tAqueous solutions of nicotinic acid (NA) were treated using a low consumption UV light source and thepotassium persulfate reagent (UV/KPS) in a falling thin film photo-reactor. Under determined optimumconditions of [KPS] = 1400 mg/L and pH 4, degradation of NA reached to 82.2% after 90 min. Presenceof conventional water contained bicarbonate, chloride and nitrate anions caused unfavorable effect;however, adding only 0.5 mg/L of Cu2+ion, as promoter, gave rise to the system capability to 97.1%degradation. Enhancement in degradation efficiency could also be achieved by using 28 kHz ultrasonicwaves in combination with the UV/KPS process. The intermediates of formic acid, malonic acid andoxalic acid were identified by GC/MS analysis and a reaction pathway was proposed. The scavenging roleof ethanol and tert-butanol reagents was followed and it was revealed that HO•and SO•−4radicals had,respectively, 53.7 and 46.3% contribution in the process degradation. In addition, the reaction kinetic wasfollowed and a pseudo first order reaction was appropriate within conventional temperature range of15–40◦C. Meanwhile, the electrical energy consumption was determined and the total operating costs,for one order of magnitude degradation, was estimated as 2.92 $/m3.’
