**1. Introduction**

Laundry activity is intensively and routinely conducted in domestic activities including homes, hotels, hospitals, as well as public laundry services. In the laundry activity, large amount of detergent as cleansing agent must be used. Further, in general, washing machines can typically produce from 50 to 200 L of effluent per wash [1], implying that laundry activity always disposes large volume of wastewater. The active component with high content in the detergent is anionic surfactant prior to linear alkyl benzene sulfonate (LAS) [1–21]. It is reasonable therefore that high concentration of LAS is contained in the laundry wastewater, as reported [2], that was around 200 mg/L from the first rinse. The presence of LAS in water can cause damage to the ecosystem thereby affecting the environment, and consumption of LAS above 0.5 mg/L can be harmful to health [1]. Considering the negative effects, treatment of LAS from laundry wastewater before reaching the environment is urgent.

Various methods have been dedicated to remove LAS surfactant in water and wastewater, such as adsorption [3–4], coagulation [2, 5–6], and filtration [7–8]. By adsorption, coagulation, and filtration techniques, the surfactant of LAS is only replaced from water to the adsorbents, coagulants and membranes with the same toxicity [1], then they are collected as hazardous solid wastes. Further the hazardous solid wastes must create new environmental problems.

In recent years, various destructive methods including biological, chemical and combination of physical–chemical techniques have been employed for removal of the LAS surfactants from waters. The destructive techniques that have been developed for removal LAS are biodegradation [9–10], ozonation [1], photocatalytic degradation over TiO2 [11–16], and Fenton and photo-Fenton [16–21]. Biodegradation of LAS in water was found to be less effective for high concentration of LAS, since the LAS is harmful for the bacteria [1]. Ozonation method for treatment of wastewater is believed to be uneconomical due to the use of the high dose of the ozone and pressurized and complicated equipment [22]. On the other hand, photo-degradation of LAS over TiO2 photocatalyst under UV irradiation and by photo-Fenton process are intensively used as the effective methods to destroy the hazard LAS into smaller and saver molecules [11]. In addition, the methods only need light, and low cost and harmless chemicals, allowing them to be applied in large scale.
