Study On Adsorption Performance And Mechanism Of Quaternary Ammonium Salt Modified Montmorillonite For Pharmaceutical Pollutants

Pharmaceuticais pollutants was a new kind of environmental pollutants,had been detected in a variety of environmental media,gradually exposed to certain harmful effects,forming a pollution of the environment.Montmorillonite was widely used in water treatment because of its abundant reserves,low cost,large specific surface area and good cation exchange capacity.However,the adsorption performance of natural montmorillonite to organic matter is very poor,and the modification can increase the layer spacing and improve the adsorption of organic matter.In this paper,modified montmorillonite by three quaternary ammonium cationic surfactants was used to adsorb pharmaceuticais pollutants in water.The main research contents are as follows:1、The quaternary ammonium salt cationic surfactant dodecyl dimethyl benzyl ammonium chloride(DDBAC)was used as the modifier to prepare D-Mt,used XRD,FT-IR,TG,BET,Zeta and SEM analysis methods.The composite material was characterized,and the adsorption effect of the material on AMP and AMX was studied.The processes are in line with the Freundlich isotherm adsorption model and pseudo-second-order kinetic model,both of which are endothermic reactions;DFT calculations had confirmed that the adsorption of D-Mt-1.4 on AMP and AMX was affected by the pH value of electrostatic action.The π/π interaction between Pharmaceuticais pollutants may also help improve the adsorption capacity of D-Mt-1.4.2、The composite material(H-Mt)was synthesized by used hexadecyldimethyl benzyl ammonium chloride(HDBAC),the adsorption effect of the material on DCF and IBU was studied.The results showed that when the dosage of modifier was 1.6 CEC,the adsorption effect was the best.The adsorption capacity of H-Mt-1.6 of DCF and IBU can reach 125.55mg/g and 81.64 mg/g.The adsorption capacity of DCF and IBU was much higher than Ca-Mt(54.02 mg/g and 13.14 mg/g,respectively),and the equilibrium could be reached after 120 min.The fitting results showed that H-Mt-1.6 adsorption processed of DCF conforms to the Langmuir adsorption model,and the adsorption processed of IBU conforms to the Freundlich adsorption model.and the results proved that the adsorption process of H-Mt-1.6 on DCF and IBU can be described by a pseudo-second-order kinetic model.The thermodynamic analysis showed that the adsorption of DCF was endothermic,and the adsorption of IBU was exothermic.3、The DHPD-Mt-x composite material was obtained by modifyed the montmorillonite with double quaternary ammonium salt cationic surfactant,and a series of characterizations such as FTIR were carried out,which proved the successful combination of double quaternary ammonium salt and montmorillonite.The effects on the adsorption performance of HOBT and PCT under different conditions was explored.When the modifier dosage was 1.8 CEC,the adsorption capacity for HOBT and PCT can reach 35.35 mg/g and 14.62 mg/g,respectively.The optimal pH was divided into 3 and 10.The effect of time on adsorption performance was explored,and adsorption isotherms were fitted to the data at different temperatures.The results showed that the adsorption process of DHPD-Mt-1.8 for HOBT conforms to the Langmuir adsorption model,and the adsorption process for PCT conforms to the Freundlich adsorption model,the adsorption process can be described by a pseudo-second-order kinetic model.The calculation of thermodynamic parameters confirmed that the process of adsorbing HOBT was a spontaneous exothermic process.The calculation of thermodynamic parameters confirms that the processed of adsorbing HOBT was endothermic.