Microwave synthesis of iodine-doped bismuth oxychloride microspheres for the visible light photocatalytic removal of toxic hydroxyl-contained intermediates of parabens: catalyst synthesis, characterization, and mechanism insight

Versatile iodine-doped BiOCl with abundant oxygen vacancies and (110) crystal planes for enhanced pollutant photodegradation

Crystal plane regulation, defect engineering, and element doping can effectively solve the problems of large band gaps, poor light absorption, and fast recombination of BiOCl. In this work, iodine-doped BiOCl (I/BiOCl) nanowafers with abundant (110) crystal planes and oxygen vacancies (OV) were prepared by a simple hydrothermal method and assessed for pollutant photodegradation. I/BiOCl with a molar ratio of I to Cl of 0.6 (I_0.6/BiOCl) degraded under visible light 95.8% of the toxic dye rhodamine B and 85.1% of the persistent antibiotic tetracycline in 5 and 10 min, respectively. In comparison, unmodified BiOCl photodegraded only between 42.0% and 48.2% of these critical water pollutants. Furthermore, I_0.6/BiOCl was highly stable with most of its photocatalytic activity remaining after 4 cycles. Three reasons explain the excellent photodegradation properties of I_0.6/BiOCl. First, the doped photocatalyst grew abundant (110) crystal planes, which inhibits the recombination of photogenerated electron-hole pairs. Second, the large quantity of OV present in I_0.6/BiOCl increased active sites for reactive oxygen species generation, improved photogenerated charge separation, and pollutants adsorption. Lastly, I_0.6/BiOCl had a modified electronic band structure enhancing light absorption. Overall, these results describe a promising photocatalyst capable of degrading efficiently major pollutants with different structures.

Toxicity and removal of parabens from water: A critical review

Parabens are biocides used as preservatives in food, cosmetics and pharmaceuticals. They possess antibacterial and antifungal activity due to their ability to disrupt cell membrane and intracellular proteins, and cause changes in enzymatic activity of microbial cells. Water, one of our most valuable natural resource, has become a huge reservoir for parabens. Halogenated parabens from chlorination/ozonation of water contaminated with parabens have shown to be even more persistent in water than other types of parabens. Unfortunately, there is dearth of data on their (halogenated parabens) presence and fate in groundwater which serves as a major source of drinking water for a huge population in developing countries. An attempt to neglect the presence of parabens in water will expose man to it through ingestion of contaminated food and water. Although there are reviews on the occurrence, fate and behaviour of parabens in the environment, they largely omit toxicity and removal aspects. This review therefore, presents recent reports on the acute and chronic toxicity of parabens, their estrogenic agonistic and antagonistic activity and also their relationship with antimicrobial resistance. This article further X-rays several techniques that have been employed for the removal of parabens in water and their drawbacks including adsorption, biodegradation, membrane technology and advanced oxidation processes (AOPs). The heterogeneous photocatalytic process (one of the AOPs) appears to be more favoured for removal of parabens due to its ability to mineralize parabens in water. However, more work is needed to improve this ability of heterogeneous photocatalysts. Perspectives that will be relevant for future scientific studies and which will drive policy shift towards the presence of parabens in our drinking waters are also offered. It is hoped that this review will elicit some spontaneous actions from water professionals, scientists and policy makers alike that will provide more data, effective technologies, and adaptive policies that will address the growing threat of the presence of parabens in our environment with respect to human health.

Recent advances in bismuth oxyhalide photocatalysts for degradation of organic pollutants in wastewater

Photocatalysis has been considered as an environmental-friendly strategy for degradation of organic pollutants to the nontoxic products of H2O and CO2. Compared to metal oxide semiconductors, BiOX (X = Cl, Br and I) photocatalysts exhibit some advantages, such as, unique layered structure, good chemical stability and superior photocatalytic activity. This review provides an overview on the controllable synthesis of BiOX-based photocatalysts and their application in photodegradation of organic pollutants. Firstly, the controllable synthesis of BiOX is introduced, including hydrothermal, solvothermal, hydrolysis, precipitation, two-phase methods, ultrasonic/microwave-assisted methods, and physical methods. Then, the doping and surface modification of BiOX are summarized, including non-metal doping, metal doping, dual doping, and the modification by introducing surface terminations or carriers. In addition, the heterojunctions of BiOX/BiOY and BiOX/Bi m O n X z are introduced. At last, the promising research trends of BiOX-based photocatalysts are put forward. The main purpose is providing practical guidelines for developing high-performance BiOX photocatalysts.