干硝化好氧颗粒污泥对Pb2+的吸附特性与机理

硝化好氧颗粒污泥具有孔隙率高、比表面积大、沉淀性能好等特征,为考察其在重金属废水处理中的应用效果,以干硝化好氧颗粒污泥为吸附剂,研究其对水溶液中Pb2+的吸附特性及影响因素. 结果表明,Langmuir等温吸附方程可以很好地拟合干硝化好氧颗粒污泥对Pb2+的吸附过程,说明Pb2+在干硝化好氧颗粒上的吸附属于单分子层吸附,25 ℃下的饱和吸附容量为79.58 mg/g,R2为0.990 1. 吸附动力学分析结果表明,该动态吸附平衡过程遵循伪二级动力学方程,废水初始ρ(Pb2+)分别为20、40、60 mg/L时,R2分别为1.000 0、1.000 0、0.999 9,同时颗粒内扩散方程RC(关联系数,分别为30.706%、28.019%、24.188%)均低于50%,表明颗粒内扩散是控制Pb2+吸附速率的关键步骤. 红外扫描分析(FTIR)结果表明,吸附过程中Pb2+主要与干硝化好氧颗粒污泥表面的O—H、N—H、CO、CC、C—OH、C—O—C等基团发生了作用. 吸附前、后的pH_ZCP(零点电荷)由2.5升至3.1,说明Pb2+在干硝化好氧颗粒污泥上的吸附属于专性吸附,即发生了紧密层吸附. 研究显示,干硝化好氧颗粒污泥对Pb2+具有较好的吸附效果,吸附机制主要包括无机微沉淀、表面络合、内层络合反应和离子交换等. 

Dried Biomass from Nitrified Aerobic Granular Sludge for Pb2+ Adsorption:Behaviors and Mechanisms

Because nitrified aerobic granular sludge exhibits high porosity, large surface area and decent separation capacity, aerobic granular sludge can be utilized as a biological adsorbent. In this study, nitrified aerobic granular sludge was used to remove Pb2+ from aqueous solution. Different initial pH values, initial Pb2+ concentrations, adsorbent doses and temperatures on Pb2+ adsorption were evaluated as well. Three types of adsorption isotherms (i.e., by Langmuir, Freundlich and Redlich-Peterson models) were investigated. The results indicated that the equilibrium was well described by the Langmuir isotherm, predicting that the adsorption of Pb2+ on nitrified aerobic granules was a monolayer adsorption. The R2 was 0.9901, and the maximum adsorption capacity was 79.58 mg/g at 25 ℃. Moreover, the equilibrium kinetic adsorption data were fitted to the pseudo-second-order kinetic equation with R2 values of 1.0000,1.0000 and 0.9999 respectively. The relation coefficients (RC), which were 30.706%, 28.019% and 24.188%, were all under 50%, showing that the sorption of Pb2+was controlled primarily by intraparticle diffusion. Fourier transform infrared spectroscopy (FTIR) results indicated that the active groups including O—H, N—H, CO, CC, C—OH and C—O—C were involved in Pb2+ adsorption. Zeta potential analysis and pH_ZCP rose from 2.5 to 3.1, demonstrating that inner-sphere adsorption happened for Pb2+ adsorption on nitrified aerobic granules. The nitrified aerobic particles were well fitted by the good adsorption function on Pb2+; the adsorption mechanisms mainly included inorganic micro precipitation, surface complexation, inner-sphere complexation reaction and ion exchange.