High Metal Content Research Articles

Simulation of the deasphalting process of crude oils: Models development and extraction conditions analysis

Heavy crude oils are under constant investigation due to light oil exhaustion. So, its use is compulsory to meet the world energy demand. Heavy crude oils present several drawbacks as high content of metals, heteroatoms, and asphaltenes, and, therefore, upgrading processes are becoming essential. A deasphalting process, conventionally used for vacuum residue upgrading, can be an interesting pretreatment to eliminate the heavier phases and ease the crude processing in conventional refining facilities. Most of the models developed for deasphalting simulation show problems to be implemented in simulation software packages. In this work, a versatile deasphalting simulation method is developed, composed by the definition of a synthetic crude oil model, formed by discrete pseudo components, and a deasphalting model approaching the process to a liquid-liquid extraction based on the thermodynamic model modified UNIFAC (Dortmund). Both models were satisfactorily validated. The deasphalting method was used to explore the solvent/crude ratio, extraction temperatures, and alternative solvents in substitution of conventional light paraffins. Higher extraction temperatures did not enhance remarkably the deasphalting process and the optimum solvent to crude ratio depends on the solvent type. Alcohols were found as promising compounds as their use is recommended by some studies and they showed great deasphalting results. • A discrete pseudocomponent-based crude oil model is developed. • A deasphalting model is proposed using a liquid-liquid equilibrium extraction and the modified UNIFAC (Dortmund) model. • The solvent selection is better from extraction yield+asphaltene reduction than from selectivity+partition coefficients. • Alcohols are found as alternative sustainable solvents for deasphalting use.

Release characteristics of arsenic, selenium, lead and transformation of minerals during ashing process of coal

In this paper, two kinds of coal (Baiyinhualignite and coal usinginEzhou Power Plant) were selected to study the occurrence of heavy metals including arsenic (As), selenium (Se) and lead (Pb) in coal and their release behaviors during the ashing process. The influence of ashing conditions on the mineral conversion was also examined by the combination with the changes of minerals in coal. The burn-out temperature of the coal was determined fromthethermalweightlosscurve by extrapolation method, and then the coal sample was ashed according to the National Standard Method of China. The obtained ash samples were characterized by XRD, XRF, and TG-DTG to analyze the change characteristics of coal minerals at different ashing temperatures. The content and occurrence of As, Se and Pb in coal samples were extracted by sequential chemical extraction method. The heavy metals in the ash sample were extracted by HNO3 + HF, and the heavy metal content in the extract was detected by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The results show that the heavy metal in BYH coal is mainly As in the form of sulfide bound state, which leads to the increasing volatility of As with temperature easily. However, the heavy metal in EZ is mainly sulfide-bound Pb, which makes it easy torelease with temperature. Se in coal mainly exists in the form of organic bound state and sulfide bound state. During coal ashing, kaolin is gradually dehydroxylated into metakaolin and finally converted into mullite; pyrite is oxidized to form hematite; gypsum is dehydrated to form anhydrite. The release rate of heavy metals is greatly affected by the combustion temperature during the ashing process. High content of heavy metals in the sulfide bound state results in high release rate with increasing the temperature.

Study of soil properties affected by leachate – A case study at Urali-Devachi, Pune, India

Landfill leachate is created via decomposition of landfill waste transported by water percolation through the soil layers. If the landfill sites are not designed properly then the leachate simply passes through the soil layers. This may create an adverse effect on the engineering properties of soil, as well as on the chemical properties viz. adsorption and retention of heavy metals. In the present study, an experimental work was carried out to examine the effects of landfill leachate contamination on the soil properties viz. physiochemical and geotechnical of an active Municipal Solid Waste (MSW) dumping site located near Pune city, India. The soil samples were collected from three different locations (at 150 m spacing) and leachate was collected from the treatment plant, located in the premises of the dumping site. The test result shows that the leachate containing the highest concentration of metals, Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). The soil sample in close proximity to the MSW dumpsite is most contaminated as compared to the furthermost soil samples, because of the high contents of organic pollutants and heavy metals. The present study clearly indicates that if the leachate is permitted to drain straightway into the surface water or infiltrates in to the groundwater it can cause adverse effect on human health and environment.

