Effective adsorption of hexavalent chromium using biopolymer assisted oxyhydroxide materials from aqueous solution

The mixed oxyhydroxide (MOH) and chitosan assisted mixed oxyhydroxide (CSMOH) adsorbents were synthesized via eco-friendly one pot co-precipitation method and their efficacy was tested towards the removal of hexavalent chromium from synthetic aqueous solution. Aluminium-lanthanum mixed oxyhydroxide (ALMOH) and chitosan/aluminium-lanthanum mixed oxyhydroxide (CSALMOH) were characterized using fourier transfer infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) with mapping, X-ray diffraction analysis, themogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The maximum adsorption capacity of Cr(VI) onto the sorbents was found to be higher at pH 4-5 with the dosage of 2 g/L at 200 mg/L dichromate solution. The sorption capacities of ALMOH and CSALMOH were 49.80 and 78.90 mg/g, respectively. Various isotherm models analysis viz., Langmuir, Freundlich and Dubinin-Radushkevich models were employed to correlate the experimental data. Thermodynamic studies were carried out to understand the nature of the sorption and feasibility of the reaction. The regeneration studies were also carried out up to 5 cycles and to examine the potential of the CSALMOH was examined.