Sustainable preparation of graphene-like hybrid nanomaterials and their application for organic dyes removal

Magnetized bentonite modified rice straw biochar: Qualitative and quantitative analysis of Cd(II) adsorption mechanism

Industrialization has caused a significant global issue with cadmium (Cd) pollution. In this study, Biochar (Bc), generated through initial pyrolysis of rice straw, underwent thorough mixing with magnetized bentonite clay, followed by activation with KOH and subsequent pyrolysis. Consequently, a magnetized bentonite modified rice straw biochar (Fe3O4@B-Bc) was successfully synthesized for effective treatment and remediation of this problem. Fe3O4@B-Bc not only overcomes the challenges associated with the difficult separation of individual bentonite or biochar from water, but also exhibited a maximum adsorption capacity of Cd(II) up to 241.52 mg g-1. The characterization of Fe3O4@B-Bc revealed that its surface was rich in C, O and Fe functional groups, which enable efficient adsorption. The quantitative calculation of the contribution to the adsorption mechanism indicates that cation exchange and physical adsorption accounted for 65.87% of the total adsorption capacity. In conclusion, Fe3O4@B-Bc can be considered a low-cost and recyclable green adsorbent, with broad potential for treating cadmium-polluted water.

Efficient and Recyclable Heterogeneous Catalyst Based on PdNPs Stabilized on a Green-Synthesized Graphene-like Nanomaterial: Effect of Surface Functionalization

This work reports for the first time a straightforward and efficient approach to covalent surface functionalization of a sustainable graphene-like nanomaterial with abundant carboxylic acid groups. This approach results in an efficient and robust chelatant platform for anchoring highly dispersed ultrasmall palladium particles with excellent catalytic activity in the reduction of both cationic (methylene blue, MB) and anionic (eosin-Y, Eo-Y) toxic organic dyes. The large-specific-surface-area (S_BET = 266.94 m²/g) graphene-like nanomaterial (GHN) was prepared through a green and cost-effective pyrolysis process from saccharose using layered bentonite clay as a template. To introduce a high density of carboxylic acid functions, GHN was first doubly functionalized by successive grafting reaction using two different strategies: (i) in the first case, GHN was first grafted by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and then bifunctionalized by chemical grafting of tris(4-hydroxyphenyl)methane triglycidyl ether (TGE). In the second case, the grafting order of the two molecules has been reversed. GHN-GPTMS-TGE provided the highest number of grafted reactive epoxy groups, and it was selected for further functionalization with carboxylic acid functions via a ring-opening reaction through a two-step hydrolysis (H₂SO₄)/oxidation (KMnO₄) approach. The GHN nanomaterial bearing carboxylic acid groups was then treated with sodium hydroxide to produce a deprotonated carboxylic acid-rich platform. Finally, due to a high density of accessible chelatant carboxylic acid groups, GHN-COO^- binds strongly a great amount of Pd²⁺ ions to form stable complexes which after reduction by NaBH₄ leads to highly dispersed, densely anchored, and uniformly distributed nanoscale Pd particles (d ∼ 4.5 nm) on the surface of the functionalized GHN. The GHN-COO^-@PdNPs nanohybrid proved to be highly efficient for dye reduction by NaBH₄ in aqueous solution at room temperature. Moreover, because of the high stability of the as-prepared graphene-like supported PdNPs, it exhibited very good reusability and could be recycled up to eight times without any significant loss in activity.