Photoreactive carbon dots modified g-C3N4 for effective photooxidation of bisphenol-A under visible light irradiation

A series of carbon dots (CDs) modified g-C3N4 (xCDs/g-C3N4; x = 0.5, 1.0, and 1.5 mL CDs solution) was synthesized via the microwave-assisted hydrothermal synthesis method for the photooxidation of bisphenol-A (BPA) under visible light irradiation. The X-ray diffraction (XRD) analysis indicates that the CDs may have a turbostratic structure and the resulting photocatalysts have distorted crystal structure, as compared with pure g-C3N4. The high-resolution transmission electron microscope (HR-TEM) analysis revealed amorphous, mono-disperse, spherical CDs with an average particle size of 3.75 nm. The distribution of CDs within the matrix of g-C3N4 appear as small dark dot-like domains. The N2 adsorption-desorption analysis indicates that the nanocomposites are mesoporous with a density functional theory (DFT) estimate of the pore size distribution between 2–13 nm. The CDs quantum yield (QY) was determined to be 12% using the UV-vis spectral analysis, where the CDs/g-C3N4 has improved absorption in the visible region than g-C3N4. The higher BET surface area of CDs/g-C3N4 provided more adsorption sites and the ability to yield photogenerated e−/h+ pairs, which caused the 1.5 CDs/g-C3N4 to have better photocatalytic efficiency compared to the rest of the systems. The highest removal, 90%, was achieved at the following optimum conditions: BPA initial concentration = 20 mg L−1, catalyst dosage = 30 mg L−1, and pH = 10. The photooxidation process is mainly driven by photogenerated holes (h+) followed by •OH and O2•−. The synthesis of the 1.5 CDs/g-C3N4 system is simple and cost-effective, where this photocatalyst is highly stable and reusable versus other systems reported in the literature

Advanced adsorptions of non-steroidal anti-inflammatory drugs from environmental waters in improving offline and online preconcentration techniques : An analytical review

Humans and animals frequently utilize nonsteroidal anti-inflammatory drugs (NSAIDs) as analgesics for various conditions. The ubiquitous use of NSAIDs has resulted in their widespread presence in environmental waters (concentrations detected in water (Malaysia) ranging from 1.40 × 10-1 to 9.72 × 10-2 mg L−1), which may threaten human health. Consequentially, continuous vigilance and resolve are indispensable for preventing any catastrophe. Numerous preconcentration techniques have been developed in response to the rising demand for a rapid, sensitive, and robust method capable of producing a dependable result (relative recoveries (RR) > 70% and limit of detection (LOD) 0.1 ng mL−1). Methods: This review aims to summarize the advancement of pre-concentration techniques using advanced adsorptive materials in quantifying NSAIDs from water mediums. Different univariate and multivariate optimization approaches for offline and online preconcentration are discussed in detail. Significant findings: The multivariate approach is more promising compared to conventional approach for developing an offline preconcentration technique. The analytical performance of online and offline preconcentration is comparable, but online preconcentration utilizes less solvent, aligning with the Green Analytical Chemistry initiative