Valorization of biomass as co-catalyst for simultaneous remediation and hydrogen production from sugar industry wastewater by catalytic wet air oxidation

Abstract

In this study, the usage of biomass-based materials as co-catalysts was tested for simultaneous sugar industry wastewater treatment/hydrogen production by catalytic wet air oxidation and the final product distribution in gas and liquid effluents were investigated. For this purpose, biochar (BC) and graphene oxide-like biomass derivative (BGO) were synthesized from corncob and coupled with LaCoO3 (LC). LaCoO3-Biochar (LC/BC) catalyst was determined as the most compatible one with pure LC in terms of removal efficiencies which were approximately 100% for total saccharide (TSC), 90% of total organic carbon (TOC) and chemical oxygen demand (COD) removal, respectively. This shows that biochar is a promising alternative to replace metal catalysts. The catalyst reusability was examined and the fresh and used catalysts were characterized by SEM-EDX, XRD, and BET analyses. There were slight decreases in catalytic activities of all catalysts including LC which were associated with the chemical and morphological alterations supported by the characterization analyses as a result of formation of acidic intermediates some of which were identified as formic acid and acetic acid in the liquid effluent. The formation of CO2 was determined as proportional with TOC reduction but the behaviour for H2 production was the opposite as a result of total oxidation in which the final products are CO2 and H2O. Although the amount of H2 produced was relatively lower for the selected catalyst LC/BC with higher treatment performance, the produced H2/initial sucrose ratio equal to 0.109 was considered as promising.