Adsorption and Desorption Mechanisms of Methylene Blue Removal with Iron-Oxide Coated Porous Ceramic Filter

Adsorption and desorption mechanisms of methylene blue (MB) removal with iron-oxide coated porous ce-ramics filter (IOCPCF) were investigated in batch and column mode. The results revealed that MB removal mechanisms included physical adsorption and chemical adsorption, of which chemical adsorption by surface ligand complex reaction played a dominant role after infrared spectrum analysis. Recycling agents were se-lected from dilute nitric acid (pH=3), sodium hydroxide solution (pH=12) and distilled water. Among three agents, dilute metric acid (pH=3) was the best recycling agent. Regeneration rate of IOCPCF arrived at 82.56% at batch adsorption and regeneration was finished in 75min at column adsorption. Adsorp-tion-desorption cycles of IOCPCF after batch and column adsorption were four and three times, respectively. Further, compared with fresh IOCPCF, MB removal rate with these desorbed IOCPCF adsorption only slightly decreased, which suggested that IOCPCF should be used repeatedly.

Corrosion and Electrochemical Behavior of 316L Stainless Steel in Sulfate-reducing and Iron-oxidizing Bacteria Solutions

Corrosion and electrochemical behavior of 316L stainless steel was investigated in the presence of aerobic iron-oxidizing bacteria (IOB) and anaerobic sulfate-reducing bacteria (SRB) isolated from cooling water systems in an oil refinery using electrochemical measurement, scanning electron microscopy (SEM) and energy dispersive atom X-ray analysis(EDAX). The results show the corrosion potential and pitting potential of 316L stainless steel decrease distinctly in the presence of bacteria, in comparison with those observed in sterile medium under the same exposure time. SEM morphologies have shown that 316L stainless steel reveals no signs of pitting attack in the sterile medium. However, micrometer-scale corrosion pits were observed on 316L stainless steel surface in the presence of bacteria. The presence of SRB leads to higher corrosion rates than IOB. The interactions between the stainless steel surface, abiotic corrosion products, and bacterial cells and their metabolic products increased the corrosion damage degree of the passive film and accelerated pitting propagation.

Effect of hydraulic retention time and pH on oxidation of ferrous iron in simulated ferruginous acid mine drainage treatment with inoculation of iron-oxidizing bacteria

The effect of hydraulic retention time (HRT) and pH on the biooxidation of ferrous iron during simulated acid mine drainage (AMD) treatment was investigated.The simulated AMD was highly acidic (pH 2.5), rich in iron (about 1700 mg/L) and copper (about 200 mg/L), and contained high concentrations of sulfate (about 4700 mg/L).The biooxidation of ferrous iron was studied in a laboratory-scale upflow packed bed bioreactor (PBR).The HRT was shortened stepwise from 40 h to 20 h, 13 h, and 8 h under the acidic environment at a pH value of 2.2.Then, the influent pH value was changed from 2.2 to 1.2 at a constant suitable HRT.Physiochemical and microbial community structure analyses were performed on water samples and stuffing collected from the bioreactor under different conditions.The results indicate that the efficiency of ferrous iron oxidation gradually decreased with the decrease of HRT, and when the HRT exceeded 13 h, ferrous iron in AMD was almost completely oxidized.In addition, the best efficiency of ferrous iron oxidation was achieved at the influent pH value of 1.8.Microbial community structure analyses show that Leptospirillum is the predominant genus attached in the bioreactor, and low influent pH values are suitable for the growth of Leptospirillum.

Corrosion and Electrochemical Behavior of 316L Stainless Steel in Sulfate-reducing and Iron-oxidizing Bacteria Solutions

Corrosion and electrochemical behavior of 316L stainless steel was investigated in the presence of aerobic iron-oxidizing bacteria IOB and anaerobic sulfate-reducing bacteria SRB isolated from cooling water systems in an oil refinery using electrochemical measurement, scanning electron microscopy SEM and energy dispersive atom X-ray analysisEDAX. The results show the corrosion potential and pitting potential of 316L stainless steel decrease distinctly in the presence of bacteria, in comparison with those observed in sterile medium under the same exposure time. SEM morphologies have shown that 316L stainless steel reveals no signs of pitting attack in the sterile medium. However, micrometer-scale corrosion pits were observed on 316L stainless steel sur- face in the presence of bacteria. The presence of SRB leads to higher corrosion rates than IOB. The interactions between the stainless steel surface, abiotic corrosion products, and bacterial cells and their metabolic products in- creased the corrosion damage degree of the passive film and accelerated pitting propagation.

