Treatment of textile effluents by chloride-intercalated Zn-, Mg- and Ni-Al layered double hydroxides

This work involved the preparation, characterization and dyes removal ability of Zn-Al, Mg-Al and Ni-Al layered double hydroxide (LDH) minerals intercalated by chloride ions. The materials were synthetized by the co-precipitation method. X-ray diffraction, Fourier transform infrared, thermogravimetric-differential thermal analysis and transmission electron microscopy characterization exhibited a typical hydrotalcite structure for all the samples. Adsorption experiments for methyl orange were performed in terms of solution pH, contact time and initial dye concentration. Experimental results indicate that the capacity of dye uptake augmented rapidly within the first 60 min and then stayed practically the same regardless of the concentration. Maximum adsorption occurred with acidic pH medium. Kinetic data were studied using pseudo-first-order and pseudo-second-order kinetic models. Suitable correlation was acquired with the pseudo-second-order kinetic model. Equilibrium data were fitted to Langmuir and Freundlich isotherm models. The maximum Langmuir monolayer adsorption capacities were 2,758, 1,622 and 800 mg/g, respectively, for Zn-Al-Cl, Mg-Al-Cl and Ni-Al-Cl. The materials were later examined for the elimination of color and chemical oxygen demand (COD) from a real textile effluent wastewater. The results indicated that the suitable conditions for color and COD removal were acquired at pH of 5. The maximum COD removal efficiency from the effluent was noted as 92.84% for Zn-Al-Cl LDH.