Mass-Transfer Simulation of Salicylic Acid on Weakly Polar Hyper-cross-linked Resin XDA-200 with Coadsorption of Sodium Ion
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PROVIDER: S-EPMC9583085 | biostudies-literature | 2022 Oct
REPOSITORIES: biostudies-literature
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Project description:l-Tryptophan (l-Trp) was separated from its aqueous solution by hyper-cross-linked resins. The adsorption and desorption performances of l-Trp on different resins were compared. The weakly polar resin XDA-200 was selected as an excellent adsorbent with high adsorption amount and easy elution. The resin has a high adsorption selectivity and strong salt resistance. The adsorption mechanism of l-Trp on resin XDA-200 was elucidated based on adsorption thermodynamics experiments, molecular dynamics simulations, and adsorption kinetics experiments. The dynamic separation process of l-Trp was finally studied. The adsorption of l-Trp on resin XDA-200 is a spontaneous process driven by adsorption enthalpy. l-Trp± is the most favorable form for l-Trp adsorption on resin XDA-200 because of the strongest affinity of l-Trp± to the resin and relatively low water solubility. The adsorption of l-Trp is mainly based on π-π and hydrophobic interactions. Surface diffusion is the sole rate-limiting step of l-Trp mass transfer on resin XDA-200. l-Trp was separated satisfactorily from l-glutamic acid (l-Glu) and NaCl with both the recovery rate and purity of l-Trp higher than 99% in the fixed bed packed with resin XDA-200.
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Project description:PurposeThe goal of the present study is to develop polymeric matrix films loaded with a combination of free diclofenac sodium (DFSfree) and DFS:Ion exchange resin complexes (DFS:IR) for immediate and sustained release profiles, respectively.MethodsEffect of ratio of DFS and IR on the DFS:IR complexation efficiency was studied using batch processing. DFS:IR complex, DFSfree, or a combination of DFSfree + DFS:IR loaded matrix films were prepared by melt-cast technology. DFS content was 20% w/w in these matrix films. In vitro transcorneal permeability from the film formulations were compared against DFS solution, using a side-by-side diffusion apparatus, over a 6 h period. Ocular disposition of DFS from the solution, films and corresponding suspensions were evaluated in conscious New Zealand albino rabbits, 4 h and 8 h post-topical administration. All in vivo studies were carried out as per the University of Mississippi IACUC approved protocol.ResultsComplexation efficiency of DFS:IR was found to be 99% with a 1:1 ratio of DFS:IR. DFS release from DFS:IR suspension and the film were best-fit to a Higuchi model. In vitro transcorneal flux with the DFSfree + DFS:IR(1:1)(1 + 1) was twice that of only DFS:IR(1:1) film. In vivo, DFS solution and DFS:IR(1:1) suspension formulations were not able to maintain therapeutic DFS levels in the aqueous humor (AH). Both DFSfree and DFSfree + DFS:IR(1:1)(3 + 1) loaded matrix films were able to achieve and maintain high DFS concentrations in the AH, but elimination of DFS from the ocular tissues was much faster with the DFSfree formulation.ConclusionDFSfree + DFS:IR combination loaded matrix films were able to deliver and maintain therapeutic DFS concentrations in the anterior ocular chamber for up to 8 h. Thus, free drug/IR complex loaded matrix films could be a potential topical ocular delivery platform for achieving immediate and sustained release characteristics.
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Project description:The mass-transfer process of l-tryptophan (l-Trp)
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Project description:Hydrogen, as a noncarbon energy source, plays a significant role in future clean energy vectors. However, concerns about the safe storage and transportation of hydrogen gas limit its wide application. Featured with high H2 volumetric density, nontoxicity, and nonflammability, formic acid (FA) is regarded as one of the most encouraging chemical hydrogen carriers. The search for heterogeneous catalysts with decent catalytic activity and stability for FA decomposition is one of the hottest research topics in this area. In this paper, three weakly basic resins with different functional groups, including D201 with -N+(CH3)3, D301 with -N(CH3)2, and D311 with -NH2, were investigated as alternative catalyst supports for Pd catalysts. The prepared basic resin-supported Pd catalysts were evaluated for the FA dehydrogenation reaction under atmospheric pressure and temperatures ranging from 30 to 70 °C. The results showed that the catalytic activity of the three different resin-supported Pd catalysts follows the order of Pd/D201 > Pd/D301 > Pd/D311. Particularly, a high turnover frequency value of 547.6 h-1 was achieved when employing Pd/D201 as the FA dehydrogenation reaction catalyst at 50 °C. The apparent activation energies for the three different Pd/resin catalysts were calculated, of which the Pd/D210 catalyst demonstrates the lowest activation energy of 42.9 kJ mol-1. The reasons for the superior catalytic behavior, together with the reaction mechanism, were then investigated and illustrated.
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Project description:Protein mobility at solid-liquid interfaces can affect the performance of applications such as bioseparations and biosensors by facilitating reorganization of adsorbed protein, accelerating molecular recognition, and informing the fundamentals of adsorption. In the case of ion-exchange chromatographic beads with small, tortuous pores, where the existence of surface diffusion is often not recognized, slow mass transfer can result in lower resin capacity utilization. We demonstrate that accounting for and exploiting protein surface diffusion can alleviate the mass-transfer limitations on multiple significant length scales. Although the surface diffusivity has previously been shown to correlate with ionic strength (IS) and binding affinity, we show that the dependence is solely on the binding affinity, irrespective of pH, IS, and resin ligand density. Different surface diffusivities give rise to different protein distributions within the resin, as characterized using confocal microscopy and small-angle neutron scattering (length scales of micrometer and nanometer, respectively). The binding dependence of surface diffusion inspired a protein-loading approach in which the binding affinity, and hence the surface diffusivity, is modulated by varying IS. Such gradient loading increased the protein uptake efficiency by up to 43%, corroborating the importance of protein surface diffusion in protein transport in ion-exchange chromatography.
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Project description:The pulverization of lithium metal electrodes during cycling recently has been suppressed through various techniques, but the issue of irreversible consumption of the electrolyte remains a critical challenge, hindering the progress of energy-dense lithium metal batteries. Here, we design a single-ion-conductor-based composite layer on the lithium metal electrode, which significantly reduces the liquid electrolyte loss via adjusting the solvation environment of moving Li+ in the layer. A Li||Ni0.5Mn0.3Co0.2O2 pouch cell with a thin lithium metal (N/P of 2.15), high loading cathode (21.5 mg cm-2), and carbonate electrolyte achieves 400 cycles at the electrolyte to capacity ratio of 2.15 g Ah-1 (2.44 g Ah-1 including mass of composite layer) or 100 cycles at 1.28 g Ah-1 (1.57 g Ah-1 including mass of composite layer) under a stack pressure of 280 kPa (0.2 C charge with a constant voltage charge at 4.3 V to 0.05 C and 1.0 C discharge within a voltage window of 4.3 V to 3.0 V). The rational design of the single-ion-conductor-based composite layer demonstrated in this work provides a way forward for constructing energy-dense rechargeable lithium metal batteries with minimal electrolyte content.
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