Removal of Congo Red from aqueous solution by adsorption on pandan leaves (Pandanus Amaryllifolius) Biochar using response surface methodology

Congo Red (CR) dye has been widely used in manufacturing industries. Improper treatment before discharge of effluents was the main factor of CR being discharged into water streams. CR may cause various of negative impacts to the environment, animal and human health when it is exposed abundantly into environment. There was a lot of studies was being conducted to show agricultural waste can be used to remove dye from effluents. Agricultural wastes were abundantly available, low cost and environmentally friendly. In this study, adsorption of pandan leaves biochar as adsorbent was investigated. Batch adsorption studies was carried out to investigate the effect of various adsorption parameters which are adsorbent dosage, contact time and pH while the responses in this study are CR removal (%) and adsorption capacity (mg/g). Range of parameters were adsorbent dosage (0.0025 g to 0.05 g), contact time (10 minutes to 60 minutes) and pH (1 to 5). Optimisation studies were performed using Response Surface Methodology (RSM). Quadratic model or second-order polynomial model containing linear and two factors terms was studied using Central Composite Design (CCD). The correlation coefficient, R2 for the quadratic model of CR removal (%) was 0.9473 whereas 0.9912 for quadratic model of adsorption capacity (mg/g). The interaction effects of the variables to the responses were studied using the two-dimensional (2D) contour plot and three-dimensional (3D) response surface graph. The optimum conditions for CR removal that predicted by RSM were found at 0.016 g of adsorbent dosage, 33.654 minutes of contact time and pH 1.165. CR removal was up to 99.949 % at desirability of 1. The predicted optimum conditions for adsorption capacity (mg/g) were found at 0.025 g of adsorbent dosage, 32.724 minutes of contact time and pH 1.015. The adsorption capacity was up to 4.8818 mg/g at desirability of 1.