Brazilian açaí berry seeds: an abundant waste applied in the synthesis of carbon-based acid catalysts for transesterification of low free fatty acid waste cooking oil.

Residues of açaí seeds (Euterpe oleracea Mart.) were a novel source for the synthesis of the acid heterogeneous catalyst applied in the conversion of low free fatty acid waste cooking oil (WCO) to biodiesel. Yield of activated carbon (AC) and catalyst (CAT), as well as density of SO3H groups and total acidity, was analyzed in an entirely random designed experiment using multiple linear regression, one-way ANOVA, and Tukey's post hoc test. Time, temperature, dosage of KOH, and ratio of H2SO4/AC were the predictor variables with 3 levels each, at a significance level of α = .05. A significant yield variation portion of AC was explained by the experimental factors (R2 = .891, F (3, 23) = 62.9, p < .0001), as did the yield of CAT (R2 = .960, F (3, 23) = 185.7, p < .0001), density of SO3H (R2 = .969, F (3, 23) = 242.2, p < .0001), and total acidity (R2 = .973, F (3, 23) = 280.6, p < .0001). Levels of time (p = .001) and KOH dosage (p = .006) were significant to the yield of AC, and temperature levels were not influent on density of SO3H (p = .731) or total acidity (p = .762). CAT showed a SBET of 249 m2 g-1, Vpore of 0.104 cm3 g-1, low crystallinity, high thermal stability, and a mesoporous amorphous structure. Optimized catalytic tests resulted in 89% conversion of WCO and 11 cycles of reuse, better than pure H2SO4 or pure KOH (p < .0001) and also better than many biomass-derived catalysts reported in the literature.

Biosorption Cu (II) by the yeast Saccharomyces cerevisiae.

With the industrial and population advances, the generation of effluents containing heavy metals has grown a lot. In this work, the commercial biomass of the yeast Saccharomyces cerevisiae Perlage® BB were carried out as Cu (II) ion biosorbent. The influence of some variables such as metal concentration, pH range, equilibrium time and biomass concentration were evaluated. The biosorption capacity was measured by adsorption isotherms, with the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. The characterization of the biomass surface were investigated by Dispersive Energy X-Ray Fluorescence Spectrometry (EDX) and Atomic Force Microscopy (AFM). The results showed that the biomass presented good biosorption efficiency. The best fit of the data was obtained with the Langmuir model, detecting the maximum biosorption capacity of 4.73 mg g-1. By the methods used in the characterization of the biomass surface, it was possible to verify the presence of the Cu (II) ion in the yeast.