Investigating the efficiency of surfactant-modified zeolites@pumice to remove phosphate from synthetic wastewater using Box-Behnken design

The discharge of phosphorus into surface waters results in overgrowth of aquatic plants and consequent eutrophication of rivers and seawaters; thus, removing this material to prevent surface-water nutrient uptake has received researchers' attention in recent years. The aim of the present study was to investigate the efficiency of stabilization of zeolite nanoparticles modified by cationic surfactant on pumice aggregates to remove phosphate from aquatic environments. In this study, zeolite nanoparticles, modified by CTAB surfactant, were stabilized on pumice aggregates substrate using heating operation; then, the structural and physical features of the prepared absorbent were analyzed using FTIR, XRD, SEM, and EDAX techniques. Experiments were designed using Box-Behnken response surface methodology to improve the variables. Variables of pH (5-9), temperature (15-45 degrees C), and amount of absorbent (5-15 g/L) were investigated. In addition, in order to investigate kinetics and adsorption isotherm, separate tests were conducted to determine the optimal amount of contact time (5-150 min) and phosphate concentration (5-28 mg/L). Results show that the optimum conditions to remove phosphate by modified aggregates were measured at a pH of 5; temperature of 45 degrees C and absorbent amount of 15 g/L. Kinetics investigations showed that phosphate removal follows the second-order model and the optimum contact time was measured at 60 min in which phosphate removal efficiency was 82.22%. The results also show that phosphate adsorption isotherm has good agreement with Langmuir isotherm. The study shows that stabilizing the modified zeolite nanoparticles using cationic surfactant on pumice aggregate is highly effective for phosphate removal, thus it can be used for removing such pollutants from aquatic environment.