The ionic rare earth separation process generates a substantial amount of ammonium-containing wastewater.This wastewater contains high concentrations of impurities such as Ca and Mg,which can easily cause equipment scaling and significantly impair the normal operation of water treatment equipment.Based on this,this study employed the P507 extraction method to remove impurity elements from wastewater,the effects of phase ratio(O/A),ammonium concentration in ammonia-saponified organic phase,and extraction stage on the removal efficiency of three major impurity elements(Ca,Mg and Zn)were systematically investigated.Additionally,the Ca removal efficiency and treatment cost in practical production were analyzed.The experimental results indicate that under the conditions of P507 extractant concentration of 1.50 mol/L,O/A=3∶1,ammonium concentration in ammonia-saponified organic phase of 0.15 mol/L,extraction time of 5 min,stripping time of 10 min,and continuous three-stage countercurrent extraction,the concentrations of Ca,Zn and Mg in wastewater decrease to 1.42 mg/L,1.00 mg/L and 3.31 mg/L,respectively,with corresponding removal rates of 100%、97.49%and 99.67%,demonstrating a remarkably effective removal efficiency.In the practical production,under the process conditions of P507 extractant concentration of 1.5 mol/L,O/A=2∶1,ammonium concentration in ammonia-saponified organic phase not exceeding 0.10 mol/L,and continuous seven-stage countercurrent extraction,the P507 extraction method exhibits excellent Ca removal efficiency from the wastewater with a removal rate of over 90%,and the wastewater treatment cost is 16.75 yuan/t,which is superior to both the removal efficiency and treatment cost of the chemical precipitation method.This fully confirms the effectiveness and economy of P507 extraction method for treating high-calcium ammonium-containing wastewater generated from rare earth separation.
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