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B Volesky

Publications and source records attributed to B Volesky.

11 recordsLinked to original sources
PubMed2003

Continuous-flow metal biosorption in a regenerable Sargassum column.

Metal biosorption behavior of raw seaweed S. filipendula in ten consecutive sorption-desorption cycles has been investigated in a packed-bed flow-through column during a continuous removal of copper from a 35mg/L aqueous solution at pH 5. The elutant used was a 1% (w/v) CaCl2/HCl-solution at pH 3. The sorption and desorption was carried out for an average of 85 and 15h, respectively, representing more than 41 days of continuous use of the biosorbent. The weight loss of biomass after this time was 21.6%. The Cu-biosorption capacity of the biomass, based on the initial dry weight, remained relatively constant at approximately 38 mg Cu/g. Loss of sorption performance was indicated by a shortening breakthrough time and a broadening mass-transfer zone. The column service time, considered up to 1 mg Cu/L in the effluent, decreased continuously from 25.4 h for the first to 12.7 h for the last cycle. The critical bed length, representing the mass-transfer zone, increased almost linearly from 28 to 34cm. "Life-factors" for S. filipendula were found to be 0.0008h(-1) for the breakthrough time and 0.008cm/h for the critical bed length, using an exponential decay and linear fitting functions, respectively. Regeneration with CaCl2/HCl at pH 3 provided elution efficiencies up to 100%. Maximum concentration factors were determined to be in the range 16-44, a decreasing tendency was observed with an increasing exposure time.

Adsorption↗
PubMed2001

Biosorption of trivalent chromium on the brown seaweed biomass.

Biosorption has attracted attention as a cost-effective means for the treatment of metal-bearing wastewater. However, the mechanism of metal binding is not clearly understood, and consequently, modeling of the biosorption performance is still raising debates. In this study, the biosorption of trivalent chromium was investigated with protonated brown alga Ecklonia biomass as a model system. Titration of the biomass revealed that it contains at least three types of functional groups. The Fourier transform infrared spectrometry showed that the carboxyl group was the chromium-binding site within the pH range (pH 1-5) used in this study, where chromium does not precipitate. The pK value and the number of carboxyl groups were estimated to be 4.6 +/- 0.1 and 2.2 +/- 0.1 mmol/g, respectively. The equilibrium sorption isotherms determined at different solution pH indicated that the uptake of chromium increased significantly with increasing pH. A model for the description of chromium biosorption was developed incorporating the hydrolysis reactions that chromium undergoes in the aquatic phase. The model was able to predict the equilibrium sorption experimental data at different pH values and chromium concentrations. In addition, the speciation of the binding site as a function of the solution pH was predicted using the model in order to visualize the distribution of chromium ionic species on the binding site.

Absorption↗
PubMed2000

Biosorption: a solution to pollution?

To solve the water pollution problem by toxic heavy metal contamination resulting from humans technological activities has for long presented a challenge. Biosorption can be a part of the solution. Some types of biosorbents such as seaweeds, molds, yeasts, bacteria or crab shells are examples of biomass tested for metal biosorption with very encouraging results. The uptake of heavy metals by biomass can in some cases reach up to 50% of the biomass dry weight. New biosorbents can be manipulated for better efficiency and multiple re-use to increase their economic attractiveness.

Adsorption↗
PubMed1999

Characteristics of Aluminum Biosorption by Sargassum fluitans Biomass.

: Biomass of nonliving brown seaweed Sargassum fluitans pretreated by different methods is capable of taking up more than 10% (11 mEq/g) of its dry weight in aluminum at pH 4.5. There are indications that the biomass hydroxyl groups were involved in sequestering the aluminum in the form of polynuclear aluminum species. Aluminum-alginate complex (like cotton candy) was formed in the aluminum sorption solution as alginate was partially released from the biomass. Aluminum uptake of S. fluitans biomass was independent of residual alginate content in the biomass. Sodium ion added for pH adjustment was not adsorbed at all in the presence of aluminum ion.

Journal Article↗
PubMed1995

Biosorption of heavy metals by Saccharomyces cerevisiae.

Abundant and common yeast biomass has been examined for its capacity to sequester heavy metals from dilute aqueous solutions. Live and non-living biomass of Saccharomyces cerevisiae differs in the uptake of uranium, zinc and copper at the optimum pH 4-5. Culture growth conditions can influence the biosorbent metal uptake capacity which normally was: living and non-living brewer's yeast: U > Zn > Cd > Cu; non-living baker's yeast: Zn > (Cd) > U > Cu; living baker's yeast: Zn > Cu approximately (Cd) > U. Non-living brewer's yeast biomass accumulated 0.58 mmol U/g. The best biosorbent of zinc was non-living baker's yeast (approximately 0.56 mmol Zn/g). Dead cells of S. cerevisiae removed approximately 40% more uranium or zinc than the corresponding live cultures. Biosorption of uranium by S. cerevisiae was a rapid process reaching 60% of the final uptake value within the first 15 min of contact. Its deposition differing from that of other heavy metals more associated with the cell wall, uranium was deposited as fine needle-like crystals both on the inside and outside of the S. cerevisiae cells.

