Adsorption of remazol brilliant blue R dye onto jackfruit peel based activated carbon: Optimization and simulation for mass transfer and surface area prediction

Abstract

Adverse effects caused by synthetic dyes can persist in the environment for a long time because they are highly soluble in water and have a stable structure. Hence, the objectives of this study were: (i) to optimize the preparation of jackfruit peel based activated carbon (JPAC) to adsorb remazol brilliant blue R (RBBR) dye and (ii) to simulate the adsorption process using Polymath mass transfer (PMT) model. The JPAC was produced through a physicochemical activation process combining potassium hydroxide, KOH, and carbon dioxide, CO2 treatments. The response surface methodology (RSM) revealed the optimum preparation conditions to be 737 °C, 1.00 h, and 1.92 g/g for activation temperature, activation time, and impregnation ratio (IR), respectively, which corresponded to 196.05 mg/g of RBBR uptakes and 33.18 % of JPAC’s yield responses. The equilibrium study disclosed that the adsorption capacity of JPAC in removing RBBR increased when RBBR starting concentration increased and the adsorption process was favoured at 50 °C (220.56 mg/g) and solution pH of 4 (85.67 mg/g). Isotherm study found the adsorption process to follow the Freundlich model whilst the Langmuir monolayer adsorption capacity, Qm was computed to be 260.46 mg/g. In terms of kinetic, the adsorption process was best described by the PMT model with mass transfer coefficient, km between 0.00069 and 0.00080 mg⋅m/L⋅s and surface area, aPMT estimation of 739.96 m2/g. This value is highly precise in comparison with the actual mesopores surface area of 706.35 m2/g (error = 4.76 %). The functional groups on JPAC’s surface were found to interact with RBBR molecules through hydrogen bonds, dipole–dipole bond and ion–dipole bonds. The thermodynamic study confirmed the adsorption process to be endothermic (ΔH° = 32.36 kJ/mol), increased randomness at the solid–liquid interface (ΔS° = 0.19 kJ/mol.K), spontaneous (ΔG° = −24.69 kJ/mol) and controlled by physisorption (Ea = 29.40 kJ/mol). Besides determining the mass transfer coefficient, this study is novel in terms of applying the PMT model to predict the surface area. Predicting the surface area provides a quick assessment of the adsorption performance of the activated carbon, thus saving time and cost compared to conducting the actual surface area characterization test.