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Dissecting the Chain Length Effect on Separation of Alkane-in-Water Emulsions with Superwetting Microchannels

Year: 2022

Journal: ACS Appl. Mater. Interfaces, Volume 14, FEB 2, page 6157–6166

Authors: Jin, Jian; Li, Hongyun; Zhao, Kaiqi; Su, Jun; Xia, Lu; Yuan, Xiaohu; Jiang, Guangming; Xu, Bo; Sun, Lidong

Organizations: National Natural Science Foundation of China [51871037]; Natural Science Foundation of Chongqing, China [cstc2021jcyj-jqX0020]; Chongqing Talents: Exceptional Young Talents Project [cstc2021ycjh-bgzxm0063, CQYC201905023]; National Key Research and Development Program of China [2020YFF0421893]; Fundamental Research Funds for the Central Universities [2019CDXYCL0031]

Keywords: oil/water separation; oil-in-water emulsion; crude oil; superhydrophilic channels; TiO2 nanotubes

Oil/water separation is an essential process in the petrochemical industry, environmental remediation, and water treatment. Alkanes are the major components of crude oil and are difficult to separate once they form emulsions in water. Much less attention has been focused on the feature of liquid alkanes that could, in turn, influence the separation process. The role of chain length is systematically studied herein by separating the alkane-in-water emulsions with superwetting titanium microchannels of 14-55 mu m. The chain length covers the entire liquid alkane spectrum with carbon numbers ranging from 6 to 16. The separation efficiency decreases while the TOC content increases with the chain length of liquid alkanes for a given channel. This is attributed to the small Ostwald ripening rate with the long chains, which stabilize the oil droplets of small sizes that could pass through the zigzag channels. Accordingly, a high separation efficiency of >99.97% and a low TOC content of <5 ppm are achieved with superhydrophilic channels of 14 mu m for alkanes with less than 12 carbons. The metallic microchannels surpass the conventional organic membranes and inorganic frameworks over the entire liquid n-alkane spectrum, paving the way for the future development of oil/water separation using porous metals.