Increasing the hydrophobicity of filter medium particles for oily water treatment using coupling agents

Generally, increasing the hydrophobicity of filter media leads to enhanced oil removal by filtration. In this study, the hydrophobicity of quartz sand filter media was increased by modifying the particles with titanate and silane coupling agents (DN101 and KH550) by dry processing. The results show that the quartz sand particle surfaces were uniformly covered with the coupling agents after surface modification, and many fine particles were observed. The optimised parameters for the surface modification procedure were a DN101:KH550 ratio of 1:2, total coupling agent amount of 1.0 wt%, reaction temperature of 60 °C and reaction time of 50 min. Under these conditions, the water contact angle on the filter media surface increased from 40.1° to 82.9°, and the effluent oil concentration decreased from 4.74 mg/L for the unmodified filter media to 2.99 mg/L for the modified filter media when the influent oil concentration was 17.3 mg/L. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results show that DN101 and KH550 formed chemical bonds with the quartz sand surface groups, resulting in the formation of a uniform, stable coating on the surface.