Treatment of leachate waters by wet peroxide oxidation with a compost-based catalyst: effect of pH
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abstract
A compost-based catalyst was synthesized by hydrothermal carbonization following the
procedure described elsewhere1 (3 g of compost in 30 mL of water, 230 °C for 2 h). The
material was assessed in the catalytic wet peroxide oxidation (CWPO) of a leachate water,
generated during an anaerobic digestion of municipal solid waste. The leachate water is
characterized by a high pollutant load (chemical oxygen demand, COD, of 60 g L-1 and total
organic carbon, TOC, of 27 g L-1). The CWPO runs were conducted at initial pH (pH0) of 3
and 6, and at the natural pH of the effluent (7.2), Ccatalyst = 1.8 g L-1, 80 °C, and the
stoichiometric concentration of H2O2 needed to mineralize the organic content (based on
COD). Fig. 1 shows the results obtained along the reaction. An acidic pH (pH0 = 3) resulted
in a more controlled, but also incomplete, consumption of H2O2, leading to a low conversion
of COD and TOC (20 and 10%, respectively). Contrarily, the natural pH led to a very fast
and uncontrolled consumption of the oxidant source, resulting in 100% decomposition of
H2O2 in less than 2 h of reaction, but failing to remove COD or TOC (negligible removal,
ca. 0%), ascribed to parasitic reactions occurring by the inefficient consumption of H2O2. At
pH0 = 6, an intermediate behavior was observed: complete decomposition of H2O2 was
possible, at a more controlled rate compared to the natural pH. The result was an increment
in COD (41%) and TOC removals (19%), almost two times than that observed at the pH0 3.
This work was financially supported by project “VALORCOMP - Valorización de compost y otros
desechos procedentes de la fracción orgánica de los residuos municipales”, with reference 0119_VALORCOMP_2_P,
through FEDER under Program INTERREG; Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM
- funded by national funds through FCT/MCTES (PIDDAC); CIMO (UIDB/00690/2020) through FEDER under Program
PT2020, and national funding by FCT, Foundation for Science and Technology, and European Social Fund, FSE, through
the individual research grant SFRH/BD/143224/2019 of Fernanda Fontana Roman.
