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Papers by Jonathan Lloyd

Geochimica et Cosmochimica Acta, 2007

Author(s): Coker, V.; Pearce, C.; Pattrick, R.; Laan, G. van der; Telling, N.; Charnock, J.; Aren... more Author(s): Coker, V.; Pearce, C.; Pattrick, R.; Laan, G. van der; Telling, N.; Charnock, J.; Arenholz, E.Lloyd.J.

Journal of hazardous materials, Jan 5, 2018

Iron nanoparticles are a promising new technology to treat contaminated groundwater, particularly... more Iron nanoparticles are a promising new technology to treat contaminated groundwater, particularly as they can be engineered to optimise their transport properties. Technetium is a common contaminant at nuclear sites and can be reductively scavenged from groundwater by iron(II). Here we investigated the potential for a range of optimised iron nanoparticles to remove technetium from contaminated groundwater, and groundwater/sediment systems. Nano zero-valent iron and Carbo-iron stimulated the development of anoxic conditions while generating Fe(II) which reduced soluble Tc(VII) to sparingly soluble Tc(IV). Similar results were observed for Fe(II)-bearing biomagnetite, albeit at a slower rate. Tc(VII) remained in solution in the presence of the Fe(III) mineral nano-goethite, until acetate was added to stimulate microbial Fe(III)-reduction after which Tc(VII) concentrations decreased concomitant with Fe(II) ingrowth. The addition of iron nanoparticles to sediment microcosms caused an in...

Small (Weinheim an der Bergstrasse, Germany), Jan 23, 2018

Copper nanoparticles (Cu-NPs) have a wide range of applications as heterogeneous catalysts. In th... more Copper nanoparticles (Cu-NPs) have a wide range of applications as heterogeneous catalysts. In this study, a novel green biosynthesis route for producing Cu-NPs using the metal-reducing bacterium, Shewanella oneidensis is demonstrated. Thin section transmission electron microscopy shows that the Cu-NPs are predominantly intracellular and present in a typical size range of 20-40 nm. Serial block-face scanning electron microscopy demonstrates the Cu-NPs are well-dispersed across the 3D structure of the cells. X-ray absorption near-edge spectroscopy and extended X-ray absorption fine-structure spectroscopy analysis show the nanoparticles are Cu(0), however, atomic resolution images and electron energy loss spectroscopy suggest partial oxidation of the surface layer to CuO upon exposure to air. The catalytic activity of the Cu-NPs is demonstrated in an archetypal "click chemistry" reaction, generating good yields during azide-alkyne cycloadditions, most likely catalyzed by the...

Environmental science & technology, Jan 21, 2015

Technetium, uranium and neptunium are contaminants that cause concern at nuclear facilities due t... more Technetium, uranium and neptunium are contaminants that cause concern at nuclear facilities due to their long half-life, environmental mobility and radiotoxicity. Here we investigate the impact of microbial reduction of Fe(III) in biotite and chlorite, and the role that this has in enhancing mineral reactivity towards soluble TcO4-, UO22+ and NpO2+. When reacted with unaltered biotite and chlorite, significant sorption of U(VI) occurred in low carbonate (0.2 mM) buffer whilst U(VI), Tc(VII) and Np(V) showed low reactivity in high carbonate (30 mM) buffer. On reaction with the microbially reduced minerals, all radionuclides were removed from solution with U(VI) reactivity influenced by carbonate. Analysis by X-ray absorption spectroscopy (XAS) confirmed reductive precipitation to poorly soluble U(IV) in low carbonate conditions: both Tc(VII) and Np(V) in high carbonate buffer were also fully reduced to poorly soluble Tc(IV) and Np(IV) phases. U(VI) reduction was inhibited under high ...

