Avaliação da eletrocoagulação e eletro-oxidação por corrente pulsada na remoção de matéria orgânica natural de água

• Ano de defesa: 2018
• Autor(a) principal: Oliveira, André Gadelha de
• Orientador(a): Nascimento, Ronaldo Ferreira do
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Eletro-oxidação; MON; Eletrocoagulação; Planejamento Box-Behnken
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/39587

Electrolytic processes using direct current (DC) and pulsed current (PC) are currently an alternative for the treatment of water and wastewater. In addition, the use of the pulsed current (PC) can be an alternative to decrease the polarization of the electrode, besides achieving lower electric energy consumption. Electrochemical processes, such as electro-oxidation and electrocoagulation (EC), are widely used to remove natural organic matter (NOM) from water. In such processes, the oxidation agents, and coagulants are produced in situ via the use of an electric current. In this work the removal of humic acid like NOM, i.e. apparent color and dissolved organic carbon (DOC), from aqueous solutions, using electro-oxidation with direct and pulsed current was studied. The electrodes used in the cell were Ru based inert electrodes. The current density (44.0 to 144 A m-2) had a slight effect on apparent color and DOC removal, with the best removal using 88 A m-2 and 30 kHz of frequency. The electrocoagulation by DC and PC to removal of natural organic matter from water was investigated. The experiments were carried out using Box-Behnken factorial design (BBD) with the response surface methodology (RSM) for the design of experiments, modelling and interpreting of the results. The electrodes used in the cell were four electrodes of aluminum. The experiment time was 10 minutes. The experimental independent variables studied were: current density (5.50 to 44.5 A m-2), electrodes spacing (ES) (2.0 to 7.6 mm), stir rate (200 to 1000 rpm), frequency (500 to 5000 Hz), humic acid (5 to 20 mg L-1) and NaCl (100 to 300 mg L-1). The final apparent color (FAC) and electric energy consumption (EEC) were used as responses to evaluate the process. The lowest FAC were 11.8 and 10.4 for pulsed and direct current, where the energy consumption were 0.3930 and 1.108 kWh m-3, respectively. The desirability conditions were found to be the central levels, where were found 18.18 HU (FAC) and 0.4280 kWh m-3 (EEC) for pulsed current, and 22.67 HU (FAC) and 0.7690 kWh m-3 (EEC) for direct current. Raw water was treated using electro-oxidation/ozonation, assessing apparent and true color, DOC, turbidity, pH, conductivity and energy consumption. The percentages of removal of apparent and true color achieved were in the range of 40.84-70.17% and 47.09-80.06%, respectively, and the electro-oxidation by direct current in the presence of ozone had the best removal efficiencies. DOC removal reached levels of 1.55-15.69%. The use of the electro-oxidation by pulsed current provided lower electric energy.