Template-Free Synthesis and Enhanced Photocatalytic Performance of Uniform BiOCl Flower-Like Microspheres

Preparation of uniform BiOCl flower-like microspheres was facilely accomplished through a simple protocol involving regulation of pH value in aqueous with sodium hydroxide in the presence of n-propanol. The as-prepared samples were characterized by a collection of techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and nitrogen adsorption-desorption isotherms. Based upon the SEM analyses, uniform microspheres could be formed with coexistence of some fragments of BiOCl nanosheets without n-propanol. The addition of appropriate amount of n-propanol was beneficial to provide BiOCl samples containing only flower-like microspheres, which were further subjected to the photocatalytic measurements towards Rhodamine B in aqueous under visible light irradiation and exhibited the best catalytic performance among all samples tested. In addition, the photocatalytic process was confirmed to undergo through a photosensitization pathway, in which superoxide radicals (center dot O-2(-)) played critical roles

Bio-safe drinking water with or without chlorine: a review

Drinking water biosafety has become an increasing concern for public health. Chlorination is widely used as the main disinfection strategy worldwide but has clear and well-known byproduct issues. The Netherlands has successfully demonstrated unchlorinated approach for almost 20 years but has not been widely adopted by other countries. To chlorine or not chlorine is becoming a critical question in front of all the water utilities. This review aims to provide a good overview of current biosafety management strategies, their disadvantages, as well as the latest developments and future trends. Firstly, the advantages and deficiencies of conventional disinfection and non-disinfection were discussed. Secondly, the commonly used and promising methods for biostability assessment are described. Finally, critical views on the strategy selection for ensuring drinking water biosafety were discussed. It is recommended to achieve both biological and chemical balance by removing pathogens while minimizing the organic matter and dosing a minimum level of disinfectants, which would represent the compromise choice between the current chlorine-based disinfection and chlorine-free strategy. It's worth noting that the complexity of ensuring biosafety lies in the variations among different regions, the selection of suitable methods should be tailored to specific situations on a case-by-case basis.Sanitary Engineerin

Study on the aging resistance of polyurethane precursor modified bitumen and its mechanism

As an environmentally friendly alternative for the production of high-performance modified asphalt by chemical reactions, a liquid-state polyurethane-precursor-based reactive modifier (PRM) was developed and employed in the asphalt modification. In contrast to the traditional solid bitumen modifier, for example, rubber and thermoplastic elastomers, the PRM as a liquid modifier has more significant advantages in reducing energy consumption and improving asphalt performance, which has attracted widespread attention. However, the aging resistance and its mechanism are not clear. In view of this, the aging performance of two PRM-modified bitumen (PRM-70 and PRM-90), under the short-term thermo-oxidative aging, long-term thermo-oxidative aging, and ultraviolet (UV) aging conditions, was investigated through chemical and mechanical methods. The results show that the PRM-90 is more susceptible to the thermos-oxidative aging and UV aging. The use of low-penetration-grade bitumen and ensuring an adequate reaction are beneficial to enhance the aging resistance of PRM-modified bitumen. The impact of aging on high-temperature performance of PRM-modified bitumen is great, followed by the low-temperature performance and the anti-fatigue performance. The mechanic-relevant rheological aging index (RAI) and fracture energy index (FEI) are recommended to evaluate aging properties for PRM-modified bitumen. This study not only provides support for further research on the relationship between the aging properties and mechanical performance of PRM-modified bitumen, but also provides a reference for conducting mechanism analysis.Pavement Engineerin

Phenolic Compounds Exuded from Two Submerged Freshwater Macrophytes and Their Allelopathic Effects on Microcystis aeruginosa

Culture solutions of the submerged freshwater macrophytes Hydrilla verticillata and Vallisneria spiralis, separately incubated at ID g of fresh weight (H) per liter for three days, were extracted by solid phase extraction (SPE) followed by liquid liquid extraction (LLE), and the acquired ethyl acetate fractions were analyzed by gas chromatograph-mass spectrometry (GC-MS) to identify potential allelochemicals exuded from these plant species. Freeze-dried plant tissues were separately methanol-extracted with a similar LLE-GC-MS procedure to compare allelochemical production and exudation. Four phenolic compounds were identified for both species: vanillic acid (VA), protocatechuic acid (PA), ferulic acid (FA), and caffeic acid (CA). H.verticillata produced 179 times the amount of phenolic compounds of V. spiralis. The phenolic contents in the culture solution were lower than 10% of those in the plant tissues for both submerged species in six of the eight cases. When evaluating the joint effects of the compounds using the Toxicity Index (TI) model, it was observed that the four phenolic compounds exerted additive and synergistic inhibition effects on the growth of Microcystis aeruginosa depending on the mixing ratios. These results indicate that H. verticillata and I! spiralis could release some phenolic allelochemicals to inhibit the growth of M. aeruginosa, and the joint action of multiple allelochemicals may be an important allelopathic pattern of submerged macrophytes to inhibit the growth of noxious cyanobacteria in natural aquatic ecosystems