Inorganic Sulfide Research Articles

Kinetics of aerobic oxidation of volatile sulfur compounds in wastewater and biofilm from sewers

Laboratory experiments were conducted to investigate the kinetics of aerobic chemical and biological oxidation of selected odorous volatile sulfur compounds (VSCs) by wastewater and biofilm from sewers. The VSCs included methyl mercaptan (MeSH), ethyl mercaptan (EtSH), dimethyl sulfide (DMS) and total inorganic sulfide, which have all been reported as the main constituents of foul sewer gas. Samples of wastewater and biofilm for the experiments were obtained from two locations that differed significantly with respect to the occurrence of VSCs. One location represented an odor hot-spot downstream of a force main and the other was a gravity sewer transporting young aerobic wastewater. The kinetics of VSC oxidation for both wastewater and suspended biofilm samples followed a first-order rate equation. The average values of the reaction rate constants demonstrated the following order of reactivity: total inorganic sulfide > EtSH ≥ MeSH >> DMS. Except for total inorganic sulfide oxidation in wastewater, kinetic parameters for each VSC were of similar magnitude for the two locations. In the wastewater from the odor hot-spot, sulfide inorganic oxidation rates were approximately 12 times faster than in the aerobic wastewater.

Identification of Potential Serum Biomarkers in Mercury-Treated Mice Using a Glycoproteomic Approach

Mercury is a well-recognized health hazard and a deleterious environmental contaminant. Exposure to mercury can cause neurotoxic manifestations, nephrotoxicity, and immune function alterations; however, the mechanisms and related proteins responsible for these effects are still unclear. Our goal is to understand the relationship between the toxicity of mercury and the proteins affected by this toxic heavy metal and to define biomarkers for mercury intoxication. Two different forms of mercury, organic methylmercury or inorganic mercury sulfide, were orally administered to the mice for 4 weeks. To reduce complexity of the serum proteome, we enriched glycoproteins from mice serum with lectin concanavalin A resin, and the tryptic peptides of the purified glycoproteins were subjected to nanoultra performance liquid chromatography-Quadrupole time-of-flight for identification and label-free quantification. In this study, we characterized approximately 209 proteins from mice serum, and, among them, 21 proteins were differentially expressed in organic methylmercury-treated mice serum compared with the control group. Two proteins, serum amyloid P component (SAP) and inter α-trypsin inhibitor heavy chain 4 (ITI-H4), were upregulated in organic methylmercury-treated mice and confirmed with different doses of both types of mercury by Western blot analysis. Results of immunohistochemistry also confirmed the validity of SAP and ITI-H4 as biomarker candidates for organic methylmercury exposure. Findings of this study may assist in understanding the relationship between toxicity of mercury and upregulated proteins in mouse serum. Furthermore, the proteins identified here might be used as biomarker candidates in mercury intoxication.

P15 Organic and inorganic hydrogen sulfide donors: Releasing properties and biological activities

The crucial role played by hydrogen sulfide in biology [1] has called for the development of new molecular tools to assist the biologists in their studies, like the numerous probes to detect hydrogen sulfide in cells synthesized in the last two years [2] During this time, hydrogen sulfide donors have emerged to replace the widely used salts NaHS or Na2S, which are instantaneous H2S donors, that consequently do not reproduce the steady biosynthesis [3] . Here, we will present our “chemist’s” approach towards such donors, with two strategies based either on inorganic or on organic molecules. The iron complex 2 from scheme A [4] , the first Fe (II)-SH complex in which the hydrogen (sulfido) ligand is stabilized by H-bond, slowly liberates H2S in organic solutions through an original equilibrium involving a protonation/deprotonation process on the ligand. On another hand, the organic donors from Scheme B [5] are activated by thiols and able to release H2S in simple buffer as well as in more complex systems like cells or tissues. In particular, the stability of the donor MeCOSSCOMe towards oxidation makes it a useful alternative to the use of sulfide salts in ex-vivo assays of the vascular function, with the lowest EC50 reported to date for the relaxation of pre-contracted rat aorta rings under the standard 95% O2/5% CO2 conditions.

