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    A data-driven approach for the study of coagulation phenomena in waste lubricant oils and its relevance in alkaline regeneration treatments

    Year: 2017

    Journal: Sci. Total Environ., Volume 599, DEC 1, page 2054–2064

    Authors: Pinheiro, C. T.; Ascensao, V. R.; Reis, M. S.; Quina, M. J.; Gando-Ferreira, L. M.

    Organizations: SOGILUB - Sociedade de Gestao Integrada de Oleos Lubrificantes Usados, Lda

    Keywords: Waste lubricant oil; Regeneration; Coagulation phenomena; Classification; Characterization; FTIR spectroscopy

    Coagulation phenomena can occur in certain types of waste lubricant oils (WLO) during regeneration processes involving alkaline treatments, causing plant shutdowns. In this context, this study addresses the nature of the compounds responsible for the coagulation phenomena after the alkaline treatment. For such, an empirical test was developed to assess the coagulation behaviour of WLO, consisting in the addition of KOH to the WLO followed by heating under stirring conditions. This test was performed on 133 samples and four coagulation classes were identified: A; B1; B2 and C. Moreover, a physicochemical characterization of WLO was carried out regarding viscosity at 40 degrees C, saponification number (SN), total acid number (TAN), surface tension, water content, elemental analysis and functional groups (FTIR). 56 samples of fresh lubricant oils for different applications were also characterized and their properties assessed and compared. Multivariate methods were applied to WLO to discriminate among coagulation classes based on FTIR spectra. It was found that coagulation.classes A and B1 exhibit statistically similar patterns for all properties determined. Spectral discriminating analysis did not reveal discriminant peaks for class B1 samples, and the presence of specific additives was pointed as the possible factor underlying the increase in viscosity in this oils. Class B2 presents the absence of additives and oxidation products as differentiating features. In addition, B2 samples showed lower TAN SN, and lower concentration of some elements. Lubricants from gear or hydraulic applications can give rise to this class of WLO. Oils of Class C are mainly composed by synthetic ester type base oils, which hamper regeneration processes using alkaline pre treatments. In future studies, WLO type A and B1 can be classified as a single class. The coagulation phenomena classification becomes A - negative, B - precipitate formation and C - positive. (C) 2017 Elsevier B.V. All rights reserved.
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