颗粒化坡缕石表征及对Pb^(2+)的吸附特性

Characterization of granulated palygorskite and its adsorption characteristics for Pb^(2+) removal

坡缕石黏土进行简单提纯后,和海藻酸钠、纯水充分混合(物料比为坡缕石∶海藻酸钠∶水=100 g∶9 g∶77 m L),并在潮湿密闭环境下浸润24 h,制成粒径5 mm颗粒。(105±2)℃干燥后,焙烧2 h,制备颗粒状坡缕石吸附剂,采用XRD、BET进行表征,通过静态吸附实验探讨了pH值、Pb^(2+)初始浓度、反应时间和反应温度对吸附的影响,确立了颗粒化吸附剂对Pb^(2+)的吸附动力学和吸附等温线。结果表明,在颗粒化后,坡缕石黏土主要XRD衍射峰得以保留;600℃下烧结,使比表面积降低,而孔容积增大。随着pH值增大,坡缕石颗粒吸附剂对Pb^(2+)的吸附量增加;随着初始浓度的增加,颗粒吸附剂对Pb^(2+)的吸附去除率逐渐降低,平衡吸附量则逐渐上升。当pH值为5.0,Pb^(2+)初始浓度2 500 mg/L时,平衡吸附量达59.85 mg/g。吸附动力学符合颗粒内扩散模型。颗粒化坡缕石吸附剂对Pb^(2+)的吸附符合Langmuir吸附等温式,属于吸热反应。

Palygorskite clay for simple purification,and sodium alginate,purewater intensive mixing （material ratio of palygorskite∶sodium alginate∶water=100 g∶9 g∶77 mL）;then,the particle of 5 mm was prepared in the wet airtight environment 24 h;Finally,after drying （105±2） ℃ and calcination 2 h,the granulated adsorbent was made.Granulated palygorskite adsorbent was characterized by XRD analysis and BET analysis.The effects of pH,initial concentration of Pb2＋,reaction time and reaction temperature were investigated by bath reactor experiments.And the kinetics and equilibrium isotherms of Pb2＋removal by granulated adsorbent were also established.Results indicated that the main diffraction peaks of palygorskite clay remained.The specific surface areas decreased obviously after calcinated under 600 ℃,while pore volume increased.With the increase of pH value,the adsorbance of Pb2＋ by granulated palygorskite adsorbent increased.With the increase of initial concentration of Pb2＋,the removal ratio decreased,and the adsorbance increased.The adsorbance was about 59.85 mg/g when pH was 5.0 and initial concentration of Pb2＋ was 2 500 mg/L.The kinetic processes of Pb2＋ removal could be described by intra-particle diffusion model.Langmuir model fitted equilibrium isotherms of Pb2＋ removal which was an endothermic process.