The effect of sodium percarbonate dose on the reduction of organic compounds in landfill leachate

Abstract

The paper discusses the issue of using classic Fenton’s reagent modification for pre-treatment of leachate from a landfill in Janczyce (Świętokrzyskie Voivodeship, Poland) – sodium percarbonate (2Na2CO3·3H2O2) was used as an alternative source of hydrogen peroxide, and hydrated iron sulphate ((II) FeSO4·7H2O) was the source of iron ions. The tests were carried out at initial process pH = 3, for different doses of the Fe2+ catalyst (ranging within 100÷5400 mgFe/L), and for mass ratio iron (II) to sodium percarbonate – 1:3. Three doses were selected after this stage, for which the following parameters were examined: the effect of initial process pH ranging between 2 and 4, the effect of oxidation process duration (30÷150 min.), and the effect of the ratio Fe2+ to sodium percarbonate (1:3, 1:5 and 1:7). The values of selected parameters (pH, COD, TOC) in leachates, both before and after the treatment process have been determined according to applicable standards. Completed tests have proven, inter alia, that the proposed implementation of the Fenton’s method with sodium percarbonate may be an effective alternative for hydrogen peroxide as an oxidiser; with an increasing dose of the 2Na2CO3.3H2O2, the improvement in landfill leachate remediation efficiency measured by decreasing TOC and COD values reaches certain extent only; the process modified with sodium percarbonate may be effective already at pH=4.

The Role of Carbonate in Catalytic Oxidations

“…These include chemical oxidation by peroxides, Fenton and Fenton-like processes (including photo-Fenton and electrochemical Fenton), ozone, photochemical processes (including solar light using TiO 2 as a photocatalyst), electrochemical processes, microwave processes, ultrasonic processes, ionizing radiation, hydrodynamic cavitation, and various combinations of these techniques . Carbonate is involved in these processes via the addition of percarbonate as an oxidizing agent, ,,− the involvement of the HCO 3 – /CO 3 2– that is always present in water, ,− and sometimes by the addition of HCO 3 – /CO 3 2– to the system …”