Investigation on the Adsorption Performance of an Ester-Linked GO-MMTA Composite for Ag + and PNP in Aqueous Solution

Abstract In recent years, nanomaterials have become promising for efficient water pollutant remediation. A graphene oxide–2-mercapto-4-methyl-5-thiazoleacetic acid (GO-MMTA) nanocomposite was prepared via covalent coupling technology and employed as an adsorbent to achieve highly selective adsorption of Ag+ and PNP in aqueous solutions. The composition, chemical states, and microstructure of the GO-MMTA composite were verified using various characterization methods. Additionally, batch adsorption experiments were conducted to evaluate its adsorption performance toward Ag+ and PNP, and the effects of initial solution pH, contact time, and temperature were investigated. The results indicated that the adsorption of Ag+ and PNP reached equilibrium within 120 min. Under optimal conditions, the maximum adsorption capacities were 1.16 and 0.61 mmol g–1 for Ag+ and PNP, respectively. The adsorption kinetics followed the linear pseudo-second-order model. Isotherm data suggest that Ag+ adsorption follows the Langmuir model, indicating a monolayer adsorption process. In contrast, PNP adsorption fits better by the Freundlich model, suggesting a multilayer adsorption process. After 10 adsorption–desorption cycles, the adsorbent remained good stability and high removal rate, confirming its excellent reusability. Overall, the GO-MMTA composite shows great potential for aqueous removal/separation of Ag+ and PNP from wastewater.