Performance of surfactant-modified forms of clinoptilolite and pumice in nitrate removal from aqueous solution

Clinoptilolite and pumice are both natural, low-cost and available sorbent materials. In this study, surfactant-modified forms of clinoptilolite (SMC) and pumice (SMP) using hexadecyltrimethylammonium bromide were used for the removal of nitrate from aqueous solutions. Batch experiments were performed to investigate the effects of factors including pH (2-10), contact time (10-180 min), adsorbent dosage (0.1-1.5 g/L) and nitrate initial concentration (30-200 mg/L) on the sorption performance. Both natural and modified forms of sorbents were characterized by X-ray fluorescence, scanning electron microscopy and Brunauer-Emmett-Teller techniques. The optimal experimental condition for both adsorbents were pH = 5, contact time = 30 min and adsorbent dose = 0.5 g/L. The equilibrium isotherm data were well described using the Langmuir model (R-2 = 0.99) with a monolayer sorption capacity of 30.2 and 27.6 mg/g for SMC and SMP, respectively. The adsorption kinetic for nitrate sorption followed the pseudo-first-order model. Results of the regeneration study showed that both sorbents could be reused for nitrate removal in several cycles. The study revealed the SMC and SMP both could be used as efficient and inexpensive materials for nitrate removal from aqueous solutions.