Degradation of chlorophenols by sonication coupled ferrate and ferrous alginate and dechlorination by iron immobilized silica

Abstract

Due to industrialization and urbanization, rapid depletion of potable water and pollution of water bodies are taking place. Grossly, polluted water has hindered the ability of nature to revive and sustain itself. This scenario had led to the formation of stringent environmental regulatory laws. Hence, researchers worldwide over are trying to develop new techniques which are effective and economical for the degradation of the recalcitrants. Chlorophenols are mainly used as disinfectants, biocides, preservatives, pesticides and in the manufacturing of other chlorinated chemicals. Experiments were conducted using +6, +2 and 0 oxidation state ofiron to degrade chlorophenols in innovative ways. The drawback of using ferrate is that it is stable only at high alkaline pH, requirement of high ferate : chlorophenol ratio, use of buffers in degradation study (not suitable for waste water) and storage. Alginate, a polymer obtained from natural source (brown algae) has been used as support material for ferrous immobilization in this research. It was coupled with sonication for better efficiency. Ferrous alginate beads were prepared using a simple protocol. It was found to be stable at pH 2, which is an added advantage as the optimal pH for Fenton s method is 2 3. The order of degradation among chlorophenols was CPgt DCPgt TCP and the degradation followed pseudo first order kinetics. Immobilization of Fe0 (ZVI) is also a topic of research for many researchers. Granular silica, which is easily available, has been experimented as a support material for ZVI. The indigenously prepared ZVI immobilized silica was found to be effective in dechlorinating the chlorophenols. The optimal pH, column height and flow rate was found to be 7, 20 cm and 0.75L/h respectively.The order of dechlorination was TCPgt DCPgt CP. All the methods developed in this study were applied to real pulp and paper industrial wastewater. The most economically viable and efficient method among them was sono heterogeneous Fenton method. newline newline newline