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

The K2CO3 activation of defatted olive cake in N-2 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 degrees 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 m(2)/g S-BET and 0.53 cm(3)/g total pore volume. Batch mode adsorption was performed at different initial dye concentrations (25-400 mg/L), pH (3-11), temperature (30-50 degrees 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.