Preparation and application of a surfactant‐modified Halloysite nanotubes for the adsorption of nitrates from aqueous solutions: Kinetic and equilibrium studies

Abstract

The current research proposes the hexadecyltrimethylammonium bromide-modified Algerian halloysite nanotubes (HNTs-CTAB) as adsorbent for nitrate ions removal from aqueous solution via electrostatic interactions. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fouriertransform infrared spectroscopy (FT-IR), and nitrogen adsorption-desorption analysis techniques have been used to characterize the prepared adsorbants. The different operating condition that may affect the adsorption of nitrate was carried out. HNTs and HNTs-CTAB adsorption capacities are considerably pH dependent. The optimum conditions for maximum removal of nitrate from aqueous solution were as follows:adsorbent masse was 40 mg, initial pH was 4, temperature was 25 C, initial nitrate concentration of 100 mg/L and equilibrium time was 3 h. Under optimal value of process parameters, maximum NO 3 À adsorption capacity of 47.4 mg/g was obtained.Kinetic investigation confirmed that the nitrate adsorption on modified HNTs followed a pseudo-second-order with correlation coefficients greater than 0.98 (R 2 = 0.9870) and that empirical Freundlich isotherm was best fitted nitrate equilibrium adsorption. The thermodynamic studies indicated that the adsorption of nitrate onto HNTs-CTAB is endothermic and spontaneous. HNTs-CTAB displayed high regeneration ability by retaining a capacity above 40 mg/g after four reuse cycles.HNTs-CTAB containing plentiful nitrate could be returned to the soil directly as an economic slow release fertilizers or a soil amendment due to its environmentalfriendly performance. Therefore, HNTs-CTAB used for remediation of wastewater might be employed easily as farmland fertilizer.