Response surface optimization of heterogeneous Fenton-like degradation of sulfasalazine using Fe-impregnated clinoptilolite nanorods prepared by Ar-plasma

Optimization of sulfasalazine degradation using the heterogeneous Fenton-like process in batch mode was investigated by response surface methodology. The plasma-treated clinoptilolite (PTC) nanorods were produced from natural clinoptilolite (NC) by Ar glow-discharge plasma owing to its cleaning and sputtering effect generating extra surface area. The PTC and NC catalysts were characterized by XRD, BET, and SEM. The morphology of NC was altered from microparticles to nanorods after plasma modification and consequently the specific surface area increased from 23.92 to 45.16 m²/g. The PTC and NC were modified by Fe-impregnation method. The catalytic performance of Fe-impregnated PTC was significantly higher than Fe-impregnated NC for degradation of sulfasalazine by the process. Central composite design (CCD) approach was performed to develop a non-linear model for determination of the degradation efficiency (DE%). The predicted data for the DE% as a function of operational parameters including initial sulfasalazine concentration (10–50 mg/L), catalyst dosage (0.5–2.5 mg/L), hydrogen peroxide concentration (1–5 mmol/L), and process time (20–60 min) were consistent with the experimental data (R² = 0.945) after 40 min of the process. The CCD model was also used to estimate the optimized experimental conditions for the sulfasalazine degradation. Environmentally friendly plasma treatment of the NC, low released iron concentration and proper reusability at the mild pH were the essential benefits of the modified PTC.