Efficient adsorption of malachite green and Congo red dyes by the surfactant (DS) intercalated layered hydroxide containing Zn2+ and Y3+-ions

Abstract Acetate intercalated layered Zn–Y hydroxide with the chemical formula Zn0.68Y0.32 (OH)2 (CH3COO)0.32.0.46H2O was synthesized by the hydrolysis of metal acetates. It was modified with dodecylsulfate (DS) by self-assembly process. The samples were characterized by powder X-ray diffraction (PXRD), FTIR, thermo gravimetric and CHNS analysis. Morphology of these samples was examined using SEM images. Bilayer orientation of the surfactant molecules in the interlayers of Zn–Y hydroxides was inferred from PXRD, FTIR spectroscopy results. Introduction of surfactant molecules in the interlayer resulted in high BET specific surface area of 279 m2/g for the sample. The lower zeta potential value of − 5 mV supported the intercalation of higher amounts of dodecyl sulfate (DS) in the interlayer. The organo modified sample was investigated as adsorbent for the removal of malachite green (MG) and Congo red (CR) dyes from water. The effects of some variables such as the contact time, adsorbent dosage, pH variation on the adsorption capacity of the surfactant intercalated hydroxide towards these dyes were studied. Adsorbent–adsorbate interaction understood by fitting the experimental isotherm data using Langmuir and Freundlich models. Kinetic studies showed that the adsorption to be promoted possibly by chemisorption. The adsorption capacity of DS-intercalated Zn–Y hydroxide was found to be 102.987 mg/g (for MG) and 96.246 mg/g (for CR). Analyses of Langmuir isotherm parameters suggested the adsorption process to be highly favorable. The adsorption capacity remained invariant over a wide pH range for both the dyes.