Mechanistic performance of organic pollutants removal from water using Zn/Al layered double hydroxides imprinted carbon composite

Abstract

A lithe zinc-aluminium layered double hydroxides were imprinted on activated carbon and fabricated Zn/Al LDHs@C composite. The composite matrix was utilized for the removal of toxic Congo Red (CR), Acid Red 1 (AR1) and Reactive Red 2 (RR2) dyes from water. The Zn/Al LDHs@C composite was characterized by Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy Dispersive X-Ray Analysis (EDAX), Brunauer-Emmett-Teller (BET), Thermogravimetric analysis-Differential scanning calorimetry (TGA-DSC) and Powder X-ray diffraction (PXRD) analytical techniques. The adsorption process was evaluated by varying the parameters such as contact time, composite dosage, pH of the solution, initial dye concentration and interfering anions. The maximum adsorption of CR, AR1 and RR2 dyes on Zn/Al LDHs@C composite were 44.09, 48.37 and 49.52 mg/g, respectively. The enhanced adsorption efficiency of the composite might be due to the existence of binding forces such as electrostatic attraction of the layered double hydroxide, hydrogen bonding sites on the Zn/Al LDHs@C and the surface complexation phenomena of the composite with the dye molecules. The Freundlich isotherm model was fit superior at the saturation point, indicating the heterogeneous surface interaction. Thermodynamic studies recommend that the adsorption process was spontaneous and endothermic in nature. The adsorption-desorption studies of Zn/Al LDHs@C composite were achieved up to five successive cycles with high efficiency. The enhanced adsorption efficiency of the Zn/Al LDHs@C composite suggested that the fabricated composite was suitable for the removal of CR, AR1 and RR2 dye molecules from water than any other developed hybrids.