P05 Nucleoside phosphorothioates as the new H2S donors

Adenosine and guanosine phosphorothioates (AMPS and GMPS) are synthetic nucleotide analogues that contain one sulfur atom instead of oxygen attached to the phosphorus atom. Previously, it has been demonstrated that histidine triad nucleotide-binding protein-1 (Hint-1) – the ubiquitously expressed nuclear protein – enzymatically decomposes AMPS and GMPS to H 2 S and AMP or GMP, respectively, in cell-free systems [1] , [2] . In addition, AMPS can enter the cell through plasma membrane ionotropic purinergic receptor P2X 7 [3] . We examined if AMPS and GMPS can be enzymatically converted to H 2 S in intact cells. The study was performed in isolated rat kidney glomeruli because endogenous H 2 S is synthesized there, and P2X 7 receptors are expressed in glomerular mesangial cells. Isolated glomeruli were incubated with AMPS or GMPS and real-time H 2 S formation was measured by the polarographic sensor. No H 2 S production was detected from either compound under baseline conditions, however, H 2 S was generated in a time- and substrate concentration-dependent manner if specific P2X 7 agonist, BzATP (10 μ M), was added. H 2 S production from AMPS or GMPS in the presence of BzATP was inhibited by P2X 7 antagonist, A-438079 (1 μ M). H 2 S formation was augmented by either hypoxic conditions (1% O 2 ) or the inhibitor of mitochondrial H 2 S oxidation, stigmatellin, and was insensitive to cystathionine γ -lyase (CSE) inhibitor, propargylglycine (PAG). No H 2 S formation was observed if AMPS or GMPS were incubated without glomeruli or when glomeruli were incubated with AMP or GMP. H 2 S production from 1 mM L-cysteine (67.3 ± 5.2 pmol/mg protein/min) was higher than from either 1 mM AMPS (27.1 ± 2.1 pmol/mg protein/min) or 1 mM GMPS (43.4 ± 4.1 pmol/mg protein/min) and was attenuated by 73% with PAG, but was insensitive to either BzATP or A-438079. AMPS, GMPS (in the absence of BzATP) as well as AMP and GMP had no effect on H 2 S production from L-cysteine. Preliminary results indicate that AMPS or GMPS are converted to H 2 S in in situ perfused rat kidney when BzATP is co-infused, which results in the increase in glomerular filtration rate (GFR) and filtration fraction. These data indicate that AMPS and GMPS may be converted to H 2 S inside the cell in CSE-independent manner but only if P2X 7 receptors are activated. Nucleoside phosphorothioates may serve as new H 2 S donors for research and possibly therapeutic purposes. The specific features of them in contrast to previously used inorganic sulfide salts or organic donors include: (i) receptor-mediated transport to the cell which may be the subject for additional regulation, (ii) enzymatic rather than chemical conversion to H 2 S, (iii) formation of endogenous, non-toxic by products: AMP or GMP.

P04 Reactivity of inorganic sulfide species towards hemeproteins model compounds. Theoretical and experimental perspective

