Adsorption of Methylene Blue and Phenol On Activated Carbon Prepared from Fox Nutshell by K2CO3 Activator

Abstract

Water pollution occurs due to rapid urbanization and industrialization. Polluted water comes from different industries like petroleum, coal processing, textile, pharmaceutical, food processing, plastic, pesticide, paper and pulp etc. are highly toxic, and effect to the living being and our environment. There are many toxic compounds present in the polluted water like inorganic and organic compounds. Methylene blue and phenol are considered as matter of interest to remove because both are toxic in nature. Various treatment processes used for the removal of phenolic compounds and dyes are adsorption, microbial degradation, wet air oxidation, ion exchange etc. Low cost adsorbent such as activated carbons are best option for removal of methylene blue and phenol from aqueous effluents. Activated carbons were prepared from Fox nutshell as an agricultural waste by chemical activation method using K2CO3 activating agent. Preparation of activated carbons were carried out at different K2CO3/Fox nutshell ratios, carbonization temperatures and activation time, which had significant effect on the performances of activated carbons like BET surface area. Specific surface area of activated carbon was maximum as 1236 m2/g at 800 ºC with activation duration of 1 h and at a K2CO3/Fox nutshell ratios mass ratio of 0.5. The porous properties, surface microstructure in addition to the surface functional groups of the prepared carbons were characterized by N2 adsorption/desorption isotherm, SEM and FTIR, respectively. The results show that both the carbonisation temperature and impregnation ratio noticeably affected the BET surface area as well as micro and mesopore volumes. Batch studies of methylene blue dye and phenol adsorption were conducted to evaluate the effect of various experimental parameters like pH, temperature, adsorbent dose, and contact time effect. The equilibrium adsorption data of methylene blue and phenol on adsorbent were analysed by the Langmuir, Freundlich and Temkin isotherm models. The isotherm data are well described by theFreundlich isotherm model for methylene Blue and phenol adsorption. Inter-particle diffusion, Pseudo-first-order, pseudo-second order models were used to analyze the kinetic data obtained at different concentrations of both adsorbates. The adsorption kinetics was well described by the pseudo-second-order kinetic model for both MB and phenol solutions. For methylene blue and phenol maximum adsorption capacity are found to 499.17 mg/g and 29.52 mg/g, respectively at 30 ºC. Thermodynamic parameters such as the standard Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) obtained in this study indicated that the adsorption of methylene blue and phenol by prepared activated carbon is spontaneous, endothermic and entropy increase in the degree of freedom (or disorder).