Adsorption Studies on Ag(I) Using Poly(N-phenylglycine) Membrane and Application in Practical Silver Recycling

Adsorption methods offer advantages in the treatment of polluted water, particularly with the removal of heavy metal ions, because they are simple in process and no secondary pollutants are involved. Conductive polymers are good adsorbents because of their diverse functional groups and large, active surface areas. Poly(N-phenylglycine) (PNPG) is an emerging conductive polymer used in adsorption studies. In this study, a PNPG membrane was prepared by vacuum filtration, and characterization studies were performed to elucidate the reaction mechanism between the PNPG membrane and Ag(I). It was found that most benzenoid diamine structures undergo a redox reaction with Ag(I), while a minority undergo chelation. Through studies on the pH influence, adsorption kinetics, and adsorption isotherms, this adsorption process fits the pseudo-second-order and Langmuir models which indicate chemical adsorption and monolayer adsorption. The maximum Ag(I) adsorption capacity of the PNPG membrane, 366 mg g(-1), was also close to the theoretically calculated value at pH 6. In addition, the PNPG membrane showed potential for the recovery of Ag from real solutions when leaching solutions of e-waste and municipal solid waste incineration fly ash were subjected to adsorption experiments.