Usage of a new macro-hierarchical graphene sponge in batch adsorption and packed column configuration for efficient decontamination of cadmium in aqueous environment

Abstract

Cadmium is one of the most harmful metallic elements which requires immediate measures on its sequestration from polluted aquatic environment. This research emphasised on the development of a new macro-hierarchical graphene oxide configuration as an adsorbing agent for cadmium decontamination in batch and continuous aqueous adsorption systems. The graphene composite was prepared by integrating graphene oxide, xanthan gum and titanium isopropoxide (GO/XG/TI) via a facile freeze-casting approach, using water as the pore forming agent. The batch equilibrium of the new cadmium-GO/XG/TI adsorption system was well predicted by the Freundlich isotherm while the kinetic performance followed closely the pseudo-second-order kinetic correlation. The regeneration results indicated that the adsorbent had the ability to retain 80.75% of its initial adsorption performance even after five successive cycles. A continuous GO/XG/TI aerogel column study was executed for the first time by altering the bed height, feed flowrate and influent concentration. The greatest bed capacity of 64.052 mg/g was attained at a column height of 3 cm, influent cadmium concentration of 100 mg/L and feed flowrate of 2 mL/min. The dynamic column data were correlated to the Adams-Bohart, Thomas and Yoon-Nelson models. Fourier-transform-infrared spectroscopy, point of zero charge and pH studies verified complexation and electrostatic interaction as the dominant mechanisms which anchored the cadmium ions onto the GO/XG/TI adsorbent. The findings from both batch and continuous packed-bed studies supported the use of as-fabricated GO/XG/TI as an efficient purifying agent for the remediation of cadmium in aqueous environment.