Zn Loading Research Articles

Soil chemistry influences the phytotoxicity of metal oxide nanoparticles

Nanoparticles (NPs) of ZnO and CuO are used in an array of different commercial products. NPs could be introduced into soils by contamination after production from distribution and use, especially from their end-of-life fate. Purposeful introduction to soils may occur in formulations as pesticides, because of their antimicrobial properties, and as fertilisers, to increase the loading of the essential metals Zn and Cu into plant tissues. Use as fertilisers must ensure that application rates do not lead to phytotoxicity. Dose-dependent phytotoxicity is seen in several crops including wheat, Triticum aestivum, when grown hydroponically or in sand. Phytotoxicity is evidenced in wheat by reduced growth and higher tissue loads of Cu or Zn than control plants. Soil properties, however, can mitigate phytotoxicity. Growth reduction in the wheat seedlings was not observed when an alkaline calcareous field soil with initial pH of 8.3 was amended with 300 mg Cu/kg soil from CuO NPs although metal loads increased in the shoots, paralleling observations with ZnO NPs. Phytotoxicity of both NPs was evident in acidic commercial field soils. The level of soluble metal released from the NPs in the aqueous phase varied with soil. Solubility was determined by the soil water pH and in part by the nature of the materials present in the plant root exudates. For example, a typical root exudate, citrate, at pH 5, dissolved more Cu from CuO NPs than did a suspension in water. These findings indicate that phytotoxicity of these metal oxide NPs in soils will vary with the properties of the soils. Consequently soil properties will influence how the NPs could be used as fertilisers.

Zn uptake behavior of rice genotypes and its implication on grain Zn biofortification.

Understanding Zn uptake dynamics is critical to rice grain Zn biofortification. Here we examined soil Zn availability and Zn uptake pathways as affected by genotype (high-grain Zn varieties IR69428 and IR68144), Zn fertilization and water management in two pot experiments. Results showed significant interactions (P < 0.05) between genotypes and Zn fertilization on DTPA (diethylenetriaminepentaacetic acid)-extractable soil Zn from early tillering to flowering. DTPA-extractable Zn in soils grown with IR69428 was positively correlated with stem (r = 0.78, P < 0.01), flagleaf (r = 0.60, P < 0.01) and grain (r = 0.67, P < 0.01) Zn concentrations, suggesting improved soil Zn availability and continued soil Zn uptake by IR69428 even at maturity. Conversely for IR68144, DTPA-extractable Zn was positively correlated only with leaf Zn uptake (r = 0.60, P < 0.01) at active tillering, indicating dependence on remobilization for grain Zn loading. Furthermore, the highest grain Zn concentration (P < 0.05) was produced by a combination of IR69428 and Zn fertilization applied at panicle initiation (38.5 μg g−1) compared with other treatments (P < 0.05). The results highlight that Zn uptake behavior of a rice genotype determines the fate of Zn from the soil to the grain. This has implications on overcoming Zn translocation barriers between vegetative parts and grains, and achieving grain Zn biofortification targets (30.0 μg g−1).

The role of natural biogeochemical barriers in limiting metal loading to a stream affected by mine drainage

Rio San Giorgio (Iglesiente, Sardinia, Italy), a stream affected by abandoned mine wastes, is characterized by dense vegetation in the streambed, mainly comprised of Phragmites australis and Juncus acutus. This vegetation creates natural biogeochemical barriers that drive mineralization processes and attenuate metals load in the stream. Several techniques, covering scales from micrometres to kilometres, were applied to investigate the biogeochemical processes: water chemistry, injected hydrologic tracer, mineralogy, microscopic investigation and X-ray spectroscopy. From this multiscale and multimethod approach, we recognized two predominant sets of biogeochemical processes: microbially driven metal sulphide precipitation, mainly resulting in pyrite formation; and plant uptake of metals that leads to formation of iron oxide-hydroxide and incorporation of Zn within the roots and aerial part (stem and leaves). The dense vegetation in the Rio San Giorgio streambed controls its morphology, velocity of streamflow, and, as reflected by observed bromide-tracer loss, enhanced water exchange between the streambed and the hyporheic zone. The combined effect of these vegetative controls is to establish biogeochemical barriers that greatly retard trace-metal mobility in the hyporheic zone. We estimated this effect can lead to an apparent decrease in Zn load up to 60%.

