Kinetics of sorption of 4-nitrophenol polymeric sorbents based on N-vinylpyrrolidone

Abstract

In operation, the kinetics of sorption of 4-nitrophenol (4-NP) from an aqueous solution onto
polymeric adsorbents obtained by radical copolymerization of a functional monomer different solvents -
vinylpyrrolidone (VP) and the crosslinker - ethylene glycol dimethacrylate (EGDMA) - in different mole
fractions. Experimentally obtained integral kinetic curves of sorption and diffusion equations are described
and chemical kinetics, which revealed limiting stage of the process. It was found that the sorption process
takes place in mixed-diffusion mode. In the first 5-7 minutes in conditions of free active sites on the surface
of the polymer sorbent absorption occurs with limiting diffusion solute through the boundary layer solution,
then the influence of the external diffusion factor is reduced, and internal diffusion - is increasing, then the
sorption process of transition to the limitation of the transfer phase of the polymer. The equations of pseudosecond-order
most adequately describe the sorption process. The paper calculated coming across as constant
of diffusion of the outer and the inner as well as the reaction rate constant pseudo-second order. The
procedure for changing the rate constants of sorption 4 NF polymer sorbents practically coincides with the
change in the rate of external diffusion, that is, the active centers in the polymer matrix affect both the
intermolecular interactions in the adsorption and phase transfer. Thus sorption 4 NF polymeric sorbents
based on N-vinylpyrrolidone jointly diffusion limited and the kinetic stage, the beginning of the process in
making a greater contribution to the external diffusion equilibrium is approached with increasing degree of
filling of the polymer - the internal. From the combination of kinetic characteristics of sorbents for
optimal concentration of 4-NP in static conditions are polymeric sorbents with a ratio of VP: EGDMA equal
to 1:30 (solvent СН3ОН and СНСl3)