GRADED CRYSTALLIZATION AND PHOSPHORUS RECOVERY BY FORM OF STRUVITE FROM PHOSPHOGYPSUM LEACHATE
Considering the non-renewable and indispensable nature of phosphorus resources,the treatment and recovery of phosphorus from phosphogypsum leachate based on the crystallization method of bird droppings has important environmental and economic significance.This paper systematically studied the feasibility of recovering phosphorus in the phosphogypsum leachate from a fertilizer company in Hubei Province and the crystallization optimization.The results showed that the main reaction parameters posed a limited effect on obtaining a higher phosphorus recovery efficiency in a single reaction process,and the maximum phosphorus recovery efficiency was only 67.8％.The latter response surface design experimental results also confirmed that after a certain stage,the increase in pH,n(Mg)/n(P),and n(N)/n(P)did not significantly enhance the phosphorus recovery efficiency.Considering the influence of various factors on phosphorus recovery,the optimal condition parameters were determined as follows:pH=8.6,n(Mg)/n(P)=1.6,n(N)/n(P)=1.Finally,a graded crystallization method was adopted,and after three crystallization cycles,phosphorus recovery efficiency reached 97.9％.After characterizing the products in the phosphorus recovery stage through EPMA,XRD and Minteq modeling analysis,the products were mainly struvite with a small amount of calcium phosphate,and the heavy metal content in struvite was extremely low,ensuring its subsequent application safely in agricultural as a potential fertilizer.
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