Magnetic Fe3O4@SiO2/Pd and Fe3O4@SiO2/Pd‐M (M=Ag, Cu and Zn) Catalysts for Selective Hydrogenation of Phenylacetylene

AbstractMagnetic core‐shell monometallic Fe3O4@SiO2/Pd and bimetallic Fe3O4@SiO2/Pd−M (M=Ag, Cu and Zn) catalysts with low Pd loading were prepared using a modified Stöber method followed by an ion‐exchange technique, and applied to the selective hydrogenation of phenylacetylene. The structure and magnetism of the catalysts were investigated using N2 physisorption, XRD, FT‐IR, ICP‐OES, H2‐TPR, CO chemisorption, DRIFTS, HRTEM and vibrating sample magnetometer. The characterization results showed that the magnetic catalyst had smaller Pd particle size than the non‐magnetic catalyst; the thinner the silica shell of the magnetic catalyst, the stronger the magnetic intensity and hence the smaller the Pd particle size; the PdM alloy was formed for bimetallic catalysts and geometric and electronic effects occur. By comparing the activity and selectivity of different catalysts, it was found that the catalyst with smaller Pd particle size generally exhibited a higher apparent activity and selectivity to styrene but a lower specific activity, demonstrating the structure‐sensitive catalytic activity for selective hydrogenation of phenylacetylene on the magnetic Pd supported catalysts. In addition, all the bimetallic catalysts displayed higher selectivity but lower activity than the monometallic catalysts as a result of the presence of the PdM alloy. In particular, a Fe3O4@SiO2/Pd−Zn catalyst with the shell thickness of about 80 nm and the Pd and Zn loadings of 0.31 and 1.79 wt%, respectively, showed the best selectivity to styrene, being 86.1 % at above 99.5 % conversion of phenylacetylene. Furthermore, this catalyst maintained its activity and selectivity even after being reused ten times.

Zn(0)-Catalyzed Ozonation Degradation of Acid Orange 7 (AO7) in Aqueous Solution

In this paper, Zn(0)-catalyzed ozonation degradation of acid orange 7 (AO7) and its impact factors including solution pH, Zn loading, and AO7 initial concentration were investigated through a series of bath experiments. The results demonstrated that Zn could markedly accelerate the degradation of AO7 by ozone (O3) and the degradation efficiency of AO7 increased by 77 and 71 % within 30 min as compared with those in the systems of O3 alone and Zn/air, respectively. The reuse of Zn resulted in a slight decline in AO7 degradation, suggesting that a coating of ZnO on the surface of Zn particles weakened Zn catalytic activity. The optimal removal of AO7 was achieved in a wide pH range of 4 to 10, and a lower or higher pH was not conducive to the degradation of AO7. In addition, the degradation efficiency of AO7 increased with Zn loading but decreased with AO7 initial concentration. The introduction of free radical scavengers into the system of AO7/Zn/O3 confirmed that O2 •−, rather than •OH, was the main free radicals responsible for the rapid removal of AO7. The degradation of AO7 by O3 assisted with Zn could be well expressed with pseudo-first-order kinetic model.

Comparison of Nutrient and Metal Loadings with the Application of Swine Manure Slurries and Their Liquid Separates to Soils.

The accumulation of phosphorus (P) and metals is a serious concern with the continuous application of manure to agricultural soils. Solid-liquid separation of swine slurry is a promising approach to reduce P and metal loadings through application of separated liquid (SL) as a nutrient source. However, little information is available on nutrient and metal loadings with the application of SL compared with unseparated raw manure (RM). We analyzed element concentrations and calculated nutrient and metal loadings for RM and their respective SL applications, considering an application rate of 100 kg total nitrogen (N) ha. Samples of SL were obtained through three separation techniques: (i) centrifugation without a flocculant, (ii) centrifugation with a flocculant, and (iii) rotary press with a flocculant. Irrespective of separation technique, calculated P loadings with the application of SL were only 50 to 70% of that of RM at equivalent rates of total N yet exceeded crop removal rate. In contrast, calculated K and Na loadings with SL application were significantly greater than with RM, indicating a possible build-up of K and Na in soil. Calculated Ca and Mg loadings were significantly greater with RM than with SL. Loadings of Al, As, Ba, Cd, Cr, Fe, Mn, Ni, Pb, Sn, Se, Ti, and V were low, whereas Cu and Zn loadings were above crop removal rates for RM and SL. For solid-liquid separation to provide a lasting solution to the problem of P and metal accumulation, the SL must be supplemented with commercial N fertilizer to meet crop N demand.

