Selective adsorption of mixed pollutants on mesoporous silicate

Abstract

Selective adsorption of mixed pollutants; heavy metals (Cd(II) and Cu(II)), Methylene blue (MB) and Octylphenol polyethoxylate (Triton X-100®) from synthetic textile wastewater was investigated by using hexagonal mesoporous silicates (HMSs). HMSs were synthesized through surfactant templating method and three of them were grafted with organic functional groups on the surface, 3-aminopropyltriethoxy, 3-mercaptopropyl and n-octyldimethyl groups. For single solution, 3-mercaptopropyl functionalized surface had highest Cd(II) and Cu(II) adsorption capacity (3.0 and 22.0 mg/g, respectively) due to chemical adsorption, however, silanol groups on pristine HMS surface exhibited highest TX-100 adsorption capacity (up to 620 mg/g) due to hydrogen bonding and surface aggregation on hydrophilic surface. For MB adsorption, OD-HMS had highest adsorption capacity (about 65 mg/g) due to strongest van der waals interaction. For bi-solution, all of adsorbents have high selectivity for heavy metals both of Cd(II) and Cu(II) in a mixture with TX-100, which is caused by changing surface characterization of adsorbents by adsorbed TX-100. But, in a mixture with heavy metal (Cd(II) and Cu(II)) and MB, all of adsorbents had lower selectivity because of active site competition. Functionalized HMSs except A-HMS have high selectivity for TX-100 in a mixture with MB, which also might be caused by active site competition and increasing of surface complexity.