二硫化钼-水滑石复合材料对水中Cu(Ⅱ)、Pb(Ⅱ)和Cd(Ⅱ)的吸附机制

Adsorption mechanisms of MoS_(2)-LDH composite for aqueous Cu(Ⅱ),Pb(Ⅱ)and Cd(Ⅱ)

二维层状纳米材料可以有效去除水中的重金属,而吸附机制一直是研究难点和热点.为进一步提升材料性能,明确吸附反应机制,以典型的水滑石和二硫化钼为原料,采用共沉淀法制备镁铝水滑石,然后利用水热法负载二硫化钼,制备了复合材料(MoS_(2)-LDH).结果表明,MoS_(2)-LDH对水中Cd(Ⅱ)、Pb(Ⅱ)和Cu(Ⅱ)的吸附作用机制包括沉淀、络合、同晶置换和静电吸引作用,其中沉淀作用为主导,贡献率占46.57%—58.32%,其次为络合作用(27.15%—32.08%)和同晶置换作用(10.75%—17.86%),静电吸引的贡献最小(3.33%—4.26%);吸附过程与拟二级动力学方程和Langmuir模型相符,最大吸附量达到48.31、71.33、77.16 mg·g^(-1).对高效去除重金属的吸附机制的详细研究,可为二维复合材料的设计合成提供理论支撑.

Two-dimensional layered nanomaterials can remove heavy metals from aqueous solutions by adsorption and the interaction mechanism is the active research focus and difficult issue.In order to increase the adsorption capability and clarify the interaction mechanism,the magnesium-aluminum layered double hydroxide(MgAl-LDH)was prepared using the co-precipitation method,and MoS_(2) was loaded using the hydrothermal method to obtain the composite of MoS_(2)-LDH.The results indicated that the adsorption mechanisms of MoS_(2)-LDH for aqueous Cd(Ⅱ),Cu(Ⅱ)and Pb(Ⅱ)involved the precipitation,complexation,isomorphic substitution and electrostatic attraction.The precipitation was the key mechanism and the contribution percentages were 46.57%—58.32%.The surface complexation(27.15%—32.08%)and isomorphic substitution(10.75%—17.86%)were followed by,and the contribution of electrostatic attraction was only 3.33%—4.26%.The adsorption process was in accordance with the pseudo-second-order kinetic equation and Langmuir isotherm model,respectively.The maximum adsorption capacities of MoS_(2)-LDH for Cd(Ⅱ),Pb(Ⅱ)and Cu(Ⅱ)reached 48.31,71.33 and 77.16 mg·g^(-1),respectively.In conclusion,the detailed adsorption mechanisms can provide theoretical support for the design and synthesis of two-dimensional composite to efficiently remove aqueous heavy metals.