The Perpartion Of Modified Clay Composites And Their Adsorption Characteristic Of The Heavy Metals

Heavy metals are closely related to the development and progress of human society,and have been widely used in electrical,light industry,machinery manufacturing,construction industry,defense industry and other fields,but also caused the heavy metal pollution more and more serious.The wastwater and nature suface water including heavy metals pollutions are the world's environmental problems.Adsorption due to its simple,convenient and high removal rate is considered to be one of the most commonly way to remove heavy metals from the solution.In this study,a series of adsorbents were synthetized to remove heavy metals from the solution through modifying the montmorillonite and halloysite,and the systematic study of the adsorption behavior of heavy metals onto adsorbens has been investigated.The important conclusions of this work are summarized as follows:(1)A new type of montmorillonite/carbon(MMT/C)adsorbent has been prepared by a one-pot hydrothermal carbonization process.The MMT/C composite was further modified to obtain functionalized MMT/C,i.e.,hydroxylated MMT/C,carboxylated MMT/C,and aminated MMT/C.The prepared MMT/C-based sorbents were systematically characterized by X-ray diffraction(XRD),specific surface area,Zeta potential,and scanning electron microscopy(SEM).Their adsorption capacity was evaluated by the removal of aqueous Pb(II)ions,following the order: carboxylated MMT/C > hydroxylated MMT/C > aminated MMT/C > MMT/C.Moreover,the influential factors for Pb(II)removal by carboxylated MMT/C composites,such as p H,temperature,and initial concentration,were thoroughly explored.The adsorption capacity increases significantly when the p H increases from 2.0 to 5.0 but with minor change beyond.The maximum adsorption capacities of MMT/C-COOH toward Pb(II)are 247.85 mg g-1.The complexation of surface groups such as –COOH on MMT/C-COOH might be responsible for Pb(II)sorption.The adsorption kinetic follows a pseudo-second order model,and thermodynamic analysis implies an endothermic and spontaneous chemisorptions process.The overall results suggest that the obtained composites are promising as an adsorbent for effectively removal of Pb(II)from water.(2)New adsorbents were successfully prepared by in-situ growing Fe3O4 nanoparticles on halloysite nanotubes(HNTs)followed by subsequent modification with silane coupling agents.The as-prepared composites were characterized by TEM,XRD,TGA,ATR-FTIR,BET,and Zeta potential.The results confirm that Fe3O4 nanoparticles were successfully decorated on internal nanotube surfaces and silane coupling agents were grafted onto the external surfaces.Among the four types of silane coupling agents modified HNTs/Fe3O4,anilino-methyl-triethoxysilane(KH-42)modified HNTs/ Fe3O4 composite exhibits the highest capacity for single adsorption of Cr(VI))and simultaneously adsorption of Cr(VI)and Sb(V).Moreover,the maximum Sb(V)removal efficiency increases from 67.0% in the single-solute system to 98.9% in the bi-solute system,suggesting that the presence of Cr(VI)enhances the Sb(V)removal by m-HNTs/Fe3O4.ATR-FTIR and XPS results reveal the existence of N–O–Cr bonds on adsorbent surfaces in the corresponding single-solute system,while Cr–O–Sb binding forms in the bi-solute system,which is responsible for the synergistic promoting effect on simultaneous adsorption of Cr(VI)and Sb(V)by m-HNTs/Fe3O4.The present work evinces that m-HNTs/Fe3O4 holds the potential in treating textile and dye wastewater with coexisting heavy metals such as Cr(VI)and Sb(V).