Catalytic Flash Gasification of EFB for Hydrogen Production Using Zeolite Supported Metal Oxide Catalysts

Empty fruit bunch (EFB) waste is produced in large amount in Malaysia from intense oil palm agriculture activity. Direct usage of EFB as a source of energy is not economically feasible and ideally should be upgraded before it can produce green energy economically. Current gasification processes produces a lot of tar while yielding low amount of hydrogen. Flash gasification of EFB with the presence of catalysts shows improvements over the uncatalysed reaction. In this study, by using a high surface area support catalyst of ZSM-5 with the presence of 1% Ni, Zn, or Fe metal loading is sufficient to enhance the hydrogen production. ZSM-5, NiO/ZSM-5, CuO/ZSM-5, Fe2O3/ZSM-5 and ZnO/ZSM-5 catalyst with 1 wt % loading were prepared via the wet impregnation method. XRD patterns of the prepared catalysts shows almost identical peaks patterns which indicates high dispersion of dopants on the support catalyst Flash gasification was carried out at 900°C under isothermal heating conditions with 10 sccm 4.99% O2 diluted in He. Syngas produced was then analysed using an online quadrupole mass spectrometer. Catalytic activity for hydrogen production is the highest for NiO/ZSM-5 followed by ZnO/ZSM-5, Fe2O3/ZSM-5, ZSM-5.

Zinc Diffusion Coatings on Aluminium for Improved Pitting Resistance

The automotive industry has replaced copper tube based heat exchangers with all-aluminium solutions during the past years in order to reduce weight, material costs and environmental impact. Conversely, the use of aluminium tubing in the HVAC&R (Heat, Ventilation, Air Conditioning and Refrigeration) heat exchanger market is limited due to the much more demanding lifetime requirements. One way of obtaining the required level of safety against failure of aluminium tubing in such applications is corrosion protection by surface modification. This work investigates the effect of surface alloying with zinc on the pitting resistance of heat exchanger tubes. Pure zinc was applied on flat, thin-walled (≈ 400 µm) multi-port extruded Al-Mn alloy tubes by thermal arc spraying immediately after extrusion, resulting in a sub-micron thick metallic Zn layer on the surface. The tubes were subsequently heat treated to obtain various Zn-rich diffusion layers ranging up to about 70 µm into the alloy substrate. Zn depth profiles were determined by glow discharge optical emission spectroscopy (GD-OES). Corrosion testing was performed by exposure to a cyclic acidified (pH 3) synthetic seawater fog test (ASTM G85 annex A3), normally referred to as the SWAAT test. Open circuit potentials were measured on separate samples as a function of time during immersion in the SWAAT solution at 25 °C. The extent of corrosion as a function of time was determined by weight loss on samples retrieved from the salt spray cabinet at predetermined time intervals for a period of up to eight weeks. The maximum pit depth on each sample was measured by use of a light microscope with a micrometre focusing dial. Ten replicate samples (each 25 mm x 100 mm in size) for each substrate/coating combination were tested, allowing analysis of the maximum pit depth data from extreme value probability plots. The open circuit potential of the Zn diffusion coated samples in artificial seawater solution was about -0.95 V (SCE), shifting only 10 mV in positive direction during 24 h of immersion. The corrosion potential of the Al-Mn alloy substrate remained constant at -0.74 V (SCE) under similar conditions. The cathodic protection provided by the Zn-rich diffusion layers effectively protected the Al-Mn alloy tubes against formation of deep pits during SWAAT testing. No pits deeper than about 50 µm had formed on the Zn diffusion coated samples after eight weeks of exposure, whereas pit depths exceeding 200 µm was observed on uncoated reference samples already after two weeks. However, weight loss measurements showed that the (uniform) corrosion rate of the anodic Zn-rich diffusion layer was nearly two orders of magnitude higher than that of the Al-Mn alloy substrate under the aggressive low pH conditions prevailing during SWAAT exposure. The results suggest that a lower Zn load than that realizable by thermal arc spraying is required to obtain optimal Zn diffusion profiles in terms of service life of the heat exchanger tubing.