Adsorption↗
PubMed1994

Advances in biosorption of metals: selection of biomass types.

Within the past decade, the potential of metal biosorption has been well established. For economic reasons, of particular interest are abundant biomass types either generated as a waste by-product of large-scale industrial fermentations or certain metal-binding algae found in large quantities in the sea. Some of these high metal-sorbing biomass types serve as a basis for newly developed metal biosorption processes foreseen particularly as a very competitive means for detoxification of metal-bearing industrial effluents. Ions of lead and cadmium, for instance, have been found to be bound very efficiently from very dilute solutions by the dried biomass of some ubiquitous brown marine algae such as Ascophyllum and Sargassum which accumulate more than 30% of biomass dry weight in the metal. Mycelia of industrially steroid-transforming fungi Rhizopus and Absidia are excellent biosorbents for lead, cadmium, copper, zinc, and uranium, binding also other heavy metals up to 25% of the biomass dry weight. The common yeast Saccharomyces cerevisiae is a 'mediocre' metal biosorbent. Construction of biosorption isotherm curves serves as a basic technique assisting in evaluation of the metal uptake by different biosorbents. The methodology is based on batch equilibrium sorption experiments extensively used for screening and quantitative comparison of new biosorbent materials. Experimental methodologies used in the study of biosorption and selected recent research results demonstrate the route to novel biosorbent materials some of which can even be repeatedly regenerated for re-use.

Absorption↗
PubMed1975

Feeding studies in rats with high protein fungus grown on natural gas.

Preliminary feeding studies were conducted with a high protein fungus (Graphium sp.) grown on natural gas. The biomass, containing approximately 50% protein, is considered a potential source of single cell protein. In short-term (1-week) experiments, rats gained weight when fed semisynthetic diets containing up to 40% of the biomass, although growth was depressed at the higher levels. Rats lost weight but survived for this length of time when fed biomass alone. Chronic toxicity was tested in a 5-month study with diets in which the casein (20% by weight) of the semisynthetic diet was either partially or entirely replaced by the proteinaceous biomass. Rats fed these diets grew more slowly but appeared normal and healthy, and no pathological changes were observed at autopsy. Some of these rats were fed a standard laboratory diet for an additional 10-month observation period, and at autopsy, one cortical adenoma of the kidney was found in a rat originally fed the lower level of Graphium biomass.

Amino Acids↗
PubMed1971

Batch production of protein from ethane and ethane-methane mixtures.

A culture of Graphium grows upon natural gas and a mineral salt solution. Ethane is the preferred substrate but methane is co-utilized. A stirred-tank type fermentor was used to study batch growth. Maximum production rate of biomass was 80 mg/liter.hr, at pH 4, using simple synthetic supporting medium with ammonium sulfate as a nitrogen source. This rate was observed after 40 hr of fermentation. A doubling time of 3.7 hr was observed. The corresponding specific growth rate was 0.187 per hr. A magnetic drive fermentor was used to study the effect of continuous recycle of gases in a gas-tight system. The rate of oxygen utilization is approximately 2.1 times higher than for ethane. Oxygen must not be allowed to become limiting in recycle gases. The calculated efficiency of overall biomass synthesis averages 30%. Hyphal and unicellular tissue of Graphium contains 52% protein. It compares favorably with standard FAO protein in its content of amino acids.

Alkanes↗
PubMedDate not supplied

Biosorption of heavy metals.

Only within the past decade has the potential of metal biosorption by biomass materials been well established. For economic reasons, of particular interest are abundant biomass types generated as a waste byproduct of large-scale industrial fermentations or certain metal-binding algae found in large quantities in the sea. These biomass types serve as a basis for newly developed metal biosorption processes foreseen particularly as a very competitive means for the detoxification of metal-bearing industrial effluents. The assessment of the metal-binding capacity of some new biosorbents is discussed. Lead and cadmium, for instance, have been effectively removed from very dilute solutions by the dried biomass of some ubiquitous species of brown marine algae such as Ascophyllum and Sargassum, which accumulate more than 30% of biomass dry weight in the metal. Mycelia of the industrial steroid-transforming fungi Rhizopus and Absidia are excellent biosorbents for lead, cadmium, copper, zinc, and uranium and also bind other heavy metals up to 25% of the biomass dry weight. Biosorption isotherm curves, derived from equilibrium batch sorption experiments, are used in the evaluation of metal uptake by different biosorbents. Further studies are focusing on the assessment of biosorbent performance in dynamic continuous-flow sorption systems. In the course of this work, new methodologies are being developed that are aimed at mathematical modeling of biosorption systems and their effective optimization. Elucidation of mechanisms active in metal biosorption is essential for successful exploitation of the phenomenon and for regeneration of biosorbent materials in multiple reuse cycles. The complex nature of biosorbent materials makes this task particularly challenging. Discussion focuses on the composition of marine algae polysaccharide structures, which seem instrumental in metal uptake and binding. The state of the art in the field of biosorption is reviewed in this article, with many references to recent reviews and key individual contributions.

Biomass↗