Effect of pH on the adsorption kinetics of Cr(VI) on sodium chlorite treated coconut coir

Abstract

Coconut coir is a low cost bioadsorbent containing large amount of lignin. In this research work sodium chlorite treated coconut coir (SCT-CC) was used to remove Cr(VI) from industrial wastewater by implementing adsorption technique through the investigation of the adsorption kinetics at different pH values. The maximum Cr(VI) adsorption capacity of SCT-CC at pH 2.00, 3.00, 5.00 and 7.00 was 24.75, 23.92, 16.07 and 6.31 mg Cr(VI) g -1 SCT-CC respectively with the dose of 7.5 g/L. The equilibrium established within three hours resulting the maximum removal (95%) of chromium. The adsorption kinetics of Cr(VI) on SCT-CC was found to be regulated by pH of the system. Rate of adsorption was the highest at pH 2.00 and the kinetic data well-fitted with Ho's pseudo second order kinetics. Fourier transform infrared (FT-IR) spectrometry analysis indicated that the carbonyl (C=O) groups and hydroxy (O-H) groups from the lignin structure in coconut coir may be involved in the mechanism of Cr(VI) adsorption and it showed good agreement with the kinetic data to elucidate the adsorption mechanism.

A Review on Natural Fiber Bio-Composites, Surface Modifications and Applications

“…The sodium chlorite method has shown promising results to reduce moisture content and to enhance the hydrophobic properties of the fiber. Sodium chlorite is utilized in bleaching the fibers to form chlorine dioxide, which reacts with lignin to effectively remove it, and also reacts with hemicellulose to improve the hydrophobic nature [ 120 , 121 ]. Steric acid contains carboxyl groups, and these groups react with hydroxyl groups to decrease their hydrophilic nature.…”

Kinetic Model for pH Variation Resulted from Interaction of Aqueous Solution Contaminated with Nickel Ions and Cement Kiln Dust

“…However, further investigations must be achieved to explore the behaviour of affinity series and sorbent selectivity under the pH effect. In the affinity series of systems with single metal, this metal with the highest affinity may rarely be affected by the existence of other heavy metals in solution [40,41].…”

Modified coconut coir to remove hexavalent chromium from aqueous solution

“…The Cr(VI) adsorption efficiency of activated carbon based on coconut shell was reported to decrease with the increase of the system pH values from 2 to 10. Islam et al (2016) showed the effect of pH on the adsorption kinetics of Cr(VI) on sodium chlorite treated coconut coir. In that case the rate of adsorption was shown to decrease as the pH was tuned from lower to higher values.…”