Kinetic insights on wet peroxide oxidation of caffeine using EDTA-functionalized low-cost catalysts prepared from compost generated in municipal solid waste treatment facilities

Assessment of Pretreatments for Highly Concentrated Leachate Waters to Enhance the Performance of Catalytic Wet Peroxide Oxidation with Sustainable Low-Cost Catalysts

“…Similar results were also reported in other studies where the effect of catalyst concentration on CWPO efficiency was analyzed. Diaz de Tuesta et al (2021) observed that increasing catalyst load from 0.5 g L −1 to 2.5 g L −1 at the same temperature (80 • C) increased caffeine removal by two times [4]. Similar results were observed for phenol abatement using a carbon black catalyst [12], an iron-based catalyst (Fe/γ-Al 2 O 3 ) [13] and a gold-based catalyst (Au/AC) [36].…”

“…As observed, the elemental composition of PC and HC catalysts was not significantly changed during their preparation when compared to RP. However, the increase in the C/H ratio of the samples (9.2, 44.0 and 11.3 for RP, PC and HC samples, respectively) indicates that carbonization was successful [4]. Higher differences were found in the ashes content, representing inorganic substances in the RP and the catalysts.…”

“…These carbonization processes also result in materials with different acid-base properties, as shown in Table 2. On one hand, PC presents strong basicity (2.5 mmol g −1 and pH PZC = 11.0), likely due to the removal of acidic functionalities during pyrolysis and the higher ash content composed of alkali and alkaline-earth metals [4]. On the other hand, HC shows a neutral acid-based character (acidity similar to basicity and pH PZC = 7.5).…”

“…First, the pH of the leachate was adjusted to the desired value (3.0 or 6.0) employing H 2 SO 4 and NaOH 1 M aqueous solutions. Then, 25 mL of the leachate water was transferred to the flask and heated to 80 • C (temperature selected according to previous works [4,35]). The addition of 30% hydrogen peroxide was split into five stepwise additions at 0, 60, 120, 180 and 240 min of reaction time (the same volume of H 2 O 2 was dosed for each load), amounting to a concentration of 85.7 g L −1 (determined based on the theoretical amount needed to mineralize all COD [34]).…”

“…Under this background and applying the directives of end-of-waste criteria, alternatives to add value to compost must be sought, supported by the perspective of a circular economy. One possible strategy is to prepare sustainable, lowcost catalysts through the pyrolysis and hydrothermal carbonization (HTC) of compost [1,4].…”