Aggregate Stability and Its Relationship with Some Chemical Properties of Red Soils in Subtropical China

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and Al oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving…

Imaging C-Fos Gene Expression in Burns Using Lipid Coated Spion Nanoparticles

MR imaging of gene transcription is important as it should enable the non-invasive detection of mRNA alterations in disease. A range of MRI methods have been proposed for in vivo molecular imaging of cells based on the use of ultra- small super-paramagnetic iron oxide (USPIO) nanoparticles and related susceptibility weighted imaging methods. Al-though immunohistochemistry can robustly differentiate the expression of protein variants, there is currently no direct gene assay technique that is capable of differentiating established to differentiate the induction profiles of c-Fos mRNA in vivo. To visualize the differential FosB gene expression profile in vivo after burn trauma, we developed MR probes that link the T2* contrast agent [superparamagnetic iron oxide nanoparticles (SPION)] with an oligodeoxynucleotide (ODN) sequence complementary to FosB mRNA to visualize endogenous mRNA targets via in vivo hybridization. The presence of this SPION-ODN probe in cells results in localized signal reduction in T2*-weighted MR images, in which the rate of signal reduction (R2*) reflects the regional iron concentration at different stages of amphetamine (AMPH) exposure in living mouse tissue. Our aim was to produce a superior contrast agent that can be administered using sys- temic as opposed to local administration and which will target and accumulate at sites of burn injury. Specifically, we developed and evaluated a PEGylated lipid coated MR probe with ultra-small super-paramagnetic iron oxide nanoparti- cles (USPION, a T2 susceptibility agent) coated with cationic fusogenic lipids, used for cell transfection and gene de- livery and covalently linked to a phosphorothioate modified oligodeoxynucleotide (sODN) complementary to c-Fos mRNA (SPION-cFos) and used the agent to image mice with leg burns. Our study demonstrated the feasibility of monitoring burn injury using MR imaging of c-Fos transcription in vivo, in a clinically relevant mouse model of burn injury for the first time.

Correlation between Iron Reducibility in Natural and Iron-Modified Clays and Its Adsorptive Capability for Arsenic Removal

The study reports aspects that allowed to correlate structural and redox properties of iron species deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous clays as well as an iron-poor clay chemically modified with Fe(III) salt (ferrihydrite species) were investigated as adsorbents of the arsenate(V) in water. The study, carried out from minerals from abundant Argentinean deposits, was conducted with the aid of different techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), Raman Spectroscopy, ICP-AES (Inductively Coupled Plasma) chemical analysis and Temperature Programmed Reduction (TPR). This last technique allowed to detect availability of iron species in oxidic environment with different structural complexity and to determine active sites, accessible for arsenate(V) adsorption. The effect was observed through temperature dependence of the first Fe(III) reduction step (below 570°C) of iron-oxide species. The sequence of reducibility: ferrihydrite > hydrous oxide (goethite) > anhydrous oxide (hematite) > structural iron in clay was in agreement with the availability of iron active sites for the reducing process as well as for the arsenate adsorption. The important role of very high iron content in original samples was also observed. The chemical activation of iron-poor clay by a simple and feasible modification with Fe(III) solutions promoted the deposition of the ferrihydrite active phase with an increase of 2.81% (expressed as Fe2O3) respect to the original content of 1.07%, constituting an accessible and eco-friendly technological alternative to solve the environmental problem of water containing arsenic.

The effect of extracellular polymeric substances (EPS) of iron-oxidizing bacteria (Ochrobactrum EEELCW01) on mineral transformation and arsenic (As) fate

Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production which reduced arsenic(As)availability.The main component of EPS secreted by iron-oxidizing bacteria(Ochrobactrum EEELCW01)was composed of polysaccharides(150.76-165.33 mg/g DW)followed by considerably smaller amounts of proteins(12.98–16.12 mg/g DW).Low concentrations of As(100 or 500μmol/L)promoted the amount of EPS secretion.FTIR results showed that EPS was composed of polysaccharides,proteins,and a miniscule amount of nucleic acids.The functional groups including-COOH,-OH,-NH,-C=O,and-C-O played an important role in the adsorption of As.XPS results showed that As was bound to EPS in the form of As3+.With increasing As concentration,the proportion of As3+adsorbed on EPS increased.Ferrihydrite with a weak crystalline state was only produced in the system at 6 hr during the mineralization process of Ochrobactrum sp.At day 8,the minerals were composed of goethite,galena,and siderite.With the increasing mineralization time,the main mineral phases were transformed from weakly crystalline hydrous iron ore into higher crystallinity siderite(FeCO_(3))or goethite(α-FeOOH),and the specific surface area and active sites of minerals were reduced.It can be seen from the distribution of As elements that As is preferentially adsorbed on the edges of iron minerals.This study is potential to understand the biomineralizationmechanism of iron-oxidizing bacteria and As remediation in the environment.