EVIDENCES OF WEATHERING OF IRON-NICKEL AND TROILITE IN THE GRUZ'KE Н4-TYPE CHONDRITE

Terrestrial weathering of the Gruz'ke chondrite was investigated by considering its initial chemical, structural, and mineralogical characteristics. The spread of corrosion and degree of alteration were related to the high content of Fe-Ni metal, the phase inhomogeneity and the different concentration of Ni in the metal, as well as, the shock metamorphism features, and the residence time of the meteorite sample in a soil environment. The formation of secondary oxide veins and oxide rims, consisting of iron hydroxide pseudomorphs was caused by the selective corrosion of kamacite α-(Fe,Ni), compared to taenite γ-(Fe,Ni) and troilite FeS. A spatial relationship between shock metamorphism features, namely areas of plastic deformation, shock heating and weathering of the meteorite matter, has been confirmed. A secondary Ni-enriched phase, which contains 71.34 to 72.94 wt.% Ni, probably corresponds to awaruite (Ni2Fe to Ni3Fe) or native nickel. This phase is described for the first time as corrosion product of Fe-Ni grains in the Gruz'ke chondrite. We assume that this phase was formed during the alteration of Fe-Ni metal. Fe was removed from the meteorite metal during the corrosion process, while sulfur was introduced. The formation of iron hydroxide pseudomorphs caused changes in primary chemical and structural properties of some crystals of nickel-iron metal and troilite. Thus, the use of weathered mineral grains to interpret the pre-terrestrial conditions of the chondrite matter formation and evolution is limited. In spite of the changes in chemical and mineral composition, the corrosion products of nickel iron and troilite have consistent low chlorine content.Therefore we assume that the akaganeite β-FeO(OH,Cl) secondary phase is unlikely to form. It will prevent further alteration of the Fe-Ni metal and ensure long-term storage and preservation of the meteorite sample for further laboratory research and storage in the museum collection.

Understanding methanol dissociative adsorption and oxidation on amorphous oxide films.

Interactions between a transition metal (oxide) catalyst and a support can tailor the number and nature of active sites, for instance in the methanol oxidation reaction. We here use ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify and compare the surface adsorbates that form on amorphous metal oxide films that maximize such interactions. Considering Al(1-x)MxOy (M = Fe or Mn) films at a range of methanol : oxygen gas ratios and temperatures, we find that the redox-active transition metal site (characterized by methoxy formation) dominates dissociative methanol adsorption, while basic oxygen sites (characterized by carbonate formation) play a lesser role. Product detection, however, indicates complete oxidation to carbon dioxide and water with partial oxidation products (dimethyl ether) comprising a minor species. Comparing the intensity of methoxy and hydroxyl features at a fixed XPS chemical shift suggests methanol deprotonation during adsorption in oxygen rich conditions for high transition metal content. However, increasing methanol partial pressure and lower metal site density may promote oxygen vacancy formation and the dehydroxylation pathway, supported by a nominal reduction in the oxidation state of iron sites. These findings illustrate that AP-XPS and mass spectrometry together are powerful tools in understanding metal-support interactions, quantifying and probing the nature of catalytic active sites, and considering the link between electronic structure of materials and their catalytic activity.

КАЧЕСТВЕННЫЕ И КОЛИЧЕСТВЕННЫЕ ХАРАКТЕРИСТИКИ ПОЧВ И СВАЛОЧНОГО ГРУНТА ПОЛИГОНА ТВЕРДЫХ КОММУНАЛЬНЫХ ОТХОДОВ

The largest SMW landfill in the Irkutsk region is that in the Irkutsk city. In 2014, high heavy metal contents were registered in landfill soil samples taken at the landfill site, and it was proposed to perform monitoring outside the landfill in 2019 and determine the pollution distribution area. In this article, the comparative analysis of the degree of heavy metal pollution of the landfill soil and soil from sanitary protection zone is presented. It was established that the studied landfill soil refers to extremely hazardous soils with heavy metal contents that are up to 68 times higher than TLV. Soil samples from the landfill-affected area also contain heavy metals in high concentrations. The manufacturing supervision of the SMW landfill should include the continuous observation of the soil, water, and air condition in the zone of possible impact of the landfill for taking timely environmental protection measures and preventing further negative impact of the landfill on the ecosystem.

Arsenic speciation and sorption in acid mine drainage and the polluted water of the Kosva river basin, Russia

Acid mine drainage (AMD) of the abandoned coal mines of the Kizelovsky coal basin (the Urals, Russia) is one of the worst natural disasters in the region. Acidic sulphate waters with a high content of metals freely flow into the surface water bodies. Arsenic, found in elevated concentrations in AMD, is an element of concern due to its potential toxicity to humans and animals. The aim of this work is determination of chemical speciation of inorganic arsenic in AMD as well as the surface water and groundwater affected by mine drainage, and assessment the natural removal of As from mine drainage due to adsorption on precipitated hydrous ferric oxide (HFO). Geochemical speciation (PHREEQC) revealed that arsenic occurs in all water samples as As(V). Surface complexation model shows that, HFO induced by the natural attenuation process may remove 46–85% of total arsenic in AMD and only 28% in polluted groundwater (on average).

Redispersion strategy for high-loading carbon-supported metal catalysts with controlled nuclearity.

