REACTION KINETICS OF POLYSTYRENE-BASED PHOSPHINIC ACID ION EXCHANGE/REDOX RESINS WITH METAL IONS

ABSTRACT

The ion exchange/redox kinetics displayed by the phosphinic acid polymer with aqueous solutions of silver and mercury is presented as a function of reaction temperature (6° to 45° C) and solution pH (0 to 5). The network variables studied include the crosslink level and macroporosity. At each pH, increasing the temperature leads to a more rapid approach to equilibrium. The amount complexed at equilibrium is lowest at pH Q relative to the higher pH solutions due to increased H⁺ competition for ligating sites. Metal ion reduction, rather than ion exchange, is the dominant component at equilibrium. Matrix rigidity and macroporosity do not affect Ag(I) kinetics. The rate of Hg(II) sorption is much faster than for Ag(I). Macroporosity is an important variable with mercury: macroporous resins complex more than twice the amount found with gels at 15 minutes contact. It is proposed that Ag kinetics are limited by a slow redox reaction while the Hg kinetics are diffusion-limited due to a fast redox reaction. Differences in reactivity arise from the reaction stoichiometry     

MECHANISM OF POLYMER-BASED SEPARATIONS. III. METAL ION LOADING CAPACITIES OF REACTIVE POLYMERS WITH SPECIFIC RECOGNITION MECHANISMS

The metal ion selectivity series displayed by a reactive polymer, the phosphinic acid ion exchange/redox resin, was determined from equinormal solutions of 1 milliequivalent metal ion per milliequivalent of polymer ligand sites and compared to results from trace ion solutions. It was found that intervention by the recognition mechanism (i.e., reduction) with Hg(II) and Ag(I) ions from pH 2 aqueous solutions led to high resin loading capacities. Thus, the phosphinic resin/Hg(II) interaction displayed a log D of 3.88, compared to 3.80 from a 10^-4 N solution, indicating that the recognition mechanism obviated any influence of a loading effect. The loading effect was apparent in Fe(III) complexatign wherein a log D of 4.94 was found from a 10^-4 N solution and 0.40 from the equinormal solution. The solution acidity was also an important determinant of selectivity: the series was Fe > Hg > Mn > Ag from 4N HNO₃ and Hg > Ag > Mn > Fe from 0.01N HN0₃. The performance of the phosphinic acid resin was contrasted to that from the non-reactive (i.e., solely ion exchanging) phosphonic acid resin.     

荷电超滤膜离子交换容量的研究

本文用化学滴定法测定了ＰＳＡ型和ＰＶＤＦ型复合荷电超滤膜的离子交换容量，较系统地研究了基膜与离子交换容量的关系，荷电剂浓度，反应温度和荷电时间等制膜条件下离子交换容量的关系，荷电膜热处理和贮存方式等对离子交换容量的影响，离交换容量与膜性能的关系。研究表明，离子交换容量表征荷电超滤膜的一个重要参数。     

OXIDATION OF C.I. ACID ORANGE 7 WITH OZONE AND HYDROGEN PEROXIDE IN A HOLLOW FIBER MEMBRANE REACTOR

The degradation of C.I. Acid Orange 7 by ozone combined with hydrogen peroxide was carried out in a hollow fiber membrane reactor, and batch recirculation mode of aqueous phase was employed. The effect of initial pH, hydroxyl radical scavenger, hydrogen peroxide concentration, liquid recirculation rate, gas flow rate, and gaseous ozone concentration on the decolorization of C.I. Acid Orange 7 was investigated. The results showed that the decolorization of C.I. Acid Orange 7 fits the pseudo-half-order kinetic model. The rate constant increased with the increase of initial pH, hydrogen peroxide concentration, liquid recirculation rate, gas flow rate, and gaseous ozone concentration. The presence of hydroxyl radical scavenger inhibited the decolorization rate by over 50%. The combination of ozone with hydrogen peroxide achieved a higher COD removal efficiency than ozone alone in the membrane reactor.