Study On Preparation And Application Of Guangxi Natural Clay Mineral

Pollutants such as organic dyes,heavy metal ions Cr(VI)and antibiotics in industrial production,livestock and poultry breeding wastewater and various pathogenic bacteria in domestic wastewater have become one of the important research topics in wastewater treatment due to their high toxicity,difficulty in degradation,high mobility and pathogenicity,but it is still a great challenge to develop environmental remediation materials that can simultaneously remove them without secondary pollution and easy recycling.Clay minerals are abundant in natural resources,as well as rich in pore structure and surface groups,and their excellent physicochemical properties and good biocompatibility make them of great value in many fields such as pollutant adsorption,catalyst carriers and antibacterial applications.Guangxi Shangsi County Illite/Smectite mixed clay(I/S)is an intermediate type mineral of montmorillonite to illite excess,which belongs to 2:1 type layered silicate minerals and consists of natural micro and nano particles,but it has the disadvantages of limited adsorption capacity,low photocatalytic activity and no bactericidal ability by itself.To address the drawbacks of I/S,columnar modification,structural reorganization and surface loading were carried out to enhance its adsorption,photocatalytic and antibacterial properties and broaden its application fields.The main work and results of the paper are as follows:1.To address the problem of limited I/S adsorption capacity,this chapter evolves and reorganizes the I/S structure by hydrothermal-roasting method to prepare hybrid zinc silicate adsorbent(Zn-Si/(I/S)),and analyzes the adsorbent morphological structure and elemental composition using various characterization techniques(XRD,XPS,SEM/TEM,BET,etc.),and the Zn-Si/(I/S)adsorbent is a 2D film-like structure.The adsorption process was simulated with RhB as the pollutant,the adsorption equilibrium time was 50 min,the adsorption amount increased with the initial concentration and temperature,and the optimal pH for adsorption was 4.In addition,the adsorption process was influenced by the structure,type and surface groups of the pollutant.The results of adsorption isotherm,kinetic and thermodynamic model fitting showed that: i)the adsorption performance depended on the pore size and surface charge rather than the specific surface area;ii)the Proposed second-order kinetic model and Freundlich isotherm model fitted the adsorption process of RhB better;iii)the thermodynamic analysis proved that the adsorption process proceeded spontaneously by heat absorption.In summary,the adsorption mechanism is controlled by electrostatic attraction,chemical conjugation,ion exchange,hydrogen bonding interactions and pore adsorption.2.The adsorption method only adsorbs pollutants from liquid phase to adsorbent surface or pore channel,which requires secondary treatment and has the problems of high cost,low efficiency and secondary pollution,while using photocatalytic technology to treat wastewater has the advantages of green and high efficiency and no secondary pollution.Therefore,in this chapter,CdS/(I/S)photocatalysts were successfully synthesized for the degradation of organic dyes and reduction of Cr(VI)by a simple hydrothermal method using I/S as a carrier.The phase composition,crystal size,microscopic morphology and optical properties of the materials were systematically characterized and analyzed.The results show that the coconut-like CdS particles are well immobilized on the I/S surface.The composites exhibit higher photocatalytic activity for the degradation/reduction of dyes and Cr(VI)than CdS and I/S alone,attributed to the support of I/S.The CdS particles have smaller size and higher dispersion,providing more active sites for the photocatalytic reaction.The cycling experiments showed that the CdS/(I/S)composites exhibited better reusability and stability,and the corresponding photocatalytic reaction mechanism was proposed by active species capture experiments.3.Dye wastewater usually also contains various pathogenic bacteria.In order to make I/S with both photocatalytic degradation of dyes and antimicrobial properties,Ag/AgBr/(I/S)bifunctional composites were synthesized by deposition precipitation method.The phase composition,crystal size,microscopic morphology and optical properties of the materials were systematically characterized and analyzed,and the photocatalytic and contact antibacterial properties of the materials were tested.25% Ag/AgBr/(I/S)showed a strong photocatalytic activity with 92% degradation of methyl orange(MO)within 20 min of light exposure.In addition,the cycling experiments showed that the composites have good recyclability and stability.A possible photocatalytic mechanism for the degradation of MO was proposed by radical capture experiments and electron paramagnetic resonance(EPR)tests.The good antibacterial effect of Ag/AgBr/(I/S)materials against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)was demonstrated by inhibition circle experiment and test tube twofold dilution method,and the antibacterial experiment of actual bacteria-containing water showed that the composites could be used for practical antibacterial purposes.This study confirms the feasibility of I/S-based materials in the fields of adsorption,photocatalysis and antibacterial,and suggests new ideas for the preparation of I/S-based functional materials for the effective removal of organic wastewater,heavy metal wastewater and pathogenic bacteria.