BACKGROUND AND OBJECTIVE: Phthalic acid has high toxicity and low degradability which has put treatment of wastewater containing this compound prior to prevent its health and environmental hazards. Present study was conducted to Optimization of (UV/Na₂S₂O₈/Fe²⁺) process for phthalic acid removal from aqueous solutions with response surface methodology.

METHODS: This is an experimental study which was conducted at laboratory scale and synthetically in the cylindrical reactor containing UV-C lamp with 16 Watt power. Effects of variables including pH of solution (3-11), reaction time (0-60 min), concentration of persulfate (0.1-0.5 mmol/L), concentration of Fe2+ (0.1-0.2 mmol/L) and initial phthalaic acid (5-50 mg/L) on efficacy of process were investigated by response surface method (box Behnken method). The residual concentration of phthalic acid was measured by HPLC at a wavelength of 254 nm

FINDINGS: The removal efficiency of phthalic acid increased by increasing pH level and reaction time. The maximum removal efficiency of phthalic acid attained as 98 percent at pH of 11, reaction time of 60 min, 0.15 mmol/L of Fe²⁺ concentration, persulfate concentration of 0.3 mmol/L and 5 mg of phthalic acid. The process of removing phthalic acid followed from first-order kinetic (R²=0.9766). The effects of all studied independent variables with p<0.05 on removal efficiency of phthalic acid were found significant.
CONCLUSION: Obtained results indicated that the UV/Na₂S₂O₈/Fe²⁺ process for removing phthalic acid from the aquatic environments has high efficiency. This issue confirms the acceptable efficiency of mentioned method for the removal of phthalic acid.