There are several hemeproteins which are able to bind sulfide species with variable affinity [1–4] . Both ligand migation and the stabilization of the coordinated sulfide show unusual behaviour in the different hemeproteins studied, as the binding affinity can not be explained only by similar structural features. In order to disentangle the molecular determinants which control sulfide affinity to hemeproteins, we focused in the characterization of the binding of H 2 S and its conjugate bases to hemeprotein model compounds, from a theoretical and experimental perspective. QM calculations were performed for five and six-coordinated core-porphyrins with H 2 S, SH − or S 2− and an imidazol ring as fifth and sixth ligands, respectively. Fully optimized geometries were obtained at the DFT level using the B3LYP, PBE and OPBE functionals and the 6–31G** basis set. We considered the low spin states of such complexes at ferric and ferrous states. Frequency calculations under the normal mode approximation were obtained at the same levels of theory. Strikingly, we note that structural parameters and vibrational frequencies are only slightly dependent of the protonation state of the sulfide. In addition, the six-coordinated active site was parametrized by means of electronic structure calculations in order to perform a classical MD simulation for microperoxidase 11 (MP11) bound to SH 2 ,SH - or S 2- . MP11 is a hemepeptide derived cytochrome c that retains the proximal histidine as fifth ligand, among the other ten aminoacids. The classical MD approach allows us to analyze the environment of the SH - , and to build initial structures for a more refined QM–MM simulation. With the aid of the latter simulation, we obtained the vibrational spectra of SH − bound to the MP11, as predictive experimental results. The Fe (III) N-acetyl microperoxidase 11 (Fe (III) NAcMP11) [5] derivative was the model compound of choice for the solution experiments of binding of inorganic sulfides, as it prevents the aggregation observed with MP11. The reaction was studied in deoxygenated solutions of Fe (III) NAcMP11 (10 -5 M, buffer phosphate pH = 6.8, 25 °C, λ max = 398 nm) by addition of aliquots of freshly prepared solutions of SHNa, at pH 11. Unlike the control experiments with free Fe (III) porphyrinates, the corresponding reduced reaction product (Fe (II) NAcMP11 λ max = 417 nm) was not obtained. Instead, a new and stable complex was formed, as evidenced by UV/Vis spectroscopy ( λ max = 410 nm); regular features describing a change from a high spin to a low spin state FeIII compound were identified [6,7] .

Nanocomposite approaches for enhancing the DC and photoconductivity of DNA films

Enhanced DC conductivity and photoconductivity of cationic carbazole tethered deoxyribonucleic acid (Cz-DNA) in film devices is achieved by incorporating mobility enhancers. An anthracene-based organic semiconductor (namely 4HPA-Ant) and the inorganic semiconductor cadmium sulfide (CdS) multipod nanocrystal (NC) were used as the mobility enhancers. Space charge limited current (SCLC) experiments show that hole mobility in CdS:Cz-DNA composite film is improved significantly, by about an order of magnitude, compared to the Cz-DNA film. Similarly, the DC conductivity of the composite film is slightly enhanced by 4HPA-Ant. The photoconductivity is also improved in the Cz-DNA composite, with both 4HPA-Ant and CdS multipod NCs. The enhancement in photocurrent is by more than an order of magnitude, as demonstrated by current–voltage (I–V) characterization using DNA composite photodetectors.

Thermodynamic and Structural Analysis of Human NFU Conformational Chemistry

Human NFU has been implicated in the formation of inorganic sulfide required for cellular iron-sulfur cluster biosynthesis. The protein contains a well-structured N-terminal domain and a C-terminal domain with molten globule characteristics that also contains a thioredoxin-like pair of redox active Cys residues that promote persulfide reductase activity. Recent reports have highlighted the existence of structural flexibility in the ISU/IscU-type scaffold proteins that mediate Fe-S cluster assembly, which is also likely to serve an important role in the pathway to Fe-S cluster maturation. We have previously reported similar structural mobility for the C-terminal domain of human NFU, a protein that has been implicated in the production of sulfide for cluster synthesis, while homologous proteins have also been suggested to serve as Fe-S cluster carriers. Herein we quantitatively characterize the structural stability of the two domains of human NFU and in particular the functional C-terminal domain. The results of differential scanning calorimetry and variable temperature circular dichroism (VTCD) studies have been used to analyze the temperature-dependent structural melting profiles of the N- and C-terminal domains, relative to both full-length NFU and an equimolar ratio of the N- and C-terminal domains, and correlated with structural information derived from NMR data. Calorimetry results indicate that the C-terminal NFU domain undergoes a significant structural stabilization following interaction with the N-terminal domain, which resulted in a novel and distinctive transition melting profile (Tm(sec) = 58.1 ± 0.4 °C, ΔHv(sec) = 60.4 ± 5.3 kcal/mol, Tm(ter) = 49.3 ± 0.3 °C, ΔHv(ter) = 71.8 ± 5.8 kcal/mol). VTCD experiments also revealed a secondary structure transition at 59.2 °C in agreement with calorimetry results. The degree of stabilization was found to be more significant in the full-length NFU, as the C-terminal domain transitions were recorded at higher temperatures (Tm(sec) = 63.3 ± 3.4 °C, ΔHv(sec) = 41.8 ± 8.2 kcal/mol). The interactions between the two domains demonstrated the hallmarks of a hydrophobic character, as increased ionic strength decreased the degree of stabilization of the C-terminal domain. An increase of 2% in α-helix content further supports interaction between the two domains, leading to greater secondary structure stabilization. Heteronuclear single-quantum coherence experiments indicate that the C-terminal domain adopts an alternate tertiary conformation following binding to the N-terminal domain. The structural rigidity of the N-terminal domain leads to an alternative conformation of the C-terminal domain, suggesting that such an interaction, although weaker than that of the covalently attached native NFU, is important for the structural chemistry of the native full-length protein. The results also emphasize the likely general importance of such structural flexibility in select proteins mediating metal cofactor biosynthesis.

