This study investigated the degradation of phenol at high concentrations from saline wastewater using UV/Persulfate (UV/PS) in a bench scale reactor. The effect of operational variables such as PS concentration (50, 80, 100, 150, and 200 mM), solution pH (3, 7, and 10), initial phenol concentration (200, 450, 1,000, 1,500, and 2,000 mg/L), and NaCl concentration (30,000, 50,000, and 70,000 mg/L) were surveyed. The results revealed that maximum removal of phenol (91%) was obtained after 60 min of reaction at PS molar concentration of 150 mM. Also, changes in pH values had no significant effect on removal efficiency and had slightly greater removal at acidic pH, so pH 3 was selected as optimum. Phenol removal efficiency was increased from 91 to 93% with an increase in the NaCl concentration from 30,000 to 70,000 mg/L, respectively. In addition, phenol removal percentages decrease with an increase in the initial phenol concentration. Efficiency of PS and UV photolysis were 30 and 21%, respectively. The results showed that UV/PS process could be optimally used to remove phenol from saline wastewater and could be effective, economically and environmentally.

Chromium (Cr) is considered to be mutagenic and carcinogenic, and is one of the most important pollutants that have been widely used in various industrial applications. Due to its adverse health impacts, Cr must be removed from effluents before being released into the water environments. The objective of the present study was to investigate the effect of electro-Fenton process (EFP) using iron electrodes in presence of sodium sulfate salt on the elimination of Cr(VI) from aqueous solution. The effect of various parameters such as pH, voltage, initial Cr(VI) concentration, hydrogen peroxide dosage and cyanide concentration (as interference ion), on the process efficiency of Cr(VI) removal have also been tested. The results indicate that the optimum pH, voltage and hydrogen peroxide dosage in EFP were determined to be 3, 30 V and 50 mL/L, respectively. The results of this research also demonstrated that EFP efficiency decreased with increasing initial Cr(VI) concentration. Moreover, EFP efficiency Cr(VI) removal decreased with increasing cyanide concentration; accordingly, the cyanide acts as interference ion in EFP and can reduce the removal efficiency of Cr(VI). According to the obtained results, the maximum removal efficiency of Cr(VI) at optimum condition was 97 % after 25 min. These findings suggest that EFP is suitable option for removing Cr(VI) from aqueous solution.

The efficiency of the electro-Fenton process (EFP) was assessed for phenol removal from saline wastewater. The influence of operational parameters, such as current density (4–16 mA/cm²), pH (2–8), H₂O₂ concentration (75–300 mg/L), reaction time (20–100 min), salinity (1–4%), and phenol concentration (250–2,000 mg/L), on the EFP were evaluated using an L25 orthogonal array design. The best conditions for removal of phenol were determined by the Taguchi method and obtained optimum condition as H₂O₂ = 150 mg/L, pH 3, current density = 8 mA/cm², reaction time = 20 min, salinity = 2%, and phenol concentration = 250 mg/L. These findings indicated that the electro-Fenton process can be used as an effective approach for removing and mineralizing phenol at high concentrations from saline wastewater.

The effect of granular coral limestone and Leca as adsorbents for removing Acid Cyanine 5R (AC5R) from aqueous solution was studied. The optimum pH and adsorbent particles size in both adsorbents were determined to be 3 and 297 μm, respectively. The optimum dosages of coral limestone and granular Leca were 0.150 and 0.145 g/mg of dye, respectively. Also, results have shown that the adsorption efficiency by both coral limestone and Leca increased with the decreasing adsorbent particles size. Moreover, under similar conditions, the maximum removal efficiency by granular coral limestone and Leca was 94% and 88%, respectively. The results revealed that the performance of granular coral limestone was better in AC5R removal than that of Leca granulated under such condition. In total, granular coral limestone and Leca act as suitable adsorbents for removing dye pollutants from an aqueous solution.