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Bed Volumes (bed + volume)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Protein stabilisation of Chardonnay wine using trisacryl and bentonite: a comparative study

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2009
Johannes De Bruijn
Summary The stabilisation of a Chilean Chardonnay wine by SP-Trisacryl-M and bentonite was investigated, evaluating protein, polyphenol and polysaccharide adsorption, turbidity and wine quality. The wine could be stabilised by adding at least 0.3 kg m,3 of bentonite or 12 kg m,3 of trisacryl, removing 95% and 76% of the wine proteins, respectively. The protein adsorption data for bentonite and trisacryl were fitted using the Freundlich isotherm. The wine protein adsorption isotherm on trisacryl was unfavourable. Protein removal from Chardonnay by trisacryl in a packed column at continuous operation was about 50% during the first 70 bed volumes (BV) of treated wine and decreased progressively until the end of the treatment (100 BV). The adsorbents showed a higher selectivity for proteins than for polyphenols and polysaccharides. A sensorial panel could not detect statistically significant differences between the bentonite and trisacryl treatments of wine at P , 0.05. [source]

Sensing of toxic metals through pH changes using a hybrid sorbent material: Concept and experimental validation

AICHE JOURNAL, Issue 11 2009
Prasun K. Chatterjee
Abstract This article reports a new hybrid sorbent material that is capable of detecting trace concentration of toxic metals, such as zinc, lead, copper, nickel, etc., through pH changes only. The material is essentially a composite granular material synthesized through rapid fusion of a mixture of amorphous hydrated ferric oxide (HFO) and akermanite or calcium magnesium silicate (Ca2MgSi2O7). When a water sample is rapidly passed through a mini-column containing this hybrid material, effluent pH at the exit always remains alkaline (,9.0) because of slow hydrolysis of akermanite and steady release of hydroxyl (OH,) ions. This exit solution turns pink through the addition of a phenolphthalein indicator. Commonly encountered electrolytes containing sodium, calcium, chloride, and sulfate have no impact on the exit pH from the mini-column. However, when trace concentration of a heavy metal (say lead) is present in the sample water, a considerable drop in pH (>2 units) is observed for the exiting solution. At this point, the solution turns colorless through the addition of a phenolphthalein indicator. Moreover, the change in the slope of pH, i.e., ,dpH/dBV, provides a sharp, noticeable peak for each toxic metal where BV is the bed volumes of solution fed. The technique allowed detection of zinc and lead through pH swings in synthesized samples, spiked Bethlehem City water, and also in Lehigh River water in the presence of phosphate and natural organic matter (NOM). Using a simple preconcentration technique, lower than 10 ,g/l of lead was detected with a significant peak. From a mechanistic viewpoint, high sorption affinity of HFO surface sites toward toxic metal cations, ability of akermanite to maintain near-constant alkaline pH for a prolonged period through slow hydrolysis and labile metal-hydroxy complex formation causing dissipation of OH, ions from the aqueous phase provide a synergy that allows detection of toxic metals at concentrations well below 100 ,g/l through pH changes. Nearly all previous investigations pertaining to toxic metals sensing use metal-selective enzymes or organic chromophores. This simple-to-operate technique using an inexpensive hybrid material may find widespread applications in the developing world for rapid detection of toxic metals through pH changes. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Online preconcentration using monoliths in electrochromatography capillary format and microchips

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007
Violaine Augustin
Abstract Online preconcentration and separation of analytes using an in situ photopolymerized hexyl acrylate-based monolith stationary phase was evaluated using electrochromatography in capillary format and microchip. The band broadening occurring during the preconcentration process by frontal electrochromatography and during the desorption process by elution electrochromatography was studied. The hexyl acrylate-based monolith provides high retention for neutral analytes allowing the handling of large sample volumes and its structure allows rapid mass transfer, thus reducing the band broadening. For moderately polar analytes such as mono-chlorophenols that are slightly retained in water, it was shown that enrichment factors up to 3500 can be obtained by a hydrodynamic injection of several bed volumes for 120 min under 0.8 MPa with a decrease in efficiency of 50% and a decrease of 30% for the resolution between 2- and 3-chlorophenol. An 8 min preconcentration time allows enrichment factors above 100 for polyaromatic hydrocarbons. The interest of these monoliths when synthesized in microchip is also demonstrated. A 200-fold enrichment was easily obtained for PAHs with only 1 min as preconcentration time, without decrease in efficiency. [source]

Treatment of Perchlorate-Contaminated Groundwater Using Highly Selective, Regenerable Ion-Exchange Technology: A Pilot-Scale Demonstration

REMEDIATION, Issue 2 2002
Baohua Gu
Treatment of perchlorate-contaminated groundwater using highly selective, regenerable ion-exchange technology has been recently demonstrated at Edwards Air Force Base, California. At an influent concentration of about 450 ,g/l ClO4,, the bifunctional anion-exchange resin bed treated approximately 40,000 empty bed volumes of groundwater before a significant breakthrough of ClO4, occurred. The presence of relatively high concentrations of chloride and sulfate in site groundwater did not appear to affect the ability of the bifunctional resin to remove ClO4,. The spent resin bed was successfully regenerated using the FeCl3,HCl regeneration technique recently developed at the Oak Ridge National Laboratory, and nearly 100 percent of sorbed ClO4, was displaced or recovered after elution with as little as about two bed volumes of the regenerant solution. In addition, a new methodology was developed to completely destroy ClO4, in the FeCl3,HCl solution so that the disposal of perchlorate-containing hazardous wastes could be eliminated. It is therefore anticipated that these treatment and regeneration technologies may offer an efficient and cost-effective means to remove ClO4, from contaminated groundwater with significantly reduced generation of waste requiring disposal. © 2002 Wiley Periodicals, Inc. [source]