Synthesis of polyacrylamide immobilized molybdenum disulfide (MoS 2 @PDA@PAM) composites via mussel-inspired chemistry and surface-initiated atom transfer radical polymerization for removal of copper (II) ions

Abstract

Abstract In present work, novel polyacrylamide immobilized molybdenum disulfide (MoS2@PDA@PAM) composites were synthesized via the mussel-inspired chemistry and surface initiated atom transfer radical polymerization (SI-ATRP). The as-prepared MoS2@PDA@PAM composites were characterized by energy dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Characterization results provide sufficient evidences for the successful functionalization of MoS2 with PAM. The products were used as adsorbents for removing of copper (II) ions. Results show the introduction of PAM onto MoS2 could enhance the adsorption capacity of MoS2@PDA@PAM towards copper (II) ions. The amount of adsorbed copper (II) ions by MoS2@PDA@PAM composites is 2.5 times that of pristine MoS2. The effects of various experimental factors on the adsorption process, including contact time, initial copper (II) ion concentrations, solution pH and temperature, were also studied in this work. The batch experiments show that the adsorption of copper (II) ions onto MoS2@PDA@PAM is dependent on time, pH and temperature. The optimum solution pH is observed at pH 7 and the increase of temperature is favorable for the adsorption of MoS2@PDA@PAM towards copper (II). Based on the experiment data, the adsorption kinetics, isotherms and thermodynamics were also investigated. The kinetics and isotherm studies show that pseudo-second-order kinetic and Freundlich isotherm models could well fit with the adsorption data. The thermodynamic results show that the adsorption of copper (II) ions on MoS2@PDA@PAM is a spontaneous and endothermic process. The adsorption process is mainly governed by the chemisorption involving the electrostatic interaction and/or chemical chelation between copper (II) ions and amino groups on the surface of MoS2@PDA@PAM. Taken together, it is proven that the PAM can be immobilized onto the MoS2 nanosheets via the mussel-inspired chemistry and SI-ATRP, and it can enhance the adsorption performance of MoS2@PDA@PAM composites, which might be used as adsorbents to remove heavy metal ions in real environment treatment.