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In this research using supported metal‑carbon membranes in a membrane percrystallisation application, we investigated the influence of metal ions on the formation of carbon during carbon membrane synthesis by combining polyvinylpyrrolidone (PVP) with various metal compounds, including zinc, potassium, barium, sodium, magnesium, calcium, and strontium, through calcination at 700 °C in a nitrogen atmosphere for the first time. These carbon membranes were then subjected to continuous percrystallisation experiments to produce dry salt crystals from salt solutions. The feed solution (3.5, 10, 20 wt% of salt) were used at 30, 50, and 70 °C for the performance evaluation. Intriguingly, the addition of metal elements to the PVP solution resulted in an enhancement in the total pore volume and surface area of the resulting carbon membranes. The PVP-Zn precursor exhibited the highest increase with a maximum improvement of 99 fold. Moreover, when compared to the PVP membranes alone, the composite membranes also exhibited higher fluxes. Among the tested composite carbon membranes, PVP-Ca, PVP-Zn, and PVP-Mg demonstrated the highest flux values, reaching an impressive 55 kg.m−2.h−1. Additionally, these membranes exhibited self-elimination, where salt was effectively removed from the membrane surface during percrystallisation testing. Thus, these membranes have the potential to be employed in desalination applications. [Display omitted] • Carbon membranes were successfully derived by combining metal-PVP. • Metal ions exerted an influence on the formation structure of the carbon membranes. • The utilisation of composite metal-PVP membranes led to an enhancement in solution flux, reaching a maximum flux of 55 kg m−2 h−1. • The particle size of salt crystals was found to be dependent on the solution flux. [ABSTRACT FROM AUTHOR]

Abstract A lower concentration of iodine (<0.2 mg/L) in the salt water used for caustic soda production is crucial to prolong the service life of ionic membrane and decrease the cost of production. The removal of iodine from salt water by resin adsorption was carried out in this work. It was found that the existing species of iodine is the key factor to affect the adsorption, and I 2 is the optimal adsorbed species in salt water through the reaction between I 2 and Cl− in the resin to form (ClI 2)−. A simple pre-treatment method was developed to transform different iodine species in salt water into I 2 by adjusting the solution to pH 1.5–2.5 and redox potential (Eh) 530–560 mV. A novel purification system for the removal of iodine from salt water was subsequently developed and constructed based on the pre-treatment method and the adsorption thermokinetics of I 2. The stability and reliability of this developed method and system were demonstrated by a scale-up experiment to remove iodine from the refined salt water used for caustic soda production, by which the concentration of iodine can be stably decreased to far <0.2 mg/L. Graphical abstract Unlabelled Image Highlights • A purification system was designed and constructed to remove iodine. • I 2 is the optimal adsorbed iodine species in salt water. • A simple pre-treatment method of salt water was developed. • Iodine can be stably decreased to <0.2 mg/L. [ABSTRACT FROM AUTHOR]

There are two characteristics of the behaviors of salt water in PRO membrane module, macro flow in the membrane module and nano behavior in vicinity of the membrane surface. It is proposed to use the numerical simulations in macro and nano fluid behaviors. It is focused on the advection of the salt water in the hollow fiber membrane module and the diffusion of molecules in vicinity of the membrane surface. The macro flow and nano behavior of salt water are simulated with 3-dimensional advection diffusion equation and the molecular dynamics, respectively. It is pointed out for the macro behavior that the distorted flow exists in the membrane module, therefore the concentration distribution is not uniform in the module. So the improvement of the membrane does not always improve the module performance. The membrane performance is closely depended on the flow condition of salt water at high performance membrane. The nano simulations indicate that the interaction between salt water and membrane surfaces affects the diffusion coefficients of the water in the vicinity of surfaces. There is a strong correlation between the diffusion coefficients of water in the vicinity of the surface and the contact angles of water on the surface. [ABSTRACT FROM AUTHOR]