Crushed Glass and Oil Extracted from Palm Oil Sludge as Primary Materials in the Production of Hydrophobic Sand for Capillary Barrier Applications

Hydrophobic-coated sand causes a reduction in infiltration, making it suitable for hydrophobic capillary barriers. Borosilicate glass waste was crushed into a synthetic sand 180 µm average, and fatty acids (PFA) were extracted from palm oil sludge. The synthetic sand was coated with PFA using mixing (POS-M) and solvent-assisted (POS-S) methods with stearic-acid-coated sand (SA) as a standard at concentrations varying from 1 to 16 g/kg. Contact angle measurements were undertaken by applying the sessile drop method. The water holding capacity of POS-M and SA were determined, and hydraulic conductivity curves were estimated with the van Genuchten model. Finally, a qualitative assessment of POS-M’s effectiveness as a capillary barrier was performed using a set of micro-tensiometers. Maximum contact angles for POS-M, POS-S, and SA were 119.73°, 118.83°, and 107.48°, respectively, and the saturated hydraulic conductivity of hydrophobized sands showed an exponential change of minus 2. Saturated conditions above the capillary barrier and unsaturated underneath were observed. In conclusion, the results indicate that the zero-waste approach applied through the reuse of solid waste from glass and palm oil production can be a waste management alternative in the production of hydrophobic sands that can be used in hydrophobic capillary barrier applications.