Investigating the efficiency of Fe3O4@SiO2@TiO2@rGO + UV+PS nanophotocatalytic process in the removal of Cefixime from aqueous solutions

Antibiotics are among the environmental pollutants with stable effects during consumption, they are rarely completely metabolized in the body and 30-90% of them are excreted through urine and feces and enter into the environment. The present study was conducted to evaluate the degradation of cefixime pollutant by photocatalyst Fe3O4@SiO2@TiO2@rGO + UV in the presence of persulfate (PS) from synthetic wastewater.

Fe3O4@SiO2@TiO2 (F@ST) photocatalyst was synthesized by co-precipitation method, and then fixed on reduced graphene oxide (rGO). The structural properties of magnetic photocatalyst were evaluated using FESEM, XRD, TEM, VSM techniques. The effect of variables such as solution pH, catalyst dosage, persulfate concentration and initial pollutant concentration on the performance of the FS@T/rGO/PS/UV process in the degradation of cefixime pollutant was investigated. After determining the optimal conditions, the influence of interfering ions and scavengers on the process, as well as the amount of recovery and reuse of the catalyst were investigated.

The synthesized photocatalyst had features such as excellent magnetic properties, crystalline and relatively spherical structure in nano size, high purity, photocatalytic properties in both ultraviolet and visible ranges. Under optimal conditions (pH=6.5-7, PS= 2mM and photocatalyst dosage= 0.1 g/L), after 60 min of oxidation time, cefixime antibiotic with a concentration of 50 mg/L and TOC, respectively, with efficiency > 98% and 55.7% were removed. The performance of the process was affected by the presence of organic scavengers (TBA, NaN3, KI and CH3OH) and interfering ions (Cl-, SO4-2, NO3- and CO3-2); so that the pollutant degradation efficiency decreased in the presence of organic scavengers and interfering ions. The effective reaction species were included h⁺, 1O2, OH• and SO4•⁻ in the degradation of cefixime by photocatalytic process in the presence of PS. The synthesized photocatalyst could be used for 4 consecutive steps, and in the fourth step, cefixime was degraded with an efficiency of 70.1%. The behavior of the photocatalytic degradation of cefixime antibiotic per unit time was a function of the pseudo-first-order kinetic model.

: FS@T/rGO/UV/PS photocatalytic process with features such as high efficiency in antibiotic degradation, easy and fast separation, pollutant mineralization, production of side products with simple molecular structure and good performance on the real wastewater sample could be used as a suitable method for industrial wastewater post-treatment as well as pre-treatment in order to reduce organic load and increase biodegradability.