Facile synthesis of corncob biochar via in-house modified pyrolysis for removal of methylene blue in wastewater

Low-cost biochar was derived from corncob Zea mays L. cultivated in Northern Thailand for animal feed by facile synthesis with in-house modified pyrolysis for 2 h at ∼500 °C, ∼10 °C min⁻¹ heating rate. Fixed-carbon, ash, %CHNSO and volatile contents of biochar were characterized and compared with pristine biomass. Thermal analysis was performed to monitor the transition of corncob biomass to biochar under the pyrolysis conditions. The physicochemical properties of biochar were investigated by scanning electron microscopy and FT-IR analysis, indicated honeycomb structure on the biochar surface with cylindrical pores and various functional groups, such as carbonyl and phenolic groups. Methylene blue adsorption in aqueous solution by biochar was studied at 25 °C. Without any chemical activation on biochar, the maximum removal efficiency of methylene blue by biochar was 16.50 mg g⁻¹. Effect of the initial concentration and the contact time on removal of methylene blue was studied to archive optimal conditions. The equilibrium adsorption of methylene blue on the biochar was well fit by the Langmuir isotherm. Kinetic of adsorption was perfectly fit by a pseudo-second order dynamic model. The results suggest low-cost corncob biochar prepared by in-house modified pyrolysis could be utilized in wastewater treatment. (paper)