Bentonite grafted with poly(N-acryloylglycineamide) brush: A novel clay-polymer brush hybrid material for the effective removal of Hg(II) and As(V) from aqueous environments

The present work was conducted to indicate bentonite grafted with poly(N-acryloylglycineamide) (PNAGA@BNT) could be applied as a novel clay-polymer brush hybrid material for the removal of Hg(II) and As(V) from aqueous environments. The PNAGA@BNT synthesized via the surface initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization method was characterized by BET analysis, Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and water contact angle measurements. Hg(II)% and As(V)% removal onto PNAGA@BNT was carried out with response surface methodology (RSM). The effects of the operating parameters, like pH, heavy metal ion concentration (C-o), PNAGA@BNT amount, and mixing time were evaluated by central composite design (CCD). The optimum Hg(II) adsorption conditions from the CCD were found to be 6.54, 24.46 mg/L, 23.98 mg, and 106.83 min for pH, C-o, PNAGA@BNT dosage, and mixing time, respectively. On the other hand, the optimum points obtained for As(V) adsorption from CCD were 4.36, 7.30 mg/L, 25.75 mg, and 83.37 min for pH, C-o, PNAGA@BNT dosage, and mixing time, in their given order. At the optimal points obtained for Hg(II) and As(V) adsorption, the maximum Hg(II)% and As(V)% removal efficiencies were 98.58 % and 90.95 %, respectively. The kinetic models with best fit were the pseudo-second-order kinetic model for Hg(II) and As(V) and Weber-Morris intraparticle diffusion was the dominant mechanism for As(V) and Hg(II). Among the isotherms, the equilibrium data best fit the Langmuir and Freundlich models for Hg(II), and the Dubinin-Radushkevich (D-R) and Freundlich models for As(V). Moreover, thermodynamic studies suggested the adsorption process was exothermic and spontaneous.