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Batch adsorption of malachite green dye from aqueous solution using sawdust of Swietenia macrophylla (mahogany wood)

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Opia C. F., Obinna N. V., Chizoruo I. F., Obinna I. B.

World News of Natural Sciences

2023

vol. 50

222-246

Sawdust of Swietenia macrophylla waste was used as a bio-sorbent for the removal malachite green from aqueous solutions in this study. Various parameters’ effect such as contact time, pH, initial dye concentration, temperature and adsorbent dosage were studied on the bio-sorbent. Spectrophotometric technique was implemented for the measurement of dye concentration before and after adsorption. The study indicated that the quantity of dye adsorbed increased steadily with increase in the dye’s initial concentration and contact time because as the concentration increases the dye molecules available for adsorption also increases. There was a sharp rise in the quantity of dye adsorbed as the pH increases from pH 2 to pH 7, equilibrium was obtained at pH 10 after which the quantity of dye adsorbed decreased with an increased to pH 12. As the temperature increases the quantity of dye adsorbed decreased, this can be attributed to an increase in solubility as the temperature increases. The experimental data were fitted to the Langmuir and Freundlich adsorption isotherms with Langmuir isotherm showing a better fit than Freundlich isotherm model, this shows that the adsorption follows a homogenous coverage signifying saturated monolayer coverage of the solute molecules on the adsorbent surface. The adsorption kinetics data were fitted to pseudo-first and pseudo-second order kinetic model with pseudo-second order kinetic model showing a better fit than pseudo-first order kinetic model, indicating that more than one process affects the adsorption of malachite green dye onto Swietenia macrophylla. In terms of thermodynamic parameters, negative values were obtained for Gibbs free energy ∆G o, indicating a spontaneous adsorption process; also the enthalpy change ∆H° was negative signifying the adsorption is exothermic in nature. Similarly, entropy ∆S° values were negative indicating that the degree of disorderliness of malachite green reduced as it got adsorbed onto the surface of the adsorbent.

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1 World News of Natural Sciences

1 2023

1 Chizoruo I. F.

1 Obinna I. B.

1 Obinna N. V.

1 Opia C. F.

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Batch adsorption of malachite green dye from aqueous solution using sawdust of Swietenia macrophylla (mahogany wood)