Advanced Materials Research Vols. 20-21

Abstract: Microbial cell – soluble species interactions can be part of technologies for the treatment of metal/metalloid and radionuclide bearing water streams in order to sequester the targeted species. Interactions of microbial cells and soluble targeted species include passive and active processes of metabolically inactive or active biomass, and result in the reduction of their mobility and toxicity. Different parts of the cell may sequester targeted species via processes such as complexation, chelation, coordination, ion exchange, precipitation and reduction. Collectively, these mechanisms have been referred to as sorption and the overall phenomenon as biosorption. The term biosorption is generally used to describe the passive interaction of microbial biomass with targeted species. The technologies based on these processes, lead to the set up of units, mainly in the form of packed bed reactors similar to the configuration of ion exchange resins reactors, placed at the end of a treatment process as a polishing stage. In order to maintain durability of the sorbent, the microbial cells harvested from different sources, are formulated into particles by way of immobilization – pelletization. In the early years of Biosorption, a significant effort was devoted to study the reusability of the sorbent by repeated sorption – desorption cycles, in order to reduce the operating cost of the technology. The availability of the biosorbent material, the reversibility of the desorption process, the presence of competing co-ions and organic molecules, posed significant scepticism and finally serious doubt about the industrial applicability of biosorption as a stand alone technology. However the mechanisms are active and present in biological reactors, and can contribute to overall species sequestering. Biological reactors based on active microbial biomass as alternative to passive sorption, exploit the self regenerating features of living biomass along with the traits of microbial metabolism. Active cells produce metabolites (i.e. EPS, simple inorganic moieties etc.) interacting chemically with the targeted species. The active biomass offers the additional attractive feature of forming biofilms on the surface of carrier materials allowing a natural way of cell immobilization. Different biofilm reactor configurations e.g. static or moving bed filters, fluidized bed reactors, rotating biological contactors support the development of biofilms. Conditions such as temperature, pH, presence of toxic compounds etc. should be considered in the applicability of the technology. Important metabolically mediated immobilization processes for metal/metalloid and radionuclide species are bioprecipitation and bioreduction. Bioprecipitation processes include the transformation of soluble species to insoluble hydroxides, carbonates, phosphates, sulfides or metal – organic complexes as a result of the microbial metabolism. In the case of biological reduction, the cells may use the species as terminal electron acceptors in anoxic environments to produce energy or reduce the toxicity of the cells microenvironment. Such processes form the basis for treatment technologies which are recently developed and applied both in pilot and full scale.

Abstract: Sugar-beet pectin gels are a novel material with applications in heavy and precious metal removal and biomass immobilization which are similar to those of alginate. This paper presents the experimental results of the kinetics of Pb(II) and Au(III) batch removal with these gels, with and without immobilized biomass of the brown algae Fucus vesiculosus. The evolution of the metal concentration, solution pH and Ca2+ liberation was determined. The biomass was characterized before and after the metal removal using SEM-EDX, FESEM, FETEM, XRD and FTIR techniques. The Pb(II) removal followed a typical biosorption kinetics with a final equilibrium metal concentration. The immobilized algae had different biosorptive behaviour than both the original sugar-beet pectin gels and the free biomass. There was no Au(III) removal with the pectin gels without algae. In the case of the immobilized biomass, the Au(III) recovery occurred in two stages, where the biosorption was followed by the reduction of the Au(III) to Au(0) due to the presence of the own algae. The Au(0) precipitated preferably on the surface of the algal biomass and in the form of colloidal gold in the solution and entrapped within the pectin gel matrix.

