| Considering the advantage of MnO2 and GNS, this paper choose GNS as a carrier, GNS/MnO2 composite was synthesized via microwave-assisted method. The surface properties of the adsorbent was explored by BET, SEM,TEM,XRD,FTIR and XPS. Batch experiments were conducted to investigate the adsorption effect of Ni2+ under different solution pH, initial concentration and contact time onto GNS/MnO2 composite in comparison with pure MnO2 and GNS. Single batch experiments were conducted to investigate the adsorption effect of Pb2+ and Cu2+. The surface interactions involved in the adsorption process were explored by modern testing methods. A conceptual model for the adsorption was proposed to illustrate the mechanisms.The results show binding of Ni2+,Pb2+ and Cu2+ onto GNS/MnO2 is highly pH-dependent with the optimum performance at about pH 6.0-7.0. Adsorption isotherm can be described by the Langmuir model for the Ni2+,Pb2+,Cu2+. The saturate adsorption capacity of Ni2+ onto GNS/MnO2 is 46.6 mg/g at room temperature, which is 1.5 and 15 times higher than those of pure MnO2 and GNS, respectively. The data fit well with Langmuir model at qmax values of 163.93 and 104.82 mg/g for Pb2+ and Cu2+, respectively. It was found that all the adsorption of Ni2+,Pb2+ and Cu2+ on GNS/MnO2 is a fast adsorption proeess that could be reached equilibrium within 2h. The adsorption proeessese could be well deseribed by the pseudo-second-order equation.The surface interactions involve in the adsorption process were explored by SEM,XRD,XPS and FTIR, the tetradentate monodentate innersphere complexes are dominant on the surface of the GNS/MnO2.GNS/MnO2 adsorbent can be used repeatedly for five ten times with 9% loss of adsorption capacity.These results demonstrate that GNS/MnO2 developed in this work can serve as an efficient adsorbent for the decontamination of heavy metal ions in water treatment. |
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