Abstract
The electro-Fenton degradation of Triclosan in aqueous solution was studied using a cylindrical reactor in which polarized carbon cloth electrodes and a cation exchange resin were employed. Using a factorial design of experiments approach, the effect of four variables (considering two levels for each one), was measured on four response parameters that reflect the electrooxidation efficiency of the electrochemical reactor. The results revealed that in all cases triclosan degradation was very efficient (above 95%) and that while there is a reasonable effect of all variables and their interactions, the one with the strongest influence on the process is the nature and magnitude of the ionic strength of the electrolytic solution. In this way, while the presence of a buffer species in this solution can keep the pH in a value that affects the generation of •OH radicals from the Fenton mixture, a high ionic strength solution can promote the elimination of Fe ionic species from the reactor by decreasing resin Fe retention due to competition effects of other ions for the binding sites of the substrate. HPLC experiments of the effluent solutions, also revealed that the degradation by-products of triclosan were dependent on the nature and ionic strength of the electrolytic solution in the electro-Fenton process under study. Finally, comparison of the different operation modes, also suggested that electro-adsorption of Fe cationic species in the negatively polarized cathode surface, is the main factor that controls Fe ion retention within the reactor.
Highlights
In recent years, the presence of emerging contaminants in water sources that are dedicated to human consumption, has been detected and pointed out as an important health problem
In the proposed treatment process, the polluted solution passes through five stages that correspond to the different sections of the reactor: (i) the Fe(II) loaded resin, (ii) the negatively polarized carbon cloth, (iii) the electrolytic solution, (iv) the positively polarized carbon cloth and, (v), the Na+-loaded resin
In the first section of the reactor (i), the triclosan solution goes through and washes out Fe(II) ions from the resin material, taking them to section ii, where the carbon cloth simultaneously acts as an adsorbent and as a cathode in which oxygen reacts to produce H2O2
Summary
The presence of emerging contaminants in water sources that are dedicated to human consumption, has been detected and pointed out as an important health problem. Emerging pollutant species are not necessarily new contaminants; they could be chemical compounds that have existed in the environment for a long time and just recently recognized as toxic or environmentally hazardous materials [1,2]. Triclosan is a popular chemical species that has been employed since the 70 ́s due to its ability to inhibit bacterial and fungi growth [3]. The presence of triclosan in urine of women that used a popular commercial toothpaste, has been reported [5]
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