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

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

de Morais Pinos, Jéssica Yasmin / de Melo, Leticia Barbosa / de Souza, Suelen Delfino / Marçal, Liziane / de Faria, Emerson Henrique

Abstract

Abstract 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 pHPZC 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 CH2, CH3, and NH2 groups, respectively. The batch adsorption equilibrium experiments revealed that Bent and Bent-CTA-DAPTMS had higher adsorptive capacity for Ni(II) (qt = 65.77 mg g⁻¹) and RB (qt = 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.

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Highlights • Intercalation of CTA cations and DAPTMS was evaluated in full by Small-Angle X-Ray Scattering. • Textural properties showed higher differences between Bent pristine and organoclays. • Adsorbents were used for Ni(II) and Rhodamine B adsorption. • Treated solids present higher affinity by organic molecules through hydrophobic and ionic interactions. • The adsorption mechanism of Ni(II) and Rhodamine B was explained by theoretical kinetic and equilibrium models.