Adsorption of crystal violet dye using Embelia schimperi biochar: optimization using response surface methodology

Crystal violet (CV) is a highly soluble dye used extensively in the textile industry and healthcare. The environmental complex structures of CV result in destructive effects on humans, animals, and the environment. In this study, adsorption of CV using Embelia schimperi biochar as an adsorbent was investigated. E. schimperi waste has unique structural properties and can be used as a biochar and utilized as a low-cost adsorbent. The experiments were two-tier designed: both the classical and optimization by response surface methodology (RSM). Three parameters were evaluated, which are adsorbent dosage, contact time, and pH, while the responses in this study are CV removal (%). Optimization studies were performed using RSM central composite Design using Minitab 17. A quadratic model was chosen for the response. The correlation coefficient, R², for the quadratic model of CV removal (%) was 0.98, and the p < 0.0001. The optimum CV removal (%) predicted was found at 98%, by using 0.11 g of adsorbent dosage, 60 min of contact time, and pH of 7.5 at desirability of 1.0. It was concluded that the spent E. schimperi biochar can be used as an effective adsorbent for CV removal from aqueous solution.