Preparation Of Organic Montmorillonite And Its Adsorption Performance For Benzotriazole Micro-pollutants And Copper Ion

Montmorillonite is a natural clay mineral with a 2:1 layered structure and has good adsorption properties.However,it has a poor adsorption effect on organic pollutant because of its surface hydrophilicity.Organo-montmorillonite can improve the adsorption performance for organic pollutant due to the increasing hydrophobicity and extanded interlayer spacing.The main research contents of this article are as follows:（1）Three gemini surfactants with different chain lengths:propylbis（dodecyldimethyl）ammonium chloride（12-3-12）,propylbis（hexadecyldimethyl）ammonium chloride（16-3-16）and propylbis（octadecyldimethyl）ammonium chloride（18-3-18）were used to modify calcium-based montmorillonite（Ca-Mt）to prepare a series of organic montmorillonites（G-Mt）.（2）The obtained G-Mt was characterized by XRD and FT-IR.The analysis results showed that the three modifiers has successfully intercalated the interlayer of montmorillonite and increased the interlayer spacing of montmorillonite.G-Mt was applied to adsorb emerging micro-contaminants（ECs）of three benzotriazoles including 1-hydroxybenzotriazole（HOBT）,benzotriazole（BTA）and 5-methylbenzotriazole（TTA）.The experimental results indicated that under the same conditions,the adsorption sequence of the three G-Mt for ECs was G₁₆-Mt>G₁₂-Mt>G₁₈-Mt.Specifically,when the added amount of 16-3-16 was 1.0 CEC,the modified montmorillonite(G₁₆-Mt)exhibited the best adsorption capacity for three ECs.Thus,G₁₆-Mt（1.0 CEC）was selected for the following adsorption experiments.（3）SEM,EDS,TG/DTG and BET analysis methods were carried out to characterize the structure and element content of Ca-Mt and G₁₆-Mt.The results suggested that 16-3-16 has successfully entered the Ca-Mt interlayer and improved the interlayer basal spacing of Ca-Mt,which was beneficial to its adsorption for benzotriazole pollutants.Thus,the conditions of solution p H,reaction temperature,the initial solution concentration and reaction time for G₁₆-Mt to absorb the three organic pollutants were further explored.It can be concluded that the optimal p H for removing HOBT,BTA and TTA was 4,9 and 9,respectively.The Langmuir isotherm model and the pseudo-second-order model fitted well the adsorption processes of the three pollutants.Thermodynamic results elucidated that the adsorption process was endothermic and spontaneous.（4）Based on the above studies,the adsorption performances of Ca-Mt and G₁₆-Mt for Cu²⁺and benzotriazole pollutants in the single adsorption system and the co-adsorption system were investigated.In the single adsorption system,G₁₆-Mt had a lower adsorption capacity for Cu²⁺than that of Ca-Mt,but has a higher adsorption capacity for three ECs.In the co-adsorption system,G₁₆-Mt exhibited more adsorption amount for three organic pollutants and Cu²⁺than Ca-Mt.The results of FT-IR and XPS implied that Cu²⁺and ECs were adsorbed onto G₁₆-Mt in the co-adsorption system by forming complexes and hydrophobic interactions.In addition,for co-adsorption systems,molecular dynamics simulation（MD）,electrostatic potential distribution（ESP）and average localized ionization energy distribution（ALIE）were combined to decode the microscopic adsorption mechanism,indicating that the synergistic effect of Cu²⁺and ECs in the co-adsorption system promoted its simultaneous removal from wastewater.This research showed that gemini surfactant modified montmorillonite was an efficient,low-cost,non-toxic adsorption material,which provided detailed experimental data for its wide application in wastewater environment.