EXTRACTION OF R-(+)-LIMONENE FROM ORANGE PEELS: ASSESSEMENT AND OTIMIZATION OF THE GREENNESS OF TRADITIONAL EXTRACTION PROCESSES

This article reports a study, performed in educational context, to increase the greenness of the extraction of R-(+)-limonene from orange peels. Protocols from the literature were evaluated with the green star (GS)metric and new protocols, based in them, were designed to increase the overall greenness. These were tested in the laboratory and their greenness was assessed by traditional greenness metrics and metrics inspired in the industrial activity. Results showed that the steam distillation technique presents the largest overall greenness when evaluated by the GS, because organic solvents are not involved, but mass and energy metrics indicate that the extractions by solvent techniques are greener. This conflict denotes the complexity of the concept of chemical greenness and the need of using several types of metrics when greenness evaluation is at stake. The results show that the inclusion of experiments on the R-(+)-limonene extraction in the educational laboratory is efficient to show the difficulties of assessing the greenness of chemistry and of implementing Green Chemistry.

本文报道了一项面向教育场景的研究，旨在提升从橙皮中提取R-(+)-柠檬烯（R-(+)-limonene）的绿色性。研究首先采用绿色星标（Green Star, GS）指标对已有文献中的提取方案进行评价，并在此基础上设计了全新的提取方案以提升整体绿色性。这些新方案均在实验室中开展了测试，并通过传统绿色性评价指标以及借鉴工业活动构建的评价指标对其绿色性进行了评估。结果显示，采用GS指标评价时，水蒸气蒸馏法展现出最优的整体绿色性，因其未使用有机溶剂；但从物质与能量指标来看，溶剂萃取法的绿色性更高。这一评价矛盾体现了化学绿色性概念的复杂性，也说明在开展绿色性评价时，需综合运用多类评价指标。研究结果表明，在教育实验室中开设R-(+)-柠檬烯（R-(+)-limonene）提取实验，可有效展现化学绿色性评价以及绿色化学（Green Chemistry）实施过程中面临的诸多难点。