Synergistic effects of sodium hypochlorite disinfection and iron-oxidizing bacteria on early corrosion in cast iron pipes

Corrosion in drinking water distribution systems(DWDSs)may lead to pipe failures and water quality deterioration;biocorrosion is the most common type.Chlorine disinfectants are widely used in DWDSs to inhibit microorganism growth,but these also promote electrochemical corrosion to a certain extent.This study explored the independent and synergistic effects of chlorine and microorganisms on pipeline corrosion.Sodium hypochlorite(NaOCl)at different concentrations(0,0.25,0.50,and 0.75 mg/L)and iron-oxidizing bacteria(IOB)were added to the reaction system,and a biofilm annular reactor(BAR)was employed to simulate operational water supply pipes and explain the composite effects.The degree of corrosion became severe with increasing NaOCl dosage.IOB accelerated the corrosion rate at an early stage,after which the reaction system gradually stabilized.When NaOCl and IOB existed together in the BAR,both synergistic and antagonistic effects occurred during the corrosion process.The AOC content increased due to the addition of NaOCl,which is conducive to bacterial regrowth.However,biofilm on cast iron coupons was greatly influenced by the disinfectant,leading to a decrease in microbial biomass over time.More research is needed to provide guidelines for pipeline corrosion control.

Simulation of the impacts of diagenesis or low-grade metamorphism on neutrophilic microaerobic Fe(II)-oxidizing biofilm

The microaerobic iron-oxidizing bacteria in circumneutral environment produce extracellular polymeric substances （EPS） with unique morphologic features, such as stalks or sheaths, which can be regarded as geobiological signatures. The Archean and early Palaeoproterozoic oceans were anoxic with high soluble Fe（Ⅱ） that were suggested to have been oxidized through the metabolism of Fe（II）-oxidizing bacteria. The precursor of the ultrafine hematite in banded iron formation （BIF）, e.g., ferrihy- drite, was suggested to be the mineral record of microbial Fe（Ⅱ）-oxidation at that time. However, both the biological materials and primary iron minerals were prone to being altered by diagenetic or low-grade metamorphic processes. This makes it diffi- cult to interpret the genesis of Precambrian BIFs. Here, we report experimental simulation on the effects of diagenesis or low-grade metamorphism on neutrophilic microaerobic Fe（Ⅱ）-oxidizing bacteria and their biomass. Stalks, sheaths, and iron oxide spheroidal aggregates are partially preserved after the 100 MPa/300℃ treatments, which indicates the mixed organic matters and iron oxides could survive the diagenetic or low-grade metamorphic processes. Some organic-mineral mixing structures carry information on microbial processes, though they appear similar to pseudomorphs of fossilized bacteria.

Remediation of arsenic-contaminated paddy field by a new iron oxidizing strain(Ochrobactrum sp.)and iron-modified biochar

Iron-oxidizing strain(FeOB)and iron modified biochars have been shown arsenic(As)reme-diation ability in the environment.However,due to the complicated soil environment,few field experiment has been conducted.The study was conducted to investigate the potential of iron modified biochar(BC-FeOS)and biomineralization by a new found FeOB to remediate As-contaminated paddy field.Compared with the control,the As contents of G_(B)(BC-FeOS),G_(F)(FeOB),G_(FN)(FeOB and nitrogen fertilizer),G_(BF)(BC-FeOS and FeOB)and G_(BFN)(BC-FeOS,FeOB and nitrogen fertilizer)treatments in pore water decreased by 36.53%-80.03%and the microbial richness of iron-oxidizing bacteria in these treatments increased in soils at the rice maturation stage.The concentrations of available As of G_(B),G_(F),G_(FN),G_(BF) and G_(BFN) at the tillering stage were significantly decreased by 10.78%-55.48%.The concentrations of non-specifically absorbed and specifically absorbed As fractions of G_(B),G_(F),G_(FN),G_(BF) and G_(BFN) in soils were decreased and the amorphous and poorly crystalline hydrated Fe and Al oxidebound fraction was increased.Moreover,the As contents of G_(B),G_(F),G_(FN),G_(BF) and G_(BFN) in rice grains were significantly decreased(*P<0.05)and the total As contents of G_(FN),G_(BF) and G_(BFN) were lower than the standard limit of the National Standard for Food Safety(GB 2762-2017).Compared with the other treatments,G_(BFN) showed the greatest potential for the effective remediation of As-contaminated paddy fields.