Cadmium-tolerant bacteria reduce the uptake of cadmium in rice: Potential for microbial bioremediation

We selected 24 bacterial isolates that could tolerate up to 2500µM CdCl2 from the soil of rice fields downstream from a zinc-mineralized area contaminated with a high level of cadmium (Cd). In the presence of 500µM CdCl2, all isolates grew slower and with a prolonged lag-phase compared to in the absence of Cd. Cd-binding capacity was high and ranged from 6.38 to 9.38log[Cd(atom)]/cell. The stability of Cd complexes in bacteria was affected by 1mM EDTA. In 500µM CdCl2, all isolates produced 0.7 to 4.8-fold more inorganic sulfide and 0.6 to 2.2-fold more thio-rich compounds containing SH groups. Out of 24 Cd-tolerant bacterial isolates, KKU2500-3, -8, -9 and -20 were able to promote the growth of Thai jasmine rice (Kao Hom Mali 105) seedlings in the presence of 200µM CdCl2, and KKU2500-3 produced the highest numbers of fibrous root. Interestingly, these 4 isolates increased Cd tolerance and decreased the accumulation of Cd in rice by 61, 9, 6, and 17% when grown in the presence of 200µM CdCl2. Of the 4 isolates, KKU2500-3 produced more inorganic sulfide when grown in CdCl2 at 500–2000µM. XANES analyses indicated that this isolate precipitated a detectable amount of cadmium sulfide (CdS) when grown in 500µM CdCl2. Thus, the isolate KKU2500-3 could possibly transform toxic, soluble CdCl2 into non-toxic, insoluble CdS. These 4Cd-tolerant bacterial isolates were identified via 16S rDNA sequencing and classified as Cupriavidus taiwanensis KKU2500-3 and Pseudomonas aeruginosa KKU2500-8, -9, and -20.

Stabilization treatment of the heavy metals in fly ash from municipal solid waste incineration using diisopropyl dithiophosphate potassium

A stabilization treatment was developed for heavy metals in fly ash from municipal solid waste incineration using the heavy metal chelator diisopropyl dithiophosphate potassium (DDP). The mechanism and effect of the DDP chelator treatment on heavy metals in the fly ash was also studied, along with the form transformation rules of the heavy metals after DDP chelator treatment. The results show that 1% DDP achieves a stabilization rate of over 95% for Pb, Zn, and Cd. The effect of DDP was better than that of inorganic stabilizers such as sodium sulphide and lime. The heavy metal concentrations in the leachate after the treatment were lower than those required by the Pollution Control Standards for Hazardous Waste Landfill (GB18598-2001). At pH 1–13, the heavy metal concentrations in the fly ash leachate were far lower than those using the inorganic stabilizers sodium sulphide and lime. DDP retains its stabilizing effect under a broader pH range. After stabilization treatment, the heavy metals in the exchangeable fraction and those bound to carbonates were mainly transformed into those bound to organic matter. This process decreases the unstable content and reduces the risk of secondary pollution of the stabilized products in the environment.

