Estudo da rea??o foto-fenton induzida por complexos ferricitrato para o tratamento de lixiviados de aterros sanit?rios

Photo-Fenton reactions induced by ferricitrate complex applied to the treatment of sanitary landfill leachate (SLL), was studied. Using a lab-scale photo-reactor with artificial UV-light source, photo-Fenton reactions and derivations (photolysis, Fenton, photo-Fenton and ferricitrate), on the decolourisation and aromatic compounds removal were evaluated. Such reactions mediated at a pH of the solution 2.8, present some limitations such as: (i) precipitation and/or volatilization of humic acids in acidification steps, (ii) a partial precipitation of ferric ions complex with the organic pollutants present in SLL; resulting in absorbance removal at 254 nm as well as decolourisation, not represented effective oxidations. However, using ferricitrate reaction mediated by pH of the solution 6, was possible eliminated the acidification step, keeping the pollutants and iron ion soluble resulting in best oxidations rate. Probably due the stability and solubility associated to ferricarboxylates such as ferricitrate, as well as the increase of photo-sensibility. After, the main operating parameters of ferricitrate reaction such as pH of the solution, iron(III):citric acid concentrations, H 2 O 2 consumed and amount of energy UV required were investigated. The best results were obtained using: pH of the solution 6.0, 100 mg Fe(III):citric acid, consuming approximately 64 mM of H 2 O 2 and ? 9 kJ UV L -1 required; leading a ? 70% and 65% decolourisation and aromatic compounds removal, respectively. In such conditions, the efficiencies of organic contents reduction as: COD (? 39%), dissolved organic carbon (DOC) (? 30%) and total dissolved nitrogen (TDN) (? 25%) were satisfactory, and maintaining BOD 5 (? 30%) probably improving the treated in terms of SLL- biodegradability (BOD 5 /COD ratio).O objetivo principal deste trabalho foi estudar a rea??o foto-Fenton induzida por complexos de ferricitrato para o tratamento de lixiviado de aterro sanit?rio (LAS), bem como, avaliar a efici?ncia de diferentes rea??es foto-Fenton e suas deriva??es (fot?lise, Fenton, foto-Fenton e ferricitrato) na remo??o dos compostos arom?ticos e descolora??o. Os principais par?metros operacionais da rea??o tais como o pH da solu??o (2,8 ? 6,0), as concentra??es dos reagentes ?on de ferro (80, 100 e 120 mg Fe L -1 ) e ?cido c?trico, consumo de H 2 O 2 e quantidade de energia UV requerida foram avaliadas utilizando um foto-reator de escala laboratorial operando em sistema batelada, beneficiado com irradia??o UV Vis artificial. Todas as rea??es testadas, exceto a fot?lise, foram eficientes na remo??o da absorv?ncia a 254 nm e descolora??o. No entanto, as rea??es utilizando pH da solu??o 2,8 foram limitadas devido ? alguns inconvenientes tais como: precipita??o e/ou volatiza??o dos ?cidos h?micos na etapa de acidifica??o e a forma??o de complexos de ferro com poluentes org?nicos presentes no LAS. Com isto, verifica- se que estes resultados n?o foram referentes a foto-oxida??o, e sim ? fase inicial de acidifica??o seguida por uma simples transfer?ncia de fases. Contudo, utilizando o complexo ferricitrato, foi poss?vel obter elevadas efici?ncias de degrada??o com o pH da solu??o neutro e pr?ximos, eliminando as etapas de acidifica??o. Os melhores resultados foram obtidos utilizando o pH da solu??o 6,0, pois este, possibilita a perman?ncia dos poluentes na solu??o e dispon?veis para oxida??o, al?m de manter os ?ons ferrosos dissolvidos. Nestas condi??es, foram obtidos cerca de 70% e 65% de descolora??o e redu??o dos compostos arom?ticos, respectivamente, consumindo aproximadamente 64 mM de H 2 O 2 e requerendo cerca de 9 kJ UV L -1 . Al?m disto, as redu??es do conte?do org?nico tais como a DQO (? 39%), o carbono org?nico dissolvido (COD) (? 30%) e o nitrog?nio total dissolvido (NTD) (? 25%) foram satisfat?rias; mantendo- se a DBO 5 , o que provavelmente melhora as condi??es tratadas em termos de biodegradabilidade do LAS (DBO 5 /DQO)