污泥基生物炭粒制备及其对Cd^(2+)的吸附效果研究

Study on the Preparation of Sludge-based Biochar Pellets and Their Adsorption Effect on Cd^(2+)

制备生物炭是污泥处置和资源化的重要途经之一。本文将污水处理厂剩余污泥制成不同粒径的污泥球粒后,分别在300、500、700℃温度条件下热解制备污泥基生物炭粒(SSBP),结合SEM、BET和FTIR等表征分析,研究其对Cd^(2+)的吸附特征及效果,同时考察了SSBP对环境的影响。研究结果表明,SSBP具有丰富的孔隙结构和官能团,属于介孔材料,且在热解温度为500℃、粒径为2 mm(BP500-2)时吸附性能最优。SSBP对Cd^(2+)的吸附动力学符合拟二级动力学方程和二阶段的颗粒内扩散方程。吸附等温线符合Langmuir模型,表明BP500-2对Cd^(2+)的吸附中,既有单分子层吸附,又有包括物理、化学吸附在内的复杂多分子吸附。SSBP的TCLP浸出值(0.68~1 mg/kg)低于SS浸出值(1.22 mg/kg),且均低于IBI及EBF提出的生物炭Cd限值(1.4~39 mg/kg,1~1.5 mg/kg),说明污泥热解显著降低了其重金属浸出,污泥基生物炭粒具有较低的环境风险。

Biochar preparation is one of the important ways of sludge disposal and resource recovery.Sludge based biochar particles(SSBP)were prepared by pyrolysis at 300,500 and 700℃,respectively.The adsorption characteristics and effects of SSBP on Cd^(2+)were studied by SEM,BET and FTIR,and the impact of SSBP on the environment was also investigated.The results show that SSBP is a mesoporous material with abundant lamellar pore structure and functional groups,and has the best adsorption performance at pyrolysis temperature of 500℃and particle size of 2 mm(BP500-2).The adsorption kinetics of Cd^(2+)by SSBP accords with the pseudo-second-order kinetic equation and the two-stage intra-particle diffusion equation.The adsorption isotherm conforms to Langmuir model,indicating that the adsorption of Cd^(2+)by BP500-2 involves both monolayer adsorption and complex multi-molecule adsorption including physical and chemical adsorption.The TCLP leaching value of SSBP(0.68~1 mg/kg)was lower than the SS leaching value(1.22 mg/kg),and both were lower than the Cd limit of biochar proposed by IBI and EBF(1.4~39 mg/kg,1~1.5 mg/kg),indicating that sludge pyrolysis significantly reduced the leaching of heavy metals.Sludge-based biochar particles have low environmental risk.