Coupling chemical coagulation and photodegradation on titaniferous sand for the treatment of tobacco effluents

Over the last decades, the world production of cigarettes has increased considerably. However, the industrial production generates large quantities of colloidal effluents consisting of toxic and recalcitrant compounds. Thus, taking account the colloidal aspect of the effluent and the persistence of some compounds, this study aims at coupling chemical coagulation and photodegradation on titaniferous sand to treat wastewater from a cigarettes plant in Senegal. The chemical coagulation was handled by aluminium sulfate. The optimal conditions of this chemical process were found at a pH of 7 and a coagulant concentration of 350.4 mg/L. In these conditions, the elimination rate of the chemical oxygen demand (COD) and suspended materials (SM) were respectively 51.32 and 76.92%. Despite its good performances, the chemical coagulation only did not come up with a standard effluent discharge. That is why the photodegradation was conducted to complete the treatment. With a maximum titaniferous sand concentration of 320 g/L, the results highlighted a COD elimination rate of 60% at an initial concentration of 240 mg/L. The COD elimination rate was highly enhanced by increasing the amount of hydrogen peroxide in the system. Indeed, the COD elimination rate was shifted from 61.2 to 72% when the rate of hydrogen peroxide varied from 0.2 to 0.6%. Key words: Tobacco effluents; chemical coagulation; photodegradation; titaniferous sand.