Removal of methylene blue from water by food industry by-products and biochars

The aim of this work was to evaluate the effectiveness of easily available food industry by-products for the removal of methylene blue (MB) from aqueous solutions. More specifically, malt spent root lets (MSR), coffee residues (KES) and their biochars were employed. The sorption of MB by pyrolyzed MSR was examined using materials pyrolyzed at temperatures ranging from 300 to 900 degrees C. High surface areas for pyrolyzed MSR were observed at pyrolysis temperatures higher than 500 degrees C, and the maximum surface area (300 m(2) g(-1)) was observed for biochar MSR pyrolyzed at 850 degrees C (MSR 850). Kinetic and isotherm experiments were conducted for the MSR, MSR 850 KES and KES pyrolyzed at 850 degrees C (KES 850). According to kinetic experimental data, sorption capacities at 120 min were over 58% of their equilibrium values for all materials used. The maximum MB sorption capacities for MSR, MSR 850, KES, and KES 850 were 73, 130, 110, and 130 mg g(-1), respectively. Continuous flow-through column experiments were conducted with KES, and the maximum MB capacity was 114 mg g(-1).