Degradation of 2-mercaptobenzothiazole in aqueous solution by gamma irradiation
Introduction
As an important chemical additive, 2-mercaptobenzothiazole (MBT) is widely used in synthesis of antibiotics, pesticides, rubber, leather, etc. According to EPA Toxic Release Inventory in 2010, total on-site and off-site disposals of MBT in USA was 190575.42 lb, of which chemical industry released 6071 lb and plastic/rubber industry released 60749.6 lb.
MBT is a condensed heterocyclic compound with a molecular weight of 167 amu (Fig. 1; Table 1). Because of its antimicrobial effect, wastewater containing MBT is usually resistant to conventional biological treatment.
For example, in the activated sludge system, MBT was found to be resistant and toxic towards activated sludges (Chudoba et al., 1977, Devos et al., 1993). Moreover, MBT even inhibited the degradation of the other heterocycles in the degradation test of heterocycle mixtures. It was reported that microorganisms composing the activated sludge from municipal wastewater treatment plant could be killed after exposure to MBT solutions for 2–3 days (Repkina et al., 1983). Dewever et al. (1994) found that 100 mg/L of MBT was enough to completely inhibit bacterial growth. In addition to the conventional activated sludge process, two-stage anaerobic and aerobic process (Reemtsma et al., 1995), the Bayer tower system (DeWever and Verachtert, 1997), etc. have also been studied. However, microbial tolerance to MBT is limited, therefore a large scale of dilution and pH adaptation were always required in order to achieve satisfactory treatment efficiency.
Recently developed advanced oxidation processes (AOPs) have been considered as an alternative for MBT removal from wastewater. Ozonation could remove MBT and its derivatives from wastewater and reduce the COD, but showed little effect on mineralization (Puig et al., 1996). Fiehn et al. (1998) found that ozonation of MBT was nearly independent of pH-values and proposed that the oxidation product was an organic sulfite. There have been several investigations on direct photolysis (Malouki et al., 2004) and TiO2-based photocatalysis of MBT. Habibi et al. (2001) found that MBT could be degraded by photocatalytic oxidation, and alkaline medium was favorable. Under optimized condition, 98% removal could be achieved with 8 h reaction time. To enhance the photocatalytic activity for MBT degradation, Li et al. (2005) improved the catalyst performance by doping TiO2 with Ce3+. In addition, peroxidase-catalyzed oxidation of MBT was recently reported (Al-Ansari et al., 2010).
Ionizing radiation, as a special kind of AOPs technology has demonstrated potential as a powerful method for degradation of recalcitrant pollutants (Kim et al., 2009, Sampa et al., 2007, Sun et al., 2013b, Vahdat et al., 2010) like halogenated organic compounds, pesticides, antibiotics, sulfonated aromatic compounds and azo dyes. This technology is also used for incomplete decomposition of the target pollutants into less toxic by-products in order to improve their biodegradability (Chmielewski, 2011, Sun et al., 2012, Sun et al., 2013a). The chemistry behind this technology is under extensive investigation (Al-Sheikhly et al., 2006, Homlok et al., 2011, Zacheis et al., 2000). But there is only one brief piece of report available regarding the ionizing radiation of MBT. Tolgyessy et al. (1986) carried out γ irradiation on 115 mg/L MBT solutions and found no significant change in COD, TOC or BOD5 within the absorbed dose range of 0–16 kGy. However, neither MBT removal efficacy nor the influence of operational parameters was mentioned.
To our knowledge, this is the first study giving an insight into the radiolytic behavior of MBT in aqueous solution. The objectives of the present work were (1) to study the radiation-induced decomposition and transformation of MBT, and the change of its biodegradability; (2) to investigate the decomposition kinetics of this compound.
Section snippets
Chemicals
MBT (2-mercaptobenzothiazole) was obtained from the SCR Corporation. The chemical structure and characteristics are displayed in Fig. 1 and Table 1. MBT and NaOH were of analytical grade. Methanol was of chromatographic purity. All chemicals were used as received without further purification.
MBT solution used in this study was diluted from the stock solution. Because of the very low solubility of MBT in neutral distilled water, stock solution was prepared from MBT solid dissolved in 5 mol/L NaOH
Radiolytic degradation of 2-mercaptobenzothiazole
Degradation of water pollutants by ionizing radiation is initiated by the primary products of water radiolysis. When aqueous solutions are irradiated, the energy of the ionizing radiation is principally absorbed by water, possibly resulting in the formation of several primary reactive species, ·OH, , ·H, and molecular products, H2 and H2O2. In this work, as the samples are air saturated, and ·H reacting with the dissolved oxygen will be converted to and HO2·. Therefore, ·OH is the
Conclusions
The results obtained showed that MBT concentration in aqueous solution decreased with increasing absorbed dose. G-values of radiolytic decomposition for MBT were 1.75 and 0.61 for absorbed doses of 500 Gy and 1500 Gy, respectively. Results showed that irradiation efficacy decreased with longer gamma exposure time, and increased with higher initial concentration.
Ionizing radiation is an effective method to remove MBT from water. However, the degradation by-products formed during irradiation can
Acknowledgments
This study was accomplished under the National High Technology Research and Development Program (No. 2009AA063905) supported by the Chinese Ministry of Science and Technology and the Independent Research Project (No. 20101081929) supported by Tsinghua University.
References (29)
- et al.
Soybean peroxidase-catalyzed removal of an aromatic thiol, 2-mercaptobenzothiazole, from water
Water Environ. Res.
(2010) - et al.
Ionizing radiation-induced destruction of benzene and dienes in aqueous media
Environ. Sci. Technol.
(2006) - et al.
A study of biodegradation/gamma-irradiation on the degradation of p-chloronitrobenzene
Radiat. Phys. Chem.
(2009) - et al.
Radiation induced decomposition of methyl tert-butyl ether in water in presence of chloroform: kinetic modelling
Water Res.
(2005) - et al.
Aquatic environmental chemistry of 2-(thiocyanomethylthio)benzothiazole and related benzothiazoles
Environ. Toxicol. Chem.
(1992) Electron accelerators for environmental protection
Rev. Accel. Sci. Technol.
(2011)- et al.
Biochemical decomposition of benzothiazoles
Acta Hydrochim. Hydrobiol.
(1977) - et al.
Electron beam irradiation of citric acid aqueous solutions containing persulfate
Sep. Purif. Technol.
(2012) - et al.
Parameters affecting the degradation of benzothiazoles and benzimidazoles in activated-sludge systems
Appl. Microbiol. Biotechnol.
(1993) - et al.
Toxicity of 2-mercaptobenzothiazole towards bacterial-growth and respiration
Appl. Microbiol. Biotechnol.
(1994)
Biodegradation and toxicity of benzothiazoles
Water Res.
Analysis of the ozonation of 2-mercaptobenzothiazole in water and tannery wastewater using sum parameters, liquid and gas chromatography and capillary electrophoresis
Water Res.
Photocatalytic mineralisation of mercaptans as environmental pollutants in aquatic system using TiO2 suspension
Appl. Catal. B: Environ.
Elimination of diclofenac from water using irradiation technology
Chemosphere
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