Preparation Of Thiol-functionalized Coal Fly Ash And Application In The Passivation Of Heavy Metal Pollution

Development of industry and urbanization have pushed not only high-speed emergency of global economic and civilization but also taken many negative impacts on environment.Environment pollution has influenced foods safety of more than 7 billion people around the world.Compared with other kinds of pollution materials,heavy metal pollution can't be degraded to clean matters,and heavy metal ions are easily dispersed in the environment attributed to its small size.Metal ions can be desapared as different kinds of speciation in environment especially in soil,and the toxicity of different speication has obvious difference.More researchers pay attention to research new passivaition that can improve heavy metal ions transfer from state with high toxicity to state with low toxicity.In this study,thiol-functionalized coal fly ash?CFA-SH?was preparated with coal fly ashs,?3-mercaptopropyl?trimethoxysilane?MPTS?,and ethanol.The experimental results showed that the CFA-SH had the best adsorption performance when the sulfuric acid concentration was 7.5 mol/L,the acidification temperature was 298 K,the coupling temperature was 60? and the coupling time was 6 hours.SEM text result CFA-SH is sphere.The double peaks of –SH appere at 2321 cm-1and 2286 cm-1 in IR text result.XPS result also shows two peaks of –SH at 163.6 e V?2p1/2?and 164.7 e V?2p3/2?.Then CFA-SH was used to adsorbent Ni²⁺,Cu²⁺,Zn²⁺,Cd²⁺,Pb²⁺ ions in water.Based on the aqueous adsorption results,the passivation processes of Ni²⁺,Cu²⁺,Zn²⁺,Cd²⁺,Pb²⁺ ions in soil were researched as well.The results show that Pb has the best adsorption efficiency in aqueous solution,which can be more than 40 mg/g.adsorption results can be described with Langmuir equation and Freundlich equation but never can be described with Dubin-Radush.It suggests that the adsorption process occurs on a homogenous surface of the CFA-SH and each binding site can only be occupied once.The adsorption process can also be described as quesdo-second-order kinetic equation,the fitting results of Weber Morris equation exhibit piecewise linearity and interrupt isn't 0,which indicates that the number of adsorption sits on CFA-SH surface makes important influence on adsorption speed,and there have to be multiple factors and processes influcening adsorption speed addition to internal diffusion rate.Based on adsorption result in solution,CFA-SH was used to passivate heavy metal in soil.In soil,the passivation efficiency of five heavy metal ions can reach 60%.After passivation,the bio-utilization speciation concentration of Pb is the minimum,it of Ni,Cu,and Zn is nearly same and higher than Pb,it of Cd is the highest.Soil nature such as liquid p H and moisture can make significant influence on passivation efficiency.Furthermore,all kinks heavy metal ions are trasnfered from high-toxic state to low-toxic state.XPS result shows that Fe oxides and Al oxides are the important factors on passivation efficiency.In this study,thiol-functionalized coal fly ash was snthesied with a simple and environmentall friendly method and used as a passivator for heavy metal pollution in the water and soil.At the same time,we compared the similarities and differences of in the technology,efficiency and mechanism of passivaition process,providing some reference to the research of passivating water and soil heavy metal pollution with one kind of passivator at the same time.