Concentrated CaCl2 Solution Research Articles

Biosynthesis of insulin-silk fibroin nanoparticles conjugates and in vitro evaluation of a drug delivery system

Silk fibroin derived from Bombyx mori is a biomacromolecular protein with outstanding biocompatibility. When it was dissolved in highly concentrated CaCl2 solution and then the mixture of the protein and salt was subjected to desalting treatments for long time in flowing water, the resulting liquid silk was water-soluble polypeptides with different molecular masses, ranging from 8 to 70 kDa. When the liquid silk was introduced rapidly into acetone, silk protein nanoparticles with a range of 40–120 nm in diameter could be obtained. The crystalline silk nanoparticles could be conjugated covalently with insulin alone with cross-linking reagent glutaraldehyde. In vitro properties of the insulin-silk fibroin nanoparticles (Ins-SFN) bioconjugates were determined by Enzyme-Linked Immunosorbent Assay (ELISA). The optimal conditions for the biosynthesis of Ins-SFN bioconjugates were investigated. The Ins-SFN constructs obtained by 8 h of covalent cross-linking with 0.7% cross-linking reagent and the proportion of insulin and SFN being 30 IU: 15 mg showed much higher recoveries (90–115%). When insulin was coupled covalently with silk nanoparticles, the resistance of the modified insulin to trypsin digestion and in vitro stability in human serum were greatly enhanced as compared with insulin alone. The results in human serum indicated that the half-life in vitro of the biosynthesized Ins-SFN derivatives was about 2.5 times more than that of native insulin. Therefore, the silk protein nanoparticles have the potential values for being studied and developed as a new bioconjugate for enzyme/polypeptide drug delivery system.

Recovery of chlorine from dilute hydrochloric acid by electrolysis using a chlorine resistant anion exchange membrane

A new chlorine resistant anion exchange membrane enables innovative possibilities for hydrochloric acid electrolysis for recovery of chlorine. This is of interest for hydrochloric acid that is neutralized in the chemical industry because purity and concentration are not sufficiently high for recycling. In the common electrolysis process hydrochloric acid is fed into the anode compartment and needs a satisfactory HCl concentration for supplying the anode with chloride ions. Using an anion exchange membrane as a cell separator the feed flows into the cathode chamber where a low HCl concentration is acceptable because Cl− ions at the anode can be supplied by addition of a salt which is not consumed. Experimental data of the membrane and the process are presented: membrane permselectivity improved up to above 97% using CaCl2 as added salt, chlorine current efficiency up to 98% and oxygen content as low as 0.5 vol%, cell voltage at 4 kA m−2 2.3 V, equivalent to 1740 kWh per t produced chlorine, even at low HCl concentrations. Thus, the power consumption is comparable with the common process. A problem of the new process is the high water transport through the membrane. Therefore, experiments for two process alternatives were carried out. Disadvantages of water transport can be avoided by using a high concentrated CaCl2 solution as anolyte and catholyte and as absorption medium for diluted HCl gas streams. Additionally, a cell design was investigated where the anode is directly connected to the membrane in an empty (gas filled) anode compartment.

Evolution of crystal size distributions in a CMSMPR—the effect of temperature, flow rate, and mixing speed with time

A continuous mixed-suspension, mixed-product removal (CMSMPR) crystallizer with automatic computer control and data acquisition was constructed. Operating this CMSMPR at rpm’s greater than 100 rpm assures well-mixed conditions. The crystallization of NaCl, an impurity in a concentrated CaCl2 solution, was performed by cooling under well-mixed conditions. Atomic absorption spectrometry (AAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) have been used to measure solution concentrations. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), light microscopy and particle size analyzer with advanced laser light scattering have been used to characterize the crystals produced by the CMSMPR crystallizer. Octahedral NaCl crystals are observed. Steady state crystal size distribution (CSD) is observed at nine to ten times the mean residence time for the crystallizer. The CSD has been analyzed to look at the details of nucleation, growth, and aggregation rate as a function of crystallization temperature, rpm, and feed flow rate with the application of a Hounslow’s constant aggregation rate equation.

Oscillatory and ion-correlation forces observed in direct force measurements between silica surfaces in concentrated CaCl2 solutions

The force between silica spheres and naturally oxidised silicon wafer has been measured in calcium chloride solutions at concentrations between 1 and 5 M using an atomic force microscope. An oscillatory force, consistent in periodicity with the expulsion of layers of ions, was found to overlay the expected van der Waals force. The extent and magnitude of the oscillations increased markedly with electrolyte concentration. Measured pull-off forces point to the oscillatory force minima being much larger in magnitude than the maxima, and appears to confirm the existence of ion correlation forces, possibly resulting from shared hydration waters forming an attractive network. Forces were also measured in 1 M NaCl solution. A monotonic repulsion was observed at short-range, in contrast with the ‘ hard-wall’ of Ca2+ ions observed in 1 M CaCl2 before expulsion at a force of 3 mN m−1. These observations suggest that calcium ions are attracted to the surface strongly enough to disrupt the hydration of the surface and/or the ions, whereas sodium ions are not. The results demonstrate a simple methodology for the direct investigation of ion-specific surface forces at high salt concentrations.

X-Ray Diffraction and Structural Properties of Aqueous Solutions of Divalent Metal-Chlorides

Abstract X-ray diffraction data are reported for aqueous solutions of CaCl2 (6.30 M), CdCl2 (0.87 and 1.26 M) and NiCl2 (1.96 and 3.88 M). The highly concentrated CaCl2 solution shows a medium range order resembling that of the corresponding hydrate crystal. The CdCl2 solutions are characterized by the presence of complexes with chloride ions in the first coordination sphere of the cation. In NiCl2 solutions, a first sphere Ni-Cl coordination can be excluded and the existence of six Ni-H2O nearest neighbour contacts is clearly confirmed. In these solutions no evidence was found for the existence of highly ordered structures; hexa-aquo cations interact with external water molecules and, at the highest concentration, some outer sphere Ni-Cl correlation is possible as due to packing.

Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds

AbstractIrrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes.