A 3D rGO/g-C₃N₄ nanocomposite loaded with Ag NPs was fabricated and this obtained nanocomposite with excellent performance was used as an adsorbent and catalyst to efficiently remove MB under visible light irradiation.

Activated carbons derived from biomass have been proved to be one of the most promising adsorbents due to their abundance, low cost, reproducibility and environmental friendliness. In this study, a simple, facile and effective pyrolysis method was demonstrated to prepare hierarchical porous biomass charcoal by using peanut shells as precursor without chemical activation in an electric muffle furnace. The obtained products hold porous structure and abundant oxygen-containing functional groups, which were mainly due to in-built template of the structure of peanut shell and the preparation process without nitrogen protection, respectively. Interestingly, the obtained biomass charcoal sample with excellent adsorptive property quickly removed Pb²⁺ (100 mg/L) and methylene blue (50 mg/L) from water with removal efficiency of 96.5% and 97.1%, and removal capacity of 48 mg/g and 24 mg/g, respectively. The synthetic process was simple and economical, and it could be used as a beneficial reference in the recycling of biomass waste.

As a basic building block of graphene-based materials, graphene oxide (GO) plays an important role in scientific research and industrial applications. At present, numerous methods have been employed to synthesize GO, there are still some issues that need to be solved, thus it is of importance to develop a green, safe and low-cost GO preparation method. Herein, a green, safe and fast method was designed to prepare GO, namely, graphite powder was firstly oxidized in a dilute sulfuric acid solution (H₂SO₄, 6 mol/L) with hydrogen peroxide (H₂O₂, 30 wt%) as oxidant, and then exfoliated to GO by ultrasonic treatment in water. In this process, H₂O₂ was the only oxidant, and no other oxidants were used, thus the explosive nature of GO preparation reaction in the conventional methods could be completely eliminated. This method has other advantages such as green, fast, low-cost and no Mn-based residues. The experimental results confirm that obtained GO with oxygen-containing groups has better adsorption property compared to the graphite powder. As adsorbent, GO can remove methylene blue (50 mg/L) and Cd²⁺ (56.2 mg/L) from water with removal capacity of 23.8 mg/g and 24.7 mg/g, respectively. It provides a green, fast and low-cost method to prepare GO for some applications such as adsorbent.

MXenes and MXene-based composite materials have potential applications in a wide range of areas due to their unique physical and chemical characteristics. At present, it is still a major challenge to develop a simple, safe, and efficient route to prepare MXenes without using fluorinated etchants. Herein, we design a facile method to prepare Ti₃C₂T_x MXene sheets by selectively etching Ti₃AlC₂ powders in an aqueous diluted H₂SO₄ solution with H₂O₂ as an oxidant. In a system of H₂SO₄ and H₂O₂, an aqueous H₂SO₄ solution with a concentration of 6 mol/L is a strongly acidic medium with no volatility, and 30% H₂O₂ acts as a strong green oxidizer without harmful by-products. The experimental process is safe and convenient to conduct in a beaker under a water bath of 40°C. The etching process can be completed in 1 h under the air atmosphere conditions. The experimental results confirmed that the etched Ti₃AlC₂ powders can be successfully separated into Ti₃C₂T_x nanosheets under ultrasound treatment without using any intercalation agent. The relevant etching mechanism is may be attributed to the synergy effect of H₂SO₄ and H₂O₂, which triggers sequential selective etching of Al layers from the Ti₃AlC₂ phase. It may provide a new green way to prepare MXene-based materials without using toxic HF or HF-containing etchants.