，Al₂O₃ and MgO in the filtrate was reduced to 0.08%，0.58% and 0.93% respectively.When ammonia was introduced into the filtrate after the removal of impurities and pH was adjusted to 9，sulfur-based ammonium phosphate was prepared after concentration and drying，and sulfur-based ammonium phosphate′s total nitrogen content was ≥16%，effective phosphorus content was ≥26%，total sulfur content was ≥11%，water-soluble phosphorus percentage of effective phosphorus was ≥75% or higher.In this way，the efficient utilization of waste phosphorus sludge was realized，which was more green and environmentally friendly.

Key words: industrial grade monoammonium phosphate, phosphate sludge, magnesium ammonium sulfate, sulfate-based ammonium phosphate