A Study Of New Adsorbent:nZVI\MCM-41\RGO Preparation And Heavy Metal Removed From Water

Graphene is a kind of carbon material which possesses lots of excellent properties,like super conductive,high thermal conductivity,good light transmission and so on.In this study,an advanced graphene composited material was prepared and used to absorb heavy metal ions from water.Firstly,the method of Hummers,Alkaline hydrothermal synthesis and liquid phase reduction was used to synthesis reduced graphene oxide?RGO?,silica molecular sieve?MCM-41?and nano zero-valent iron?nZVI?respectively.Then,the new environmental material nZVI\MCM-41\RGO was composited by the method of liquid impregnation.These materials were measured by SEM,FT-IR,XRD,XPS,MOSSBAURE and BET.The results of these measurements proved that nZVI\MCM-41\RGO has part of porous structure,lots of kinds of oxygen-containing groups in it or sign its surface,and its chemical property steady enough for store.BET test outcome indicated that the value of nZVI\MCM-41\RGO specific surface area is 15.935 m²/g,total pore volume is 0.0461cc/g,mean pore size is 23.82nm.Secondly,cadmium,copper and nickel ions removal from aqueous solutions using nZVI\MCM-41\RGO were investigated under batch conditions.The removal rate were 92%?73%and 71%with optimum uptake?qe,exp?of 21.64mg/g,16.92mg/g and 24.99mg/g for Cd²⁺,Cu²⁺,Ni²⁺respectively,under conditions of shaking,the adsorbent dosing quantity of2g/L,the metal ion concentration of 50mg/L.Modelling of sorption kinetics indicates that the pseudo second order?PFO?model described the sorption of cadmium,copper and nickel ions.Isotherm modelling was carried out and the results indicated that the Freundlich model was the better isotherm for the description of Cd²⁺,Cu²⁺,Ni²⁺sorption by the adsorbent.This adsorption process could be a spontaneous multilayer adsorption process?Endothermic and entropy increase also calculated by the isothermal thermodynamic parameters no matter experiment situations in which ultrasonic wave and constant temperature bath oscillator.Both chemical and physical adsorption existed in different heavy metal ions adsorption processes,and the chemical adsorption played a main role.The value of solution pH and environment temperature had important influence in the ability of adsorption about nZVI\MCM-41\RGO.To better evaluate nZVI\MCM-41\RGO ability,the different adsorbents which had been made included nZVI\MCM-41\RGO,nZVI\RGO\MCM-41 and MCM-41\nZVI\RGO.Three adsorbents were used to adsorb Pb²⁺,Zn²⁺,Cu²⁺,Ni²⁺,Cr³⁺,Cd²⁺for their selective adsorption.The results indicated that the ability of nZVI\MCM-41\RGO absorb Pb²⁺and Cr³⁺was better than others.When metal ion concentration was 300mg/L,adsorptive time was1260min,theremovalrateofnZVI\MCM-41\RGO,nZVI\RGO\MCM-41and MCM-41\nZVI\RGO for Pb²⁺were 100%,83%,62%respectively,while Cr³⁺were 100%,99%,63%.The influence of common cation,anion and humic acid in water for adsorption process was researched.The results showed that the impact of cation were lower than anion,could indicated resistance water hardness of nZVI\MCM-41\RGO.After selective adsorption coefficient data calculation,the numerical size order was F^->Cl^->NO₂^->SO₄^2->NO₃^->PO₄^3-for Cr³⁺,NO₂^->Cl^-for Pb²⁺.In addition,humic acid would enhanced adsorption and the time to adsorption equilibrium was shorter than that of without humic acid.Finaly,the adsorption mechanism analysis of nZVI\MCM-41\RGO had been analysised in this study.Different metal ion's adsorptive mechanisms were similar,except the affect degree of different oxygen-containing functional groups.A lot of nZVI\MCM-41\RGO surface oxygen-containing functional groups as well as the electrostatic interaction between adsorbat and adsorbent were the most important factors for adsorption mechanism.Intraparticle diffusion modelling showed that intraparticle diffusion may not be the only mechanism that influenced the rate of ions uptake,also included surface diffusion adsorption and the reductive adsorption of nano-scale iron.In addition,The problems could be solved by new eco-friendly material nZVI\MCM-41\RGO,such as RGO that uneasy to separate from water completely,nZVI easy to oxidation and MCM-41 pore heat stability.This research could widen the area of adsorbent's adhibition,provide new ideas for the innovative development of adsorbent,as well as provide the credible data to the research of adsorption performance.