The effect of a catecholate chelator as a redox agent in Fenton-based reactions on degradation of lignin-model substrates and on COD removal from effluent of an ECF kraft pulp mill.
We evaluated the effect of a catecholate chelator as a redox agent in Fenton-based reactions (known as chelator-mediated Fenton reaction-CMFR), in the presence of three different transition metals ions (Fe(2+), Fe(3+) and Cu(2+)) by determining the oxidative capability of CMFR towards lignin-model substrates. The potential application of mediated Fenton-based reactions as a novel process to treat pulp mill effluent was evaluated and monitored by chemical oxygen demand (COD) and total phenol removals from a combination of the effluents generated during an ECF bleaching stage. The catecholate chelator 3,4-dihydroxiphenilacetic acid (DOPAC) reduced both Fe(3+) and Cu(2+), in addition, the maximum Cu(2+) reduction activity was reached in a shorter time than for Fe(3+) reduction, however, the highest metal reduction activity was observed with Fe(3+). When DOPAC was added to Fenton-based reactions (Fe(3+)/H(2)O(2), Fe(2+)/H(2)O(2), Cu(2+)/H(2)O(2)) an increase in oxidative activities of these reactions were found as they resulted in great degradation improvement of the lignin-model substrates azure B, phenol red and syringaldazine. The same increase in oxidative capability of Fenton-based reactions in the presence of DOPAC was observed after effluent treatment, expressed by the increase in COD removal, namely, an increase in the range of about 70% in COD removal when Fe(2+) or Fe(3+) was the catalytic metal and about 25% for Cu(2+). However CMFR lead to an increase in total phenol content. As COD removal by CMFR system using Fe(3+) and Fe(2+) was not significantly different and that Fe(3+) ions promoted lesser increase in total phenol content, Fe(3+) was chosen for experimental optimization. At optimum conditions, 75% of COD and 30% of total phenol removal were achieved.
Arantes
Valdeir
V
Department of Biotechnology, Faculdade de Engenharia Química de Lorena, FAENQUIL, CP 116-12.600-970 Lorena, SP, Brazil. arantes@debiq.faenquil.br
Milagres
Adriane Maria Ferreira
AM
D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry; D008031:Lignin / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D019800:Phenol / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
D007220:Industrial Waste; D015102:3,4-Dihydroxyphenylacetic Acid; D019800:Phenol; D003300:Copper; D008031:Lignin; D007501:Iron; D010100:Oxygen