Evolution of the metal and metalloid content along the bioethanol production process

Abstract

Metal concentration has been determined through inductively coupled plasma mass spectrometry for bioethanol samples, raw materials employed to obtain this biofuel and samples taken from different critical points of the production process. In this way it has been possible to study the evolution of the elemental content all along the bioethanol production process, and to establish the origin of the metals present in the final samples, on the other. Moreover, the steps of the production process where metals were either removed from the biomass or accumulated in the biofuel were identified. Four different acid sample treatments were compared through the analysis of two biomass certified reference materials (CRM) and. the analytical procedure was validated by means of CRMs analysis. The results revealed that, for the most suitable method (nitric acid microwave digestion), recoveries for the analytes of interest went from 90% to 110%. Furthermore, good short-term and long-term precision and acceptable limits of detection (LOD) were obtained. Two different production lines were studied and slight differences were detected in terms of concentration of minor elements (Cd, Co, Sb, Pb and V). The raw material was identified as the most important source of metals found in the final samples. Meanwhile the distillation step caused 1000 to 10000 times decrease in metals concentration in the final bioethanol as compared to the initial biomass.

Profiling of Organic Compounds in Bioethanol Samples of Different Nature and the Related Fractions

“…It is important to remark that the latter sample contains around 4 g L –1 1-propanol and more than 1.5 g L –1 isoamyl alcohol ( Table 4 ). Samples B40 and B42 correspond to the product obtained from beet raw materials (B41), following the bioethanol production process described in ref ( 27 ). As expected, the latter sample (B41) contained a higher concentration of additional products than the bioethanol obtained at the end of the process.…”

“…Most of the analytes of this group could appear as a consequence of the incomplete fermentation process. Nevertheless, compounds such as acetaldehyde or formaldehyde could be added to water during the sugar extraction process to avoid the growth of bacteria, thus remaining in the final biofuel after the distillation process …”

Aerosol dilution for the introduction of complex matrix samples in plasma-based spectrometry techniques: a tutorial review

“…The method was applied for the determination of elements in bioethanol (45% in w) and other mixtures such as methanol (2% in w) and acetonitrile (70% in w), as well as in the case of acid solutions obtained from biomass decomposition. [75][76][77]…”

Direct lead isotopic analysis of bioethanol by means of multi-collector ICP-mass spectrometry with a total consumption sample introduction system

“…Recent studies suggested however that the main source of lead in bioethanol is the raw material and that the samples are not polluted during the production process. 49 In any case, further work is required to elucidate the sources of the lead isotopic variability in bioethanol.…”