玉米秸秆生物质炭对铅的吸附动力学特征

摘要

选用玉米秸秆为原材料,采用限氧裂解法制备生物质炭.研究了其对Pb2+的吸附动力学特征,并探讨了不同温度、pH值、离子强度对吸附效果的影响.结果表明,生物质炭对Pb2+的吸附过程均表现一致,0~4 h内为快速吸附阶段,吸附速率较快,此后呈现为慢速吸附阶段,直至30 h基本达到吸附平衡.随着温度(25~55 ℃)和pH值(3~6)的升高,生物质炭对Pb2+的饱和吸附量增加.而随着离子强度(CaCl2 0.005~0.05 mol/L)的增大,生物质炭对Pb2+的饱和吸附量降低.拉格朗日准二级动力学方程能更好的拟合生物质炭对Pb2+的吸附过程.说明该吸附过程为化学吸附.且内扩散模型对吸附初始阶段的数据拟合效果也较好,这表明Pb2+在生物质炭上吸附速率同时受颗粒内扩散过程和外扩散过程的控制.%The biochar was prepared by pyrolyzing corn straw under a limited oxygen condition.The experiments were performed to explore the adsorption kinetic characteristics of Pb2+ on the biochar and investigate the effect of temperature,pH and ionic strength on this adsorption.The result showed that the sorption process of Pb2+ on the biochar was consistent.The rapid sorption step was in 0~4 h,and the adsorption rate is fast.After that,it appeared as a slow adsorption step.The reaction approached equilibrium at about 30 h.With the increase of temperature (25~55 ℃) and pH (3~6),the saturated adsorption capacities of Pb2+ on biochar was increased.And with the increase of ionic strength (CaCl2 0.005~0.05 mol/L),the saturated adsorption capacity of Pb2+ on biochar was decreased.Lagrangain quasi-second-order kinetics equation was described well for the adsorption of Pb2+ onto the biochar.It showed that the adsorption process dominated by chemical adsorption.The adsorption was also fitted by intraparticle diffusion model.The adsorption rate was not only controlled by the intraparticle diffusion,but also controlled by the extraparticle diffusion.