Machine learning for total organic carbon analysis of environmental water samples using high-throughput colorimetric sensors

Process of total organic carbon (TOC) prediction using colorimetric sensors and machine learning (ML).

Electrochemical stability of metformin in NaHCO3 and Na2SO4 water solution at Au, GC and IrOx electrodes

In this study the electrochemical behavior of metformin (MET), oral antihyperglycaemic agent, was assayed at three different electrodes. The drug standard was investigated by cyclic voltammetry and square wave voltammetry via its electrooxidation at Au and glassy carbon electrode in 0.05 M NaHCO3. Under these conditions transformation of MET to corresponding N-carbonyl guanidine via oxime intermediate is suggested. The stability of MET was tested under directed stress conditions using IrOx electrode with sodium sulphate as an electrolyte and cyclic 4-amino-2-imino-1-methyl-1,2-dihydro-1,3,5-triazine appeared as the main end-product. The courses of the electrochemical processes at three electrodes were followed by UV spectroscopy and evaluated by total organic carbon analysis.

Photodegradation of chlorpyrifos in water by UV/H2O2 treatment: toxicity evaluation

Chlorpyrifos (CP) is an organophosphorus pesticide widely used in agriculture. Due to its toxicity, it has been necessary to develop a treatment to eliminate the environmental wastes generated by this substance. The combination of UV radiation and hydrogen peroxide seemed an interesting option to reduce the concentration of CP in water, as it has proved to be a simple and effective method to degrade other similar pesticides. The purpose of this work is to study the effect of different initial concentrations of H2O2 on the degradation of commercial CP in water using UV/H2O2. Conversions of 93% were achieved in 20 min with 450 mg L−1 of H2O2 initial concentration (0.16 mg of CP degraded per mg of H2O2 consumed). The total organic carbon analysis showed interesting mineralization values, reaching a 70% conversion after 4 h of reaction. In addition, this degradation procedure leads to a clear reduction of the toxicity of the reaction mixture over Vibrio fischeri.

Mineralization of Azo Dye Using Combined Photo-Fenton and Photocatalytic Processes under Visible Light

Visible-light-assisted photodegradation of an azo dye, Reactive Red 180 (RR180), in the presence of nitrogen-doped TiO2 (N-TiO2) has been studied. The photodegradation of RR180 is evaluated through decolorization studies and total organic carbon analysis. The efficacy of hydrogen peroxide (H2O2), potassium peroxomonosulfate (oxone or PMS), and potassium peroxodisulfate (PDS) in improving the photodegradation of the dye in the N-TiO2-RR180 system is also examined. The effect of combining photo-Fenton-like reaction with N-TiO2-mediated photodegradation of RR180 under visible light has been investigated. The photoactivity of N-TiO2-RR180-Fe3+/Cu2+-oxidant systems is compared with the individual techniques of photocatalysis and photo-Fenton-like reactions. The coupled system possesses superior photomineralization ability towards the abatement of RR180.

Photodegradation of Pb-3,4-dihydroxybenzoic acid complex under UV light illumination

The degradation of 3,4-dihydroxybenzoic acid (3,4-DHBA) in the presence and absence of Pb2+ under UV illumination was studied. Addition of Pb2+ caused the formation of precipitate during photoreaction when the solution pH was higher than 6. The presence of Pb2+ remarkably inhibited the degradation of 3,4-DHBA and its photodegradation intermediates, while complexation of 3,4-DHBA and its photodegradation intermediates with Pb2+ decreased the free Pb2+ in aqueous solutions. Molecular oxygen played an important role in photodegradation of 3,4-DHBA in the presence of Pb2+. UV–Vis spectroscopy was used to investigate the interaction between Pb2+ and 3,4-DHBA at different pH conditions, and FT-IR was used to characterize the precipitate formed during photoreaction. The mineralization of 3,4-DHBA was investigate by total organic carbon analysis.