| Environmental Hormone, or Endocrine Disrupting Chemicals (EDCs), is a category of xenochemicals which could affect endocrine system and reproductive system of human and wildlife, and even cause carcinogenic, teratogenetic or mutagenic effects.4-tert octylphenol (4-OP), one of the EDCs, has the strongest estrogenic effect among alkylphenols (APs). Owing to its extensive usage in industry, 4-OP has been widely distributed in water environment through air diffusion, precipitation, surface runoff and sewage discharge, and it has been detected in numerous rivers and lakes in China and abroad.4-OP is stable in environment, hardly degraded and tends to bio-accumulate, which makes the research of its removal very urgent and important.As an advanced Oxidation technology in degradation of refractory organic chemicals, UV irradiation was studied in this article. Degradation of 4-OP in different reaction systems under 185 nm and 254 nm irradiation was investigated. According to thin aqueous layer reaction conditions, a spiral photoreactor was developed for lab-scale pilot test. This research was expected to provide basic theory for application of UV irradiation in degradation of EDCs, and provide theoretical and technical support for advanced purification of drinking water. The results show that:In thin aqueous layer reaction system, the efficiency of degradation of 4-OP was high under the irradiation of 185 nm UV light. Over 95% of 4-OP was removed after illumination for 45 min. The degradation reaction was found to accord with apparent first-order kinetics with rate constant of 8.82×10-2 min-1.4-OP removal percentage increased obviously with decreasing initial concentration. Nearly 100% of 4-OP was degraded after irradiation for 20 min when the initial concentration of 4-OP was 2 mg·L-1. The removal percentage increased when irradiation distance decreased. But considering that irradiation area decreased with decreasing irradiation distance, increasing irradiation distance could increase the total removal amount of 4-OP. When the thickness of aqueous layer was increased up to 4mm, the removal percentage decreased while total removal amount increased.Samples irradiated under 185nm UV light were analyzed. After a serial of photochemistry reactions,6 highly matched organics were detected which were assumed to be the byproducts of the degradation process. With a longer reaction period, no peaks were detected by HPLC and GC-MS. By contrast, the TOC of the irradiated samples didn't decrease with the removal of 4-OP, but rather, it kept nearly constant, which suggested that 4-OP was not mineralized. It is believed that 4-OP was decomposed to some small organic molecules under the irradiation of 185nm UV light.Spiral photoreactor system (SPS) obviously promotes direct photodegradation. It took only 6.5 min to remove 96.78% of 4-OP under 185 nm UV light. And It took 40 min to remove 93.27% of 4-OP under 254 nm UV light.90% of 4-OP removal was achieved within an irradiation period of 30min after the SPS was internal-surface sintered with TiO2 thin films which is conventionally employed as a catalyst. The photocatalytic rate of 4-OP was obviously increased when the initial concentration of 4-OP was decreased. All the reactions were found to accord with apparent first-order kinetics.The byproducts of photocatalytic degradation under 254 nm UV light were analyzed using LC-MS and total organic carbon analyzer. The M/Z of these two byproducts was 222 and the structures were confirmed. After 45 min irradiation,28% of 4-OP was mineralized. The reaction solution irradiated for more than 45 min in the photoreactor was analyzed by HPLC and GC-MS and no peaks were detected, which suggested that 4-OP was completely mineralized.
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