Preparation of Hydrophilic/Hydrophobic Membranes from Sio2-Modified Waste Masks for Efficient Continuous Oil/Water Separation

Environmental issues caused by frequent oil spills and the discharge of oily wastewater have become increasingly serious and a green and efficient method of separating oil/water is urgently needed. Polypropylene is increasingly being researched as an excellent membrane material in oil/water separation. With the spread of the Corona Virus Disease 2019 (COVID-19), it makes waste masks a new challenge for mankind. In this work, waste masks (WM) were modified into two kinds of membranes with totally distinct wettability. Robust SiO2 nanoparticles was loaded onto the waste masks by in situ chemical deposition, followed by grafting with dopamine (WM-SiO2/DA) and octadecyltrichlorosilane (WM-SiO2/OTS), respectively. As a result, the prepared WM-SiO2/DA membranes were superhydrophilic with a water contact angle of 0° and a flux of 6793 L·m-2·h-1(water). The WM-SiO2/OTS membranes were hydrophobic with a water contact angle of 147.5° and a flux of 13867 L·m-2·h-1(CCl4). Both membranes exhibited separation efficiencies in exceed 98.0%, while showing good stability in different salt solutions (MgSO4, Na2SO4, CaCl2, NaCl, Mg(NO3)2) and acid-base solutions (pH=1-14). And all have good reusability, with no significant decrease in flux and separation efficiency after 20 consecutive oil/water separations, showing great promise for application in oil/water separation processes. In addition, based on the above encouraging results, a T-shaped device equipped with WM-SiO2/DA and WM-SiO2/OTS was designed subtly. Using this device, oil/water mixtures can be separated continuously, regardless of the relative density of oil/water. Consequently, this work provides an effective and promising way for waste masks upcycling, especially in the field of oil/water separation.