The present work highlights the preparation of activated carbons (ACs) using spent coffee grounds, an agricultural residue, as carbon precursor and two different activating agents: water vapor (ACW) and K2CO3 (ACK). These ACs presented the microporous nature and high surface area (620–950 m2 g−1). The carbons, as well as a commercial activated carbon (CAC) used as reference, were evaluated as phenol adsorbent showing high adsorption capacity (≈150 mg g−1). The investigation of the pH solution in the phenol adsorption was also performed. The different activating agents led to AC with distinct morphological properties, surface area and chemical composition, although similar phenol adsorption capacity was verified for both prepared carbons. The production of activated carbons from spent coffee grounds resulted in promising adsorbents for phenol removal while giving a noble destination to the residue.
Natural limonite, after a simple magnetic separation, was investigated as a low-cost catalyst in a Fentonlike system. The materials were characterized with temperature-programmed reduction (TPR), infrared spectroscopy, N 2 adsorption/desorption, and 57 Fe Mossbauer spectroscopy. Results showed that the main iron oxide phases in the materials were goethite (RFeOOH) and maghemite (γFe 2 O 3 ) before and after the magnetic separation, respectively. The catalytic tests were carried out using quinoline as a model compound because it simulates the behavior of an important class of pollutants present in the fuel, i.e., nitrogen-containing compounds from contaminated petroleum. Quinoline was found to be oxidized through a successive hydroxylation mechanism. These results strongly suggest that highly reactive hydroxyl radicals, generated during the reaction involving H 2 O 2 on the catalyst surface, are responsible for this oxidation and confirm that the material is an efficient heterogeneous Fenton-like catalyst.
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