含糖废水活性污泥制备生物柴油的方法探究

本研究以处理葡萄糖废水的活性污泥为研究对象,考察了细胞破壁方法、油脂萃取溶剂及甲酯化方案对制备生物柴油的影响,并提出适用于活性污泥制备生物柴油的方法,以期为实现剩余污泥资源化、降低生物柴油生产成本提供技术支持.实验采用了盐酸加热、盐酸加热-超声、超声及液氮冷冻4种细胞破壁方法,选用二氯甲烷-甲醇和正己烷-甲醇-丙酮两种油脂萃取溶剂组合,使用油脂萃取-甲酯化(两步法)和原位甲酯化(一步法)两种方案,以降解含糖废水的活性污泥为原料,制取生物柴油.研究结果表明,盐酸加热破壁配合二氯甲烷-甲醇提取油脂的两步法获得的生物柴油产量最高,每克污泥(干重)的生物柴油产量达(60.4±3.5)mg·g-1.超声破壁一步法虽产量偏低((45.5±3.2)mg·g-1,以SS计),但步骤相对简单,化学试剂用量少.通过GC-MS分析发现,不同甲酯化方案所制备的脂肪酸甲酯(FAMEs)在组分上差别不大,除了含有月桂酸甲酯、肉豆蔻酸甲酯、棕榈油酸甲酯、棕榈酸甲酯、油酸甲酯、硬脂酸甲酯,还含有5种带甲基支链的脂肪酸甲酯及两种单不饱和脂肪酸甲酯,这可能对改善生物柴油的低温流动性有一定的帮助.

Advantageous production of biodiesel from activated sludge fed with glucose-based wastewater

In order to reutilize excess sludge and decrease the cost of lipid feedstocks, this study investigated the production of biodiesel from activated sludge fed with glucose-based synthetic wastewater. Four methods of cell-disruption were employed, including heating with hydrochloric acid, heating with hydrochloric acid followed by ultrasound, ultrasound and frozen in liquid nitrogen. Two mixed solvents were utilized, i.e. dichloromethane-methanol and hexane-methanol-acetone. Two transesterification strategies were adopted, the two-step method with lipid extraction followed by transesterification and the one-step method of in situ transesterification. Different biodiesel production approaches were tested to determine the one with the highest biodiesel gravimetric yield and the most fatty acid methyl esters (FAMEs) components. The research findings suggested that the highest gravimetric yield ((60.4±3.5) mg·g^-1 SS) could be obtained by using the two-step transesterification strategy based on cell-disruption heating with hydrochloric acid and lipid extraction by dichloromethane-methanol solvent. Although the gravimetric yield of one-step transesterification strategy based on cell-disruption by ultrasound was only (45.5±3.2) mg·g^-1 SS, the procedures were simpler and chemical dosage were less used than the two-step approach. GC-MS analysis of FAMEs revealed that the FAMEs components of two different transesterification strategies were similar. The activated sludge produced not only methyl esters of lauric acid, tetradecanoic acid, palmitoleic acid, palmatic acid, oleic acid and stearic acid, but also five methyl branched FAMEs and two monounsaturated FAMEs which possibly improve the low-temperature fluidity of biodiesel.