Wash Stream Research Articles

Numerical Characterization of Diffusion-Based Extraction in Cell-Laden Flow Through a Microfluidic Channel

Cells are routinely cryopreserved in dimethyl sulfoxide (DMSO), a cryoprotective agent, for medical applications. Infusion of a DMSO-laden cell suspension results in adverse patient reactions, but current DMSO extraction processes result in significant cell losses. A diffusion-based numerical model was employed to characterize DMSO extraction in fully developed channel flow containing a wash stream flowing parallel to a DMSO-laden cell suspension. DMSO was allowed to diffuse across cell membranes as well as across the channel depth. A variety of cases were considered with the ultimate goal of characterizing the optimal geometry and flow conditions to process clinical volumes of cell suspension in a reasonable time (2-3 ml/min). The results were dependent on four dimensionless parameters: depth fraction of the DMSO-laden stream, Peclet number, cell volume fraction in the DMSO-laden stream, and cell membrane permeability parameter. Smaller depth fractions led to faster DMSO extraction but channel widths that were not practical. Higher Peclet numbers led to longer channels but smaller widths. For the Peclet values and channel depths considered (>or=500 microm) and appropriate permeability values, diffusion across cell membranes was significantly faster than diffusion across the channel depth. Cell volume fraction influenced the cross-stream diffusion of DMSO by limiting the fluid volume fraction available in the contaminant stream but did not play a significant role in channel geometry or operating requirements. The model was validated against preliminary experiments in which DMSO was extracted from suspensions of B-lymphoblast cells. The model results suggest that a channel device with practical dimensions can remove a sufficient level of contaminant within a mesoscale volume of cells in the required time.

Treatment of the butadiene washing stream from a synthetic rubber industry and recovery of p-TBC

Butadiene is marketed containing p-tertbutylcatechol (p-TBC), a polymerization inhibitor that should be removed before butadiene utilization in synthetic rubber production. p-TBC can be removed from butadiene by washing with sodium hydroxide (NaOH) solution, producing a wastewater with pH 14, which contains high amounts of p-TBC, a toxic chemical compound. The aim of this work was to develop a treatment process that could reduce the content of p-TBC from the wastewater. Since p-TBC is very soluble in basic, but not in neutral and acid solutions, acidification tests were performed with phosphoric acid (H3PO4) to precipitate p-TBC. Reaction between NaOH and H3PO4 can result in crystallization of large amounts of salt without p-TBC precipitation. Under selected acidifying conditions p-TBC precipitates and the wastewater COD is highly reduced (> 90/o). Chromatographic determinations showed that the precipitated p-TBC could be recovered with 99% purity.

Effect of particle size based separation of milled corn stover on AFEX pretreatment and enzymatic digestibility

Particle size and compositional variance are found to have a substantial influence on ammonia fiber explosion (AFEX) pretreatment and enzymatic hydrolysis of lignocellulosic biomass. Corn stover was milled and fractionated into particle sizes of varying composition. The larger particle size fractions (rich in corn cob and stalk portions) were found to be more recalcitrant to hydrolysis compared to the smaller size fractions (rich in leaves and husk portion). Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR) were used for biomass surface and bulk compositional analysis, respectively. The ESCA results showed a 15-30% decrease in the O/C (oxygen to carbon) ratio after the pretreatment indicating an increase in the hydrophobic nature of biomass surface. FTIR results confirmed cleavage of the lignin-carbohydrate complex (LCC) for the AFEX-treated fractions. The spectroscopic results indicate the extraction of cleaved lignin phenolic fragments and other cell wall extractives to the biomass surface upon AFEX. Water washing of AFEX-treated fractions removed some of the hydrophobic extractives resulting in a 13% weight loss (dry weight basis). Phenolic content of wash stream was evaluated by the modified Prussian blue (MPB) method. Removal of ligno-phenolic extractives from the AFEX-treated biomass by water washing vastly improved the glucan conversion as compared to the unwashed samples. Reduction in substrate particle size was found to affect the AFEX process and rate of hydrolysis as well. Implications of the stover particle size, composition, and inhibitory role of the phenolic fragments on an integrated biorefinery are discussed.

Integrated AMP–PAN, TRUEX, and SREX testing. I. Extended flowsheet testing for separation of surrogate radionuclides from simulated acidic tank waste