Surface chemistry and corrosion behaviour of 304 stainless steel in simulated seawater containing inorganic sulphide and sulphate-reducing bacteria

Although many studies have been carried out regarding the role of sulphide anions in promoting microbial corrosion of various metal substrates, very little is known about the differences between inorganic sulphide and biogenically-derived sulphide by sulphate-reducing bacteria (SRB) and what the reasons for differing corrosion behaviour between the two types of sulphide may be towards common metals. In this study, various electrochemical and surface analytical techniques were employed to study the effect of the inorganic and biogenic sulphide (active SRB present) on the surface chemistry and corrosion behaviour of 304 stainless steels in a simulated seawater-based modified Baar’s (SSMB) medium. Clear differences in the surface chemistry of the sulphurised passive film by inorganic and biogenic sulphide (active SRB present) were quantified by X-ray photoelectron spectroscopy (XPS). The transformation of metal sulphides in abiotic and biotic sulphide solutions with the exposure time was correlated with different corrosion behaviour of 304 stainless steels.

S3 and S4 abundances and improved chemical kinetic model for the lower atmosphere of Venus

Mixing ratios of S3 and S4 are obtained from reanalysis of the spectra of true absorption in the visible range retrieved by Maiorov et al. (Maiorov, B.S. et al. [2005]. Solar Syst. Res. 39, 267–282) from the Venera 11 observations. These mixing ratios are fS3=11±3ppt at 3–10km and 18±3ppt at 10–19km, fS4=4±4ppt at 3–10km and 6±2ppt at 10–19km, and show a steep decrease in both S3 and S4 above 19km. Photolysis rates of S3 and S4 at various altitudes are calculated using the Venera 11 spectra and constant photolysis yields as free parameters.The chemical kinetic model for the Venus lower atmosphere (Krasnopolsky, V.A. [2007]. Icarus 191, 25–37) has been improved by inclusion of the S4 cycle from Yung et al. (Yung, Y.L. et al. [2009]. J. Geophys. Res. 114, E00B34), reduction of the H2SO4 and CO fluxes at the upper boundary of 47km by a factor of 4 in accord with the recent photochemical models for the middle atmosphere, by using a closed lower boundary for OCS instead of a free parameter for this species at the surface, and some minor updates.Our model with the S4 cycle but without the SO3+2 OCS reaction suggested by Krasnopolsky and Pollack (Krasnopolsky, V.A., Pollack, J.B. [1994]. Icarus 109, 58–78) disagrees with the observations of OCS, CO, S3, and S4. However, inclusion of the S4 cycle improves the model fit to all observational constraints. The best-fit activation energy of 7800K for thermolysis of S4 supports the S4 enthalpy from Mills (Mills, K.C. [1974]. Thermodynamic Data for Inorganic Sulfides, Selenides and Tellurides. Butterworths, London).Chemistry of the Venus lower atmosphere is initiated by disequilibrium products H2SO4 and CO from the middle atmosphere, photolysis of S3 and S4, and thermochemistry in the lowest scale height. The chemistry is mostly driven by sulfur that is formed in a slow reaction SO+SO, produces OCS, and results in dramatic changes in abundances of OCS, CO, and free sulfur allotropes. The SX+OCS fraction is constant and equal to 20ppm in the lower atmosphere. A source of free sulfur on Venus is in the lower atmosphere, and the calculated S8 mixing ratio is 2.5ppm above 40km and results in condensation and formation of aerosol sulfur near 50km. Therefore the model does not support sulfur as the NUV absorber that was observed by Venera 14 above 58km. Sources and sinks of the major chemical products in the model are briefly discussed. The model predicts a significant abundance of 3.5ppb for SO2Cl2 above 25km. This prediction of SO2Cl2 as well as that in the photochemical model for the middle atmosphere (Krasnopolsky, V.A. [2012]. Icarus 218, 230–246) may stimulate search for this species. A modified concept of the fast and slow sulfur cycles in the middle and lower atmospheres, respectively, has been presented and discussed. Some sources of the model uncertainty are briefly discussed.

