Malachite green dye adsorption by jackfruit based activated carbon: Optimization, mass transfer simulation and surface area prediction

Abstract

The exposure of basic dye towards human and environment can caused severe adverse effects. Hence, this study aimed (i) to optimize the adsorption of malachite green (MG) dye onto jackfruit peel based activated carbon (JPAC) by using response surface methodology (RSM) and (ii) to simulate the mass transfer process using Polymath mass transfer (PMT) model. The RSM revealed that the optimum activation temperature, activation time and potassium hydroxide (KOH) impregnation ratio, IR to be 782 °C, 1 h and 2.96 g/g which translated into 66.80 mg/g of MG adsorption and 34.52 % of JPAC's yield. The Freundlich isotherm model described the adsorption process the best while the Langmuir monolayer adsorption capacity was computed to be 376.33 mg/g. The kinetic data obeyed the PMT model the best where the rate constant, KPMT decreased from 1.20 to 0.41 h−1 as the MG concentration increased from 25 to 300 mg/L. Also, the PMT model was succeeded in predicting the surface area, aPMT of JPAC to be 807.77 m2/g and this value is comparable with the actual JPAC's mesopores surface area of 714.25 m2/g (error 11.58 %). The adsorption of MG onto JPAC was aided by several functional groups such as primary or secondary alcohol, non-bonded hydroxy group and methoxy through ion-dipole force and dipole-dipole force. Based on thermodynamic parameters, MG-JPAC adsorption system was endothermic in nature (∆H° = 37.12 kJ/mol), had an increment of randomness at solid-liquid interface (∆S° = 0.19 kJ/mol·K), spontaneous in nature (−20.11 kJ/mol) and physisorptionally governed (Ea = 9.46 kJ/mol).