<p>The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The mechanism uses zero-valent iron activated by oxygen at room temperature to generate Hydroxyl-free radicals that subsequently oxidize organic constituents and clean wastewater. The effects of the iron mass, the pH and the organic matter concentration have been studied. Our experimental results demonstrate that the continuous presence of oxygen and iron in an acidic solution with a pH 2-4 allows the generation of maximum hydroxyl free radicals. The lack of oxygen prevents oxidative reaction, and then the generation of free radicals cannot occur. Coloration of OMW disappeared and phenolic compound decreased after 40 minutes of reaction time. The results show that Fe⁰/H⁺ /air or oxygen, could be considered as an effective alternative solution for the treatment of OMW.</p>

The beetroot fibers were used to decontaminate water polluted by methylene blue dye (MB), to remove heavy metals from wastewater and to soften hard water. In order to improve the adsorbent performance and to determine the optimum conditions of industrial wastewater cleaning, the effect of fiber particle sizes, initial concentrations of pollutants, pH of aqueous solutions and effluent rates on the cleaning procedure were investigated. Data showed that the efficiency of cleaning increased when fiber particle size decreased (from mm to µm scale). Optimum pH value for adsorption was 6 to 6.5. Maximum metal cations retention or hardness of modified fibers by sodium dodecyl sulfate (SDS) was estimated at 70 mg per gram of fiber; while the maximum retention of methylene blue was found to be 300 mg of dye per gram of fiber. Chemical modification of fibers by an anionic surfactant such as sodium dodecyl sulfate increased the efficiency of the dye elimination by 2-fold when compared to unmodified fibers. The adsorption parameters were determined using Langmuir and Freundlich isotherms.