Corrosion Resistance of Zinc-Rich Metallic Coatings on Aluminum

Thin walled aluminum heat exchanger tubes, with solid-solution Zn-rich surface are widely used by the automotive industry and considered by the HVAC&R (Heat, Ventilation, Air Conditioning and Refrigeration) market for improved corrosion resistance against pitting. It is well known that alloying Al with Zn causes decrease in the corrosion potential in chloride solution.1 Thus, Zn-rich coating can provide cathodic protection to the aluminum substrate, in particular prevent pitting corrosion. However, corrosion rate of Zn itself is quite high in chloride solution.2 This work investigates the extent to which the self-corrosion of the Zn-rich layer can be a limiting factor in determining the service life time of the heat exchanger tubes. Zinc was applied on AlMn alloy extruded tubes by thermal arc spraying immediately after extrusion. Typical Zn load on the surface was 0.8 ± 0.2 mg/cm2. The tubes were subsequently subjected to heat treatment at various temperatures (350 - 430°C) and durations to obtain solid-state AlZn alloy diffusion layer with varying thickness and Zn-concentration profiles at the surface of the AlMn substrate. The Zn depth profiles were characterized by glow discharge optical emission spectroscopy (GD-OES). Corrosion rate was determined by weight loss resulting from immersion for predetermined times in acidified artificial sea water solution of pH 3 at 25°C for slight acceleration of the corrosion rate, during which the open circuit potential change was recorded with respect to time. The morphology and composition of the Zn-rich layer before and after corrosion were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).The Zn concentration distribution in the layer could be modeled by the solution to Fick's 2nd law with appropriate boundary conditions, giving an effective diffusion coefficient for Zn in the Al substrate of order 10-10 cm2/s in the temperature range of interest, varying according to the Arrhenius law with respect to temperature. Zn-rich layer thickness obtained on the samples heat treated at selected conditions varied approximately in the range 35 to 80 µm with increasing heat treatment temperature and time, corresponding to Zn surface concentrations of 28 to 7 wt%, respectively. Reduction in thickness due to corrosion, calculated from the weight loss measurements by taking into consideration the density depth-profile of Zn, which was obtained from the GD-OES data, increased with increasing thickness of the Zn-rich layer. Unexpectedly, decreasing Zn concentration level in the layer did not have a significant effect on the corrosion rate, unless it was lower than a threshold of a few wt%, which appeared to be sufficient to give the necessary protection. The results confirmed also that Zn gave satisfactory protection against pitting corrosion. Corrosion potential of samples as coated with Zn (no heat treatment) reached the pitting potential of the AlMn substrate in about 4 days. After 11 days of immersion, corrosion potential of the samples heat treated at 350°C for 2 hours increased up to about 30 mV below the pitting potential of the substrate, while the corrosion potential of the samples heat treated at 430°C for 4 hours remained about 120 mV lower than the pitting potential of the substrate. The reduction in thickness after 11 days of immersion for those heat treatment conditions was 23 µm and 54 µm, respectively. These results indicate that optimal Zn concentration and Zn-rich layer thickness, in terms of service life and loss of thickness, lie at levels much lower than those used in this study. The optimal concentration needs to maintain the corrosion potential at a level lower than the critical pitting potential. At the same time, the Zn concentration level in the layer has to be low enough to restrict the rate of self-corrosion, such that the layer thickness can also be reduced to give sufficiently long service life time. The well-known relationship between the corrosion potential of AlZn alloys and Zn concentration1 was extended over a wide concentration range and related further to the corrosion rate in acidified synthetic seawater. The database thus developed is useful for optimizing the Zn-rich layer thickness and Zn concentration profile in the layer to minimize uniform corrosion, and therefore maximize service lifetime, without reducing the protection against pitting.

