Comparative ecotoxicity study of glycerol-biobased solvents

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Abstract
Environmental context: The search for alternative solvents to prevent environmental damage is one of the main interests in ‘green’ sciences. Five of these new substances from biodiesel production were evaluated to assess their negative environmental effects. The results obtained showed that three of these chemicals may be harmless for short exposure in aquatic biomodels. Although more tests are required, this family of compounds promises to be safe and useful for industrial purposes. Glycerol-biobased ethers have a high potential as solvents owing to their chemical inertness and diversity, which allows modulation of their properties, such as polarity, hydrophobicity or viscosity, depending on the specific needs in each case. Despite their renewable source, the environmental compatibility of these solvents needs to be checked. The acute ecotoxicity of five glycerol-derived solvents (3-ethoxy-1,2-propanediol, 1,3-diethoxy-2-propanol, 3-butoxy-1,2-propanediol , 1,3-dibutoxy-2-propanol and 1,2,3-tributoxypropane ) was evaluated in a systematic study using several bioindicators covering the trophic chain (the crustacean Daphnia magna, the fish Danio rerio and the green alga Chlamydomonas reinhardtii). These results were compared with the previously studied bioindicator Vibrio fischeri. According to the hypothesis of the present work, the toxicity of these solvents increased as a function of their lipophilicity, which is related to the increase in the number and length of the alkyl chains in the basic structure; accordingly, the least toxic compound for all the aquatic organisms was 3-ethoxy-1,2-propanediol and the most toxic solvent was 1,2,3-tributoxypropane, except in the case of D. rerio and V. fischeri, with 1,3-dibutoxy-2-propanol the most toxic chemical. Potential damage caused by eventual emissions, was evaluated using the Environmental Health and Safety Approach, a methodology used for detecting risks related to the environment and the human health. Using available physicochemical and toxicity data, each chemical compound receives a score for the categories health, safety and environment. The best candidates considered as least dangerous for a short exposure time according to the studied biomodels are 3-ethoxy-1,2-propanediol, 3-butoxy-1,2-propanediol and 1,3-diethoxy-2-propanol.

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