Mesoporous and high-surface-Area activated carbon from defatted olive cake by-products of olive mills for the adsorption kinetics and isotherm of methylene blue and acid blue 29

Abstract

The K2CO3 activation of defatted olive cake in N2 atmosphere was attempted for activated carbon (DOC-AC) preparation to test its ability for the adsorption of methylene blue (MB) and acid blue 29 (AB 29). The optimum conditions obtained by Box–Behnken design was 3.0 g/g impregnation ratio, 800 °C activation temperature, and 120 min activation time. These conditions led to 20.84 % carbon yield and 98.92 % MB, and 94.63 % AB 29 removal. The best DOC-AC showed a highly porous structure with 988.75 m2 /g SBET and 0.53 cm3 /g total pore volume. Batch mode adsorption was performed at different initial dye concentrations (25–400 mg/L), pH (3–11), temperature (30–50 °C), and contact time (0–26 h). The kinetic and equilibrium adsorption data of both dyes were fitted to pseudo-second-order and Langmuir models, respectively. Monolayer adsorption capacities were 359.38 mg/g for MB and 157.58 mg/g for AB 29. After six successive regeneration cycles, the adsorption efficiency for both dyes was > 70 %, indicating good potential of the DOC-AC for commercial applications.