Adsorption of Organic Solutes on Membrane Filters during Aqueous Phase Filtration. I. Basic Rate and Equilibrium Studies Using Toluidine Blue

Abstract

Membrane filters are made from a wide variety of polymeric materials, in a wide range of pore sizes, and are used in large numbers (several hundred million per year) to filter particulates from many types of solutions. However, during filtration, organic solutes are adsorbed by these membranes, often quite extensively. Thus, the composition of the filtrate can be very different from that of the original solution. A systematic study has been initiated to quantify and explain the adsorption of organic solutes during membrane filtration as affected by membrane type (material, pore size, presence/absence of wetting agents), solute type, pH, ionic strength, and filtration flow rate. Our first studies have employed a dye (toluidine blue) as the dissolved organic solute, and 11 membrane filters made of mixed cellulose esters, polyvinylidene difluoride, polytetrafluoroethylene, and polycarbonate. The results of these studies, which are both equilibrium and kinetic in nature, are presented. These results indicate how adsorption effects may be minimized.     

Nanopore/electrode structures for single-molecule biosensing

Biological and solid-state nanopores have recently attracted much interest as ultrafast DNA fragment sizing and sequencing devices. Their potential however goes far beyond DNA sequencing. In particular, nanopores offer perspectives of single-molecule (bio)sensing at physiologically relevant concentrations, which is key for studying protein/protein or protein/DNA interactions. Integration of electrode structures into solid-state nanopore devices moreover enables control and fast switching of the pore properties, e.g. for active control of biopolymer transport through the nanopore. We present some of recent work in this area, namely the fabrication and characterization of nanopore/electrode architectures for single-(bio)molecule sensing. Specifically, we introduce a new technique to fabricate ultra-small metal nanopores with diameters smaller than 20 nm based on ion current feedback (ICF) controlled electrodeposition. It offers precise control of the pore conductance, is easily multiplexed, and can be extended to a wide range of different metals.     

Ionothermal synthesis of aluminophosphates used for ion exchange: Influence of choline chloride/urea ratio

A wide variety of industrial processes produce aqueous effluents that contain heavy metals. Considering the toxicity of metal polluted wastewaters, ion exchange appears as an easy and inexpensive option to remove metal ions from these effluents. There is currently much investigation on synthetic and natural materials to be used as cation exchangers. Among these materials, using microporous molecular sieves have been proposed due to their high surface area, porous diameter and ion exchange capacity. In this work, aluminophosphates (AlPOs) were prepared by the ionothermal method using the eutectic mixture urea/choline chloride (CCh) as solvent and template. Different CCh ratios in the eutectic mixture used in gel synthesis resulted in different structures with very distinguished ion exchange capacities. The main structures obtained were SIZ-2 and AlPO-CJ2. Varying the percentage of CCh in the gel synthesis mixture, it was observed that the AlPO-CJ2 structure is obtained using CCh percentages greater than 50%, while SIZ-2 is obtained using 25% and 33.3% CCh. The structure-directing the interrupted structure are the ammonium cations coming from the partial decomposition of urea. The SIZ-2 prepared using 25% CCh has a somewhat higher ion exchange capacity than that observed using 33.3% CCh. This result is very interesting since CCh is the most expensive component in the eutectic mixture.     

On the geometry control of magnetic devices: Impact of photo-resist profile, shadowing effect, and material properties

In this paper, we described how to control the magnetic junction critical dimension (CD) and profile defined by ion beam milling and its implication to device performance. The impact of standing waves on breaking the photo-resist and on the resultant junction defects have been highlighted. The ideal device profile and geometry are also discussed.     

