Preparation And Adsorption Performance Of Layered Double Hydroxide And Its Derivatives

The heavy metal ion of wastewater generated during industrial activities will pose a threat to the surrounding ecological environment and human health.Layered double hydroxides（LDHs）are widely concerned about their application prospects in sewage treatment due to their positive charges in the lamellar structure and exchangeable anions between layers.However,their practical applications are restricted due to their shortcomings of easy aggregation in water bodies and small application scope.To address the above issues,this paper proposes two solutions:（1）load LDHs onto a substrate with a large specific surface area to increase the adsorption reaction area.（2）by etching and calcining the LDHs,defect spinels that can adsorb metal cations are obtained.To address the above issues,the following research has been conducted in this work:1.Mg Al-LDHs,Ca Fe-LDHs,and Ca Mg Al-LDHs were successfully prepared by hydrothermal and colloidal grinding methods,and the adsorption mechanisms of the three materials were studied.The mechanism of removing Cr₂O₇^2-ion by Mg Al-LDHs is interlayer anion exchange,and the mechanism of removing Ni²⁺ion by Ca Mg Al-LDHs and Ca Fe-LDHs is isomorphous substitution reaction.Subsequently,several different LDHs/vermiculite composite materials（LDHs are Mg Al-,Ca Fe-,Ca Al-,and Ca Mg Al-LDHs）were prepared by hydrothermal and colloidal impregnation methods.The composite materials have a multi-level layered structure,which increases the adsorption reaction area of LDHs.The adsorption performance of the composite material was tested,and the experimental results showed that the hydrotalcite/vermiculite composite material had good adsorption performance for metal ions.2.Spinel materials with defect vacancies were prepared by etching and calcining LDHs,and the adsorption performance of spinel on Zn²⁺and Mg²⁺ions was studied.The method of etching can create pores and defect vacancies in spinel,which is conducive to the adsorption of metal ions.Mg Al₂O₄exhibits selective adsorption for Zn²⁺ions,while Zn Al₂O₄does not exhibit selective adsorption.The theoretical maximum adsorption capacity of Mg Al₂O₄for Zn²⁺ions is 77.64 mg·g^-1,while the theoretical maximum adsorption capacity of Zn Al₂O₄for Zn²⁺ions and Mg²⁺ions is 34.79 mg·g^-1and 29.53 mg·g^-1.