Abstract
The present study aims to investigate the applicability of γ-Al2O3 nanoparticles (NPs) adsorbent for removal of arsenite and arsenate from aqueous solution. The nano-adsorbent was characterized using zeta potential analysis, dynamic light scattering, field emission scanning microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Batch adsorption studies were carried out to optimize adsorption parameters such as contact time, stirring speed, initial arsenic concentration, adsorbent dose, pH and effect of different competing anions. Langmuir adsorption capacities obtained at 298 K are 769.23 µg/g and 1000 µg/g for As(III) and As(V) removal correspondingly. The adsorption mechanism was well established by pseudo-second-order kinetic model. Negative values of enthalpy (ΔH°) obtained during adsorption [− 29.12 kJ/mol and − 35.55 kJ/mol for As(III) and As(V), respectively] confirmed the process was exothermic in nature. The negative values of ΔG° [− 6.14 to − 3.86 kJ/mol for As(III) and − 9.32 to − 6.68 kJ/mol for As(V)] further affirmed that the adsorption process is spontaneous in nature. There was no requirement of additional external energy supply for the enhanced removal as the adsorption was less favoured at high temperature. Phosphate and sulphate had the profound effect on reduction in the removal efficiency. Good regenerating efficiency of γ-Al2O3 NPs up to fourth cycle implied economic feasibility of the adsorbent. The effectiveness of γ-Al2O3 was also proved for removal of arsenic from real arsenic-contaminated groundwater.
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