Adsorption of toxic crystal violet dye using rice husk: equilibrium, kinetic, and thermodynamic study

Bio-sorbents have arisen as prospective remediation substantial for the exclusion of colorants. Rice husk, a generally accessible agricultural waste material in Pakistan, was chosen as an adsorbent material for the elimination of synthetic CV tint from a watery solution. The adsorption revisions of mutagenic CV tint from watery solution have been conducted on untreated rice husk by adjusting diverse parameters like adsorbent particle size (105, 210, and 500 mesh sizes), initial dye concentrations (300–450 mg/L), contact interval (5–120 min), pH (1–11), temperature (0°C–50°C) and adsorbent dosage (0.1–1.0 g). Freundlich, Langmuir, and Dubinin–Radushkevich (D–R) adsorption lines were analyzed utilizing the experimental statistics. Freundlich and D–R isotherms fit best with experimental data having R2 values 0.998 and 0.999, respectively. The pseudo-second-order shows excellent agreement out of all the adsorption kinetics because R2 = 1. Thermodynamic parameters (variation in Gibb’s free energy (ΔG°), variation in enthalpy (ΔH°), and variation in entropy (ΔS°)) were also debated and verified. The results indicate that the adsorption process shows feasibility, exothermic behavior, and a positive value of entropy (ΔS°) indicates that randomness prevails the adsorption process in this study. These optimum conditions results in 90.24% of crystal violet dye removal and the maximum adsorption capacity found out was 53.00 mg/g. Applicability of maximum conditions with tap water results in 80.6% removal of CV dye which indicates that rice husk might be able to recycle at a low price and proved effectual adsorbent material for the elimination of crystal violet tint from discarded water.