Fabrication of superhydrophilic and underwater superoleophobic quartz sand filter for oil/water separation

To improve the oil/water separation efficiency of granular filtration, chitosan and SiO2 nanoparticles have been grafted onto the surface of quartz sand to prepare a superhydrophilic and underwater superoleophobic chitosan coated quartz sand filter media (CHQS). The separation efficiency of the CHQS for a mixture of engine oil and water has reached 99.99%, and the oil concentration in the separated water is only 1/8 of that from the pristine quartz sand filter. The outlet oil concentration of the emulsified oily wastewater is 24.4 percentage points lower than that of the pristine quartz sand filter. The water and oil hydraulic conductivities have increased by 19% and decreased by 6%, respectively, compared to the pristine quartz sand filter. The filter shows strong stability under harsh environments. The results indicate that the CHQS is feasible for highly efficient oil/water separation.