Photocatalytic Degradation of 2,4-Dichlorophenoxyacetic Acid Using Concentrated Solar Radiation:  Batch and Continuous Operation

Abstract

Solar photocatalytic oxidation (PCO) for the degradation of liquid and gaseous pollutants is receiving increasing attention. In the present investigation, an attempt has been made to demonstrate the feasibility of a novel slurry photoreactor for the mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) by using a semiconductor photocatalyst (TiO2), air, and concentrated solar radiation. The photocatalytic degradation (PCD) of 2,4-D using concentrated solar radiation in both batch and continuous bubble column reactors has been studied. The photocatalytic reaction takes place on the surface of the catalyst material. Therefore, the adsorption behavior of 2,4-D on the catalyst has also been investigated. The effects of the presence of anions and the pH of the wastewaters are reported. The photocatalytic degradation studies of 2,4-D in the novel slurry bubble column indicate that this type of reactor can be used commercially for the treatment of wastewater from a plant manufacturing 2,4-D.

Hydrothermal electrocatalytic oxidation for the treatment of herbicides wastewater

“…At a high pH level, H 2 O 2 decays fast which forms a barrier to the creation of ·OH radical, and greatly inhibits the decay of 2,4-D (Chu 2001); on the other hand, pH affects the state of ionization of the substrate and, hence, its adsorption to the catalyst. Greater adsorption of 2,4-D was observed under nonionized and low-pH condition (Kwan and Chu 2004;Kamble et al 2004). In this study, the pH is uncontrolled in the reaction system with the initial pH of 3.5.…”

“…The decay of 2,4-D was also pH dependent. Studies indicated that the highest decay rates of 2,4-D were observed at acidic pH and were followed at basic pH, and the lowest decay rates were observed at neutral pH (Chu 2001;Kwan and Chu 2004;Kamble et al 2004). It is likely, on the one hand, that pH severely affects the self-decomposition of H 2 O 2 .…”

Perspectives and Advances in Photocatalysis

“…The results obtained with commercial sevnol were consistent with those of pure carbaryl, although the reaction was slower. Other pesticides degraded by photocatalysis include 2,4-dichlorophenoxyacetic acid (2) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea or diuron (5) (a phenylurea pesticide) (Malato et al 2003;Kamble et al 2004). …”

Relevance of Photocatalysis prior to Biological Treatment of Organic Pollutants – Selection Criteria

“…Previously, it was demonstrated that the alkoxyl radical anion (-OCH2COOH group) is replaced by an . OH radical, leading to the formation of 2,4-dichlorophenol [71]. The formation of this intermediate implies a high degree of selectivity for .…”