Kinetics studies of trichlorophenol destruction by chelate-based Fenton reaction

The use of hydroxyl radical-based reaction (Fenton reaction) for the destruction of organic pollutants has been widely reported in the literature. However, low pH requirement, precipitate formation problem, and rapid peroxide consumption rate make the application of conventional Fenton reaction difficult. A chelate-based Fenton reaction can prevent Fe(OH)₃ (s) precipitation even at neutral pH condition and reduce the H₂O ₂ consumption rate by controlling Fe²⁺ concentration. The chelating agent combines with Fe²⁺ or Fe³⁺ to form stable metal-chelate complexes in solution. This decreases the concentration of Fe ²⁺ in the solution so that reactions can be carried for longer contact times. The major objective of this study was to establish the role of the chelating agent and to obtain oxidation rates for various reaction conditions using a model chlorinated organic compound. Experimental results (with citrate as chelating agent) for 2,4,6-trichlorophenol (TCP) showed that the TCP dechlorinations were highly effective even at pH values > 5. Although the main focus of this research is the application of monomeric chelate (such as citrate) in the Fenton reaction, the role of polymeric chelate (such as polyacrylic acid) has also been explored. Rate models for the chelate-based Fenton reaction were developed by adding the effects of iron chelation chemistry along with the well-known OH· formation and decomposition kinetics.