Stabilization of Bentonite Nanoparticles Modified by Cationic Surfactant on Pumice Aggregates for the Removal of Nitrate from Aqueous Solution

Nitrate contamination in water resources has become an important issue because of the environmental issue and potential risk to human health. The aim of this study is investigating the stabilization of modified bentonite nanoparticles by cationic surfactant on pumice aggregates to remove nitrate from aqueous environments. Bentonite nanoparticles were investigated by XRD, EDAX, and SEM techniques after modification by CTAB surfactant with the thermal method on the substrate of Pumice aggregate stabilization and physical and structural characteristics of the adsorbent. In this research, response surface method based on the Box-Behnken model was used for evaluation of the effects of independent variables such as pH, temperature and the amount of adsorbent on the response function and prediction of the best response value. Langmuir and Freundlich isotherm models were used for calculating the equilibrium constants and pseudo-first and second order constants. According to the results, the optimum nitrate removal efficiency was determined 63.49% based on the Box-Behnken model in pH = 5, the adsorbent concentration of 15 g/L, and temperature 35°C. As well, the nitrate removal rate was increased by increasing the amount of adsorbent and contact time unless the removal efficiency was decreased with an increase in pH and initial nitrate concentration. Isotherm surveying showed that the laboratory data had better agreement with Langmuir isotherm and the best kinetic model of adsorption was determined by the pseudo-second-order kinetic model. Also, the recovery efficiency in 5 cycles of absorption and desorption was observed more than 85%. This study showed that modified Pumice aggregates could be used as an effective and economical adsorbent for pollutants elimination.