Research On Adsorption Of Heavy Metals And Organic In Aqueous Solution By Bentonite And Its Modified Materials

Bentonite is a kind of alum inosilicate clay contains water that is abundant in China.Because bentonite has a large theoretical specific surface area,ion exchange and other special physical and chemical properties,bentonite and its modified materials are extensively applied in wastewater treatment and soil remediation.The research and application of bentonite materials also have practical value and significance.Based on the adsorption effect of natural bentonite on heavy metal ions in wastewater,organic modification and inorganic modification of bentonite have been manufactured in this paper,modern analysis methods adopted to characterize the material.The modified materials were used to adsorb heavy metal ions and organic compounds in aqueous solution.The adsorption mechanism and influencing factors of the modified materials on the target were explored.These investigations were expanded functional modification method of bentonite,provided the theoretical basis and technical foundation.The main contents are as follows:（1）In the first chapter,the water problems of world and the status of China’s water resources,the sources of heavy metal wastewater and effective treatment methods have been summarized.It introduced the significant role of bentonite as natural clay in environmental management,and combined the properties of bentonite to explore its inorganic and organic modifications as well as the principle of the method,described the practical effects of the modified bentonite adsorbent.（2）In the second chapter,adsorption properties of natural bentonite were explored.The adsorption to Pb²⁺and Cu²⁺of aqueous solution on sodium bentonite（Na-bent）and lithium bentonite（Li-bent）was studied.The effects of different influencing factors on the adsorption results were also explored and the adsorption results showed that the adsorption capacities of sodium bentonite（Na-bent）were better than that of Lithium bentonite（Li-bent）.In the kinetic adsorption experiments,the optimal adsorption amounts of Pb²⁺and Cu²⁺were separately 111.0 mg/g and 56.2 mg/g.About isothermal adsorption experiments,the optimal adsorption amounts of Pb²⁺and Cu²⁺were respectively 149.8 mg/g and 63.0 mg/g.Based on the adsorption data and the characterization results of bentonite,the sodium bentonite（Na-bent）would participated the following natural material modification experiments.（3）In the third chapter,a modification method combining inorganic acid activation with silanization organic modification has been proposed.Bentonites were activated to varying degrees by the function of different concentrations of hydrochloric acid,0.5 M,2.0 M,and 4.0 M,then silylation was conducted on the basis of activated bentonite.3-aminopropyltriethoxysilane（APTES）which include amino functional group grafted to the surface of activated bentonite has used to form chelates with cadmium ions in aqueous solution to adsorb and remove heavy metal ions.The experimental data indicated the dynamic adsorption in agreement with the pseudo-secondary kinetic adsorption model and the isothermal adsorption was consistent with the Langmuir isotherm model,therefore the chemical adsorption dominated the adsorption process.The adsorbent Ben-NH₂-4.0M which modified by 4.0M hydrochloric acid has possessed the optimal adsorptive capacity.The maximum adsorption capacity of kinetics adsorption and isothermal adsorption were respectively60.8 mg/L and 161.3 mg/L.Therefore,in a certain range of concentration of acid,the higher concentration of acid-activated bentonite modified sorbent could well remove heavy metal ions in aqueous solution,which can be widely used in many fields as a potential adsorbent.（4）In the fourth chapter,a kind of hydrotalcite-like modified bentonite adsorbent containing lanthanum ion（Ben-HTlc）has been developed.The modern characterization methods were used to characterize the sorbent synthesized by urea hydrolysis method.The adsorption behavior of modified bentonite in aqueous solution on heavy metal ions and dyes was explored.In order to obtain the optimal adsorption conditions for the three elements,the influencing factors have been optimized,such as the pH value of the solution,the reaction time,and the concentration of the target solution.For single-component adsorption of lead ions,copper ions,and methyl orange（MO）,the pH of the control solution was 6.5±0.1,and the dynamic adsorption reached the adsorption equilibrium in 20 minutes,and the maximum adsorption capacity of isothermal adsorption were 384.6 mg/g,156.3 mg/g,333.3 mg/g,respectively.The order of adsorption capacities to three substances estimated by the langmiuer equation was:Pb²⁺>MO>Cu²⁺.The modified materials exhibited excellent repeated adsorption and regeneration adsorption capabilities and the breakthrough adsorption results showed that hydrotalcite-modified bentonites can effectively adsorb heavy metal ions and dyes in aqueous solutions,implying the potential of hydrotalcite-like modified bentonites in contaminant removal and adsorption.（5）In the fifth chapter,the research conclusion,innovations and prospects of the full text were all described which provide research ideas and technical support for subsequent research.