Wastewater treatment of biodiesel production using persulphate ion as an oxidant.

  • Maria Teresa Borralho Polytechnic Institute of Beja, School of Agriculture, Department of Technology and Applied Sciences, http://orcid.org/0000-0002-9305-2082
  • Ana Pardal Polytechnic Institute of Beja, School of Agriculture
  • Solange Coelho Polytechnic Institute of Beja, School of Agriculture
Keywords: Potassium monopersulfate, Chemical oxidation, Chemical Oxygen Demand, Wastewater from biodiesel purification


Introduction: The production of biodiesel produces a highly polluting effluent, because presents high values of Chemical Oxygen Demand (COD), oils and fats, among other contaminants. Sodium persulphate is a powerful oxidant (Eº = 2.1V). In addition to the direct oxidation that is favored in alkaline media, it can be induced by photolytic processes, catalytic and / or catalytic photos forming sulphate radicals (Eº = 2.6 V) thus providing reaction mechanisms with free radicals like hydroxyl radicals.

Methods: In this work the effect of the potassium monopersulphate compound (2KHSO5.KHSO4K2SO4), (Oxone) on the removal of COD in residual water from the biodiesel purification step was tested.

Results: The tests, direct oxidation at alkaline pH and catalytic oxidation with cobalt ions, Co(II), showed that the former, for Oxone concentrations of 1.00x10-2 M and 4.00x10-3 M, were not effective because no decomposition occurred, for reaction times over three hours, thus not occurring removal of COD. In the catalytic assays combinations were tested, varying between 5.00x10-3 M and 7.50x10-2 M for the oxidant and 0.10 μM and 1.00 μM for the catalyst. The complete decomposition of the oxidant was always verified between 15 min. and 2 h. The tests with the lowest concentration of cobalt showed COD removal rates around 20% and the highest one reached 60%. 

Conclusions: The most favorable assay achieves significant COD removals, but not enough for the effluent to be discharged in the hydric medium according the portuguese legislation.

Author Biographies

Maria Teresa Borralho, Polytechnic Institute of Beja, School of Agriculture, Department of Technology and Applied Sciences,

Department of Technology and Applied Sciences

Research Center- Fiber Materials and Environment, FibEnTech

Ana Pardal, Polytechnic Institute of Beja, School of Agriculture

Department of Technology and Applied Sciences

Research Center: Fiber Materials and Environment, FibEnTech


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