Résumé
Treatment of oily wastewater has been still a challenge to environmental scientists. In this study, waste autoclaved aerated concrete (AAC) grains from a concrete manufacturing plant were collected and modified with stearic acid to evaluate the possibility of using them as low-cost filtration media for the removal of oil from water. The modification factors such as percentage of surface modifying agent - stearic acid (0.4%, 0.6%, 0.8%, 1%, 2% by weight), mixing durations (3 h, 6 h, and 9 h), and different grain sizes (0.1-0.2 mm; 0.63-1.25 mm; and 1.25-2.5 mm) were all evaluated in this study. The results showed that waste AAC with a grain size of 0.1-0.2 mm modified with 2% stearic acid in 9 h had only 24% (by weight) wetted during the wetting test. The filtration column test with oily wastewater using modified AAC and original AAC grains proved the oil removal performance depends on filtration flow modes (downflow, upflow, or up-downflow), types of filtration media (single or dual filtration layers), and initial oil concentrations. The COD removal and total oil removal efficiencies were 55-82% and 75-90%, respectively, depending on the testing conditions.