生物炭对磷石膏中磷的固化作用

Stabilization of phosphorus in phosphogypsum by biochar

磷石膏中的磷在雨水淋滤作用下浸出,将污染堆场附近水体。本研究采用生物炭固化磷石膏中的磷,以减少其对周遭水体的污染。主要通过模拟固化实验和对照浸出实验,分析生物炭用量、反应时间和温度、初始pH值对固化效果的影响,通过XRD、SEM-EDS分析固化后的生成物。实验结果显示,在生物炭用量为25 mg时,单位固化量达到最大值13.20 mg/g;在反应温度T=293 K、初始pH=7条件下,反应平衡时间72 h时浸出液的磷平衡浓度C_(e)=1.40 mg/L;温度提升有助于提高生物炭的固化效果,当T=308 K时,浸出液的磷平衡浓度C_(e)=0.167 mg/L;碱性条件有利于固化反应持续进行,在pH=11条件下,浸出液的磷平衡浓度C_(e)=0.153 mg/L。实验结果表明生物炭对磷石膏中的磷具有明显的固化效果。磷石膏中的二水硫酸钙溶解后,Ca^(2+)与表面带负电的生物炭结合,在生物炭显微结构的凹陷处,化学吸附溶液中的磷酸根生成了絮状、团簇状的羟基磷灰石(HAP)沉淀,从而使浸出磷得到有效控制。

The phosphorus in phosphogypsum leaches out under the eluviation of rainwater and will pollute the wa⁃ters near the storage site.In this study,biochar was used to solidify the phosphorus in phosphogypsum to reduce its impact on the surrounding waters.The experiment mainly included simulating solidification experiment and leaching out experiment,analyzed the effects of biochar dosage,reaction time and temperature,initial pH value on solidifi⁃cation effect.The products after solidification were analyzed by XRD and SEM⁃EDS.The results showed that the biochar had an obvious solidification effect on phosphorus in phosphogypsum,the maximum solidifying capacity per unit reached 13.20 mg/g;under the condition of T=293 K and initial pH=7,the reaction equilibrium time was 72 h,and the equilibrium phosphorus concentration of the leaching solution C_(e)=1.40 mg/L;the temperature increase was helpful to improve the solidifying effect of biochar,when the reaction temperature T=308 K,the equi⁃librium phosphorus concentration of the leaching solution C_(e)=0.167 mg/L;the alkaline condition was conducive to the continuous solidification reaction,under the condition of pH=11,the equilibrium phosphorus concentration of the leaching solution C_(e)=0.153 mg/L.The CaSO_(4)·2H_(2)O in phosphogypsum was dissolved,Ca^(2+)was combined with the surface of biochar which is electronegative,chemical adsorbing phosphate radical in the solution,formed floccu⁃lent,clustered hydroxyapatite(HAP),the leaching phosphorus can be effectively controlled.