组合离子技术在硅基材料芯片中的应用

将组合技术和离子束技术结合起来。用于硅基发光材料的研究。用组合离子束技术在硅基材料上制备了６４个直径为２ｍｍ的单元－材料芯片,并对硅基材料芯片各进行了卢瑟辐背散射,质子弹性散射和扫描阴极射一发光特性分析。     

锂离子二次电池研究进展

本文综述了锂离子二次电池的研制开发的最新成果;讨论了这些可充锂离子电池的应用前景。     

Internal ion transport in ionic 2D CuInP2S6 enabling multi-state neuromorphic computing with low operation current

Memristor-based neuromorphic computing is promising for artificial intelligence. However, most of the reported memristors have limited linear computing states and consume large operation energy which hinder their applications. Herein, we report a memristor based on ionic two-dimensional CuInP₂S₆ (2D CIPS), in which up to 1350 linear conductance states are achieved by controlling the migration of internal Cu ions in CIPS. In addition, the device shows a low operation current of ∼100 pA. Cu ions are proven to move along the electric field by in-situ scanning electron microscopy and energy dispersive spectroscopy measurements. Furthermore, complex signal transport among multiple neurons in the brain is imitated by 2D CIPS-based memristor arrays. Our results offer a new platform to fabricate high-performance memristors based on ion transport in 2D materials for neuromorphic computing.     

Isotherm and kinetic sorption of some lanthanides and iron from aqueous solution by aluminum silicotitante exchanger

Sorption of La³⁺, Eu³⁺, and Fe³⁺ onto new synthetic inorganic ion exchange material of aluminum silicotitante was investigated. The aluminum silicotitante (EX₁, EX₂, and EX₃) are synthetic with different concentration ratio (0.1:0.1:0.003, 0.1:0.1:0.1, and 0.1:0.1:0.1) at aging time 4, 4, and 1 day, respectively. The equilibrium kinetic for La³⁺, Eu³⁺, and Fe³⁺ onto EX₁, EX₂, and EX₃ materials takes about 120?min which is considered as a fast kinetic process. Sorption results were fitted using different kinetic models such as pseudo-first-order, pseudo-second order, and intraparticle diffusion models. The results indicated that the sorption of La³⁺, Eu³⁺, and Fe³⁺ onto EX₁, EX₂, and EX₃ materials is highly fit with the pseudo-second order model. Equilibrium data were described by the Langmuir, Freundlich isotherm models. The Langmuir isotherm model was fitted to the experimental data better than the Freundlich isotherm. The thermodynamics parameters (positive values of ΔH°, ΔS° and negative values of ΔG°) indicated the binding systems between the materials and adsorbate were endothermic, entropy gained and spontaneous in nature. The experimental data indicated that, aluminum silicotitante could be used as an efficient sorbent for La³⁺, Eu³⁺, and Fe³⁺. Maximum sorption % at equilibrium is 92.7, 99.0, and 78.5% for La³⁺, Eu³⁺, and Fe³⁺, respectively.     

Removal of Cr(III) in the fixed bed column and batch reactors using as adsorbent zeolite NaX

In this work, the uptake capacity of Cr(III) ions in NaX zeolite was investigated. The experiments were carried out in continuous and batch systems at . The batch isotherm evidenced an irreversible shape with a maximum chromium uptake of 3.61 meq/g. The column experiments were carried out at pH=3.5, with a flow rate of 9 ml/min and an average particle size of 0.180 mm. The dynamic system provided a distinct ion-exchange mechanism, which generated a favorable isotherm with a chromium uptake of 3.27 meq/g. A mathematical model was also applied to represent the dynamics of the sorption of the column. The model considered the axial dispersion in the column and the intraparticle diffusion as the rate-controlling step. The dynamic isotherm was successfully modeled by the Freundlich equation and the mathematical model described well the experimental dynamic data for the feed concentrations from 0.3 up to 3.0 meq/g.     

Ion exchange of Cs ion in acid solution with potassium cobalt hexacyanoferrate

Potassium cobalt hexacyanoferrate (KCoFC) was synthesized for removal of Cs ions in acid waste solution. The synthesized KCoFC. was stable in nitric acid solution of pH= 1 and showed high selectivity for Cs ion over Sr and Na ions. The K_d,cs for 0.01 N Cs ion solution at pH=2 was about 3.6x 10³ mL/g in the presence of the same concentrations of Sr and Na ions, respectively. In the binary ion exchange system, both the Dubinin-Polanyi model and Langmuir model fit the experimental data, although the Dubinin-Polanyi model fit more correctly than the Langmuir model. However, in the multi-component system, only the modified Dubinin-Polanyi model, which is a semiempirical equation, fit the experimental data accurately. The ion exchange capacity of KCoFC. for Cs ion obtained by the Dubinin-Polanyi equation was 1.72 meq/g.