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The removal of emergent contaminants via adsorption on granular activated carbon, prepared from Macauba palm, has been studied, contributing to the recovery of the residual biomass, endocarp, obtained in the Macauba palm oil extraction process. The material was characterized by different techniques, such as Raman spectroscopy, thermal analysis, adsorption/desorption of N, zeta potential, and scanning electron microscopy. The N adsorption studies showed that the material presents wide micropores and narrow mesopores, and has a surface area of 907.0 m g. Its maximum adsorption capacity towards the three main emerging contaminants (bisphenol A, ethinylestradiol, and amoxicillin) is much higher than that obtained with benchmark adsorbents (0.148, 0.104, and 0.072 mmol g, respectively). The influence of temperature and pH on the adsorption was also analyzed, allowing an improved description of the adsorption mechanism and showing very promising results.

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SiO2-SO3H, with a surface area of 115 m2·g−1, pore volumes of 0.38 cm3·g−1 and 1.32 mmol H+/g, was used as a transesterification catalyst. Triglycerides of waste cooking oil reacted with methanol in refluxing toluene to yield mixtures of diglycerides, monoglycerides and fatty acid methyl esters (FAMEs) in the presence of 20% (w/w) catalyst/oil using the hydrophilic sulfonated silica (SiO2-SO3H) catalyst alone or with the addition of 10% (w/w) co-catalyst/oil [(Bun4N)(BF4) or Aliquat 336]. The addition of the ammonium salts to the catalyst lead to a decrease in the amounts of diglycerides in the products, but the concentrations of monoglycerides increased. Mixtures of (Bun4N)(BF4)/catalyst were superior to catalyst alone or Aliquat 336/catalyst for promoting the production of mixtures with high concentrations of FAMEs. The same experiments were repeated using DMSO as the solvent. The use of the more polar solvent resulted in excellent conversion of the triglycerides to FAME esters with all three-catalyst media. A simplified mechanism is presented to account for the experimental results.

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In this work, we investigated a series of carbon nitride-based nanomaterials (CNs), i.e., H-PHI, mpg-C3N4, PCN, Na-PHI, Mg-PHI, CN-OA-m, and LiK-PHI, as candidate catalysts for biodiesel synthesis. The heterogeneous catalyst design based on CNs, with tunable catalytic sites and inexpensive syntheses, can allow biodiesel production to become a more sustainable process, helping to meet future energy demands. Transesterification of canola oil with methanol using LiK-PHI as a catalyst, under the optimized conditions, displayed the best performance for biodiesel production with 94% of yield and catalyst loading of 1.6 wt %. The outstanding performance exhibited by LiK-PHI is owed to this sample presenting the highest concentrations of basic sites, among the CN materials tested, directly correlated with the alkali metal content. This is an important information to understand the very nature of these basic active sites, which were exploited in this work to boost the catalyst efficiency among the best in the field. Moreover, the biodiesel produced under the best conditions, using LiK-PHI, was verified in relation to the number of esters and glycerides in this product. All values are within the values previously established by legislation, 97.6% ± 0.1 and 0.20%, respectively, which indicates the high quality of biodiesel produced.