Supported low-nuclearity metal catalysts integrating single atoms or small clusters have emerged as promising materials for diverse applications. While sophisticated synthetic methods provide a high level of nuclearity control in the subnanometre regime, these routes do not fulfil the requirements for translation into industrial practice of (i) effectiveness for high metal contents and (ii) facile scalability. Herein, we present a gas-phase redispersion strategy consisting of sequential C2H2 and HCl treatments to gradually disperse Ru, Rh and Ir nanoparticles supported on commercial activated carbon with metal content up to 10 wt% and initial average sizes of ≈ 1 nm into small clusters and eventually single atoms. Avoidance of nanoparticle surface overchlorination, which hinders C2H2 adsorption, is identified as key for the redispersion process, as demonstrated by the inefficacy of both C2H2–HCl cofeeding and inverse sequence (i.e., HCl first) treatments. Precise size control (±0.1 nm) is enabled by regulating the number of C2H2–HCl cycles. Detailed characterisation by X-ray absorption spectroscopy, electron paramagnetic resonance and time-resolved mass spectrometry reveals that the redispersion occurs via a layer-by-layer mechanism. Specifically, the migration of surface chlorinated metal species to the carbon support is induced by the C2H2 treatment, depleting accessible surface Cl atoms, while the subsequent HCl treatment rechlorinates the cluster surface. The strategy paves the way for the generation of high-density metal sites with tuneable nuclearity for tailored applications.

Assessment of heavy metal contamination in soil around Piyungan Landfill, Yogyakarta, Indonesia

One of the negative impacts of the landfill as solid waste disposal is soil contamination by heavy metals. This study assessed heavy metals impact, especially Pb, Cu, Zn, and Cd, in the soil in Piyungan landfill, Bantul, Yogyakarta, Indonesia. The assessment was conducted by analyzing 15 soil samples from 25 cm depth in the study area, which was divided into three-zone. The study results showed that generally, the highest content of metals was found in zone II, which is located near or directly situated in a landfill site. The pollution index (PI) calculated showed in order Cd>Cu>Pb>Zn. The result also indicates that Cd has the highest pollution index and even the highest risk compared to Pb, Cu, and Zn. The eco-risk index (RI) calculation showed that the value was 29 to 70 demonstrating a low class. The result also indicates that the accumulation of heavy metals investigated in this study was normal, and that the ecological risk was relatively low.

Bioaccumulation of Trace Metals for Daily Fish Consumption from Selected Former Tin Mining Ponds in Peninsular Malaysia: A Review on Safety of Fish Consumption

Tin mining was the predominate mining industry in Malaysia, especially during the mid-19th century. Most of the former mining areas have been reused for aquaculture purposes. Fish produced from former mining areas have been misunderstood as a high health risk if consumed due to their likelihood of containing high heavy metal content in their tissue. Therefore, we review national information on trace metals levels in the tissue of fish from selected former mining ponds in Peninsular Malaysia, together with background concentration of trace metals in their surroundings and food security and human health implications. Seven trace metals (Cu, Zn, As, Cd, Pb, Cr, and Ni) were observed in the water column and sediment. Various reports showed that background trace metal concentrations in the former mining area are mostly lower than several established limits (which were used as the main reference), except for the areas that were being treated for secondary use. Trace metal concentrations in the fish tissue also showed the same trend of high concentrations due to improper or unfinished treatment of former mining ponds. In the context of food safety, various local reports have shown that the consumption of aquaculture products from former mining areas over a lifetime is unlikely to cause any harmful effects and hence may be regarded to be safe. However, these findings are restricted due to the limited studies in Peninsular Malaysia. Therefore, extensive study regarding this particular issue is highly recommended

Influence of the Metal Incorporation into Hydroxyapatites on the Deactivation Behavior of the Solids in the Esterification of Glycerol

The effects of the metal incorporation into hydroxyapatites on the deactivation behavior of the solids were examined in the esterification of glycerol (EG) reaction. The introduction of Cu, Co, or Ni ions by ion exchange in calcium-deficient hydroxyapatites resulted in active catalysts for the EG reaction. The metal contents were varied from 2.0 to 17.0%, providing better performances at rather high metal contents. Part of metal species existed in the hydroxyapatite lattice structure and also as isolated Cu2+, Ni2+, and Co2+ entities on the surface, as shown by XPS and EPR. The effects of the reaction temperature, reaction time, and glycerol to acetic acid molar ratios were deeply investigated. The spent solids used in this study were characterized by XRD, FTIR, SEM-EDS, chemical analyses, EPR, and XPS. The Cu2+–OH acid pairs could promote a superior catalytic performance of Cu-containing hydroxyapatites due to the resistance of these solids against leaching of the active species, which is even better than those of Co and Ni-containing counterparts with high metal contents. Cu into hydroxyapatite had a good reusability and long-term utilization for five consecutive cycles of 24 h under a glycerol to acetic acid molar ratio of 0.25 at 80 °C, and longer reaction times provide triacetin formation. This was due to the fact that Cu was stabilized by interacting with Ca, PO4, and OH sites into the hydroxyapatite lattice, being highly active for the EG reaction. The results also revealed that isolated Cu2+ sites played an important role in enhancing the glycerol conversion, intrinsically due to the Cu-containing hydroxyapatites ability to avoid strong adsorption of glycerol oligomers on the catalytic sites.