Circulation and accumulation of harmful elements in blast furnace and their impact on the fuel consumption

The circulation and accumulation of harmful elements in blast furnace were investigated. The results show that the maximum concentration of K and Na in the belly is about 50 times of that in the charge. The zinc increased by 80 times and the Pb is insignificant. The impact of the circulation and accumulation of K, Na, Pb and Zn on the fuel consumption was quantitatively analyzed using Rist diagram. The results show that the gas utilization decreased and the coke rate increased linearly with the increase of load and accumulation times of each harmful element. Given the accumulation times of each element, the loading of Na, K, Zn and Pb into BF leads to the increase of coke rate by 13.99 kg/tHM, 6.25 kg/tHM, 3.63 kg/tHM and 0.02 kg/tHM, respectively. The increased coke rate and the decreased gas utilization under various loads and accumulation times of each element was estimated.

Engineering high Zn in tomato shoots through expression of AtHMA4 involves tissue-specific modification of endogenous genes.

BackgroundTo increase the Zn level in shoots, AtHMA4 was ectopically expressed in tomato under the constitutive CaMV 35S promoter. However, the Zn concentration in the shoots of transgenic plants failed to increase at all tested Zn levels in the medium. Modification of Zn root/shoot distribution in tomato expressing 35S::AtHMA4 depended on the concentration of Zn in the medium, thus indicating involvement of unknown endogenous metal-homeostasis mechanisms. To determine these mechanisms, those metal-homeostasis genes that were expressed differently in transgenic and wild-type plants were identified by microarray and RT-qPCR analysis using laser-assisted microdissected RNA isolated from two root sectors: (epidermis + cortex and stele), and leaf sectors (upper epidermis + palisade parenchyma and lower epidermis + spongy parenchyma).ResultsZn-supply-dependent modification of Zn root/shoot distribution in AtHMA4-tomato (increase at 5 μM Zn, no change at 0.5 μM Zn) involved tissue-specific, distinct from that in the wild type, expression of tomato endogenous genes. First, it is suggested that an ethylene-dependent pathway underlies the detected changes in Zn root/shoot partitioning, as it was induced in transgenic plants in a distinct way depending on Zn exposure. Upon exposure to 5 or 0.5 μM Zn, in the epidermis + cortex of the transgenics’ roots the expression of the Strategy I Fe-uptake system (ethylene-dependent LeIRT1 and LeFER) was respectively lower or higher than in the wild type and was accompanied by respectively lower or higher expression of the identified ethylene genes (LeNR, LeACO4, LeACO5) and of LeChln. Second, the contribution of LeNRAMP2 expression in the stele is shown to be distinct for wild-type and transgenic plants at both Zn exposures. Ethylene was also suggested as an important factor in a pathway induced in the leaves of transgenic plants by high Zn in the apoplast, which results in the initiation of loading of the excess Zn into the mesophyll of “Zn accumulating cells”.ConclusionsIn transgenic tomato plants, the export activity of ectopically expressed AtHMA4 changes the cellular Zn status, which induces coordinated tissue-specific responses of endogenous ethylene-related genes and metal transporters. These changes constitute an important mechanism involved in the generation of the metal-related phenotype of transgenic tomato expressing AtHMA4.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2990-x) contains supplementary material, which is available to authorized users.

Biomarker responses of Eisenia andrei to a polymetallic gradient near a lead mining site in North Tunisia

Eisenia andrei earthworms were exposed for 7 and 14 days to six samples of soil taken from around an abandoned lead (Pb) mine and characterized by different levels of metal contamination (S6-S1, this latter being the most contaminated soil). The organisms were analyzed for metal bioaccumulation and for biological parameters as biomarkers of stress (lysosomal membrane stability; lipofuscin lysosomal content; lysosomal/cytoplasmic volume ratio) and genotoxicity (Micronucleus frequency). Chemical analysis showed the loads of Pb, Cd, Zn, and Cu in the worms following exposure. Among the stress biomarkers, lysosomal membrane stability was significantly affected in the coelomocytes of the earthworms exposed already 7 days to different contaminated soils. Organisms exposed for 14 days to S1 showed in the cells of the chloragogenous tissue, a particularly relevant increase in lipofuscin, a biomarker of oxidative stress, and an increase in the lysosome/cytoplasm volume ratio, indicating stressful condition at the tissue level. Moreover, in the same conditions, a decrease in total body weight was observed. At the longer exposure time, the coelomocytes of worms exposed to S1, S2, and S3 (soils with higher metal concentrations) showed a significant increase in micronuclei (MNi) frequency. Expressions of the P21 and topoisomerase genes, which are involved in DNA repair, showed significant up-regulation in the cells of worms exposed to S1, S2, S3, S4 and to a less extend S6. This may indicate that the worms were only able to successfully reduce the level of DNA damage in S4 and S5 if considering MN frequency data. The biomarker data was integrated by the Earthworm Expert System, allowing an objective interpretation of the complex biological data and clearly defining the areas in which the presence of chemicals is toxic for the edaphic organisms.