PloS one, 2015

Biogeochemical processes mediated by Fe(III)-reducing bacteria such as Shewanella oneidensis have... more Biogeochemical processes mediated by Fe(III)-reducing bacteria such as Shewanella oneidensis have the potential to influence the post-closure evolution of a geological disposal facility for radioactive wastes and to affect the solubility of some radionuclides. Furthermore, their potential to reduce both Fe(III) and radionuclides can be harnessed for the bioremediation of radionuclide-contaminated land. As some such sites are likely to have significant radiation fluxes, there is a need to characterise the impact of radiation stress on such microorganisms. There have, however, been few global cell analyses on the impact of ionizing radiation on subsurface bacteria, so here we address the metabolic response of S. oneidensis MR-1 to acute doses of X-radiation. UV/Vis spectroscopy and CFU counts showed that although X-radiation decreased initial viability and extended the lag phase of batch cultures, final biomass yields remained unchanged. FT-IR spectroscopy of whole cells indicated an ...

Chem. Sci., 2015

Luminescence spectroscopy, microscopy and lifetime image mapping offers new insights into the bio... more Luminescence spectroscopy, microscopy and lifetime image mapping offers new insights into the bioreduction of Geobacter sulfurreducens with uranyl.

Although there is consensus that microorganisms significantly influence uranium speciation and mo... more Although there is consensus that microorganisms significantly influence uranium speciation and mobility in the subsurface under circumneutral conditions, microbiologically mediated U(VI) redox cycling under alkaline conditions relevant to the geological disposal of cementitious intermediate level radioactive waste, remains unexplored. Here, we describe microcosm experiments that investigate the biogeochemical fate of U(VI) at pH 10−10.5, using sediments from a legacy lime working site, stimulated with an added electron donor, and incubated in the presence and absence of added Fe(III) as ferrihydrite. In systems without added Fe(III), partial U(VI) reduction occurred, forming a U(IV)-bearing non-uraninite phase which underwent reoxidation in the presence of air (O 2) and to some extent nitrate. By contrast, in the presence of added Fe(III), U(VI) was first removed from solution by sorption to the Fe(III) mineral, followed by bioreduction and (bio)magnetite formation coupled to formation of a complex U(IV)-bearing phase with uraninite present, which also underwent air (O 2) and partial nitrate reoxidation. 16S rRNA gene pyrosequencing showed that Gram-positive bacteria affiliated with the Firmicutes and Bacteroidetes dominated in the postreduction sediments. These data provide the first insights into uranium biogeochemistry at high pH and have significant implications for the long-term fate of uranium in geological disposal in both engineered barrier systems and the alkaline, chemically disturbed geosphere.

Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacteriu... more Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, was tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR). The performance of this biomaterial, targeting aqueous Cr(VI) removal, was compared to a synthetic alternative, nano-scale zero valent iron (nZVI). Samples of highly contaminated alkaline groundwater and COPR solid waste were obtained from a contaminated site in Glasgow, UK. During batch reactivity tests, Cr(VI) removal from groundwater was inhibited by ∼25% (BnM) and ∼50% (nZVI) when compared to the treatment of less chemically complex model pH 12 Cr(VI) solutions. In both the model Cr(VI) solutions and contaminated groundwater experiments the surface of the nanoparticles became passivated, preventing complete coupling of their available electrons to Cr(VI) reduction. To investigate this process, the surfaces of the reacted sam...

Geomicrobiology Journal, 2012

... 2009a38. Langley, S, Igric, P, Takahashi, Y, Sakai, Y, Fortin, D, Hannington, M and Schwarz-S... more ... 2009a38. Langley, S, Igric, P, Takahashi, Y, Sakai, Y, Fortin, D, Hannington, M and Schwarz-Schampera, U. 2009a. ... Subsurface waters. In situ dialysis chambers (“peepers”) were used to sample the sedimentary porewaters at each site (Carignan 19844. Carignan, R. 1984. ...

Environmental Science & Technology, 2006

Environmental Microbiology, 2014

Chemical Geology, 2011

... Edwards, KJ, Bach, W., McCollom, TM, Rogers, DR, 2004. Neutrophilic iron-oxidizing bacteria i... more ... Edwards, KJ, Bach, W., McCollom, TM, Rogers, DR, 2004. Neutrophilic iron-oxidizing bacteria in the ocean: Their habitats, diversity, and roles in mineral deposition, rock alteration, and biomassproduction in the deep-sea. Geomicrobiology Journal 21 (6), 393-404. ...

