Adsorption of chromium ions from tannery effluents onto activated carbon prepared from rice husk and potato peel by H3PO4 activation

Ephraim Vunain,Joel Brian Njewa,Timothy Tiwonge Biswick,Adewale Kabir Ipadeola

doi:10.1007/s13201-021-01477-3

Ephraim Vunain, Joel Brian Njewa + Show 2 more

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https://doi.org/10.1007/s13201-021-01477-3

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Abstract

Two biomass agricultural waste materials; rice husks (RH) and potato peels (PP) were used as precursors for preparation of activated carbons by chemical activation using phosphoric acid for adsorption of hexavalent chromium [Cr(VI)] from tannery effluents. The prepared rice husk (RH–AC) and potato peel activated carbon (PP–AC) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. Adsorption experiments were performed by varying pH, agitation speed, contact time, adsorbent dose and initial metal ion concentration. Freundlich, Langmuir and Temkin isotherms were used to analyze the equilibrium data obtained at different adsorption conditions. It was found that the adsorption isotherms were well fitted by the Freundlich equation and the adsorption process was found to follow pseudo-second-order rate kinetics. Adsorption results obtained show a maximum Cr(VI) uptake being attained at pH 2.0, with chromium removal efficiency of 99.88% and 99.52% for RH–AC and PP–AC, respectively. RH–AC and PP–AC are effective adsorbent for the removal of chromium(VI) ions from wastewater.

Highlights

Water pollution from anthropogenic activities is a common problem nowadays
The present study has shown the effectiveness of activated carbons derived from the agro-wastes through chemical activation for the removal of chromium ions from tannery effluents
The efficacy of rice husks (RH)–AC and potato peels (PP)–AC was evaluated through batch adsorption study with a variation on solution pH, initial concentration, adsorbent dosage, contact time and agitation speed

Summary

Introduction

Water pollution from anthropogenic activities is a common problem nowadays. Chromium sulfate is a compound that is most commonly used in tanneries to stabilize animal hides by cross linking the collagen fibers and the exhausted effluents produced by leather tanneries is rich in chromium (Taylor et al 2014). The effluents from the tanning process contain both Cr(III) and Cr(VI) in high concentrations ranging from tens to hundreds of mg/L (Yavuz et al 2006). Cr(III) is only toxic to plants in very high concentrations and is less toxic, or nontoxic, to animals, the hexavalent form (Cr(VI)) has been considered more harmful to public health due to its carcinogenic, hemotoxic, and genotoxic properties (Nahid et al 2020; Yavuz et al 2006). The objective of this work is to investigate the performance of RH–AC and PP–AC for Cr(VI) removal from tannery wastewater at different experimental conditions. Parameters such as initial pH, adsorbent dosage, initial concentration and agitation speed were investigated to find their effects on the adsorption of Cr(VI)

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