Optimization of malachite green adsorption from aqueous solution onto Anchote peel based activated carbon using Box Behnken design

¹ Institute of Technology, School of Water Resource and Environmental Engineering, Haramaya University, P.O. Box 138, Dire Dawa, Ethiopia
² Civil Engineering Department, The Papua New Guinea University of Technology, Papua New Guinea
³ Department of Chemical Engineering, College of Engineering and Technology, Wachemo University, P.O.Box. 667, Hossana, Ethiopia

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 5 February 2026

Abstract

Malachite green–contaminated wastewater discharged without proper treatment poses serious risks to human health and the environment. Therefore, this study evaluated the adsorptive removal of malachite green from aqueous solution using activated carbon derived from anchote peel. The adsorbent was prepared via chemical activation with phosphoric acid followed by thermal activation in the absence of oxidizing agents. Adsorption optimization was performed using the Box–Behnken design of response surface methodology with four variables: pH (3, 6, 9), initial dye concentration (50, 100, 150 mg/L), adsorbent dosage (0.5, 1.0, 1.5 g/100 mL), and contact time (30, 60, 90 min), resulting in 30 experimental runs. The maximum dye removal efficiency of 99.07% was achieved at pH 9, 50 mg/L initial concentration, 1.5 g/100 mL dosage, and 90 min contact time. ANOVA confirmed strong agreement between adjusted and predicted values (R² = 0.9935 and 0.9917) based on the quadratic regression model. These findings demonstrate that anchote peel–based activated carbon is an efficient adsorbent for malachite green removal, and its optimization using the Box–Behnken design provides a promising approach for large-scale treatment of dye-laden industrial wastewater