Separations Technology最新文献

A novel method to recover dilute volatile solutes from aqueous solutions places pure silicalite powder in the annular space between two concentric porous pipes. Solute-rich fluid flows through the silicalite bed. When the bed is fully loaded, it is regenerated by passing steam through heat exchange tubes that are in intimate contact with the bed. In the case of ethanol, this system is able to produce 24wt% ethanol from a 1wt% solution in a single step. Because butanol is more nonpolar, the system is able to produce 50wt% butanol from a 1wt% solution in a single step. It is estimated that recovering 1% ethanol costs $0.0493/ L of 95% EtOH, whereas recovering 1% butanol costs $0.0277/L of pure BuOH. This cost is less than 4% of the selling price of butanol, which suggests this is a promising technique for product recovery in the acetone/butanol fermentation. This technology also has potential uses in removing volatile solutes from polluted water

This paper presents the quantitative formulation of the convective diffusion equation for particle deposition in ideal deposition systems. Collectors considered include the rotating disk, stagnation-point flow, parallel-plate channel, isolated sphere, and a porous medium composed of uniform spheres. For each collector, the complete particle transport equation, proper boundary conditions, and expressions for the particle deposition rate are formulated. Also presented are numerical procedures for solving the convective diffusion equation. Simulations for the effect of various physical and chemical-colloidal variables on the rate of particle deposition are presented and discussed. The theories presented apply to particle deposition from dilute suspensions in which interparticle interactions are negligible.

The removal of acetonitrile (ACN) from reversed-phase high performance liquid chromatography (RP-HPLC) effluent fractions often presents a problem. High concentrations of ACN place a tough demand on the equipment in terms of solvent resistance. Energy cost is also a concern when ACN is removed by evaporation or freeze-drying. This work shows that a phase separation occurs for ACN-water solutions at -17°C. The top phase contains 88 (volume)% ACN, and the bottom phase is 65% water. Since the bottom phase contains 35% ACN, it is not frozen. Surprisingly, proteins such as human growth hormone and its analogs remain in the bottom phase 99% or more after a phase separation. This appears to be an easy and energy efficient method to remove the majority of ACN after RP-HPLC.

The flux of permeate in the separation by the direct-contact membrane distillation process as a function of membrane characteristics and operating conditions was considered. The expressions describing the vapor transfer through a hydrophobic membrane, the temperature at the surface of the membrane, and changes of temperature and concentration solutions along the module in the countercurrent device were derived and proposed. The theoretically predicted results show about 85–90% agreement with the experimental data. The utility of equations in the separation technology was pointed out.

Electrophoresis is an exceptionally effective method for separating small particles or large molecules in the colloidal size range, and is widely used in biological and clinical studies to separate cells, viruses, and large proteins. It has become the standard analytical tool for detecting the presence of these materials. Despite the success of electrophoresis in analytical and research applications, there has been much less success in using electrophoresis in preparative-scale applications to separate large quantities of materials. A new or modified concept is described that eliminates some of the most serious problems that have arisen in adopting electrophoresis for preparative-scale separations. The new concept uses a narrow-gap flow system between the electrodes and eliminates or greatly reduces problems with thermal convection. In addition, the narrow gap can be a convenient annular region between two cylindrical electrodes. The electric potential is applied across the annulus (or across the narrow flow channel) and the potential applied to the electrodes is reversed periodically. Between the reversals of the electric field, the inner electrode (or one side of the narrow flow gap) is rotated periodically in different directions. This periodic motion and alternating of the applied field displaces charged particles in the angular direction. The rate of displacement depends on the electrophoretic mobility of the particles.

A silicalite/polyethylene mixture was sintered to the exterior of a heat exchanger tube allowing regeneration by steam or hot water, rather than by inefficient, hot stripping gases. Ethanol, acetone, and butanol were adsorbed onto the silicalite until a final bulk concentration of 4 g/L was obtained. Single-step desorption would enrich ethanol 5.2 times, 1-butanol 9.3 times, and acetone 10.1 times. In an attempt to increase the product concentration even more, the silicalite was regenerated using “temperature-programmed desorption,” where the water was selectively removed at a lower temperature and the solute was selectively removed at a higher temperature. The high-temperature desorption enriched ethanol up to 11.1 times, 1-butanol 4.44 times, and acetone 22.1 times, but at the expense of lower solute recovery. Temperature-programmed desorption was able to significantly enrich the product compared to single-step desorption except for butanol, for which higher regeneration temperatures were required.

A theory is constructed to describe quantitatively the dynamic behavior of the primary and secondary drying stages of the freeze-drying of pharmaceutical crystalline and amorphous solutes. Experimental data for the freeze-drying of cloxacillin monosodium salt and skim milk are obtained using a pilot freeze-dryer. The comparison of the theoretical results with the experimental data shows that the agreement between experiment and theory is good.

Bentonite beds, initially 0.5–2.0 cm in height, were dewatered by electroosmosis with a constant current of 90 mA. The fraction of the initial water removed increased most rapidly for the thinnest bed, in contrast to results with constant voltage dewatering. To realize the full potential of thin beds for fast dewatering, constant current should be used.

The minerals calcite and barite are essentially nonmagnetic and cannot be recovered in the magnetic fraction during high gradient magnetic separation. A novel concept of using magnetic surfacant to render the material magnetic has been investigated using manganese stearate and oleate as surfacants. The effect of various parameters has been studied. The technique developed has immense potentiality.