Silica-carbon quantum dots decorated titanium dioxide as sunlight-driven photocatalyst to diminish acetaminophen from aquatic environment

The presence of pharmaceutical compound (i.e., acetaminophen) in aquatic environment has been declared as environmental issue since researchers found that it has potential risk to human health. Photocatalytic process as a promising method for waste degradation commonly employs titanium dioxide, TiO2. However, TiO(2 )has narrow light absorption and rapid charge recombination resulting in ineffective photocatalytic activity. In this study, silica - carbon quantum dots (Si-CQDs) from rice husk are decorated into TiO2 matrix through facile mixing approach to minimize the limitations of TiO2. Preliminary studies regarding TiO2 transformation and SiCQDs incorporation in various amount were systematically investigated. It is observed that 1 wt% is the optimum amount of Si-CQDs in composite in order to maximize the photocatalytic ability of TiO2. Under sunlight irradiation, 1 wt% Si-CQDs/TiO2 composite is able to completely degrade 5 mg/L of acetaminophen within 240 min (33.3 % faster than pure TiO2). The excellent performance of the composite is attributed to synergistic effect of Si-CQDs addition on TiO2 surface, which acted as photo sensitizer and electron trapper. Si-CQDs extend light absorption of TiO2 by reducing band gap energy from 3.20 to 3.12 eV, as confirmed by UV-vis Diffuse Reflectance Spectroscopy (DRS) spectra. Photoluminescence (PL) spectra and N-2 sorption isotherm reveal that Si-CQDs addition prolongs the lifetime of charge separation and improves surface area (17 % larger than TiO2), respectively. The composite of Si-CQDs/TiO2 also demonstrates good stability which is beneficial for pharmaceutical waste removal in the future.