Adsorption of crystal violet dye by using a low-cost adsorbent – peanut husk

Abstract

Nowadays, industrial effluent containing textile dyes is considered a major environmental con-cern. Crystal violet (CV) is one of the vital textile dyes of the triphenylmethane group and it is known for its mutagenic and mitotic poisoning nature so it must be treated. This study aims to evaluate the adsorption potential of peanut husk (PH) towards CV dye removal. Adsorption studies are conducted to study the effects of different parameters on adsorption such as particle size of adsorbent (105, 210, and 500 mesh sizes), initial dye concentration (5–100 mg/L), contact time (5–120 min), pH (1–11), temperature (0–60°C), and adsorbent dosage (0.1–1.0 g). Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models are applied to experimental data for the determination of the nature of adsorption. The kinetic studies have been carried out using the pseu-do-first-order, pseudo-second-order, and intra-particle diffusion model for adsorption of CV on PH. Thermodynamic parameters such as changes in Gibb’s free energy (∆G), enthalpy (∆H), and entropy (∆S) are also determined. Optimum conditions for maximum removal of toxic CV dye from waste-water on PH includes 210 mesh size, 100 ppm initial dye concentration with 10 min contact time at temperature 30°C using 0.1 g of adsorbent. Alkaline medium favors adsorption of CV onto the surface of PH and its maximum removal is observed at a pH of 8. These optimum conditions result in 90% removal of CV dye from aqueous solution and the maximum adsorption capacity found out was 20.95 mg/g. Applicability of this developed procedure with tap water is 83.16% indicating that the PH is a promising adsorbent for the removal of cationic CV dye from the aqueous solution.