Adsorption of Cu(II) by Poly-γ-glutamate/Apatite Nanoparticles

Poly-gamma-glutamate/apatite (PGA-AP) nanoparticles were prepared by chemical coprecipitation method in the presence of various concentrations of poly-gamma-glutamate (gamma-PGA). Powder X-ray diffraction pattern and energy-dispersive spectroscopy revealed that the main crystal phase of PGA-AP was hydroxyapatite. The immobilization of gamma-PGA on PGA-AP was confirmed by Fourier transform infrared spectroscopy and the relative amount of gamma-PGA incorporation into PGA-AP was determined by thermal gravimetric analysis. Dynamic light scattering measurements indicated that the particle size of PGA-AP nanoparticles increased remarkably with the decrease of gamma-PGA content. The adsorption of aqueous Cu(II) onto the PGA-AP nanoparticles was investigated in batch experiments with varying contact time, solution pH and temperature. Results illustrated that the adsorption of Cu(II) was very rapid during the initial adsorption period. The adsorption capacity of PGA-AP nanoparticles for Cu(II) was increased with the increase in the gamma-PGA content, solution pH and temperature. At a pH of 6 and 60 degrees C, a higher equilibrium adsorption capacity of about 74.80 mg/g was obtained. The kinetic studies indicated that Cu(II) adsorption onto PGA-AP nanoparticles obeyed well the pseudo-second order model. The Langmuir isotherm model was fitted well to the adsorption equilibrium data. The results indicated that the adsorption behavior of PGA-AP nanoparticles for Cu(II) was mainly a monolayer chemical adsorption process. The maximum adsorption capacity of PGA-AP nanoparticles was estimated to be 78.99 mg/g.

Automated summary

The PGA-AP nanoparticles were prepared and their adsorption capacity for Cu(II) was investigated, showing that the adsorption capacity was influenced by the content of gamma-PGA, solution pH, and temperature, with the adsorption behavior mainly being a monolayer chemical adsorption process.