Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung, Taiwan.
Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung, Taiwan.
J Colloid Interface Sci. 2016 Sep 15;478:97-106. doi: 10.1016/j.jcis.2016.05.057. Epub 2016 Jun 1.
To demulsify oil-in-water (O/W) emulsions, a zinc-based zeolitic imidazolate framework (ZIF-8) was employed for the first time to remove oil droplets from water. ZIF-8 exhibits a high surface area and positive surface charges, making it a suitable adsorbent to adsorb negatively-charged oil droplets. Adsorption behaviors of oil droplets to ZIF-8 were studied by analyzing the adsorption kinetics and isotherm with theoretical models. The activation energy of adsorption of oil droplets to ZIF-8 was determined as 24.1kJmol(-1). The Langmuir-Freundlich (L-F) model was found to be most applicable to interpret the isotherm data and the predicated maximum adsorption capacity of ZIF-8 can reach 6633mgg(-1), revealing a promising capability of ZIF-8 for demulsification. Factors influencing the adsorption of oil droplets to ZIF-8 were investigated including temperature, pH, salt and surfactants. The adsorption capacity of ZIF-8 for oil was improved at elevated temperatures, whereas alkaline condition was unfavorable for the adsorption of oil droplets due to the electrostatic repulsion at high pH. The adsorption capacity of ZIF-8 remained similar in the presence of NaCl but it was reduced in the presence of surfactants. ZIF-8 was regenerated by a simple ethanol-washing method; the regenerated ZIF-8 exhibited more than 85% of regeneration efficiency over six cycles. Its crystalline structure also remained intact after the regeneration. These characteristics indicate that ZIF-8 can be a promising and effective adsorbent to remove oil droplets for demulsification of O/W emulsions.
为了使水包油（O/W）乳液破乳，我们首次采用基于锌的沸石咪唑酯骨架（ZIF-8）从水中去除油滴。ZIF-8 具有高表面积和正表面电荷，使其成为一种合适的吸附剂，可以吸附带负电荷的油滴。通过分析吸附动力学和吸附等温线与理论模型，研究了油滴对 ZIF-8 的吸附行为。确定了油滴吸附到 ZIF-8 上的活化能为 24.1kJmol(-1)。发现 Langmuir-Freundlich（L-F）模型最适用于解释等温线数据，并且预测的 ZIF-8 的最大吸附容量可以达到 6633mgg(-1)，这表明 ZIF-8 具有很好的破乳能力。研究了影响油滴吸附到 ZIF-8 的因素，包括温度、pH 值、盐和表面活性剂。升高温度可以提高 ZIF-8 对油的吸附能力，而碱性条件不利于油滴的吸附，因为在高 pH 值下会产生静电排斥。在存在 NaCl 的情况下，ZIF-8 的吸附容量相似，但在存在表面活性剂的情况下，吸附容量会降低。ZIF-8 可以通过简单的乙醇洗涤方法进行再生；在六个循环中，再生后的 ZIF-8 的再生效率超过 85%。其晶体结构在再生后也保持完整。这些特性表明，ZIF-8 可以作为一种有前途且有效的吸附剂，用于去除 O/W 乳液中的油滴以实现破乳。