Abstract: Palladized biomass of typical Gram negative bacteria (Desulfovibrio desulfuricans and Escherichia coli) is well documented as a potentially useful catalyst for reduction of metallic species such as Cr(VI). This bionanocatalyst can be sourced from Pd-waste and scrap leachates via biocrystallization. A major industrial application of precious metal catalysts is in hydrogenation and hydrogenolysis reactions whereby, respectively, H is added across unsaturated bonds and halogen substituents can be removed from aromatic rings. Gram positive bacteria have not been evaluated previously as potential supported Pd-bionanocatalysts. We compare the activity of ‘Bio-Pd(0)’ supported on the fundamentally different Gram negative (Desulfovibrio) and Gram positive (Bacillus) bacterial surfaces, and evaluate the activity of the two types of ‘Bio-Pd(0)‘ in a standard reference reaction, the hydrogenation of itaconic acid, against a commercially available catalyst (5% Pd on carbon). The results show that the bionanocatalysts have a similar activity to the commercial material and biomanufacturing from waste sources may be an economic alternative to conventional processing for catalyst production as precious metal prices continue to rise.

Abstract: Sorption of Co(II) on the biogenic Mn oxide produced by a Paraconiothyrium sp.-like strain was investigated. The biogenic Mn oxide, which was characterized to be poorly crystalline birnessite (Na4Mn(III) 6Mn(IV) 8O27 ·9H2O) bearing Mn(III) and Mn(IV) in the structure, showed approximately 6.0-fold higher efficiency for Co(II) sorption than a synthetic Mn oxide. XP-spectra of Co 2p for the biogenic and synthetic Mn oxides after Co(II) sorption indicate that Co was immobilized as Co(III) on the surface of Mn oxides, clearly suggesting that redox reaction occurs between Co(II) ions and each Mn oxides. The Co(II) ions would be initially sorbed on the vacant sites of the surface of biogenic Mn oxide, and then oxidized to Co(III) by neighbor Mn(III/IV) atoms to release Mn(II). For the synthetic Mn oxide, release of Mn(II) was negligibly small because the oxidant is only Mn(IV) in ramsdellite (γ-MnO2). The Mn(II) release from the biogenic Mn oxide during Co(II) adsorption would be not only from weakly bounded Mn(II), but also from redox reaction between Mn(III/IV) and Co(II) ions.

Abstract: To compare Cr (VI) tolerance, biosorption and bioaccumulation for initial carotenoidsproducing yeast Rhodotorula mucilaginosa UCM Y-1776 and its mutants, twenty stable mutants with various intensity of colors were obtained using nitrosoguanidine (NSG). The ultraviolet was found to be inefficient as a mutagen in our study. Light- and non-pigmented mutants (4L and 2) demonstrated a significant growth inhibition by 30 mg/l Cr (VI) whereas wild strain was able to grow at much higher chromium concentrations (500 mg/l). Cr (VI) sorption ability of R. mucilaginosa UCM Y-1776 was higher than those of mutants. Cr (VI) sorption/uptake parameters (Qmax, b) were found to be close for initial pink-pigmented R. mucilaginosa UCM Y-1776 (Qmax = 950 5M/g), and its light-pigmented mutant 4L (Qmax = 678 5M/g) and non-pigmented mutant 2 (Qmax = 790 5M/g) by non-living biomass. Non-pigmented “white” mutant 2 showed the highest ability to sorb chromium ions by living biomass (Qmax = 1020 mmol/g). The least chromiumtolerant light-pigmented (mutant 4L) and non-pigmented yeasts showed the highest chromium uptake for living biomass. The results showed that the presence of carotenoids did not affect Cr (VI) ions sorption by yeast biomass which could highlight significance of chitin and glucan-mannoprotein complex in chromium biosorption. However pigment absence increased Cr (VI) bioaccumulation by living yeast demonstrating the protective role of carotenoids against hexavalent chromium toxicity.