Growth, biochemical variables, and zinc bioaccumulation in Nile tilapia, Oreochromis niloticus (L.) as affected by water-born zinc toxicity and exposure period

The present study was carried out to investigate the effect of sublethal zinc (Zn) concentrations on growth performance, biochemical variables, and Zn residues in various organs of Nile tilapia, Oreochromis niloticus (L.). Fish (25 ± 0.5 g) were exposed to 0.0, 3.5, or 7.0 mg Zn L−1 for 1 or 6 weeks. Fish growth was significantly reduced with increasing Zn concentrations. However, fish exposed to 7.0 mg Zn L−1 grew less quickly than those of the control group. Likewise, best feed intake and feed conversion ratio were obtained at the control group. Furthermore, glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, and cortisol increased significantly with increasing Zn concentrations and exposure time, with maximal values in the 7.0 mg Zn L−1 treatment after 6 weeks. Meanwhile, highest values of serum protein and lipids were obtained in the control fish reared for 6 week, whereas their lowest values were observed in fish exposed to 7.0 mg Zn L−1 for 1 week. There was no significant change in whole-body moisture content of fish due to Zn exposure, although crude protein and total lipid contents decreased significantly with increasing Zn concentrations. In addition, Zn exposure increased total ash contents and Zn residues in different investigated fish organs. The Zn concentrations in all fish organs were time-dependant and the Zn residues after 1 week were found to follow the order of gills > liver > kidney > muscle, meanwhile after 6 weeks it followed the order of liver > kidney > gill > muscle. The present findings revealed that liver and kidney tissues are the prime sites of Zn bioaccumulation, while Zn load in the muscle was for low as compared to other organs.

Improving Rice Zinc Biofortification Success Rates Through Genetic and Crop Management Approaches in a Changing Environment.

Though rice is the predominant source of energy and micronutrients for more than half of the world population, it does not provide enough zinc (Zn) to match human nutritional requirements. Moreover, climate change, particularly rising atmospheric carbon dioxide concentration, reduces the grain Zn concentration. Therefore, rice biofortification has been recognized as a key target to increase the grain Zn concentration to address global Zn malnutrition. Major bottlenecks for Zn biofortification in rice are identified as low Zn uptake, transport and loading into the grain; however, environmental and genetic contributions to grain Zn accumulation in rice have not been fully explored. In this review, we critically analyze the key genetic, physiological and environmental factors that determine Zn uptake, transport and utilization in rice. We also explore the genetic diversity of rice germplasm to develop new genetic tools for Zn biofortification. Lastly, we discuss the strategic use of Zn fertilizer for developing biofortified rice.

Catalytic co-aromatization of ethanol and methane

This study demonstrates the technical feasibility of simultaneously converting ethanol and methane into liquid hydrocarbons at mild reaction conditions (400°C and 1atm) over silver and/or zinc modified zeolite catalysts. After GC–MS analysis, it is worth noting that aromatics are the major compounds contained in the liquid product collected from the run when 1%Ag/ZSM-5, particularly after H2 pretreatment, is charged. Compared to the performance exhibited from the run with pure HZSM-5 support engaged, Ag addition into the HZSM-5 framework favors aromatics formation, which might be closely associated with better Ag dispersion and more abundance of strong surface acidic sites where aromatization might take place while Zn loading exerts a detrimental effect on the production of aromatics but promotes the ether generation possibly through dehydration reaction. Referred to that from its N2 counterpart, the increased aromatics formation of the collected liquid product when methane is present indicates that methane existence might facilitate ethanol aromatization. Moreover, combined with the increased carbon number in the formed aromatics from CH4 run when H2 run is referred and zero liquid formation from CH4-alone test as well as more prominent endothermic feature of methane run and more importantly the notably increased 13C signals in 13C NMR spectra of the liquid product collected during ethanol conversion under 13CH4 environment, all the observations suggest that methane might be activated nonoxidatively and converted into higher hydrocarbons, preferentially into aromatics if suitable catalyst is charged under the assistance of co-existing oxygenated hydrocarbon. The reported synergetic effect could potentially lead to the more economic utilization of abundant natural gas and cellulosic ethanol.

