Global NEST Journal, Vol 19, No 1, pp 115-121 Copyright© 2017 Global NEST Printed in Greece. All rights reserved Samarghandi M.R., Mehralipour J., Azarin Gh., Godini K. and Shabanlo A. (2017), Decomposition of sodium dodecylbenzene sulfonate surfactant by Electro/Fe 2+ -activated Persulfate process from aqueous solutions, Global NEST Journal, 19(1), 115-121. Decomposition of sodium dodecylbenzene sulfonate surfactant by Electro/Fe 2+ -activated Persulfate process from aqueous solutions Samarghandi M.R., Mehralipour J., Azarian G., Godini K. * and Shabanlo A. Department of Environmental Health Engineering, Faculty of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran Received: 30/06/2016, Accepted: 20/10/2016, Available online: 08/03/2017 *to whom all correspondence should be addressed: e-mail: kgoodini@razi.tums.ac.ir Abstract The decomposition of sodium dodecylbenzene sulfonate (SDBS), which is a dangerous and anionic surfactant, was investigated by the electro/Fe 2+ /persulfate process from aqueous solutions. The activation of persulfate anion and production of active radicals were performed by means of heat, UV and iron ions (released from iron electrodes). The findings illustrated that the pH value of the solution, initial concentration of persulfate anion, the amount of input voltage and iron dosage were entirely effective in SDBS removal. Nearly 100% of SDBS was removed under the optimum conditions: pH 3, voltage 10 V, anion persulfate concentration 25 mM l -1 , iron ion dosage 0.25 g l -1 and reaction time 25 min. Furthermore, the application of the persulfate anion process in concert with the electrochemical process, in order to generate electrical iron and persulfate activation, had a better performance compared to separate methods. Keywords: Electro/Fe 2+ -activated persulfate decomposition, sodium dodecylbenzene sulfonate, Active radicals 1. Introduction Surfactants are divided into four groups: anionic, cationic, nonionic and amphoteric. Anionic surfactants are widely used; linear alkylbenzene sulfonates (LAS), from this group, were introduced in 1964 as easily biodegradable alternatives to highly branched tetrapropylbenzene (Manousaki et al., 2004) and are solely produced approximately 2.5 tones yearly. Sodium dodecylbenzene sulfonate (SDBS), a representative LAS molecule, (Manousaki et al., 2004) is being used largely because it lacks benzene ring in its structure (Otero et al., 2012). SDBS, which is an anionic surfactant, has various applications in industry: stabilization of colloids, washing of metals, production of cleaners and flotation of minerals. Moreover, it is known as persistent organic pollutants (POPs) (Zhang et al., 2012). Common methods for surfactant removal from aqueous environments are as follows: chemical and electrochemical oxidation, membrane processes, precipitation, photocatalytic degradation, adsorption and biological measures (Tran et al., 2009), some of which are expensive and the other have low performance efficiency. For example, recycling of SDBS from absorbents is very difficult even though adsorption is regarded as an inexpensive method (Zhang et al., 2012). Of course, activated sludge can effectively treat surfactants from wastewaters; however, under anaerobic conditions the amount of surfactant increases dramatically in the effluent (Tran et al., 2009; Méndez-Díaz et al., 2010). Advanced oxidation processes (AOPs) are novel methods for removing organic matters from water solutions by generating oxidizing radicals (Matilainen and Sillanpää, 2010). From frequently used in situ chemical oxidation, persulfate has been more taken into account because of its powerful oxidation–reduction potential (E 0 =2.01 V). It is a rather stable oxidant in water; however, it can be activated by UV, heat, base, or transition metals to create a stronger oxidant, sulfate radical (SO4 •− , E 0 =2.6 V); following reactions (1 and 2) take place in the application of persulfate (Wang et al., 2013; Zhou et al., 2013): S2O8 2- + heat or UV → 2SO4 • ¯ (1) M (n+1)+ + S2O8 2- → 2SO4 • ¯ + M n+ (2) This oxidant has been used for treating several pollutants like ethyl carbonate (Gu et al., 2013), chlorophenol (Sohrabi et al., 2013), bisphenol A (Jiang et al., 2013) and so forth. As mentioned above, one of the ways to activate persulfate is using metal ions such as iron and cobalt. Recently, great attention has been taken to iron because it is nontoxic, cheap and effective. Reactions 3-5, which happen in the presence of iron, are as follows (Ahmad et al., 2013): S2O8 2- + 2Fe 2+ → 2Fe 3+ + 2SO4 2- (3) S2O8 2- + Fe 2+ → Fe 3+ + SO4 2- + SO4 •¯ (4) SO4 •¯ + Fe 2+ → Fe 3+ + SO4 2- (5) The activation of persulfate by Fe (II) has two main problems: first, by adding Fe (II) to the reactor, the