Facile synthesis of Zn(Al)O/C for effective adsorption of organic dye and waste resource utilization

Abstract

With the growing severity of water pollution, it is imperative to develop environmentally friendly and efficient adsorbents for effective water treatment. In this study, highly active Zn(Al)O embedded in carbon nanosheets (Zn(Al)O/C) was synthesized through a simple pyrolysis process of terephthalate anion (TA)-intercalated ZnAl-layered double hydroxide (ZnAl-TA LDH) nanosheets under a nitrogen atmosphere. Compared to Zn(Al)O obtained from ZnAl-TA LDH calcined in air, the Zn(Al)O/C composite exhibits superior adsorption performance toward Congo red (CR), with a capacity of 2235.7 mg g⁻¹versus 1768.1 mg g⁻¹, which can be attributed to its higher specific surface area, smaller Zn(Al)O nanoparticle size, and uniformly distributed carbon matrix. Comprehensive characterization results demonstrate that Zn(Al)O/C retains the “memory effect” characteristic of Zn(Al)O, enabling reconstruction of the layered structure during CR adsorption and thereby generating numerous active sites on the surface to coordinate with CR molecules. Moreover, the abundant surface functional groups (e.g., –COOH, –OH) in the carbon matrix enhance the material's resistance to pH variations, resulting in high CR adsorption capacity over a broad pH range (4–12). Furthermore, N/S co-doped porous carbon derived from organic components in the adsorbed solid waste demonstrates significant photocatalytic hydrogen production activity (2080 μmol h⁻¹ g⁻¹). This work presents a promising strategy for the fabrication of high-performance adsorbents and the high-value utilization of waste resources.