Selectively catalytic upgrading of bio-oil to aromatic hydrocarbons over Zn, Ce or Ni-doped mesoporous rod-like alumina catalysts

Zn, Ce or Ni metal was doped on mesoporous rod-like Al2O3 prepared by using cationic surfactant cetyl-trimethyl ammonium bromide (CTAB) assisted hydrothermal method for in-situ catalytic upgrading of bio-oil derived from the fast pyrolysis of sunflower stalk. The morphology, crystal structure, surface area, reduction behaviour and acidity of the as-prepared catalyst were characterized. Uniform rod-like γ-Al2O3 particles with a surface area as high as 412m2/g and an average mesopore diameter of 3.51nm were obtained at a CTAB/Al molar ratio of 0.5 and Zn, Ce or Ni metal was found to be able to homogeneously disperse on it. The catalysts with 2.5wt.% metal (Zn, Ce or Ni) loading amount exhibited the high catalytic activity and selectivity for upgrading of bio-oil with high content of oxygenated components to aromatic hydrocarbons, especially benzene, toluene and xylene (BTX). The total relative maximum hydrocarbon amount of 92% in the upgraded bio-oil was obtained by using 2.5wt.% Ni/Al2O3. Four-cycle reusability test indicated that the metal-doped microporous rod-like γ-Al2O3 alumina catalysts had long-term stability in their performance. Moreover, the regeneration of spent catalysts (4th reuse) by calcination at 650°C in air for 30min recovered their activity perfectly. It is expected that such metal-doped rod-like alumina catalysts can be applied as bio-oil upgrading catalysts in a practical process.

Effects of exposure to zinc oxide nanoparticles in freshwater mussels in the presence of municipal effluents

Zinc oxide (nano-ZnO) nanoparticles are used in the production of transparent sunscreens and cosmetics, which are released into surface waters and municipal wastewater effluent. The purpose of this study was to examine the toxicity of nano-ZnO in the presence of municipal effluents to freshwater mussels Elliptio complanata. Mussels were exposed for 21 days at 15 o C to nano-ZnO and ZnCl2 in the presence of 10 % dilution of primary-treated municipal effluent. After the exposure period and 24-h depuration step, mussels were analyzed for total Zn in gills and digestive gland, free Zn, metallothioneins (MT), oxidative stress (glutathione S-transferase and LPO), endoplasmic reticulum stress (heat shock proteins and protein ubiquitination) and genotoxicity. The data revealed that although total Zn loadings did not change with these treatments, Zn levels in digestive gland were elevated in mussels exposed to nano-ZnO but not with ZnCl2 in the presence of municipal effluent. Free Zn levels in the gills were elevated in mussels exposed to the municipal effluent, but decreased in mussels exposed to nano-ZnO. MT in digestive gland showed a similar pattern and was negatively associated with free and total Zn. GST activity was significantly reduced by both nano-ZnO and municipal effluent and was negatively correlated with MT levels, suggesting the involvement of MT in the sequestration of reactive oxygen species. Discriminant function analysis showed that the municipal effluent related effects differed from the unexposed mussels and nano-ZnO exposed mussels in terms of the following responses: free Zn in gills and digestive gland and GST activity. Nano-ZnO related effects also involved GST activity, MT and protein ubiquitination, which suggests a combination of oxidative stress and reticulum endoplasmic stress. In respect with oxidative stress, the oxidative properties of nano-ZnO and ZnCl2 are dampened in the presence of the municipal effluent.

