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 m2/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.

Comparative and Equilibrium Studies on Anionic and Cationic Dyes Removal by Nano-Alumina-Doped Catechol Formaldehyde Composite

Nano-alumina-doped catechol formaldehyde polymeric composite was prepared, characterized, and applied as an adsorbent for the removal of an anionic dye Congo red (CR) and a cationic dye SafraninO (SF), by adsorption process especially from aqueous solutions. Characterizations such as particle size distribution, zeta potential, BET, FTIR, and FESEM-EDAX were carried out for the adsorbent prepared. All experiments were conducted at the batch condition to study the effects of initial dye concentration (CR: 30–90 mg/L and SF: 10–50 mg/L), pH (2–11), temperature (25–55°C), and adsorbent dosage (0.05–0.3 g) on dye removal. The isotherm models (Langmuir, Freundlich, and Temkin) were analyzed for this adsorption work. The kinetic data obtained were analyzed by the pseudo-first-order, pseudo-second-order, Bangham, and Chien–Clayton equations. Dyes adsorption data were well fitted with the Freundlich isotherm equilibrium model and the pseudo-second-order kinetic model. Study results suggested that the nano-alumina-polymeric composite could be an effective adsorbent for anionic dye rather than cationic dye.