Determination of optimum extinction wavelength for paracetamol removal through energy efficient thin film reactor

Abstract

Abstract Paracetamol (PAM) mineralization through nano-composite thin film (TF) based photocatalytic system was investigated under variable operational conditions. The experiments were conducted using a non-stirred flow through coated tubular quartz reactor (TQR). Elimination of energy demand arising from stirring and aeration through the developed TF reactor configuration was also among the main research interests. Ag-doped Si-TiO 2 TFs were grown on Si-decorated inner surface of the TQR using sol-gel dip coating technique. The fabricated TF was characterized by SEM-EDS, TEM, AFM, XPS and UV vis spectroscopy methods. TF-based PAM mineralization kinetics were observed for both UV vis and UV wavelengths using pure, Si-Ti and Ag-doped Si-TiO 2 TF(s). The direct and indirect optical ban gap energies (BGE) for the Ag doped Si-TiO 2 TF were estimated to be 2.56 eV and 2.86 eV respectively. While no visible light activity was observed for pure TiO 2 TF, Ag-doped Si-TiO 2 TF exhibited significant PAM degradation activity for λ > 400 nm with a k obs value of 2.1 ± 0.1 10 −3 min −1 . In addition to known phenolic and carboxylated intermediates, UV vis spectroscopy, HPLC–MS and UPLC–MS/MS measurements indicated α-cyano-4-hydroxicinnamic acid (αPHC) formation as a result of photo-addition reactions under UV C irradiation. Experimental results also indicated that αPHC blocks h + /e − formation completely. Paracetamol could be degraded economically under UV B irradiation through the fabricated TF reactor without stirring, aeration or adding external electron acceptors.