study of visible-light photocatalytic degradation of 2,4-dichlorophenoxy acetic acid in batch and circulated-mode photoreactors

The consumption of pesticides and chemical fertilizers is one of the major environmental and health problems. in this report, 2,4-dichlorophenoxyacetic acid (2,4-d) was chosen to evaluate the impact of photodegradation using led (light-emitting diode) (400 and 365 nm) sources in batch and programmable circulated-mode photoreactors respectively. a β-cyclodextrin (β-cd) grafted titanium dioxide p25 (p25/β-cd) and complexation of 2,4-d and β-cd were synthesized via photoinduced and spray-drying methods, respectively. the structures were characterized. moreover, we investigated the effects of the amount of catalyst, the β-cd amount on bed catalyst, irradiation time, kind of photoreactor on the photocatalytic degradation efficiency. based on the results of experiments in batch reactor, the optimum amount of tio2, β-cd grafted by catalyst were 1 and 0.1 g/l, respectively. in batch-mode the photodegradation efficiency of 2,4-d after 5 h with p25, p25/β-cd as a photocatalyst and 2,4-d/β-cd complex with p25 photocatalyst were approximately 81, 85 and 95% respectively. after 8 h of irradiation in circulated-mode reactor, degradation yields with p25, p25/β-cd and 2,4-d/β-cd complex along with p25 were 89, 91 and 96% respectively. on the other hand, the circulated-mode photoreactor with high efficiency was appropriate to degradation of the high concentration of 2,4-d solution (200 mg/l). after 5 successive cycles with 25 h of irradiation, p25 and p25/β-cd maintained as high 2,4-d removal efficiency as 82.6, 84% respectively, with excellent stability and reusability. the photodegradation method can be used as an effective and environmental friendly process in the degradation of organic compound.