Application of surfactant-modified montmorillonitefor As (III) removal from aqueous solutions: kinetics and isotherm study

The prime objective of this research was to develop a systematic method for the removal of arsenic (III) from aqueous solutions by adsorption. Thus, montmorillonite modified with tetradecyltrimethylammo-nium bromide (TTAB) was utilized to prepare an outstanding sorbent. Subsequently, this novel material was characterized and identified completely by different techniques: X-fluorescence spectrometer (XRF), Sear’s procedure (titratin method), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Moreover, the effects of solution pH (4–12), surfactant loading rates (20– 200 cation exchange capacity (CEC) of the clay), contact time (10 min–5 h), pollutant concentration (500–3000 µg/l), temperature (15–45 °C) and adsorbent dose (0.1–1.0 g) on the adsorption process were investigated. At the optimum values, the effects of contact time on adsorption and the dependency of adsorption data to different kinetic models like pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion were assessed; it was found that the process of arsenic (III) removal followed a pseudo second-order kinetic model (R2 = 0.9998). Following the optimization of the variables, by fitting the experimental equilibrium to the Langmuir, Freundlich, Temkin and Dubinin-Radush-kevich models and the respective information for each model and their applicability were examined to understand the conceptual of the adsorption. According to R2 (0.9999) and maximum adsorption capacity (1.48 mg g–1), it was found that the adsorption process followed the Langmuir model. The thermodynamic study also showed the spontaneous and endothermic nature of the adsorption process. © 2018 Desalination Publications. All rights reserved.