Photocatalytic treatment of valproic acid sodium salt with TiO2 in different experimental devices: An economic and energetic comparison

Abstract

Valproic acid sodium salt (VA) removal by heterogeneous photocatalysis was investigated in four different devices. An economic and energetic comparison was performed with three reactors based on artificial irradiation (BLB, black light blue lamps, λ=365nm; UVC, λ=254nm; SB, Xe lamp, solar simulator) and a solar pilot plant based on compound parabolic collectors (CPC). For the highest TiO2 concentration used (0.4g/L), the best results in VA degradation and TOC removal were obtained for CPC (91% and 50%, respectively). Costs related to electricity consumption for operation and sampling were considered for this comparison. The lower cost per treated volume (0.48€/L) and per mg VA treated (0.012€/mg) also correspond to CPC device. However, BLB gives the best result in cost per ppm reduction (0.027€/ppm), which shows the importance to have a clear specification of the considered volume and of the total volume treated. Concerning the energetic questions, in the case of laboratory scale, the energy spent in analysis can represent up to 90% of total energy. The efficiency in ppm reduction is higher for BLB (4.77ppm/kWh) while the highest efficiency in mg of pollutant reduction corresponds to CPC (11.12mg/kWh). Summarizing, the use of more adequate radiation and geometry make BLB and CPC good alternatives for the efficient treatment of VA.