Unveiling the visible-light-driven photodegradation pathway and products toxicity of tetracycline in the system of Pt/BiVO4 nanosheets.

The antibiotics pollution has currently captured increasing concerns due to its potential hazards to the environment and human health. The development of efficient and viable techniques for the removal of antibiotics is one of the research hotspots in fields of wastewater treatment and pharmaceutical industry. Although the photodegradation of antibiotics is widely studied, the evolution and toxicity of degradation intermediates have been rarely documented. Herein, Pt nanoparticles (NPs) decorated BiVO4 nanosheets (Pt/BiVO4 NSs) that exhibit excellent tetracycline (TC) photodegradation activity and stability have been prepared. Especially, the TC degradation efficiency reaches ca. 88.5% after 60 min under visible light irradiation, which is superior to most of the metal loaded two-dimensional photocatalysts reported hitherto. The excellent photocatalytic activity is attributable to the enhanced light absorption capacity and charge separation efficiency in Pt/BiVO4 NSs. h+, •O2- and •OH are the main active species for TC degradation, resulting in three possible degradation pathways. Furthermore, we first verify that TC solutions treated by Pt/BiVO4 NSs are harmless to Escherichia coli K-12 and various bacteria in natural rivers, which would not stimulate Escherichia coli to produce antibiotics resistance genes (ARGs). This work develops an environmentally friendly photodegradation strategy using Pt/BiVO4 NSs with potentials for efficient remediation of antibiotics pollution in wastewater.

In situ immobilization of ultra-fine Ag NPs onto magnetic Ag@RF@Fe3O4 core-satellite nanocomposites for the rapid catalytic reduction of nitrophenols.

Novel magnetic Ag@RF@Fe3O4 core-satellite (MCS) nanocomposites were prepared through in situ photoreduction upon bridging Fe(III) and Ag+ via hydroxyl groups in resorcinol formaldehyde (RF) resin by virtue of the coordination effect. The catalytic activity of MCS nanocomposites was evaluated based on catalytic 4-nitrophenol (4-NP) reduction with NaBH4 as the reducing agent. It was noteworthy that the MCS-3 was beneficial to obtain a superior reaction rate constant of 2.27 min-1 and a TOF up to 72.7 h-1. Moreover, the MCS could be easily recovered by applying an external magnetic field and was reused for five times without significantly decrease in catalytic activity. Kinetic and thermodynamic study revealed that catalytic 4-NP reduction using MCS nanocatalysts obeyed the Langmuir-Hinshelwood mechanism and was controlled by the diffusion rate of substrates. Overall, the immobilization of ultra-fine Ag nanoparticles and the extremely negative potentials around MCS nanocomposites, which were effective for the diffusion of reactants, synergistically accelerated the catalytic reduction reactions.

Mixed phase nano-CdS supported on activated biomass carbon as efficient visible light-driven photocatalysts.

Semiconductors are promising photocatalysts for the use of sunlight in energy conversion and environmental remediation. To this end, various synthetic pathways have been proposed to increase their photocatalytic efficiency, catalytic stability, recycle, and reuse. In this work, mixed phase CdS nanoparticles were loaded on the surface of activated biomass carbons to prepare composite photocatalysts via hydrothermal syntheses, which were further applied to photocatalytic degradation of rhodamine B (RhB) under visible irradiation. The composite photocatalysts displayed considerable specific surface area (up to 672 m2 g-1) and suitable band gap energy of ca. 2.1 eV. Due to the excellent light adsorption ability and chemical stability, these composite photocatalysts exhibited excellent photocatalytic capacity toward RhB degradation under visible irradiation. Moreover, the photocatalytic stability was also demonstrated by cyclic experiments, by which the composite photocatalysts retained over 80% of the initial catalytic activity after 4 consecutive runs.

Assessment of tea garden soils at An'xi County in southeast China reveals a mild threat from contamination of potentially harmful elements.

An extensive study of the spatial distribution characteristics of potentially harmful elements (PHEs) in tea (Camellia sinensis (L.) O. Kuntze) garden soils and ecological risk assessment at An'xi County, the birthplace of oolong tea in China, was implemented. A total of 78 soil samples were examined to determine the concentration of five PHEs (As, Cd, Cr, Hg and Pb), soil organic matter and pH by using geostatistical approaches combined with geographical information system analysis. All PHEs presented in the study area were slightly higher than their background values for provincial and national standards except Cr. Moreover, ecological risk assessment of PHEs in the tea garden soils at An'xi County was performed by means of the Håkanson method. The average ecological potential risk index (Er) of the five PHEs followed a descending order of Cd > Hg > Pb > As > Cr, and suggested a moderate ecological risk in the study area.

Photodegradation of Rhodamine B over Biomass-Derived Activated Carbon Supported CdS Nanomaterials under Visible Irradiation.

A family of new composite materials was successfully prepared through the deposition of as-synthesized CdS nanomaterials on lotus-seedpod-derived activated carbon (SAC). The SAC supports derived at different activation temperatures exhibited considerably large surface areas and various microstructures that were of great importance in enhancing photocatalytic performance of CdS@SAC composite materials toward the photodegradation of rhodamine B (RhB) under visible irradiation. The best-performing CdS@SAC-800 showed excellent photocatalytic activity with a rate constant of ca. 2.40 × 10-2 min-1, which was approximately 13 times higher than that of the CdS nanomaterials. Moreover, the estimated band gap energy of CdS@SAC-800 was significantly lowered down to 1.99 eV compared to that of the CdS precursor (2.22 eV), which suggested considerable strength of interface contact between the CdS and SAC support, as well as efficient light harvesting capacity of the composite material. Further photocatalytic study indicated that the SAC supports enhanced the separation of photogenerated electrons and holes in this system. Improved photocatalytic activity of the composite materials was largely due to the increased generation of catalytically active species such as h+, OH•, [Formula: see text] etc. This work provided a facile and low-cost pathway to fabricate photocatalysts for viable degradation of organic dye molecules.