Abstract: The study describes the sorption of Cr, Cu, Mn and Zn by Pseudomonas aeruginosa AT18 isolated from a site contaminated with petroleum and heavy metals. The concentrations studied (mgL-1) were Cr-50, Cu-49, Mn-60 and Zn-70. The solution pH and ionic strength were very important factors in the metal biosorption performance and the biosorption capacity of Pseudomonas aeruginosa AT18 for Cr3+ Cu2+, Mn2+ and Zn2+. In aqueous solution the biosorption increased with increasing pH in the range 5.46-7.72. The results obtained in the experimental assays show that Pseudomonas aeruginosa AT18 has the capacity for biosorption of the metallic ions Cr3+, Cu2+ and Zn2+ in solutions, although its capacity for the sorption of manganese is low (22.39 mg Mn2+/g of biomass) in comparison to the Cr3+, Cu2+ and Zn2+ ions, as shown by the individual analyses. However, 20% of the manganese was removed from an initial concentration of 49.0 mgL- 1, with a Qm value similar to that obtained in solutions containing mixtures of Cr3+ Cu2+, Mn2+ and Zn2+. The chromium level sorbed by Pseudomonas aeruginosa AT18 biomass was higher than that for Cu, Mn and Zn, with 100% removal in the pH range 7.00-7.72 and a Qm of 121.90-200.00 mg of Cr3+/g of biomass. The remove of Cr, Cu and Zn are a result also of precipitation processes.

Abstract: Our previous study has demonstrated that industrial waste biomasses of Penicillium oxalicum var. Armeniaca and Tolypocladium sp., could be used for biosorption of Cd, Pb, Hg and Cr(VI). The objective of the present study was to investigate the biosorption mechanisms, while using FT-IR spectroscopy and SEM technique. SEM microscopic observations (coupled with EDX analysis) confirmed the presence of the target metals on the biosorbents surface. Carboxyl groups were identified by FT-IR spectra analysis on the surface of Tolypocladium sample, while the alkaline treated Penicillium sample was characterized by the presence of amine groups. It was proved that the metal biosorption slightly modified the FT-IR spectra, while the mentioned functional groups were involved in the uptake mechanism (chelation on nitrogen containing groups and ion exchange on carboxyl groups).

Abstract: Granulated Tolypocladium biomass (industrial waste) was tested as mercury biosorbent in continuous mode (fixed bed column). Supplied material contained approx. 70% of fungal biomass and 30% of inert material (diatomaceous earth). Prior to column experiments, batch sorption was also performed. The results of batch experiments were compared to our previous results obtained for powdered biomass (100% biomass material) and an important drop of sorption capacity was observed. For column experiments, the bed height and flow rate were kept constant and the influence of both initial mercury concentration and bead size was investigated. The Adams Bohart, the Thomas and the Yoon and Nelson models were used for the characterization of breakthrough curves.

Abstract: It was the aim of this work to investigate the sorption characteristics of the Biocer material that consists of cells of Bacillus sphaericus that are immobilised on a ceramic carrier material, performing column experiments with model waters and real mine drainage waters from a U remediation site in East Germany. In column experiments a nearly quantitative sorption of Cu2+ was performed from solutions of different Cu2+ concentrations and at different flow rates. The desorption of the Cu2+ in the columns was nearly quantitative in a very short time. The columns could be regenerated 16 times without a substantial loss of the sorption capacity of the material. In experiments with U using real drainage waters, a specific U sorption capacity of 2.34 mg/g was determined. By variation of the experimental parameters, the long-term stability and sorption properties of the Biocer columns can be substantially improved.

Abstract: Biogenic iron sulphides are excellent adsorbents for various heavy metals ions. Consequently, they have practical application for the elimination of heavy metals from waste waters. One of the principles for the iron sulphides preparation is the application of sulphatereducing bacteria. This biological-chemical method is based on the ability of these bacteria to reduce sulphates to hydrogen sulphide, which binds with the ferrous cations to form insoluble precipitates – iron sulphides. Under certain bacterial growth conditions biogenic iron sulphides can be magnetic. The aim of this work is to study the possibility of using SRB for the preparation of iron sulphides, which were used subsequently in the framework of sorption tests to eliminate copper ions from model solutions.