ChemInform Abstract: Strongly Coupled Inorganic/Nanocarbon Hybrid Materials for Advanced Electrocatalysis

AbstractReview: 90 refs.

Sulfidation Mechanism for Zinc Oxide Nanoparticles and the Effect of Sulfidation on Their Solubility

Environmental transformations of nanoparticles (NPs) affect their properties and toxicity potential. Sulfidation is an important transformation process affecting the fate of NPs containing metal cations with an affinity for sulfide. Here, the extent and mechanism of sulfidation of ZnO NPs were investigated, and the properties of resulting products were carefully characterized. Synchrotron X-ray absorption spectroscopy and X-ray diffraction analysis reveal that transformation of ZnO to ZnS occurs readily at ambient temperature in the presence of inorganic sulfide. The extent of sulfidation depends on sulfide concentration, and close to 100% conversion can be obtained in 5 days given sufficient addition of sulfide. X-ray diffraction and transmission electron microscopy showed formation of primarily ZnS NPs smaller than 5 nm, indicating that sulfidation of ZnO NPs occurs by a dissolution and reprecipitation mechanism. The solubility of partially sulfidized ZnO NPs is controlled by the remaining ZnO core and not quenched by a ZnS shell formed as was observed for partially sulfidized Ag NPs. Sulfidation also led to NP aggregation and a decrease of surface charge. These changes suggest that sulfidation of ZnO NPs alters the behavior, fate, and toxicity of ZnO NPs in the environment. The reactivity and fate of the resulting <5 nm ZnS particles remains to be determined.

Soil sulphur speciation in two glacier forefield soil chronosequences assessed by SK‐edge XANES spectroscopy

SummaryIn regions with little atmospheric input of sulphur (S) and S‐poor parent material, the bio‐availability of S, which is dependent on its speciation, may limit ecosystem production and succession. In our study, soil S speciation in two glacier forefield soil chronosequences (Hailuogou Glacier, Gongga Shan, China; Damma Glacier, Swiss Alps) was investigated for the first time. Different S species were quantified by synchrotron‐based X‐ray absorption near‐edge structure (XANES) spectroscopy at the S K‐edge. Both chronosequences show similar patterns and pedogenetic trends of their topsoil S status. Topsoil concentrations of total S were correlated with the concentrations of organic carbon and pedogenic Fe/Al oxyhydroxides. Both moraine materials contained inorganic sulphides, which in the topsoil were oxidized within 30 (Hailuogou) or 75 years (Damma) of soil development after deglaciation. About 50% of total S in the fresh moraine material at Hailuogou and 75% of that in the 15 year‐old soil at Damma was organically‐bound. During initial soil development, the contribution of organic S to total S increased at the expense of inorganic sulphide and sulphate, resulting in organic S percentages &gt; 90% of total topsoil S after 30 (Hailuogou) and 75 (Damma) years of pedogenesis. Organic S compounds with electronic oxidation states of the S atom &gt; + 1.5 (sulphoxides, sulphones, sulphonates and ester sulphates) dominated the organic S pool in all soils. Hence, microbial degradation of non‐sulphide organic S (sulphonates and ester sulphates) is probably important to mitigate S scarcity caused by limited availability of SO42−‐S in these soils. Changes in topsoil S speciation during initial stages of pedogenesis and ecosystem succession in glacier forefields under a cool, humid climate appear to be governed by combined effects of mineral weathering (oxidation of inorganic sulphides and formation of S‐adsorbing sesquioxides), accumulation and microbial turnover of soil organic matter and the type of vegetation succession.