Synthesis promotion and product distribution for HZSM-5 and modified Zn/HZSM-5 catalysts for MTG process

In this study presented here, attempt is made to development of active zeolite base catalyst for gasoline production in methanol to gasoline (MTG) catalytic process based on wet impregnation technique. Synthesis and improvement methods for ZSM-5 zeolite are essential for a wide variety of different reactions in the chemical industry. In this regard, HZSM-5 and promoted Zn/HZSM-5 samples are prepared. HZSM-5 is synthesized by NaOH treatment and then it is promoted using wet impregnation technique. Distribution of hydrocarbons, which produced in catalytic reaction of methanol to gasoline process, are reviewed over synthesized HZSM-5 and promoted samples with Zinc (Zn) element in a fixed-bed continuous flow reactor. The reaction is performed with weight hourly space velocity (WHSV) equal to 4 (gmethanol)·(gcatalysth)−1, at ambient pressure and 370°C. The zeolite samples after preparation are characterized by XRD, SEM, TPD-NH3 and N2 adsorption/desorption isotherms tests. We have finally managed to identify optimized Zn impregnated catalyst (Zn/HZSM-5) that is exhibited good improvements in liquid hydrocarbons production compared to other prepared samples. Optimized sample is prepared with Zn loading equal to 0.75wt.%. For optimized sample, the results showed that in gas phase, produced C5+ component is increased; in addition, produced dimethyl ether and unreacted methanol are decreased compare to other prepared samples. Also in liquid phase, produced xylene and alkyl aromatic components are increased about 9.33%; in addition yield of produced hydrocarbons (produced gasoline) are increased. Also, 30% increase in the weight of oil cut over optimized sample is observed.

Contamination, toxicity and risk assessment of heavy metals and metalloids in sediments of Shahid Rajaie Dam, Sefidrood and Shirinrood Rivers, Iran

In this paper, the heavy metals and metalloids (As, Cd, Co, Cr, Ni, Cu, Pb and Zn) levels were studied to investigate their contamination and ecological effects in surface sediments of Shahid Rajaie Dam Lake and two major upstream rivers. Contamination factor and modified degree of contamination values indicate a very low to considerable contamination effects for the studied sediments while pollution load index indicates no pollution (except five stations). The comparison of selected elements concentrations with sediment quality guidelines reveal that the average concentration of As, Cr and Ni in the present sediments is higher than threshold effect level. In addition, Ni shows higher concentration than probable effect level and effect range low values. These sediments based on PELQ and ERMQ calculations, for Cr, As, Cd, Zn, Cu, Ni and Pb are slightly toxic. The result of enrichment factor evaluation similarity to principal component analysis indicates that the main source of Pb, Cd, and Zn for 15.38–42.3 percentages of samples is anthropogenic. PC1 agrees with the measured enrichment factor suggesting a geogenic source for Cu, Mn, As, Cr, Al, Co, Ni and Sc in the sediment samples. Higher positive loadings of P with Ni and Co for a small number of sediment probably indicate amplified concentration due to anthropogenic sources such as application of phosphorus fertilizers in the agricultural lands. High positive loading of Pb, Zn and Cd with organic carbon (OC) and clay reveals a significant role of OC and clay in the dissolution and distribution of Pb, Zn and Cd in the dam’s lake sediments. In summary, the present study has provides a practical baseline data for the long-term monitoring of heavy metals pollution in the study area.

Influence of the state of Zn species over Zn-ZSM-5/ZSM-11 on the coupling effects of cofeeding n-butane with methanol

Combination of the exothermic methanol aromatization with the endothermic n-butane aromatization provides a good way to meet the increasing demand for aromatics. Here, a series of Zn-ZSM-5/ZSM-11 catalysts were prepared with different introduction methods. The influence of location and state of Zn species on the coupling effects of cofeeding n-butane with methanol were investigated in detail. UV–vis, H2-TPR and XPS spectra were applied to reveal the state of the Zn species on different catalysts. Quantitative results of NH3-TPD and Pyridine-FTIR were provided to compare the acidity changes of the catalyst after Zn loading. Physical mixing method led to high portion of bulk ZnO particles outside the channel which could promote the formation of C2C4 light alkane in cofeeding reaction. Ion exchange and impregnation modes were beneficial for the formation of ZnOZn bridging species in the micropore channel. ZnOZn bridging species was found to increase the promoting effect of cofeeding n-butane with methanol on aromatics selectivity.