RESUMEN
Equilibrium partitioning of ions between a membrane and a contiguous external solution strongly influences transport properties of polymeric membranes used for water purification and energy generation applications. This study presents a theoretical framework to quantitatively predict ion sorption from aqueous electrolytes (e.g., NaCl, MgCl2) into charged (i.e., ion exchange) polymers. The model was compared with experimental NaCl, MgCl2, and CaCl2 sorption data in commercial cation and anion exchange membranes. Ion sorption in charged polymers was modeled using a thermodynamic approach based on Donnan theory coupled with Manning's counter-ion condensation theory to describe non-ideal behavior of ions in the membrane. Ion activity coefficients in solution were calculated using the Pitzer model. The resulting model, with no adjustable parameters, provides remarkably good agreement with experimental values of membrane mobile salt concentration. The generality of the model was further demonstrated using literature data for ion sorption of various electrolytes in charged polymers, including HCl sorption in Nafion.
RESUMEN
In this contribution, chemical sensor for the detection of aqueous ammonia has been fabricated using UV-curable polyurethane acrylate (PU) and nanohybrids (NH-1, NH-3 and NH-5). PU has been prepared by reacting polycaprolactone triol (PCLT) and isophorone diisocyanate (IPDI) while the nanohybrids, NH-1, NH-3, and NH-5 have been synthesized by solution blending method using PU with 1, 3, and 5 wt% loading levels of C-20B. PU and their nanohybrids showed higher sensitivity investigated by I-V technique using aqueous ammonia as a target chemical. All the nanohybrids showed higher sensitivity as compared to neat PU. The sensitivity increased with increase in clay content and the nanohybrid containing 5 wt% of clay showed the highest sensitivity (8.5254 µA cm(-2) mM(-1)) with the limit of detection (LOD) of 0.0175 ± 0.001 µM, being 7.8 times higher than pure PU. The calibration plot for all the sensors was linear over the large range of 0.05 µM to 0.05 M. The response time of the fabricated sensor was <10.0 s. Therefore, one can fabricate efficient aqueous ammonia sensor by utilization of nanohybrid as an efficient electron mediator.
