Bentonite functionalized with amine groups by the sol-gel route as efficient adsorbent of rhodamine-B and nickel (II)

Environmental issues caused by population growth and increased industrial activity have become the object of criticism and discussion. This study evaluates how efficiently surfactant-modified bentonite bearing amine groups removes the metal nickel(II) and the dye rhodamine-B (RB) from wastewaters. First, hybrid inorganic-organic materials were obtained by intercalation of a bentonite (Bent) with the surfactant cetyltrimethylammonium bromide (CTA), followed by functionalization with [N-3 (trimethoxysilyl)propyl] ethylenediamine (DAPTMS) by the sol–gel process. Then, the resulting materials were characterized by X-ray diffraction, infrared absorption spectroscopy, thermal analysis, specific surface area analysis, Small-Angle X-ray Scattering, and pH _PZC and tested as adsorbents of Ni(II) or RB by the batch method. X-ray diffraction confirmed that the Bent interlayer space expanded after intercalation with CTA —the basal space varied from 1.3 nm in Bent to 1.8 nm in Bent-CTA and to 1.6 nm in Bent-CTA-DAPTMS. Infrared absorption spectroscopy attested that Bent-CTA-DAPTMS contained organosilane and surfactant: the spectra displayed bands at 2925, 2853, 1470 cm ⁻¹, assigned to the CH ₂, CH ₃, and NH ₂ groups, respectively. The batch adsorption equilibrium experiments revealed that Bent and Bent-CTA-DAPTMS had higher adsorptive capacity for Ni(II) (q _t = 65.77 mg g ⁻¹) and RB (q _t = 0.98 mg g ⁻¹), respectively. The use of nonlinear equation models revealed that Ni(II) or RB adsorption onto the investigated materials followed pseudo-second-order kinetics, thereby confirming the high affinity between adsorbent and contaminants.