Ultrasound-assisted adsorption of paraquat herbicide from aqueous solution by graphene oxide/ mesoporous silica

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

We summarise current state-of-the-art efficient visible-light driven heterojunction water splitting photo(electro)catalysts and describe how theoretical modelling of electronic structures at interfaces can explain their functionality. Solar driven catalysis on semiconductors to produce clean chemical fuels, such as hydrogen, is widely considered as a promising route to mitigate environmental issues caused by the combustion of fossil fuels and to meet increasing worldwide demands for energy. The major limiting factors affecting the efficiency of solar fuel synthesis include; (i) light absorption, (ii) charge separation and transport and (iii) surface chemical reaction; therefore substantial efforts have been put into solving these problems. In particular, the loading of co-catalysts or secondary semiconductors that can act as either electron or hole acceptors for improved charge separation is a promising strategy, leading to the adaptation of a junction architecture. Research related to semiconductor junction photocatalysts has developed very rapidly and there are a few comprehensive reviews in which the strategy is discussed (A. Kudo and Y. Miseki, Chemical Society Reviews , 2009, 38, 253–278, K. Li, D. Martin, and J. Tang, Chinese Journal of Catalysis , 2011, 32, 879–890, R. Marschall, Advanced Functional Materials , 2014, 24, 2421–2440). This critical review seeks to give an overview of the concept of heterojunction construction and more importantly, the current state-of-the art for the efficient, visible-light driven junction water splitting photo(electro)catalysts reported over the past ten years. For water splitting, these include BiVO 4 , Fe 2 O 3 , Cu 2 O and C 3 N 4 , which have attracted increasing attention. Experimental observations of the proposed charge transfer mechanism across the semiconductor/semiconductor/metal junctions and the resultant activity enhancement are discussed. In parallel, recent successes in the theoretical modelling of semiconductor electronic structures at interfaces and how these explain the functionality of the junction structures is highlighted.

In recent years, many studies have been devoted to investigate the application of biochar for pollutants removal from aqueous solutions. Biochar exhibits a great potential to efficiently tackle water contaminants considering the wide availability of feedstock, low-cost and favorable physical/chemical surface characteristics. This review provides an overview of biochar production technologies, biochar properties, and recent advances in the removal of heavy metals, organic pollutants and other inorganic pollutants using biochar. Experimental studies related to the adsorption behaviors of biochar toward various contaminants, key affecting factors and the underlying mechanisms proposed to explain the adsorption behaviors, have been comprehensively reviewed. Furthermore, research gaps and uncertainties that exist in the use of biochar as an adsorbent are identified. Further research needs for biochar and potential areas for future application of biochars are also proposed.