Xolisa Shaun Mayama | University of Pretoria (original) (raw)

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Papers by Xolisa Shaun Mayama

Research paper thumbnail of Adsorption of phenol and chromium (VI) from aqueous solution using exfoliated graphite: Equilibrium, kinetics and thermodynamic studies

Arabian Journal of Chemistry, 2021

Several industrial effluents contain Cr (VI) and phenol in varying concentrations. These compound... more Several industrial effluents contain Cr (VI) and phenol in varying concentrations. These compounds are highly toxic even at low concentrations. In this study, Exfoliated Graphite (EG) was investigated as an adsorbent towards the removal of these contaminants. This was motivated by its availability, ease of synthesis and high surface area. The exfoliation process resulted in graphite that had a worm-like accordion structure and an increased surface area from 2.4 to 22.4 m 2 g À1. The optimum loading for both pollutants was 30 g/L and equilibrium was attained in a 48 h period. Maximum Cr (VI) removal (89.8%) occurred under acidic conditions (pH 2) while phenol was preferentially removed (62.3%) under basic environments (pH 12). Three non-linear adsorption models, namely Redlich-Peterson, Freundlich and Langmuir were evaluated. The Redlich-Peterson isotherm, with an exponential constant, b=°0.8982 best described the equilibrium data for Cr (VI) with a regression coefficient of R 2 =°0.9965 while the Langmuir isotherm accurately described the phenol adsorption with a regression coefficient of R 2 =°0.9975. The pseudo-second order rate equation adequately represented the experimental data for phenol and Cr (VI) with regression coefficients greater than 0.99. Adsorption thermodynamic studies revealed that the attachment of phenol and Cr (VI) onto EG was a feasible, endothermic and spontaneous process.

Research paper thumbnail of Adsorption of phenol and chromium (VI) from aqueous solution using exfoliated graphite: Equilibrium, kinetics and thermodynamic studies

Arabian Journal of Chemistry, 2021

Several industrial effluents contain Cr (VI) and phenol in varying concentrations. These compound... more Several industrial effluents contain Cr (VI) and phenol in varying concentrations. These compounds are highly toxic even at low concentrations. In this study, Exfoliated Graphite (EG) was investigated as an adsorbent towards the removal of these contaminants. This was motivated by its availability, ease of synthesis and high surface area. The exfoliation process resulted in graphite that had a worm-like accordion structure and an increased surface area from 2.4 to 22.4 m 2 g À1. The optimum loading for both pollutants was 30 g/L and equilibrium was attained in a 48 h period. Maximum Cr (VI) removal (89.8%) occurred under acidic conditions (pH 2) while phenol was preferentially removed (62.3%) under basic environments (pH 12). Three non-linear adsorption models, namely Redlich-Peterson, Freundlich and Langmuir were evaluated. The Redlich-Peterson isotherm, with an exponential constant, b=°0.8982 best described the equilibrium data for Cr (VI) with a regression coefficient of R 2 =°0.9965 while the Langmuir isotherm accurately described the phenol adsorption with a regression coefficient of R 2 =°0.9975. The pseudo-second order rate equation adequately represented the experimental data for phenol and Cr (VI) with regression coefficients greater than 0.99. Adsorption thermodynamic studies revealed that the attachment of phenol and Cr (VI) onto EG was a feasible, endothermic and spontaneous process.

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