This study was aimed to prepare cocoa nibs based activated carbon (CNAC) via chemical activation for methylene blue (MB) dye adsorption from aqueous solution. The activation process was performed at 500°C under inert condition using K2CO3 as activation agent. The effect of contact time and initial concentration of adsorbate on the adsorption process were examined. Langmuir isotherm model fitted well the adsorption equilibrium data with monolayer adsorption capacity of 64.98 mg/g at 30°C. The adsorption kinetic was found to follow the pseudo-second-order kinetic model. Keywords: Activated carbon, Chemical activation, Cocoa nibs, Methylene blue.

Remazol brilliant blue R dye (RBBR) brings toxicity to living organisms once it enters the environment. This study utilized response surface methodology (RSM) and Polymath software for optimization and mass transfer simulation purposes, respectively. RSM revealed that the optimum preparation conditions of meranti wood-based activated carbon (MWAC) were 441 W, 5.76 min, and 1.35 g/g for radiation power, radiation time, and KOH:char impregnation ratio (IR), respectively, which translated into 86.39 mg/g of RBBR uptakes and 31.94 % of MWAC’s yield. The simulation study predicted the mass transfer rate, rm to be 112.20 to 1007.50 s 1 and the adsorption rate, k1 to be 3.96 to 4.34 h 1 . The developed model predicted the adsorption surface area, am to be 790.04 m2 /g and this value is highly accurate as compared to the actual mesopores surface area of 825.58 m2 /g. Mechanism analysis divulged that the interaction that occurred between RBBR molecules and MWAC’s surface were hydrogen bond (methylene and alkyne), dipole–dipole force (alkyl carbonate, terminal alkyne, and methoxy), and ion–dipole force (primary amine). The isotherm and kinetic studies found that the adsorption data obeyed the Freundlich model and pseudo-first-order (PFO) model the best, respectively. The Langmuir maximum adsorption capacity, Qm was computed to be 327.33 mg/g. Thermodynamic parameters were calculated to be 4.06 kJ mol 1 , 0.06 kJ mol 1 K 1 , –22.69 kJ mol 1 , and 16.03 kJ mol 1 for DH , DS , DG , and Ea, respectively, which signified the adsorption process studied was exothermic, spontaneous and governed by physisorption.

Polluting the environment with synthetic dyes can adversely affect humans, animals, and plants. This study aimed to produce optimized palm-trunk-based activated carbon (PTAC) using response surface methodology (RSM) to remove methylene blue (MB) dye. The PTAC was prepared by physical activation with microwave radiation and carbon dioxide (CO2) gasification. The RSM revealed the optimal PTAC preparations with an activation time of 4 minutes and a radiation power of 501 W, respectively. Optimized PTAC removed 91.25 % of the MB dye, and the PTAC yield was 32.37 %. The Brunauer- EmmettTeller (BET) surface area of this sample is 772.35 m2 /g, the pore volume is 0.45 cm3 /g, and the fixed carbon content is 74.30 %. The pores created in PTAC is mesopores type of pores, with an average diameter of 3.88 nm. The Freundlich model performed the best on the adsorption isotherm which signified the multilayer coverage of MB occurred on the surface of PTAC. The maximum monolayer adsorption capacity, Qm computed from Langmuir model was found to be 312.50 mg/g. In terms of kinetic study, the pseudo-second-order (PSO) model performed the best with rate constant, k2 decreased from 0.087 to 0.016 g/mg.h when MB initial concentration increased from 25 to 300 mg/L. The thermodynamic study revealed that the adsorption of MB onto PTAC was endothermic in nature (H° = 34.48 kJ/mol), spontaneous (G° = -5.22 to -8.99 kJ/mol) and governed by physisorption (Ea = 7.33 kJ/mol). Therefore, PTAC showed excellent application in dyes wastewater treatment systems.

This research aims to optimize preparation conditions of coconut-shell-based activated carbon (CSAC) and to evaluate its adsorption performance in removing POP of dichlorodiphenyltrichloroethane (DDT). The CSAC was prepared by activating the coconut shell via single-stage microwave heating under carbon dioxide, CO2 flow. The total pore volume, BET surface area, and average pore diameter of CSAC were 0.420 cm3/g, 625.61 m2/g, and 4.55 nm, respectively. The surface of CSAC was negatively charged shown by the zeta potential study. Response surface methodology (RSM) revealed that the optimum preparation conditions in preparing CSAC were 502 W and 6 min for radiation power and radiation time, respectively, which corresponded to 84.83% of DDT removal and 37.91% of CSAC’s yield. Adsorption uptakes of DDT were found to increase with an increase in their initial concentration. Isotherm study revealed that DDT-CSAC adsorption system was best described by the Langmuir model with monolayer adsorption capacity, Qm of 14.51 mg/g. The kinetic study confirmed that the pseudo-second-order model fitted well with this adsorption system. In regeneration studies, the adsorption efficiency had slightly dropped from 100% to 83% after 5 cycles. CSAC was found to be economically feasible for commercialization owing to its low production cost and high adsorption capacity.