| 1. |
- Dopson, Mark, et al.
(författare)
-
Metal resistance or tolerance? : Acidophiles confront high metal loads via both abiotic and biotic mechanisms
- 2014
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- All metals are toxic at high concentrations and consequently their intracellular concentrations must be regulated. Extremely acidophilic microorganisms have an optimum growth of pH <3 and proliferate in natural and anthropogenic low pH environments. Some acidophiles are involved in the catalysis of sulfide mineral dissolution, resulting in high concentrations of metals in solution. Acidophiles are often described as highly metal resistant via mechanisms such as multiple and/or more efficient active resistance systems than are present in neutrophiles. However, this is not the case for all acidophiles and we contend that their growth in high metal concentrations is partially due to an intrinsic tolerance as a consequence of the environment in which they live. In this perspective, we highlight metal tolerance via complexation of free metals by sulfate ions and passive tolerance to metal influx via an internal positive cytoplasmic transmembrane potential. These tolerance mechanisms have been largely ignored in past studies of acidophile growth in the presence of metals and should be taken into account.
|
|
| 2. |
- Lützenkirchen, Johannes, et al.
(författare)
-
Potentiometric titrations as a tool for surface charge determination
- 2012
-
Ingår i: Croatica Chemica Acta. - : Croatian Chemical Society. - 0011-1643 .- 1334-417X. ; 85:4, s. 391-417
-
Tidskriftsartikel (refereegranskat)abstract
- This article summarizes methods for determining proton surface charge at mineral/water interfaces. It covers conventional experimental procedures and discusses problems with the techniques. Also it involves recommendations for obtaining reasonable and comparable results. The term "comparable results" refers to comparison between results for the same solid as obtained in different laboratories. The most important parameters for the surface titrations are discussed. We also propose a reference titration procedure that would allow direct, unbiased comparisons of experimental data. The article finally includes a check-list for researchers and reviewers which should allow limiting the amount of titration data that are not useful for future uses.
|
|
| 3. |
- Lövgren, Lars, 1955-, et al.
(författare)
-
Immobilisation of trace metals in sulfidic mine tailings
- 2011
-
Ingår i: Mine Water - managing the Challenges. - Aachen, Germany : RWTH Aachen University, Institute of Hydrogeology. - 9783000355431 ; , s. 387-391
-
Konferensbidrag (refereegranskat)abstract
- Metals released by oxidation of sulfide minerals may be associated to minerals in tailings. This study comprises field sampling, chemical and mineralogical characterisation, structural investigations and quantification of the tailings uptake capacity by batch uptake and column experiments. Uptake capacity of tailings of different composition sampled at the mines in Kristineberg, Aitik and Zinkgruvan has been studied for Cu and As. The metal removal capacity relates to the acid neutralising capacity and the sulfide content. Results indicate arsenic and copper to bind by similar processes to minerals. Binding mechanisms has been studied by X-ray Absorption Near Edge Structure (XANES).
|
|
| 4. |
- Mangold, Stefanie, 1981-, et al.
(författare)
-
Extreme zinc tolerance in acidophilic microorganisms from the bacterial and archaeal domains
- 2013
-
Ingår i: Extremophiles. - : Springer Science and Business Media LLC. - 1431-0651 .- 1433-4909. ; 17:1, s. 75-85
-
Tidskriftsartikel (refereegranskat)abstract
- Zinc can occur in extremely high concentrations in acidic, heavy metal polluted environments habited by acidophilic prokaryotes. Although these organisms are able to thrive in such severely ntaminated ecosystems their resistance mechanisms have not been well studied. Bioinformatic alysis of a range of acidophilic bacterial and archaeal genomes identified homologues of several own zinc homeostasis systems. These included primary and secondary transporters, such as the imary heavy metal exporter ZntA and Nramp super-family secondary importer MntH. Three idophilic model microorganisms, the archaeon 'Ferroplasma acidarmanus', the Gram negative cterium Acidithiobacillus caldus, and the Gram positive bacterium Acidimicrobium ferrooxidans, were lected for detailed analyses. Zinc speciation modeling of the growth media demonstrated that a large action of the free metal ion is complexed, potentially affecting its toxicity. Indeed, many of the tative zinc homeos! asis genes were constitutively expressed and with the exception of 'F. acidarmanus' ZntA, they were t up-regulated in the presence of excess zinc. Proteomic analysis revealed that zinc played a role in idative stress in At. caldus and Am. ferrooxidans. Furthermore, 'F. acidarmanus' kept a constant level intracellular zinc over all conditions tested whereas the intracellular levels increased with increasing nc exposure in the remaining organisms.
