Improvement of the Carbocatalytic Degradation of Pharmaceuticals in Water by the Use of Ultrasound Waves

Abstract

A carbonaceous material obtained from wood wastes (SW-Mn) was initially used for the removal of pharmaceuticals in water by a carbocatalytic system. The SW-Mn material adsorbed only 41% of the diclofenac (DCF) and 3% of the valsartan (VAL). Interestingly, SW-Mn activated peroxymonosulfate (PMS) and presented a significant increase in the removal rate of DCF, surpassing 90%, while VAL achieved a 24% removal rate at 20 min of treatment. The carbonaceous material was not effective in activating peroxydisulfate or hydrogen peroxide. Nevertheless, the addition of ultrasound waves at 40 kHz to the carbocatalytic system (SW-Mn +PMS) significantly enhanced VAL degradation, exhibiting a high synergy index (4.98). The routes of the degradation were determined using scavengers, and XPS and EPR analyses, evidencing the main action of singlet oxygen in both carbocatalytic and sonocarbocatalytic systems. It is important to note that radicals also participated in the sonocarbocatalytic process, albeit with a minor contribution. The reuse of SW-Mn was tested during various cycles, showing up to a 39.2% VAL degradation rate after the third consecutive reuse. Moreover, the sonocarbocatalytic system was applied to a sample of irrigation crop water spiked with VAL. The treatment induced a partial elimination of the pollutant due to some interfering effects of the matrix components.