Wang Xiao, Zhu Jiaxin, Xia Shuwei, Wang Haizeng
Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China Qingdao 266100 China
RSC Adv. 2022 Sep 28;12(43):27698-27708. doi: 10.1039/d2ra05322e.
Due to the reversible nature of reactions in biodiesel production, a purification process is necessary for the biodiesel to meet international standards. As an effective method, dry washing has been applied in biodiesel purification for years, but it still faces limitations and challenges. In this work, a magnesium silicate (MS) was synthesized using the hydrothermal method. Two types of composite membranes were prepared by doping the prepared magnesium silicate into polyethersulfone (PES) casting and electrospinning, respectively. Structural and physical properties of the composite membranes were characterized. The composite membranes were applied as adsorbents to remove free fatty acids (FFAs) from crude biodiesel. Adsorption isotherm and kinetic studies were performed at different temperatures (20, 40 and 60 °C). For both membranes, the obtained adsorption capacity was higher at low temperature (20 °C). Maximum adsorption capacity was found with the electrospun membrane to be 852 mg g, calculated from the Langmuir model. Adsorption kinetics for both membranes can be well described using the pseudo-second-order model. In addition, the internal diffusion was not negligible during the adsorption process based on the intraparticle diffusion analysis. As revealed by thermodynamic study, the adsorption processes were all exothermic with a spontaneous nature. Reusability of the membrane adsorbents was evaluated, in which the electrospun membrane showed a promising performance with 94% adsorption capacity remaining over 8 cycles of adsorption and desorption.
由于生物柴油生产中反应的可逆性，生物柴油需要经过纯化过程才能达到国际标准。作为一种有效方法，干洗已应用于生物柴油纯化多年，但仍面临局限性和挑战。在本研究中，采用水热法合成了硅酸镁（MS）。分别通过将制备的硅酸镁掺杂到聚醚砜（PES）铸膜液中以及进行静电纺丝制备了两种复合膜。对复合膜的结构和物理性能进行了表征。将复合膜用作吸附剂以去除粗生物柴油中的游离脂肪酸（FFA）。在不同温度（20、40和60℃）下进行了吸附等温线和动力学研究。对于两种膜，在低温（20℃）下获得的吸附容量更高。根据朗缪尔模型计算，静电纺丝膜的最大吸附容量为852 mg/g。两种膜的吸附动力学都可以用准二级模型很好地描述。此外，基于颗粒内扩散分析，吸附过程中内部扩散不可忽略。热力学研究表明，吸附过程均为放热且具有自发性质。对膜吸附剂的可重复使用性进行了评估，其中静电纺丝膜表现出良好的性能，在8次吸附和解吸循环后仍保留94%的吸附容量。
