Enzymatic generation of hydrogen peroxide and gluconic acid chelate for chloro-organic destruction by modified Fenton reaction

Various remediation technologies are being developed for the destruction of groundwater pollutants like 2,4,6-trichlorophenol (TCP) and polychlorinated biphenyls (PCBs). This paper is focused on the oxidative dechlorination of TCP by chelate-based Fenton reaction near neutral pH using enzymatically generated hydrogen peroxide and chelate gluconic acid. For the application of Fenton reaction in in-situ remediation, its successful operation near neutral pH is essential. Hence, Fenton reaction is carried out in the presence of chelates that sequester ferrous and ferric ions, making its operation near neutral pH possible. The on-site simultaneous production of hydrogen peroxide and a non-toxic chelate for in-situ remediation of toxic organics by Fenton reaction is highly desirable. For this purpose, well-known enzyme glucose oxidase (GOx), and inexpensive reactants such as glucose and air were used. The study involved developing the correct protocols for the simultaneous enzymatic generation of hydrogen peroxide and chelate gluconic acid for the dechlorination of chlorinated organics by Fenton reaction. The oxidation of glucose was carried out using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for the homogeneous and heterogeneous systems, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. The Fenton reaction was carried out at varying ratios of gluconic acid:Fe and under different pH conditions, and their effect on the decomposition of TCP and H ₂O ₂ was studied. The reaction rate was modeled in terms of the oxidation of parent compound TCP and decomposition of H ₂O ₂.