Vitex doniana seed activated carbon for methylene blue adsorption: equilibrium and kinetics

This study evaluated the characteristics of zinc chloride modified vitex doniana seed activated carbon (VDZnCl2) for the removal of methylene blue. VDZnCl2 was characterized for textural properties, surface morphology and surface chemistry. Batch adsorption of methylene blue by VDZnCl2 was evaluated for the effects of concentration, contact time, adsorbent dosage, and solution pH. The surface area increased from 14 to 933 m(2)/g with porous texture to facilitate adsorption. The SEM micrograph showed varieties of pores with widened cavities. The FTIR spectra showed the characteristics of O-H and C=C groups commonly found in carbonaceous materials. The maximum methylene blue adsorption was recorded as 238 mg/g at concentration range of 1-800 mg/L and VDZnCl2 dosage of 50 mg. Sips isotherm fitted well with the equilibrium data, suggesting that the adsorption by VDZnCl2 was a physical process onto its heterogeneous surface, while the applicability of pseudo-first-order kinetics implies that external diffusion was the rate controlling mechanism. The performance put up by VDZnCl2 suggested that it is a potential adsorbent substitute for dye wastewater treatment. NOVELTY STATEMENTVitex doniana commonly known as black plum is a deciduous flowering tree that grows around West Africa. Over 80% of the fruit is seed, and often discarded. To date, this seed has received marginal recognition as activated carbon feedstock for the removal of dyes and organic pollutants. However, there is no known study on the synthesis of zinc chloride (ZnCl2) modified activated carbon from vitex doniana seed and its adsorption of methylene blue from wastewater. Therefore, this study was a first-time attempt of the synthesis of ZnCl2 modified activated carbon adsorbent from vitex doniana and its removal of methylene blue from wastewater. This work systematically encouraged indigenous adsorbent synthesis for wastewater treatment and contribution to sustainable development goals.