Synthesis of Nano and Micro-Organobentonite Using Hexadecyltrimethylammonium Bromide and Evaluation of Their Absorption Efficiency and Release of Nitrate in Aqueous Solution

Organoclays are natural clay minerals modified through polymer compounds and applied for especial purposes. By being done so, the clay layers are permanently propped with high surface areas in the interlayers. The objective followed in this study was to find out the absorption efficiency and release of nitrate in aqueous solutions through modified Iranian bentonite (Arak). Micro and nano-bentonites were first modified by hexadecyltrimethylammonium bromide, a cationic surfactant. The adsorption efficiencies within 0, 3, 6, 9, 14, 20, 30 and 40 mM nitrate (by modified micro and nano-organobentonite particles) in surfactant loadings of 100 and 200% CEC were investigated in a completely randomized factorial design. Furthermore, to identity the stability of adsorbed nitrate by modified bentonite, the nitrate desorption process was performed at nitrate concentrations of 6 and 20 mM within 15, 30, 45 minutes and in 1, 2, 8 and 16 hours in a completely randomized factorial design. The results indicated that absorption efficiency of nitrate by nano-organobentonite with surfactant loading of 200% CEC in 3, 6, 9, 14, 20, 30 and 40 mM nitrate were 96, 94, 91, 90, 84, 76 and 68%, whereas in micro-organobentonite were 87, 92, 89, 86, 74, 80 and 68% respectively. The results finally revealed that concentration of surfactant was significant on adsorption and release of nitrate (p≤0.01), but the size particles was not significant (p≤0.01). Nano-bentonite in 200% CEC of HDTMA and low concentration of nitrate benefits from a highest adsorption efficiency (96%) with minimum release of 3.7%.