Research On The Performance Of Heavy Metal Adsorption By Activated Carbon Based Composite Adsorbent

In recent years,continuous population growth,rapid industrialization and increasing urbanization have introduced heavy metals into the water environment.Heavy metal ions persist in the ecosystem due to their non-degradable nature,and their toxicity and bioaccumulation trends in the environment seriously threaten human health problems.With the vigorous development of printing and dyeing,metal processing,electroplating,nuclear power,tannery,textile and other industries,a large amount of heavy metal wastewater is discharged into water bodies,leading to water pollution,so it is urgent to develop a water treatment technology for heavy metal wastewater.Adsorption method is a typical method to treat heavy metal wastewater,and the key of this method is to screen adsorbent with excellent and cheap adsorption performance.In this paper,based on the research results of the group,we prepared PACAMC,a composite adsorbent based on powdered activated carbon（PAC）,polymeric aluminum chloride（PACl）,polyacrylamide（PAM）and humic acid（HS）as substrates,and systematically investigated the performance and adsorption mechanism of PACAMC in removing metal ions from the perspectives of group structure,physicochemical properties and influencing factors.The main research contents and conclusions are as follows.（1）The composite adsorbent material PACAMC was successfully fused and prepared from PAC,HS,PAM and PACl.The morphology,structure and chemical properties of PACAMC were characterized using SEM,FTIR,EDS,PSDA,BET,XPS and surface charge analysis.The results showed that the surface of PACAMC was rough and irregular with a large number of non-uniform pores.p H_PZCvalue of PACAMC was 5.3.PACAMC was deeply fused by chemical reaction and functional functional groups（-COOH,-OH and-NH₂）were introduced to provide more active sites that can interact with heavy metal ions.（2）In this paper,PACAMC was used for the adsorption of Cr（Ⅵ）in aqueous solution.The effects of different experimental conditions and coexisting ions on the adsorption capacity of Cr（Ⅵ）were investigated.Under the experimental conditions,the adsorption amount of Cr（Ⅵ）by PACAMC was 26.440 mg·g^-1,and the removal rate of Cr（Ⅵ）was as high as 95.16%.The higher adsorption capacity of PACAMC for Cr（Ⅵ）at lower p H values reflects that electrostatic interactions are the main driving force controlling the Cr（Ⅵ）binding mechanism.Kinetic studies showed that the pseudo-secondary and Elovich models were in good agreement with the experimental data.The adsorption isotherms can be well described by the Temkin model,indicating that the adsorption mechanism is monolayer-multilayer hybrid adsorption.The thermodynamic parameters indicate that the adsorption of Cr（Ⅵ）by PACAMC is a spontaneous heat absorption process.The adsorption mechanism of Cr（Ⅵ）by PACAMC is mainly controlled by the electrostatic attraction between Cr（Ⅵ）and the protonated functional groups of PACAMC,and Cr（Ⅵ）is reduced to Cr（III）and accompanied by the presence of physical adsorption.（3）In this paper,PACAMC was used for the adsorption of Mn（Ⅱ）in aqueous solution.The effects of different experimental conditions and coexisting ions on the adsorption capacity of Mn（Ⅱ）were investigated.The removal efficiency of PACAMC for Mn（Ⅱ）under the experimental conditions was as high as 94.62%and the adsorption capacity was 23.655mg·g^-1.The adsorption process was more consistent with the pseudo-secondary kinetic model,Elovich model and Temkin isothermal adsorption model.The adsorption of Mn（Ⅱ）by PACAMC was an endothermic spontaneous reaction.The main mechanism of PACAMC to remove Mn（Ⅱ）is chemical complexation and electrostatic interaction.