Synthesis, characterisation and application of organic and inorganic bentonite for the removal of gentian violet

Abstract

ABSTRACT The intensive use of dyes in industry has caused serious pollution problems, due to industrial wastewater discharges. It is well known that dyes have harmful effects on humans, animals, and other living beings. Therefore, the treatment of industrial wastewater before its release into the environment requires great attention. This work is devoted to the study of the effect of organic modifications by DMSO and/or CTAB and an inorganic modification by spinel oxide ZnCr2O4 on the structural and textural properties of local clay (M’Zila bentonite). The materials resulting from these modifications are used as adsorbents for a cationic dye such as gentian violet. These materials were synthesised and characterised by XRD, FTIR, BET and SEM. These analyzes confirmed the considerable changes in the structure of the clays modified by DMSO and/or CTAB- ZnCr2O4, the formation of pillared bentonites and the increase in the basal spacing’s of the modified clays by 15.05 Å for the bentonite of M’Zila at 23.80 Å for bentonite-CTAB-ZnCr2O4 (BCZnCr), at 27.37 Å for bentonite-DMSO-ZnCr2O4 (BDZnCr) and at 25.89 Å for bentonite-DMSO-CTAB-ZnCr2O4 (BDCZnCr).These modifications produced a rougher and more porous surface, resulting in a significant increase in the specific surface area from 60.13 m2 g−1 for sodium bentonite to 104.63 m2 g−1 for BCZnCr and 104.59 m2 g−1 for BDCZnCr. The adsorption of gentian violet was carried out under the following conditions: solid liquid ratio: 1 g/L, pH = 10 and contact time at equilibrium 1 h. The adsorption kinetics perfectly follows the pseudo second order model as well as that of intraparticle diffusion for all materials. The isotherms are of type S; they are well described by the Langmuir-Freundlich model. The thermodynamic parameters indicate that the physisorption of gentian violet by the different materials is spontaneous, exothermic, and disordered.