Engineering Research Center for Waste Oil Recovery Technology and Equipment, Ministry of Education, Chongqing Technology and Business University , Chongqing 400067, China.
Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
Environ Sci Technol. 2016 Jul 19;50(14):7650-7. doi: 10.1021/acs.est.6b01152. Epub 2016 Jun 30.
This work report a facile approach to efficiently separate surfactant-stabilized water (droplet diameter of around 2.0 μm) from water-in-oil emulsion via converting liquid water into solid crystal water followed by removal with centrifugation. The liquid-solid conversion is achieved through the solid-to-solid phase transition of calcium sulfate hemihydrate (CaSO4. 0.5H2O, HH) to dihydrate (CaSO4·2H2O, DH), which could immobilize the water into crystal lattice of DH. For emulsion of 10 mg mL(-1) water, the immobilization-separation process using polycrystalline HH nanoellipsoids could remove 95.87 wt % water at room temperature. The separation efficiency can be further improved to 99.85 wt % by optimizing the HH dosage, temperature, HH size and crystalline structure. Property examination of the recycled oil confirms that our method has neglectable side-effect on oil quality. The byproduct DH was recycled to alpha-HH (a valuable cemetitious material widely used in construction and binding field), which minimizes the risk of secondary pollution and promotes the practicality of our method. With the high separation efficiency, the "green" feature and the recyclability of DH byproduct, the HH-based immobilization-separation approach is highly promising in purifying oil with undesired water contamination.
本工作报告了一种简便的方法，通过将液态水转化为固态结晶水，然后通过离心去除，从水包油乳液中高效分离表面活性剂稳定的水（直径约为 2.0 μm 的液滴）。通过半水硫酸钙（CaSO4.0.5H2O，HH）向二水硫酸钙（CaSO4·2H2O，DH）的固-固相变实现液-固转化，DH 可以将水固定在晶格中。对于 10mg/mL 的水乳液，使用多晶 HH 纳米椭球体的固定-分离过程可以在室温下去除 95.87wt%的水。通过优化 HH 用量、温度、HH 尺寸和晶体结构，分离效率可进一步提高至 99.85wt%。对回收油的性能检测证实，我们的方法对油质几乎没有副作用。副产物 DH 被回收为α-HH（一种在建筑和粘结领域广泛使用的有价值的胶凝材料），最大限度地降低了二次污染的风险，提高了我们方法的实用性。HH 基固定-分离方法具有高效的分离效率、“绿色”特征和 DH 副产物的可回收性，在净化含有水污染物的油方面具有广阔的前景。
