Valorization of spent activated carbon in glycerine deodorization unit for methylene blue removal

Abstract

Spent Calgon Filtrasorb activated carbon (SAC) from glycerine deodorization unit was evaluated for the removal of methylene blue (MB). The SAC was used without further modification. The SAC was characterized for BET surface area, pH, pHpzc and FTIR to determine the textural and chemical properties of SAC. The batch adsorption study of MB was carried out under different initial concentrations (5–500 mg/L), pH (2–11) and contact time (0–200 h). The SAC was found to have high BET surface area, pore volume and average pore diameter of 735 m2/g, 0.292 cm3/g and 2.56 nm, respectively. The properties of SAC contributed to high MB adsorption capacity of 283 mg/g. The equilibrium data fitted well with Langmuir model, indicating monolayer adsorption; while the activation energy (Ea) of Dubinin–Radushkevitch (D–R) model is lower than 8 kJ/mol, signifying physisorption. The adsorption kinetics was best illustrated by pseudo-second-order model, while the intraparticle diffusion and Boyd models suggested that film diffusion is the rate-controlling step. These findings showed that Calgon Filtrasorb SAC from glycerine deodorization unit can be potentially reused an adsorbent for the removal of dyes.