Mechanisms Regulating Mercury Bioavailability for Methylating Microorganisms in the Aquatic Environment: A Critical Review

Mercury is a potent neurotoxin for humans, particularly if the metal is in the form of methylmercury. Mercury is widely distributed in aquatic ecosystems as a result of anthropogenic activities and natural earth processes. A first step toward bioaccumulation of methylmercury in aquatic food webs is the methylation of inorganic forms of the metal, a process that is primarily mediated by anaerobic bacteria. In this Review, we evaluate the current state of knowledge regarding the mechanisms regulating microbial mercury methylation, including the speciation of mercury in environments where methylation occurs and the processes that control mercury bioavailability to these organisms. Methylmercury production rates are generally related to the presence and productivity of methylating bacteria and also the uptake of inorganic mercury to these microorganisms. Our understanding of the mechanisms behind methylation is limited due to fundamental questions related to the geochemical forms of mercury that persist in anoxic settings, the mode of uptake by methylating bacteria, and the biochemical pathway by which these microorganisms produce and degrade methylmercury. In anoxic sediments and water, the geochemical forms of mercury (and subsequent bioavailability) are largely governed by reactions between Hg(II), inorganic sulfides, and natural organic matter. These interactions result in a mixture of dissolved, nanoparticulate, and larger crystalline particles that cannot be adequately represented by conventional chemical equilibrium models for Hg bioavailability. We discuss recent advances in nanogeochemistry and environmental microbiology that can provide new tools and unique perspectives to help us solve the question of how microorganisms methylate mercury. An understanding of the factors that cause the production and degradation of methylmercury in the environment is ultimately needed to inform policy makers and develop long-term strategies for controlling mercury contamination.

Corrosion Inhibition of Cu-Ni (90/10) Alloy in Seawater and Sulphide-Polluted Seawater Environments by 1,2,3-Benzotriazole

The inhibiting effect of 1,2,3-benzotriazole (BTAH) against the corrosion of Cu-Ni (90/10) alloy in seawater and seawater polluted with inorganic sulphide was studied by electrochemical impedance studies (EISs), potentiodynamic polarization studies, and cyclic voltammetric (CV) and weight-loss studies. Surface examination studies were carried out by X-ray photo electron spectroscopy (XPS) and scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX). EIS studies have been carried out in seawater and 10 ppm of inorganic sulphide containing seawater in the absence and presence of BTAH at different concentrations, different immersion periods, and at different temperatures. Appropriate equivalent circuit model was used to calculate the impedance parameters. The potentiodynamic polarization studies inferred that BTAH functions as a mixed inhibitor. The impedance, polarization, and weight-loss studies showed that the inhibition efficiency of BTAH is in the range between 99.97 and 99.30% under different conditions. Cyclic voltammeric studies show the stability of the protective BTAH film even at anodic potentials of +550 mV versus Ag/AgCl. All these studies infer that BTAH functions as an excellent inhibitor for Cu-Ni (90/10) alloy in seawater and sulphide-polluted seawater. XPS and SEM-EDX studies confirm the presence of protective BTAH film on the alloy surface.

Strongly Coupled Inorganic/Nanocarbon Hybrid Materials for Advanced Electrocatalysis

Electrochemical systems, such as fuel cell and water splitting devices, represent some of the most efficient and environmentally friendly technologies for energy conversion and storage. Electrocatalysts play key roles in the chemical processes but often limit the performance of the entire systems due to insufficient activity, lifetime, or high cost. It has been a long-standing challenge to develop efficient and durable electrocatalysts at low cost. In this Perspective, we present our recent efforts in developing strongly coupled inorganic/nanocarbon hybrid materials to improve the electrocatalytic activities and stability of inorganic metal oxides, hydroxides, sulfides, and metal-nitrogen complexes. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of inorganic nanomaterials on the functional groups of oxidized nanocarbon substrates including graphene and carbon nanotubes. This approach affords strong chemical attachment and electrical coupling between the electrocatalytic nanoparticles and nanocarbon, leading to nonprecious metal-based electrocatalysts with improved activity and durability for the oxygen reduction reaction for fuel cells and chlor-alkali catalysis, oxygen evolution reaction, and hydrogen evolution reaction. X-ray absorption near-edge structure and scanning transmission electron microscopy are employed to characterize the hybrids materials and reveal the coupling effects between inorganic nanomaterials and nanocarbon substrates. Z-contrast imaging and electron energy loss spectroscopy at single atom level are performed to investigate the nature of catalytic sites on ultrathin graphene sheets. Nanocarbon-based hybrid materials may present new opportunities for the development of electrocatalysts meeting the requirements of activity, durability, and cost for large-scale electrochemical applications.

