Evaluation of adsorption properties of organic wastes in aqueous media for arsenic removal

Arsenic is toxic and one of the most prominent environmental challenges especially in water quality. The World Health Organization recommends 10 µg/L as the acceptable level limit in drinking water. The use of materials that are easily reproducible, economical and are envisaged as ‘waste’ is paramount in water treatment technologies sustainability. In this study, organic wastes: rice husks (RH) and orange peels powder (OPP) were used as adsorbents in arsenate contaminated drinking water treatment to ascertain purification properties. The adsorbents were processed into two different particle sizes: 841 µm and 42.5 µm powders via sieve analysis. These adsorbents were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy for morphological and functional group studies, respectively. The batch adsorption studies show that arsenic removal efficiency of the adsorbents with smaller particle size (425 µm) was greater than with larger particle size (841 µm) being 96.38% and 82.2%, respectively, for the same mass of rice husk (RH). The adsorption mechanisms for the rice husk (RH) can be described as chemisorption process since it best fits the pseudo-second-order model. The isotherm modeling of the adsorption data was found to be described using the Freundlich isotherm model. The adsorption data for orange peels powder (OPP) were, however, best described by Langmuir isotherm and pseudo-second-order kinetics models. The organic wastes, RH and OPP were found to be efficient in the removal of Arsenic(V) from contaminated waters.