纳米石膏颗粒晶格转化高效分离油包水乳液

Separation of water or oil from their liquid mixture is crucial for many chemical and environmental processes, especially for the recycling of oil that contains undesired water and the remediation of water system polluted by oil. This project aims to develop a facile approach to efficiently separate surfactant-stabilized water (water content <10 mg mL-1 and droplet diameter <5 μm) from the water-in-oil emulsion via converting liquid water into crystal water followed by removal through centrifugation. The liquid-solid conversion can be achieved by 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. The special nanosize and the inherent cementitious property of HH will promote the separation efficiency and minimize the solid residues. Through the characterization of the interface between the HH and droplet, the change of the HH nanoparticle in crystal structure, size and shape, as well as the transfer path of water molecules, the mechanism involved in the water/oil separation by HH nanoparticle (the demulsifying and water immobilization) is investigated. The thermodynamic and kinetic conditions for HH-DH transition in emulsion and the relationship between the properties of HH particles and the separation efficiency are also studied, hoping to optimize the operating conditions and evaluate their prospect in practical application. The whole project is expected to develop a simple and efficient separation technology for water-in-oil emulsion, and introduce a new idea and method different from the conventional separation technology such as machinery, adsorption and filtration. The successful implementation of this project will have a positive role to address the problems in water-in-oil emulsion regeneration.

油水分离是当前处理处置各类含水工业废油，修复环境水体油液污染的关键技术。本项目拟研究一种特别针对水含量较低（<10 mg/mL），分散水滴较小（<5μm）、含表面活性剂稳定的油包水乳液分离技术，即利用纳米半水石膏颗粒向二水石膏转化时晶体内部[-Ca-SO4-Ca-SO4-]链空间排布转变，将水固定于石膏颗粒内，而后通过脱除固相颗粒实现油水分离，纳米石膏的尺寸效应及其特殊的水化胶凝特性可提高油水分离效率和固相脱除率。通过表征分离过程颗粒与水滴界面特征变化、石膏颗粒晶格、尺寸及形貌渐变过程，和水分子转移路径，探究石膏颗粒分离油包水乳液机制（破乳及水分固定反应机制）；通过石膏转化热力学相图/动力学条件，及石膏颗粒表面特性对分离效果影响研究，优化反应参数，评估技术适用条件。项目的顺利实施可望获得一种简单高效且针对油包水乳液的分离技术，对当前水油环境污染修复及废油资源化技术有积极推动作用。

油料是人类重要的资源，随着石油开采技术的提高和经济活动的快速增长，人类共有的石油资源正在逐渐枯竭，而与此同时大量废油的排放对海洋、江河，土壤、大气等环境的污染也正在加剧。本质上，废油只是一种“放错了地方的有用资源”。因此，对废油采用先进的技术进行资源化利用，节约人类共有的油料资源，尤其是在污染的源头进行有效治理，对环境保护可起到事半功倍的效果。目前，废油资源化技术的难点在于对油包水乳液的分离，油包水乳液中的水往往是极小的液滴形式稳定的分散在油中。实现油包水乳液的分离是提升废油资源化的技术水平的瓶颈。针对上述问题，本项目研发了通过纳米半水石膏颗粒材料的晶格固定水分技术，即利用半水石膏向二水石膏转化时晶体内[-Ca-SO4-Ca-SO4-]链空间排布转变将水固定于石膏颗粒内，而后通过脱除固相颗粒实现油水分离，纳米石膏材料的尺寸效应及其特殊的水化胶凝特性可提高油水分离效率和固相脱除率。该技术尤其适用于处理含有微量水分（含量低于10 mg mL-1），水滴尺寸较小（小于5 μm），粘度较大的油包水废油，分离效率极高，且材料稳定易于再生利用。在此技术支撑下，本项目主要研发了纳米硫酸钙小球、半水硫酸钙纳米线、层状镁铝金属氢氧化物三种高效油包水乳液分离材料。为深入探究分离机制，本项目还通过研究相关操作条件的影响机制，包括操作温度、颗粒特性（粒径；形貌；晶形）、矿物添加量、油品种类、乳液特征（水滴粒径；乳液稳定性）和颗粒特性（表面润湿；表面电荷）等，在分离效率的基础上建立分离过程表征，结合表征结果进一步提出分离油包水乳液的机制。可帮助使用者更好的利用材料进行油水分离，也可以为其他研究者提供研究新型油水分离材料的思路。概括而言，本项目提出的利用纳米半水石膏材料晶格固定分离油包水乳液的新思路，从分子层面提升分离效果，极大加深了对破乳机制的理解，提高了废油资源化技术的理论水平。