Systematic Assessment of the Influence of Hydrogen Peroxide Dosage on Caffeine Degradation by the Photo-Fenton Process

Abstract

Caffeine degradation performance via photo-Fenton treatment was investigated under different dosage conditions. Experiments were planned according to a design of experiments to characterize hydrogen peroxide dosage protocols. Fenton reagent loads were first determined after a preliminary study. The addition of a fixed hydrogen peroxide load was controlled by an initial load fraction and the span of the continuous flow producing the total load. The experiments were carried out using 12 L solution samples of commercial coffee (300 mg L −1 , approximately 17 mg L −1 of caffeine). Hence, HPLC data revealed that all treatments completely removed caffeine from samples, while TOC monitoring revealed reductions of up to 70%. Using reaction conversion as a performance index, the methodological approach presented enabled a comparison of dosage protocols and determination of those producing enhanced results. For the particular case addressed, the operation scheme that most increased treatment performance produced a conversion which was 25% higher than that obtained without dosage.

Discoloration and Organic Matter Removal from Coffee Wastewater by Electrochemical Advanced Oxidation Processes

“…2). In general, the TOC removal results compare well with previous reported organic removals (which are often around 85 % (Bejankiwar et al 2003;Tokumura et al 2006;Zayas et al 2007;Tokumura et al 2008;Kondo et al 2010;Yamal-Turbay et al 2012)). However, what is noteworthy in this research is that high levels of mineralization were observed within a reasonably short time frame, which is important given that real-world, coffee pulping wastewater was being used (which, by its very nature, is considerably more complex than its synthetic counterpart).…”

“…The wastewater was first adjusted to a pH of 2.9-3.0 (with dilute H 2 SO 4 ) before Fenton reagents were added at levels identical to the EAOP tests (i.e., Fe 2+ =0.3 mmol L −1 ). Because H 2 O 2 was not being generated in situ, H 2 O 2 aliquots of 0.25 mmol L −1 (Section 3.3) were added every hour to keep a sufficient concentration of reactant in solution that was available for degradation of organic material (Yamal-Turbay et al 2012). A long wave lamp, as described above, was used for the PEF test.…”

“…However, based on the UV-Vis absorption spectra of the sample (Fig. 3) and reported wavelengths of maximum absorption (λ max ) for chlorogenic acid and its derivatives (325-336 nm) (Zhao et al 2010;Narita and Inouye 2013), phenolic compounds (280 nm) (Monteagudo et al 2011), and caffeine (274 nm) (Yamal-Turbay et al 2012;Trovó et al 2013), it is suspected that these kind of molecules were present in the raw wastewater and were degraded during the electrochemical oxidation process. Figure 4 indicates that the four electrochemical methods removed more color (89-93 %) than the chemical Fenton (58 %) and photo-Fenton (61 %) processes after 4 h of reaction time.…”

“…Previous studies investigating AOPs for the treatment of coffee wastewater seem to have focused on either the application of AOPs after biological or physical-chemical pre-treatment methods (Bejankiwar et al 2003;Zayas Pérez et al 2007;Kondo et al 2010); or the use of synthetic, instant-coffee solutions (Tokumura et al 2006(Tokumura et al , 2008Yamal-Turbay et al 2012;Satori and Kawase 2014). Further research is needed to achieve a robust, stand-alone system capable of treating a real coffee wastewater.…”

Removal of psychoactive pharmaceutical caffeine from water by electro-Fenton process using BDD anode: Effects of operating parameters on removal efficiency

“…The solution was stirred continuously throughout the process with a magnetic bar at a speed of 450 rpm on a magnetic stirrer CB162 from Stuart (United Kingdom). Likewise aeration with compressed air at a speed of [35] 0.2 L/min was ensured for the whole duration of electro-Fenton and also 5 min before starting the electrolysis in order to saturate the solution with oxygen. The current intensity and voltage were monitored in real time on a power supply HM8040-3 by Hameg Instruments.…”