Adsorption mechanisms of MoS2-LDH composite for aqueous Cu(Ⅱ),Pb(Ⅱ)and Cd(Ⅱ)
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 MoS2 was loaded using the hydrothermal method to obtain the composite of MoS2-LDH.The results indicated that the adsorption mechanisms of MoS2-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 MoS2-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.
heavy metal wastewateradsorption mechanismprecipitationcomplexation
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