Photocatalytic degradation of tetracycline in aqueous systems under visible light irridiation using needle-like SnO2 nanoparticles anchored on exfoliated g-C3N4

Background Pharmaceuticals is one of the groups of contaminants of emerging concern that are resistant to decomposition or removal by most of the existing water and wastewater treatment procedures, hence the need to develop techniques to facilitate the removals of this group of organic contaminants from water systems. In this study, needle-like SnO2 nanoparticles was synthesised and loaded on exfoliated g-C3N4 nanosheet through a hydrothermal method, for use as sensitive visible light induce-photocatalyst for the decomposition of tetracycline in aqueous systems. The synthesised composites was characterized and analysed for the nature of the heterojunction between the SnO2 nanoparticle and g-C3N4 nanosheet using microscopic and spectroscopic techniques. Results The composites were of improved surface properties and enhanced visible-light absorption. The synthesised SnO2/g-C3N4 nanocomposites with various amounts of SnO2 (10–50 mg), employed in the degradation of tetracycline under visible light irradiation, were of good degradation efficiency. The degradation efficiencies of tetracycline by 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SnO2/g-C3N4 photocatalyst were 81.54%, 90.57%, 95.90% and 92.15% as compared to g-C3N4 and SnO2 with 40.92% and 51.32% degradation efficiencies. The synergistic interaction between the needle-like SnO2 and exfoliated g-C3N4 nanosheet promoted the separation of photogenerated electron holes pairs, which enhanced their migration rate between SnO2 and g-C3N4 heterojunction, thereby facilitating the degradation of tetracycline. The ·O2− was noted to be the major reactive species in the photocatalytic of the 3 wt.% SnO2/g-C3N4 nanocomposite. Conclusion The fabricated SnO2 nanoparticles anchored on exfoliated g-C3N4 showed good performance for the decomposition of tetracycline in water, with possible application on other pharmaceuticals having same moiety (similar chemical structures).

Interphase distribution of a number of polybasic carboxylic acids in aqueous two-phase systems based on polyethylene glycol-1500

In this work, we studied the interphase distribution of a number of polybasic carboxylic acids, in particular, malic, succinic, glutaric, citric, ascorbic and tartaric in two-phase aqueous systems polyethylene glycol-1500 (PEG-1500) - sodium sulfate - water and PEG-1500 - ammonium sulfate - water. Using the spectrophotometric method of analysis, quantitative characteristics (interfacial distribution and degree of recovery) of the extraction of carboxylic acids were determined. In conclusion, it was found that the considered two-phase aqueous systems are promising in the process of extraction of polybasic carboxylic acids. In particular, the system polyethylene glycol 1500 - sodium sulfate - water has effective extraction properties for succinic malic and ascorbic acids. On the other hand, depending on the composition of the extraction systems, the quantitative characteristics for citric, glutaric and tartaric acids practically do not differ.

A Highly Stable Eu−MOF Multifunctional Luminescent Sensor for the Effective Detection of Fe3+, Cr2O72−/CrO42− and Aspartic Acid in Aqueous Systems

Heavy metal ions were common pollutants in water pollution. Amino acids, as important substances in organisms, participate in many life activities. The detection of heavy metal ions and amino acids...

Effect of pH-Regulation on the Capture of Lipopolysaccharides from E. coli EH100 by Four-Antennary Oligoglycines in Aqueous Medium

Bacterial lipopolysaccharides (LPS) are designated as endotoxins, because they cause fever and a wide range of pathologies in humans. It is important to develop effective methodologies to detect trace quantities of LPS in aqueous systems. The present study develops a fine-tuning procedure for the entrapment of trace quantities of LPS from E. coli EH100. The capture agents are self-assemblies (tectomers) formed by synthetic four-antennary oligoglycine (C-(CH2-NH-Gly7)4, T4). Based on previously performed investigations of bulk and adsorption-layer properties of aqueous solutions containing T4 and LPS, the optimal conditions for the entrapment interactions are further fine-tuned by the pH regulation of aqueous systems. A combined investigation protocol is developed, including dynamic light scattering, profile analysis tensiometry, microscopic thin-liquid-film techniques, and transmission electron microscopy. The key results are: (1) two types of complexes between T4 and LPS are generated—amphiphilic species and “sandwich-like” hydrophilic entities; the complexes are smaller at lower pH, and larger at higher pH; (2) an optimum range of pH values is established within which the whole quantity of the LPS is entrapped by the tectomers, namely pH = 5.04–6.30. The obtained data substantiate the notion that T4 may be used for an effective capture and the removal of traces of endotoxins in aqueous systems.

Thermodynamic Modeling of Multicomponent Rare Earth Nitrates Aqueous Systems

Solubility constants of rare earth (RE) nitrates crystalline hydrates are determined in a wide temperature range (−30 to 120°C), salts solubilities and phase diagrams of water–RE nitrate systems are calculated. For multicomponent (n > 5) solutions of RE nitrates the assessment of solution properties as well as phase diagrams are shown to be feasible within experimental uncertainty. In case of mixtures of RE nitrates with similar hydrodynamic radii of ions, the parameters of RE1–RE2 interparticle interaction can be ignored without losing accuracy of thermodynamic modeling.

Kinetics and Equilibrium Modeling of Single and Binary Adsorption of Aluminum(III) and Copper(II) Onto Calamansi (Citrofortunella microcarpa) Fruit Peels

The introduction of heavy metal wastes in the environment has posed health risks to both human and animals due to their toxicity. Since then, different studies have been explored for the possibility of utilizing new, low–cost, and sustainable adsorbent materials to get rid of heavy metals in the wastewater streams and aqueous solutions. This present study aimed to investigate and compare the adsorption ability of powdered calamansi (Citrofortunella microcarpa) fruit peels (PCFP) for the elimination of both Al(III) and Cu(II) ions in single (non–competitive) and binary (competitive) aqueous systems by batch adsorption techniques. Scanning electron microscopic and spectroscopic techniques were used to characterize the surface morphologies for the biosorbent and quantify the removal rates of heavy metal, respectively. Models were then used to describe in detail about the adsorption kinetics and isotherms for both single and binary metal systems. The influence and dependency of different experimental conditions on adsorption performance were also analyzed. The PCFP derived biosorbent was successful in removal of both Al(III) and Cu(II) ions in single (non–competitive) and binary (competitive) aqueous systems with 99, 70 and 91% adsorption rates, respectively. The biosorption process follows the Ho’s pseudo–second order kinetics. Furthermore, the Langmuir isotherm model was found helpful in explaining the adsorption mechanism. The dominating electrostatic interaction between adsorbents and adsorbates demonstrates monolayer adsorption at the binding sites on the surface of the peeling. Finally, the findings of this study will contribute to a better understanding of the adsorption process, as well as future system design applications in the treatment of heavy metal containing waste effluents.