Three unit operations for the removal of selected fission products, actinides, and Resource Conservation and Recovery Act metals (mercury and lead) were integrated successfully and tested at the Idaho National Engineering and Environmental Laboratory (INEEL) for extended run times with simulated acidic tank waste. The unit operations were ion exchange (IX) for Cs removal, followed by transuranic extraction (TRUEX) for Eu (actinide surrogate), Hg, and Re (Tc surrogate) removal, and subsequent strontium extraction (SREX) for Sr and Pb removal. Approximately 45 L of simulated acidic tank waste were processed through three IX columns, packed with composite ammonium molybdophosphate–polyacrylonitrile (AMP–PAN) sorbent for Cs removal. The IX system was operated continuously for ∼34 hr at 22 bed volumes (BV) per hour through the first two columns, each sized at 60 cm3 BV and operated to 100% breakthrough. The experimental breakthrough data were in excellent agreement with modeling predictions based on data obtained with much smaller (1.5 cm3) columns. The third column (220 cm3 BV) was used for polishing and Cs removal after breakthrough of the upstream columns. Cesium removal was >99.83% in the IX system and interference from other species was not observed. The IX effluent was processed through a TRUEX solvent extraction flowsheet to remove Eu (Am surrogate), Hg, and Re (Tc surrogate) from the simulated waste. The TRUEX flowsheet test was performed using 23 stages of 3.3 cm centrifugal contactors, operated a total of 71.3 hr, and processed ∼41 L of the IX effluent using 1.5 L of TRUEX solvent with constant solvent recycle. The TRUEX solvent was recycled through the flowsheet an estimated 17 times. Greater than 99.999% of the Eu, 96.3% of the Hg, and 56% of the Re were extracted from the simulated feed and recovered in the strip and wash streams. Over the course of the test, there was no detectable build-up of any components in the TRUEX solvent. The raffinate from the TRUEX test was processed subsequently through a SREX solvent extraction flowsheet to remove Sr, Pb, and Re (Tc surrogate) from the simulated waste. The SREX flowsheet test was performed using the same centrifugal contactors used in the TRUEX test after reconfiguration and the addition of three stages. Approximately 51 L of TRUEX raffinate was processed through the system during 77.9 hr of continuous operation with 1.5 L of SREX solvent and continuous solvent recycle. The SREX solvent was recycled through the system an estimated 45 times without measurable build-up of any components in the solvent. Approximately 99.9% of the Sr, >99.89% of the Pb, and >96.4% of the Re were extracted from the aqueous feed to the SREX flowsheet and recovered in the strip and wash sections.

Multi-site detection in flow analysis: Part 2. Monosegmented systems with relocating detectors for the spectrophotometric determination of boron in plants

Monosegmented systems with detector relocation are proposed. The sample is injected with an air plug positioned at its tailing portion in order to minimize dispersion. After the peak maximum, the detector is displaced from its original position, allowing the air phase to be discarded without flowing through it. The sample portion inside the detector is either trapped or pushed towards waste. The advantages and limitations of the approach are described, and the need for an optional washing stream is discussed. As an application, an improved system for the spectrophotometric determination of boron is plants is proposed. Four samples are simultaneously processed at a sampling frequency of 120 h −1. With a low reagent consumption (0.52 mg of Azomethine-H per determination), the system yields precise results (R.S.D. < 3%), in agreement with those given by inductively coupled plasma atomic emission spectrometry.

Configuration with internally coupled valves to overcome shortcomings in the simultaneous determination of nitrite and nitrate by flow-injection analysis

A configuration with internally coupled valves and a reductant column located in the loop of the secondary valve is proposed for the simultaneous determination of nitrite and nitrate. Depending on the column characteristics, a washing stream flowing in the opposite direction to the sample may or may not be required. The washing step may conveniently be performed by use of the proposed configuration.

A Model of Coal Cleaning for Sulfur Emissions Reduction

This paper presents results of multivariate regression models developed to estimate the properties and cost of U.S. coals washed for varying degrees of sulfur removal using commercially available physical coal preparation processes. The models allow washed coal characteristics to be predicted from information on coal origin, heating value, ash, and sulfur content. The models were developed by first "processing" each of the 710 coals in the U.S. Bureau of Mines (USBM) coal washability data base through a coal preparation plant computer model which optimizes plant performance to achieve a desired washed coal quality. Washability data are adjusted to account for the inefficiencies of coal washing equipment, and the actual coal sizes treated by various plant wash streams. Since different plant designs may be capable of achieving a given level of sulfur removal, three nominal levels of plant complexity (Levels 2, 3, 4) were included to identify the most economical alternative. The washed coal characteristics thus derived were then analyzed using standard statistical techniques to develop regression equations linking washed coal properties and cost to raw coal properties for each of 18 geographical regions encompassing the entire U.S. These regression models are incorporated in the Advanced Utility Simulation Model (AUSM) to estimate the economic potential of coal washing as a sulfur abatement strategy, in conjunction with other options available to coal-fired power plants. Modeling results for Pennsylvania showed that washed coals frequently were selected as part of a cost-effective control strategy, accounting for 10 to 30 percent of the total emissions reduction, and that "local coal" restrictions significantly increase the use of washed coal as an SO2 control strategy. Hypothetical requirements for mandatory coal cleaning, however, were found to be costly and ineffective.

Decontamination of Carbonate Containing Process Streams in Nuclear Fuel Reprocessing by Ion Exchange Chromatography

A new procedure has been developed to decontaminate carbonate wash streams relevant to the Purex process from alpha-emitting actinides (238U, 237Np, 240Pu) and the fission products (95Zr, 144Ce, 10...