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In this paper, new adsorbents with high mechanical strength chitosan-graphene oxide (CS-GO) and chitosan-titanium dioxide (CS-TiO 2 ) were synthesized by using glutaraldehyde as crosslinking agent, and the adsorption behavior of Pb (II) and V (V) on them were investigated. The materials were characterized by scanning electron microscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The effects of initial metal ion concentration and contact time on the removal of V (V) and Pb (II) by CS-GO and CS-TiO 2 were investigated. Characterization results showed that the hydroxyl group of GO/TiO 2 reacted with the amino group of chitosan. A comparison of the kinetic models against experimental data showed that the kinetics react system was best described by the pseudo-second-order model. indicating that chemical adsorption was the main adsorption force. the Langmuir adsorption model and Freundlich model agreed well with the experimental data. The removal capacity of Pb (II) by CS-GO and CS-TiO 2 were lower than those of V (V). The uncross-linked -OH and CO were the main adsorptive sites for Pb (II) removal, while uncross-linked -OH and -NH 2 played an important role in removing V (V). These findings provided insights on the removing lead and vanadium pollution., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

From the viewpoint of sustainability, graphene-like metal-free 2D nanomaterials (GMFs) hold great potential in different photocatalytic fields due to their distinct structures and properties. Although their lattice structures are highly similar, the properties of these nanomaterials are in vast diversity owing to the uniqueness of particular atomic arrangement, thus giving rise to their multi-faceted functionalities in photocatalytic process. In this review, we summarize the latest progress of GMFs and their hybrid composites in photocatalytic field, including graphene and its derivatives, hexagonal boron nitride (h-BN), graphitic carbon nitride (g-C 3 N 4 ), black phosphorus (BP) and emerging 2D covalent organic frameworks (COFs). Their unique 2D structure and key photocatalytic properties are firstly briefly introduced. Then a critical discussion on their multiple roles in the activity enhancement of composite photocatalysts is emphasized, which in turn points out the direction of maximizing their functions and guides our efficient construction of hybrid photocatalysts based on above 2D nanomaterials. On this basis, a summary about the hybridization of above 2D metal-free materials is presented, and the merits of 2D/2D hybrid systems are elaborated. Last, we wrap up this review with some summative remarks, covering understanding their own unique strengths and weaknesses by comparison and proposing the major challenges and perspectives in this emerging field., (Copyright © 2021 Elsevier Ltd. All rights reserved.)