Carbon and nitrogen removal from glucose-glycine melanoidins solution as a model of distillery wastewater by catalytic wet air oxidation

Sugarcane molasses distillery wastewater contains melanoidins, which are dark brown recalcitrant nitrogenous polymer compounds. Studies were carried out in batch mode to evaluate Pt and Ru supported catalysts in the Catalytic Wet Air Oxidation (CWAO) process of a synthetic melanoidins solution, prepared by stoichiometric reaction of glucose with glycine. The addition of a catalyst slightly improved TOC removal compared with the non-catalytic reaction, and especially promoted the conversion of ammonium produced from organically-bound nitrogen in melanoidins to molecular nitrogen and nitrate. The selectivity to N-2 attained 89% in the presence of the Pt catalysts in the reaction conditions used (TOC = 2200 mg L-1, TN = 280 mg L-1, 0.5 g catalyst loaded with 3% metal, 210 degrees C, 70 bar total air pressure). To avoid leaching of the active metal by organically-bound nitrogen, the reaction was very efficiently performed in a two-step reaction consisting in WAO to convert nitrogen into ammonium, before the introduction of a catalyst. (C) 2016 Elsevier B.V. All rights reserved.