Applied and Environmental Microbiology, 2008

Fe(III)-respiring bacteria such as Shewanella species play an important role in the global cycle ... more Fe(III)-respiring bacteria such as Shewanella species play an important role in the global cycle of iron, manganese, and trace metals and are useful for many biotechnological applications, including microbial fuel cells and the bioremediation of waters and sediments contaminated with organics, metals, and radionuclides. Several alternative electron transfer pathways have been postulated for the reduction of insoluble extracellular subsurface minerals, such as Fe(III) oxides, by Shewanella species. One such potential mechanism involves the secretion of an electron shuttle. Here we identify for the first time flavin mononucleotide (FMN) and riboflavin as the extracellular electron shuttles produced by a range of Shewanella species. FMN secretion was strongly correlated with growth and exceeded riboflavin secretion, which was not exclusively growth associated but was maximal in the stationary phase of batch cultures. Flavin adenine dinucleotide was the predominant intracellular flavin ...

Microorganisms have been producing nanoparticles for billions of years and by controlling and tun... more Microorganisms have been producing nanoparticles for billions of years and by controlling and tuning this productivity they have the potential to provide novel materials using environmentally friendly manufacturing pathways. Metal-reducing bacteria are a particularly fertile source of nanoparticles and their reduction of Fe (III) oxides leads to the formation of ferrite spinel nanoparticles, especially magnetite, Fe 3 O 4. The high yields produced by extracellular biomineralising processes make them commercially attractive, and the production of these bionano ferrite spinels can be tuned by doping the precursor Fe(III) phase with Co, Ni, Zn, Mn and V. The oxidation state of the cations and the sites of substitution are determined by X-ray absorption spectroscopy (XAS), especially by examination of metal Ledge spectra and X-ray magnetic circular dichroism (XMCD). Vanadium substitution in bionano ferrite spinels is revealed for the first time, and substitution in the octahedral site as V(III) confirmed. Bionanomagnetite is shown to be effective in the remediation of azo dyes with the complete breakdown of Remazol Black B to colourless amines and acids. XMCD shows this to involve oxidation of the surface Fe(III) and the potential for regeneration of the nanoparticles.

Mercuric chloride solutions have historically been used as pesticides to prevent bacterial, funga... more Mercuric chloride solutions have historically been used as pesticides to prevent bacterial, fungal and insect degradation of herbarium specimens. The University of Manchester museum herbarium contains over a million specimens from numerous collections, many preserved using HgCl 2 and its transformation to Hg 0 v represents a health risk to herbarium staff. Elevated mercury concentrations in work areas (∼1.7 g m −3) are below advised safe levels (<25 g m −3) but up to 90 g m −3 mercury vapour was measured in specimen boxes, representing a risk when accessing the samples. Mercury vapour release correlated strongly with temperature. Mercury salts were observed on botanical specimens at concentrations up to 2.85 wt% (bulk); XPS, SEM-EDS and XANES suggest the presence of residual HgCl 2 as well as cubic HgS and HgO. Bacterially derived, amorphous nanospheres of elemental selenium effectively sequestered the mercury vapour in the specimen boxes (up to 19 wt%), and analysis demonstrated that the Hg 0 v was oxidised by the selenium to form stable HgSe on the surface of the nanospheres. Biogenic Se 0 can be used to reduce Hg 0 v in long term, slow release environments.

The bioproduction of nano-scale magnetite by Fe(III)-reducing bacteria offers a potentially tunab... more The bioproduction of nano-scale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens, by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different 2 biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles has been investigated by X-ray magnetic circular dichroism and indicates the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimised biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently in the less harmful trivalent form.

Biologically synthesized magnetite (Fe 3 O 4) nanoparticles are studied using x-ray absorption an... more Biologically synthesized magnetite (Fe 3 O 4) nanoparticles are studied using x-ray absorption and x-ray magnetic circular dichroism following exposure to hexavalent Cr solution. By examining their magnetic state, Cr cations are shown to exist in trivalent form on octahedral sites within the magnetite spinel surface. The possibility of reducing toxic Cr(VI) into a stable, non-toxic form, such as a Cr 3+-spinel layer, makes biogenic magnetite nanoparticles an attractive candidate for Cr remediation.