Oily water is widely generated during global industrialization processes and seriously harms the environment and people’s health in a wide range of ways.^1,2  Accidents involving oil spills, from the Lakeview Gusher oil spill in 1910 to the Deepwater Horizon oil spill in 2010, release millions of tonnes of crude oil into the environment, especially the marine areas, every year and produce large quantities of oily water.^3,4  Besides the petroleum industry, oily water is also widely generated by diverse industrial technologies, such as the food, textile, leather, steel and metal finishing industries etc.¹  In a broader sense, oily...