|
|
| 5. |
- Mustafa, Majid, 1987-
(författare)
-
Removal of Micropollutants from Wastewater : evaluation of effect of upgrading ozonation to electro-peroxone
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The United Nations (UN) has adopted 17 “Sustainable Development Goals” (SDGs) to achieve a clean, better and sustainable future. SDG 6 is to ensure that everyone has access to clean water and sanitation by 2030. According to the UN Educational, Scientific and Cultural Organization (UNESCO), more than 80% of wastewater produced from human actions is discharged into rivers or seas without any pollution removal. Thus, the presence of micropollutants (MPs: including, inter alia, pharmaceuticals, biocides and personal care products) in wastewaters is a major challenge that poses potential threats not only to aquatic system but also to humans due to their potential toxicity and potential to induce antibiotic resistance. Wastewater treatment plants (WWTPs) are considered hotspots for release of MPs as the current treatment processes are not designed to remove them. This thesis is based on studies described in four appended papers (Papers I-IV) designed to help efforts to solve these problems by investigating the factors involved and developing advanced treatment processes for removing MPs.Ozonation is one of the most intensively studied and widely used advanced treatment processes for removing MPs. However, due to ozone’s (O3) chemical selectivity, it cannot remove resistant MPs so its use (without additional treatments) results in their release into the environment. Thus, key objectives were to evaluate effects of switching to a new emerging process called electro-peroxone (E-peroxone) on MPs’ removal, by inserting two electrodes into an ozonation reactor. Its potential utility for other applications were also investigated.Paper I addresses effects of upgrading from ozonation to E-peroxone on pharmaceuticals’ removal at lab-scale, using a quantitative structure-activity relationship (QSAR) model. For this purpose, the relationship between QSAR model-predicted second-order rate constants of ozone’s reactions with pharmaceuticals (kO3 values) and ratios of experimentally determined pseudo-first order rate constants of E-peroxone and ozonation (kEP/kOZ values) was examined. Results showed that E-peroxone accelerated the removal of O3-resistant pharmaceuticals. In addition, the QSAR model predicted kO3 values for 491 pharmaceuticals, which suggested that large numbers of pharmaceuticals have high O3 resistance. Paper II addresses the removal of antimicrobials, including biocides and antibiotics, by E-peroxone and ozonation in relation to the water matrix. The results indicated that all studied antibiotics were effectively removed by both processes. In contrast, most of the biocides were at most moderately reactive with ozone, so their removal rate by ozonation was lower. The E-peroxone process increased their removal rate (i.e. removed them much more rapidly) by enhancing formation of hydroxyl radicals (•OH). Paper III reports the design, construction and tests of a pilot-scale mobile E-peroxone and ozonation system for removing naturally occurring MPs in secondary wastewater effluents. The tests included assessments of a new, scalable graphene modified carbon brush cathode for the E-peroxone process, which was found to enhance removal of moderately O3-reactive MPs significantly, and O3-resistant MPs moderately, while consuming similar amounts of electrical energy, or even less, for removing most of the MPs used in the experiments. Paper IV describes the regeneration of spent activated carbon, used for removing ionic MPs, by E-peroxone and ozonation. Both processes restored the activated carbon’s sorption efficiency to similar (or even higher) levels than that of virgin activated carbon, for all tested MPs except perfluorooctanoic acid (PFOA). It was concluded that sorption of MPs on regenerated activated carbon is mainly driven by interactions between ionic forms of the MPs with activated carbon’s charged surfaces rather than their interactions with pores in the activated carbon.
|
|
| 6. |
|
|
| 7. |
- Nelson, Hanna, 1976-, et al.
(författare)
-
Surface complexation modelling of arsenate and copper adsorbed at the goethite/water interface
- 2013
-
Ingår i: Applied Geochemistry. - Oxford : Elsevier. - 0883-2927 .- 1872-9134. ; 35, s. 64-74
-
Tidskriftsartikel (refereegranskat)abstract
- The co-adsorption of Cu(II) and arsenate onto the surface of goethite has been studied by performing adsorption experiments and potentiometric titrations, and a surface complexation model has been developed to describe the experimental results. Models for the binary systems, Cu-goethite and arsenate-goethite, were acquired separately and the model parameters were then included in the ternary system, together with the solubility products of solid Cu(II) arsenates reported in the literature. The adsorption of Cu(II) was described applying a model in which Cu(II) forms bidentate bridging mono- and binuclear surface complexes. According to recent interpretations of ATR-FTIR and EXAFS data the arsenate ions are assumed to be coordinated in a monodentate fashion to singly coordinated hydroxyl groups at the surface, and hydrogen-bonded to neighbouring triply coordinated surface oxide sites. In the case of co-adsorption of Cu(II) and arsenate, the adsorption could not be predicted by applying the combined model from the two binary systems. Two ternary Cu(II)-arsenate-goethite surface complexes must be included, one complex in which an arsenate ion is coordinating to surface Fe(III) (≡FeOAsO3Cu0.5-) and one complex in which arsenate is bound to the surface by coordinating to an adsorbed Cu(II) ion (≡(Fe3OFeOH)Cu2(OH)2HAsO41-). No solid Cu (II) arsenate phases were formed under the experimental conditions in the present study. From constructed predominance area diagrams, the significance of adsorption and precipitation processes are discussed. Furthermore, calculated solubility of Cu(II) and As(V) is used to indicate optimum conditions for the cleaning of contaminated natural waters.
|
|
| 8. |
|
|
