Degradation of caffeine by photo-Fenton process: Optimization of treatment conditions using experimental design

• Published in: Chemosphere (Oxford) 2013-01, Vol.90 (2), p.170-175
• Main Authors: Trovó, Alam G., Silva, Tatiane F.S., Gomes, Oswaldo, Machado, Antonio E.H., Neto, Waldomiro Borges, Muller, Paulo S., Daniel, Daniela
• Format: Article
• Language: English
• Subjects: Advanced oxidation processes; Applied sciences; caffeine; Caffeine - analysis; Caffeine - chemistry; decaffeination; dissolved organic carbon; Drinking water and swimming-pool water. Desalination; effluents; Exact sciences and technology; experimental design; General purification processes; hydrogen peroxide; iron; mineralization; Models, Chemical; Photochemical Processes; Pollution; sewage treatment; Sewage treatment plant; Stimulant; Sunlight; Surface response methodology; Surface water; toxicity; Waste Disposal, Fluid; wastewater; Wastewaters; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water treatment and pollution
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2012.06.022

► Experimental design was modeled for caffeine degradation by photo-Fenton process. ► A good agreement between experimental and theoretical results was reached. ► Under optimized conditions, it was efficiently degraded, even in the most complex media. ► Less H2O2 was required to remove a high organic load. ► Caffeine degradation did not generate toxic intermediates. The degradation of caffeine in different kind of effluents, via photo-Fenton process, was investigated in lab-scale and in a solar pilot plant. The treatment conditions (caffeine, Fe2+ and H2O2 concentrations) were defined by experimental design. The optimized conditions for each variable, obtained using the response factor (% mineralization), were: 52.0mgL−1caffeine, 10.0mgL−1Fe2+ and 42.0mgL−1H2O2 (replaced in kinetic experiments). Under these conditions, in ultrapure water (UW), the caffeine concentration reached the quantitation limit (0.76mgL−1) after 20min, and 78% of mineralization was obtained respectively after 120min of reaction. Using the same conditions, the matrix influence (surface water – SW and sewage treatment plant effluent – STP) on caffeine degradation was also evaluated. The total removal of caffeine in SW was reached at the same time in UW (after 20min), while 40min were necessary in STP. Although lower mineralization rates were verified for high organic load, under the same operational conditions, less H2O2 was necessary to mineralize the dissolved organic carbon as the initial organic load increases. A high efficiency of the photo-Fenton process was also observed in caffeine degradation by solar photocatalysis using a CPC reactor, as well as intermediates of low toxicity, demonstrating that photo-Fenton process can be a viable alternative for caffeine removal in wastewater.