Heterogeneous Fenton degradation of oxalic acid by using silica supported iron catalysts prepared from raw rice husk

Iron impregnated catalyst (RHSi-Fe) prepared from raw rice husk was used in the degradation of aqueous oxalic acid at acidic pH. The prepared catalyst was characterized using various analytical techniques. X-ray diffraction (XRD) and Energy dispersive X-ray (EDX) analysis were employed to characterize the catalyst which consistently confirmed the presence of silica as a major constituent in amorphous form. Scanning Electron Microscope (SEM)/EDX results indicated that the metal was present as agglomerates and the Fe ions were not homogeneously distributed in RHSi-Fe catalyst. Presence of SiOFe bond was also evident from the FTIR analysis. Percentage degradations of oxalic acid were 20.18 and 59.06 corresponding to the homogeneous (Fe(III)) and heterogeneous (RHSi-10Fe) catalytic degradations, respectively. Influence of different reaction operating parameters like iron loading to silica matrix, mass of prepared solid catalyst, initial concentration of substrate (oxalic acid), oxidant (hydrogen peroxide) and reusability of the catalyst on degradation of oxalic acid was investigated. RHSi-10Fe catalyst caused 59.06% degradation in 60 min. 1 g/L of RHSi-10Fe dosage was found to be optimum for effective degradation of oxalic acid. Oxalic acid degradation was improved by increasing temperature from room temperature (303 K) to 343 K. About 69.71% of oxalic acid was degraded within 60 min at a temperature of 343 K. The present study finally helps to get a biogenic catalyst which act as a heterogeneous catalyst on degradation of oxalic acid.