A novel 3D N-, S-rich GO composite: Preparation, characterization and its selective adsorption properties for Cd2+ from aqueous solution

Background

Self-assembled GO-based 3D composites with porous or layered architectures have shown distinct qualities in terms of excellent selectivity and high stability. The functionalization of GO with N- and S-rich compounds can enhance its selectivity by increasing active sites for the adsorption of Cd²⁺.

Method

By decorating GO with 2-mercapto-1,3,4-thiadiazole (MTD), a novel, environment-friendly, and cost-effective 3D MTD@GO_2:1/100 °_{C/2 h} composite with abundant active sites was successfully fabricated using a convenient facile one-step hydrothermal method. The 3D MTD@GO_2:1/100 °_{C/2 h} composite demonstrated exceptional selectivity and efficiency in removing Cd²⁺ from aqueous solutions.

Significant findings

The batch adsorption studies were conducted to enhance the adsorption efficiency of 3D MTD@GO_2:1/100 °_{C/2 h} composite toward Cd²⁺ ions, and an excellent adsorption capacity of 37.176 mg∙g^-1 was obtained under optimized conditions (t = 40 min, pH= 7, T = 298 K). The adsorption kinetic, isothermal, and thermodynamic studies showed that adsorption data were better demonstrated with the pseudo-second-order model (R²= 0.999), and the Langmuir isotherm model suggested that the heterogeneous, surface chemisorption at monolayer coverage was the rate-limiting step, and the adsorption was endothermic. Analytical techniques such as SEM for morphology, elemental mapping analyses, and EDS, The Brunauer-Emmett-Teller (BET) method was used to determine the specific surface area (SSA), while the Barrett-Joyner-Halenda (BJH) method was utilized to analyse the pore size distribution., Zeta potential for surface charge, TGA for thermal stability, FT-IR for functional groups, and XPS were used to understand the adsorption mechanism and characterize the prepared 3D MTD@GO_2:1/100 °_{C/2 h} composite. The 3D MTD@GO_2:1/100 °_{C/2 h} composite with good stability also had a strong possibility of Cd²⁺ ion recovery (R = 92.94 %) from aqueous solution, and a promising ability to be reused for up to seven cycles. With these prominent qualities of selective adsorption for Cd²⁺ ions, the 3D MTD@GO_2:1/100 °_{C/2 h} composite can be a suitable and sustainable material for wastewater treatment in practice.