Determination of short-chain carboxylic acids and non-targeted analysis of water samples treated by wet air oxidation using gas chromatography-mass spectrometry

Enhanced photocatalytic activity of glyphosate over a combination strategy of GQDs/TNAs heterojunction composites

A photocatalytic process was used to effectively remove glyphosate, an emerging pollutant and contaminant, through advanced oxidation. For this purpose, a feasible combination strategy of two-step anodisation and electrodeposition methods were proposed to fabricate graphene quantum dots (GQDs) supported titanium dioxide nanotube arrays (TNAs). The resultant GQDs/TNAs heterojunction composite exhibited significant degradation reactivity and circulation stability for glyphosate due to its excellent photo-generated electron and hole separation ability. After the introduction of GQDs into TNAs, the photodegradation efficiency of glyphosate increased from 69.5% to 94.7% within 60 min under UV-Vis light irradiation (λ = 320-780 nm). By analysing the intermediate products and through the evolvement of heteroatoms during glyphosate photodegradation, alanine and serine were discovered for the first time, and a detailed degradation mechanism of glyphosate was proposed. This study indicates that GQDs/TNAs heterojunction composite can almost completely degrade the glyphosate into inorganics under the appropriate conditions.

Synthesis of silver nanoparticles using bio valorization coffee waste extract: photocatalytic flow-rate performance, antibacterial activity, and electrochemical investigation

It is well known that biogenic synthesis, as compared to other processes, has proven to be highly effective in the fabrication of silver nanoparticles (AgNPs). Thus, our current study focused on synthesizing AgNPs using coffee waste extract (CWE). CWE contains many compounds identified by HPLC, which reduce, cap, and stabilize AgNPs in its solution. The as-synthesized AgNPs were produced with a monodispersed small size around 20 nm and exhibited in-plane dipole plasmon resonances of hexagonal nanoplates. AgNPs were characterized by both physical and spectroscopic methods, which confirmed their nanoscale dimensions with a hexagonal shape. The as-prepared AgNPs (12 mg) enabled the photodegradation of phenol compounds (20 mL) with a removal efficiency of ~ 94.6% in a short time in the presence of citric acid. Additionally, the second promising application of AgNPs was the tendency to remove the hazard 2,4 dinitroaniline (2,4 DNA) with a percent more than 97% while using only 7 mg of AgNPs. Moreover, the green synthesized AgNPs are superior in inhibiting bacterial growth and killing most infected microbes such as B. subtilis, P. aeruginosa, S. aureus, and E. coli. The electrochemical characteristics of the AgNPs were evaluated using a three-electrode system. The calculated specific capacitance was 280 F g-1 at 0.56 A g-1. Furthermore, after 1000 cycles at 2.2 A g-1, the AgNPs electrode demonstrates an excellent cycling stability behavior with 94.8% capacitance retention. Based on the previous promising results, it can be concluded that CWE is an environmentally benign extract to prepare AgNPs with low cost, saving and easily used for many great domains in photocatalytic, phenol compound removals, and production of functional nanodevices.