摘要
以城市污水污泥为原料,探究二氧化碳对污泥热解过程磷迁移转化的影响.通过磷连续分级提取法(SMT)研究了磷在污泥热解产物中的赋存形态,通过X射线衍射分析(XRD)测定了污泥热解产物内部的晶体结构,通过磷生物有效性测试评价了污泥热解产物中磷的生物有效性.SMT结果表明,在 700℃以上时反应气氛发挥重要作用,CO2 气氛更有利于固相产物中磷元素的富集和固存,其能促进有机磷(OP)向无机磷(IP)的转化以及非磷灰石无机磷(NAIP)向磷灰石无机磷(AP)的转化,并抑制IP的释放.XRD分析发现,污泥中 NAIP的主要存在形式为磷酸铝盐和磷酸铁盐,高温时CO2 气氛下的磷酸钙和镁盐含量高于N2 气氛.磷生物有效性测试结果显示,CO2 气氛对磷的生物有效性具有更显著的提升作用,在 900℃和CO2 气氛下,磷表现出最佳的生物有效性,此时在2%柠檬酸(CA)溶液中的磷溶解度达到最大值80.77 mg/g,对应AP相对含量达到峰值23.31 mg/g.
Abstract
The effect of carbon dioxide on phosphorus migration and transformation during sludge pyrolysis was investigated using municipal sewage sludge as raw material.The phosphorus accumulation in the sludge pyrolysis products was investigated by continuous graded phosphorus extraction(SMT),the crystal structure of the sludge pyrolysis products was determined by X-ray diffraction(XRD),and the bioavail-ability of phosphorus in the sludge pyrolysis products was evaluated by phosphorus bioavailability test.The results of the SMT showed that the reaction atmosphere played an important role above 700℃,and the at-mosphere of CO2 was more favorable to the enrichment and sequestration of phosphorus in the solid-phase products,which could promote the conversion of organic phosphorus(OP)to inorganic phosphorus(inor-ganic).XRD analysis showed that the main forms of NAIP in sludge were aluminum and iron phosphate,and the content of calcium and magnesium phosphate in CO2 atmosphere was higher than that in N2 at-mosphere at high temperature.The results of phosphorus bioavailability test showed that CO2 atmosphere had a more significant enhancement effect on the bioavailability of phosphorus,which showed the best bio-availability at 900℃and CO2 atmosphere,when the phosphorus solubility in 2%citric acid(CA)solu-tion reached a maximum of 80.77 mg/g,corresponding to the peak relative AP content of 23.31 mg/g.
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