Effect of phosphoric acid treatment on kaolinite supported ferrioxalate catalyst for the degradation of amoxicillin in batch photo-Fenton process

The effects of phosphoric acid treatment on kaolinite (Kaol) as catalyst support were investigated in this study. The results showed that as the acid concentration was increased from 5 to 10 M, there was increment in the specific surface area from 18.78 in Kaol to 36.0 and 145.5 m2 g− 1 in 5 M acid treated Kaol supported catalyst (5 M-AT-KaolCat) and 10 M acid treated Kaol supported catalyst (10 M-AT-KaolCat), respectively. Characterization results showed that 10 M-AT-KaolCat has higher percentage of Fe than the 5 M-AT-KaolCat due to the effect of acid treatment which provided larger surface area for its anchoring. Consequently, degradation efficiency is comparably faster in 10 M-AT-KaolCat with about 99% of 40 ppm amoxicillin degraded in 8 min without pH adjustments while it takes 12 min using 5 M-AT-KaolCat. The degradation process showed initial enhanced degradation efficiency with increase in the catalyst loadings which later decreased due to the scavenging effect of excess catalyst loading on the reactive hydroxyl radical. The catalysts showed high resistance to leaching due to the presence of the ferrioxalate (FeOx) ligands and the effect of phosphoric acid modification which introduces monolayer of phosphate functional group on the catalyst support through which the FeOx ligands were properly anchored.