分步沉淀去除磷酸铁生产废水中的磷酸根和硫酸根

采用分步化学沉淀法分别脱除并回收磷酸铁生产废水中的高浓度磷酸根和硫酸根。实验结果表明:在以n(Fe~(3+))∶n(PO_4~(3-))=1.0的比例加入硫酸铁、反应时间为40 min、反应温度为25℃、废水初始p H为8.17、反应30 min时二次调节废水p H至5.50的条件下,磷酸根去除率可达98%以上,所得沉淀中Fe和P的质量分数分别为36.77%和18.81%,成分简单,回收价值高;采用氢氧化钙作为沉淀剂,在n(Ca~(2+))∶n(SO_4~(2-))=1.0的条件下可将废水中硫酸根质量浓度由78.62 g/L降至2.16 g/L,硫酸根去除率为97.3%,硫酸钙回收量为120.2 g/L;最终出水的磷酸根质量浓度小于0.5 mg/L,满足GB 8978—1996《污水综合排放标准》的一级标准。

Removal of phosphate radical and sulfate radical from ferric phosphate production wastewater by stepwise precipitation

The high concentration PO₄^3- and SO₄^2- in ferric phosphate production wastewater were removed and recovered by stepwise chemical precipitation process. The experimental results showed that：Under the conditions of adding ferric sulfate with n（Fe³⁺）∶n（PO₄^3-）=1.0,reaction time 40 min,reaction temperature 25 ℃,initial wastewater pH 8.17 and second adjustment pH 5.50 at 30 min,the PO₄^3- removal rate reached above 98%,and the mass fraction of Fe and P in the precipitate was 36.77% and 18.81% respectively,which indicated that the composition of the precipitate was simple and its recycling value was enormous;Under the conditions of using calcium hydroxide as the precipitant and n（Ca²⁺）∶n（SO₄^2-）=1.0,the mass concentration of SO₄^2- in the wastewater was reduced from 78.62 g/L to 2.16 g/L,the SO₄^2- removal rate was 97.3%,and the recovery of calcium sulfate was 120.2 g/L;The PO₄^3- mass concentration of the final effluent was less than 0.5 mg/L,which met the first grade standard of GB 8978-1996.