Lead tolerance in plants: strategies for phytoremediation

Lead (Pb) is naturally occurring element whose distribution in the environment occurs because of its extensive use in paints, petrol, explosives, sludge, and industrial wastes. In plants, Pb uptake and translocation occurs, causing toxic effects resulting in decrease of biomass production. Commonly plants may prevent the toxic effect of heavy metals by induction of various celular mechanisms such as adsorption to the cell wall, compartmentation in vacuoles, enhancement of the active efflux, or induction of higher levels of metal chelates like a protein complex (metallothioneins and phytochelatins), organic (citrates), and inorganic (sulphides) complexes. Phyotochelains (PC) are synthesized from glutathione (GSH) and such synthesis is due to transpeptidation of γ-glutamyl cysteinyl dipeptides from GSH by the action of a constitutively present enzyme, PC synthase. Phytochelatin binds to Pb ions leading to sequestration of Pb ions in plants and thus serves as an important component of the detoxification mechanism in plants. At cellular level, Pb induces accumulation of reactive oxygen species (ROS), as a result of imbalanced ROS production and ROS scavenging processes by imposing oxidative stress. ROS include superoxide radical (O2(.-)), hydrogen peroxide (H2O2) and hydroxyl radical ((·)OH), which are necessary for the correct functioning of plants; however, in excess they caused damage to biomolecules, such as membrane lipids, proteins, and nucleic acids among others. To limit the detrimental impact of Pb, efficient strategies like phytoremediation are required. In this review, it will discuss recent advancement and potential application of plants for lead removal from the environment.

Biomimetic Sulfide Oxidation by the Means of Immobilized Fe(III)‐5,10,15,20‐tetrakis(pentafluorophenyl)porphin under Mild Experimental Conditions

This paper describes the oxidation of inorganic sulfide to sulfate, minimizing the formation of elemental sulfur. The described catalytic reaction uses dilute hydrogen peroxide at nearly neutral pH values in the presence of a bioinspired, heterogenized, and commercial ferriporphin. A substantial increase of the percentage of sulfide converted to sulfate is obtained in comparison with the yields obtained when working with hydrogen peroxide alone. The biomimetic catalyst also proved to be a much more efficient catalyst than horseradish peroxidase. Accordingly, it could be suitable for large‐scale applications. Further studies are in progress to drive sulfate yields up to nearly quantitative.

Tribochemical Study of Two Ashless Triazine Derivatives as Additives in Rapeseed Oil

The ashless 2,4-bis-dipropylamino-6-(O,O’-dibuthyldithio- phosphate)-s-1,3,5- triazine (PrBT) and 2,4-bis-morpholinyl-6- (O,O’-dibuthyldithiophosphate) -s-1,3,5 -triazine (MoBT), were prepared and their tribological behaviors as additives in rapeseed oil(RSO) were evaluated using a four-ball tester. The worn surfaces of the steel balls were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy(XPS). The results indicate that the additives possess good load-carrying capacities. Moreover, they both have good antiwear and friction-reducing property at relatively middle concentration(1~2 wt%) and under all test loads, and in some condition, these triazine derivatives can replace the zinc dialkylthiophosphate. The results of XPS analyses illustrate that the prepared compounds as additives in RSO forms a protective film containing inorganic sulfide, sulfate, oxidized compounds and organic nitrogen-containing compounds on the metal surface during the sliding process.