Zhongzheng Xu1, Lin Li2, Jiawei Liu1, Caili Dai1, Wen Sun1, Jia Chen1, Zhixuan Zhu1, Mingwei Zhao3, Hongbo Zeng4. 1. Shandong Key Laboratory of Oilfield Chemistry, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China; Key Laboratory of Unconventional Oil & Gas Development, China Universcity of Petroleum (East China), Ministry of Education, Qingdao 266580, China. 2. Shandong Key Laboratory of Oilfield Chemistry, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China; Key Laboratory of Unconventional Oil & Gas Development, China Universcity of Petroleum (East China), Ministry of Education, Qingdao 266580, China. Electronic address: lilin@upc.edu.cn. 3. Shandong Key Laboratory of Oilfield Chemistry, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China; Key Laboratory of Unconventional Oil & Gas Development, China Universcity of Petroleum (East China), Ministry of Education, Qingdao 266580, China. Electronic address: zhaomingwei@upc.edu. 4. Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada. Electronic address: hongbo.zeng@ualberta.ca.
Abstract
HYPOTHESIS: Superhydrophilic/underwater superoleophobic membrane constructed by hydrophilic polymers possesses great advantage in the separation of oily waste water, due to its intrinsic oil-repellent property. The formation of hydration layer to repel and block oil is considered as the mechanism of underwater superoleophobicity and subsequent oil/water separation. Constructing a stable hydrophilic polymer network on the substrate surface would significantly improve the robustness of hydration layer. EXPERIMENTS: In this work, a feasible and universal mussel-inspired dip-coating method was developed for constructing stable hydrophilic polymer network onto target substrate surface, via successively immersing substrate membranes into aqueous solutions of polydopamine (PDA) and catechol-functionalized hydrophilic polymer (CFHP). After pre-wetting with water, the polymer network would swell with water to form a thin and stable water film layer, serving as a barrier against oil penetration. FINDINGS: The as-prepared CFHP/PDA modified membranes exhibit outstanding performance in separating various oil/water mixtures and oil-in-water emulsions stabilized by surfactants, with separation flux up to 5641.1 L·m-2·h-1 and separation efficiency achieving 99.98%. The surface modification method developed in this work can be easily extended to various materials and membrane systems, for achieving a variety of practical applications such as industrial wastewater treatment.
HYPOTHESIS: Superhydrophilic/underwater superoleophobic membrane constructed by hydrophilic polymers possesses great advantage in the separation of oily waste water, due to its intrinsic oil-repellent property. The formation of hydration layer to repel and block oil is considered as the mechanism of underwater superoleophobicity and subsequent oil/water separation. Constructing a stable hydrophilic polymer network on the substrate surface would significantly improve the robustness of hydration layer. EXPERIMENTS: In this work, a feasible and universal mussel-inspired dip-coating method was developed for constructing stable hydrophilic polymer network onto target substrate surface, via successively immersing substrate membranes into aqueous solutions of polydopamine (PDA) and catechol-functionalized hydrophilic polymer (CFHP). After pre-wetting with water, the polymer network would swell with water to form a thin and stable water film layer, serving as a barrier against oil penetration. FINDINGS: The as-prepared CFHP/PDA modified membranes exhibit outstanding performance in separating various oil/water mixtures and oil-in-water emulsions stabilized by surfactants, with separation flux up to 5641.1 L·m-2·h-1 and separation efficiency achieving 99.98%. The surface modification method developed in this work can be easily extended to various materials and membrane systems, for achieving a variety of practical applications such as industrial wastewater treatment.