Partial oxidation of landfill leachate in supercritical water: Optimization by response surface methodology

To achieve the maximum H₂ yield (GY_H2), TOC removal rate (TRE) and carbon recovery rate (CR), response surface methodology was applied to optimize the process parameters for supercritical water partial oxidation (SWPO) of landfill leachate in a batch reactor. Quadratic polynomial models for GY_H2, CR and TRE were established with Box-Behnken design. GY_H2, CR and TRE reached up to 14.32mmol·gTOC^-1, 82.54% and 94.56% under optimum conditions, respectively. TRE was invariably above 91.87%. In contrast, TC removal rate (TR) only changed from 8.76% to 32.98%. Furthermore, carbonate and bicarbonate were the most abundant carbonaceous substances in product, whereas CO₂ and H₂ were the most abundant gaseous products. As a product of nitrogen-containing organics, NH₃ has an important effect on gas composition. The carbon balance cannot be reached duo to the formation of tar and char. CR increased with the increase of temperature and oxidation coefficient.