氧化钙对污泥炭重金属稳定性及其吸附性能的影响

Effect of CaO on heavy metals stability and adsorption properties of sludge⁃derived biochar

鉴于CaO对生物质的热解产气、焦油重整具有催化作用,并可显著提升生物炭的吸附性能,将CaO与市政污泥以1∶10的质量比混合共热解,制备改性污泥炭(BC-Ca)。研究了CaO对污泥炭特性及重金属(Pb、Zn、Cu、Cr、Mn)形态分布的影响,采用风险评价编码法(RAC)评价污泥炭的生态风险,并采用静态吸附实验考察改性污泥炭对Cr(Ⅵ)的吸附效果。结果表明:BC-Ca中Zn、Pb、Cr、Mn和Cu处于残渣态(F4)的比例较未改性污泥炭(BC)分别增加11.76%、13.03%、26.96%、5.55%和2.11%,且均为RAC低风险;BC-Ca的比表面积较BC增大122.99%,孔隙结构得到改善;BC-Ca对Cr(Ⅵ)的吸附过程符合Langmuir等温吸附模型和拟二级动力学模型,吸附容量随着温度的升高而增大,吸附速率主要由化学吸附机理控制;BC-Ca对Cr(Ⅵ)的最大吸附容量较BC提高51.13%,去除率显著提高。

In view of the catalytic effect of CaO on gas production and tar reforming during biomass pyrolysis process,which can significantly improve the adsorption performance of biochar,the modified sludge derived biochar(BC-Ca)was prepared by copyrolysis of CaO and sewage sludge at a mass ratio of 1∶10.The effect of CaO on the characteristics of the sludgederived biochar,as well as the speciation distribution of heavy metals(Pb,Zn,Cu,Cr,Mn)were investigated.The ecological risk of the biochar was assessed based on the risk assessment code(RAC).The adsorption properties of the modified sludge derived biochar on Cr(Ⅵ)was evaluated by the static adsorption experiments.The results showed that compared with unmodified biochar(BC),the fraction of residual state(F4)of Zn,Pb,Cr,Mn,and Cu in BC-Ca were increased by 11.76%,13.03%,26.96%,5.55%,and 2.11%,respectively,which were all in a low risk condition according to the RAC standard.Compared with BC,the specific surface area of BC-Ca was increased by 122.99%,indicating that the microstructure performance of BC-Ca was improved.The adsorption behavior of BC-Ca for Cr(Ⅵ)was described by the Langmuir model and pseudosecond order dynamic sorption model,indicating that the adsorption capacity of BC-Ca was increased with increasing temperature,and the adsorption rate was mainly controlled by chemical adsorption mechanism.The maximum adsorption capacity of BC-Ca for Cr(Ⅵ)was improved by 51.13%than that of BC,showing outstanding removal effect on Cr(Ⅵ).