Eugen Pincovschi

Kinetic analysis of Zn(II) removal from water on a strong acid macroreticular resin using a limiting bidisperse pore model

Abstract H + /Zn 2+ integral interdiffusion coefficients on Vionit CS 32 resin (–SO 3 H, styrene-divinylbenzene copolymer with a macroporous skeleton) were obtained using the Ruckenstein bidisperse pore model for a two-stage ion exchange process, considering the macropore diffusion to be much faster than microporous diffusion. The H + /Zn 2+ ion exchange rate on the macroporous resin was measured at 298 K using a potentiometric method. The experimental conditions were selected to favour a particle diffusion rate-controlling mechanism, subsequently confirmed by the variation of exchange rate with resin bead size and stirring speed. The H + /Zn 2+ integral interdiffusion coefficients in the macropores were obtained as a function of the ionic composition of the resin for different values of the ratio, β / α , of micropore and macropore uptake at equilibrium. Using several discrimination criteria, it was established that the most appropriate value for the system was β / α =0.2.

Kinetics of Cesium and Strontium Ions Removal from Wastewater on Gel and Macroporous Resins

Abstract Ion exchange kinetics of H+/Cs+ and H+/Sr2+ on strong and weak acid resins with gel and macroporous matrices was investigated at constant temperature. The rate was measured in a batch reactor using a potentiometric method under conditions favoring a particle diffusion controlled mechanism. Intraparticle interdiffusion coefficients were obtained by modeling the data with quasi‐homogeneous resin phase and bidisperse pore kinetic models, considering a two‐stage and parallel diffusion in macro‐ and micro‐pores, respectively. The ratios of the functional groups grafted in the micro‐ and macro‐pores were evaluated for different cases. The macroporous matrix produces a greater retarding effect than the gel skeleton.

PROTON / NICKEL(II) INTERD1FFUSION COEFFICIENTS ON STRONG ACID RESINS

ABSTRACT Ion exchange kinetics between proton and nickel(II) ions on sulfonic acid cation resins, with polystyrene-divinylbenzene matrix, type gel and macroporous, in high concentration of the external solution was studied at 298 K using a potentiometric method. The ratio between the amount of ions in the resin and in the solution phase was kept smaller than 0.1. The integral interdiffusion coefficients were determined using the quasi-homogeneous resin phase kinetic models at infinite and finite solution volume. The results were compared and discussed in terms of their range of validity. The influence of the ionic composition of the ion exchanger and matrix nature (gel or macroporous) on the integral interdiffusion coefficients was investigated and discussed. The simpler infinite solution volume kinetic model gives higher values for the integral interdiffusion coefficients than the Patersons finite solution volume model. The numerical values of the integral interdiffusion coefficients are greater for gel than for macroporous type resin up to

A Procedure to Monitor Sulfonation of Macroporous Styrene‐Divinylbenzene Resins

Abstract The ratio between the number of functional groups grafted in micro and macropores for Purolite C 150 resin, a macroporous styrene‐divinylbenzene copolymer, with –SO3H functional groups, was evaluated using a kinetic procedure based on a bidisperse pore model. The proposed procedure requires potentiometric measurement at constant temperature in batch system of the fractional approach to equilibrium for H+/Na+ ion exchange process on the macroporous resin in concentrated external solution, 1.00 mol/L NaCl. The macropore integral interdiffusion coefficients were computed at each point on the fractional approach to equilibrium versus time curve, for different values of the β/α parameter of the model, which is three times the ratio of micropore and macropore uptake at equilibrium. Several discrimination criteria were used to select a reliable β/α value. The result for Purolite C 150 resin is β/α ≤ 0.03; the ratio between the sulfonic groups grafted onto micro and macropores is equal to or lower than 1/100.