Estimation of the Pb Content in a Tailings Dam Using a Linear Regression Model Based on the Chargeability and Resistivity Values of the Wastes (La Carolina Mining District, Spain)

The study area is located in the old mining district of Linares–La Carolina (southeastern Spain), the largest global producer of lead between 1875 and 1920. The selected environmental liability is the dam of the Federico mine and the waste that was generated during the flotation process. Geophysical techniques were applied along the slope of the dam, specifically ERT and IP. In total, 26 waste samples were taken along the entire slope of the dam, in which a high metal(oid) content was identified, sometimes much higher than the reference levels established by European and regional legislation for contaminated soils. The concentrations of Pb, As, and Ba stood out, with mean values of 4863 mg·kg−1, 89 mg·kg−1, and 794 mg·kg−1, respectively. Univariate and multivariate statistical analysis could characterize the distribution of the contents of the different elements along the slope, defining the associations and dispersion patterns of the metal(oid)s in the interior structure of the mine wastes. With the results of the Pb content (the most abundant metal in mineral paragenesis), a mathematical model was obtained by linear regression that related the variability of this cation with the variation in electrical resistivity and chargeability obtained by geophysical techniques.

Elemental state of the organism of workers and population as manifestation of adaptation to the technogenic effect of metals: new methodological approaches

The problem of adaptive, prepathological and pathological reactions of the body to the action of exogenous chemicals is closely intersected with the assessment of the norm and its fluctuations. The imbalance of chemical elements in the human body directly affects the functioning of almost all organs and systems, causing significant stress of adaptation mechanisms. In this article we study the elemental state of the human body depending on the physiological state (endocrine pathology and professional contact with heavy metals), analyze the correlation between macro- and microelements and assess the degree of adaptability of the body. In the work the elemental state of the human body, taking into account not only the absolute values of the concentrations of elements in the hair and whole blood was studied, the adaptability of the body according to the indicators of elemental imbalance in the blood and hair of volunteers, individuals with endocrine pathology (autoimmune thyroiditis and type II diabetes mellitus) and for those working in conditions of contact with heavy metals (for jewelers, welders and batterymen) is analyzed. The results of the study indicate that various non-specific adaptation reactions are accompanied by changes in the elemental state of a person. Under the prevailing pathology of the endocrine system (diabetes mellitus or autoimmune thyroiditis), the adaptation of the body was determined as a stage of tension and is associated with the duration of the disease. In persons exposed to professional contact with heavy metals (Mn, Cr, Pb, Ag), adaptation depended on the nature and duration of professional contact with them: the highest tension of adaptation processes was found in jewelers, and the least in welders and batterymen, which is associated with the duration of professional contact with these metals. The high number of connections between the elements indicates the tension of adaptive reactions in people with endocrine pathology and especially in jewelry workers. Adaptation to the high content of metals in the air of welders and batteries due to the longer experience of these workers and adaptation to production conditions with a decrease in the number of correlations between the elements, as a means of reliable operation.

Distribution of nutrients and phosphorus recovery in hydrothermal liquefaction of waste streams

Hydrothermal liquefaction (HTL) of phosphorus (P) rich wastes is a promising technology to recover P in solid form. For the applicability as fertilizer, the HTL solids should contain nutrients, in particular P, in plant available form and low concentrations of heavy metals. In the present study, the fate of P and other nutrients has been studied by performing HTL of four P-rich wastes. The effect of temperature on the distribution of the HTL products and nutrients has been investigated. It was found that up to 100% of the total P can be accumulated in the solid phase. However, the bioavailability of P decreased to 0.6–1% and the concentrations of heavy metals exceeded threshold values for fertilizers. Due to the limited P bioavailability and high contents of heavy metals, the reclamation of P as struvite is also calculated. Based on these estimations, between 42 and 93% of P can be recovered as struvite.

Extraction of Selected Metals from Waste Printed Circuit Boards by Bioleaching Acidophilic Bacteria

Technological innovations and increased demand for electronic devices resulted in production of more and more waste with highmetal content. Worldwide, 50 million tons of WEEE (Waste from Electrical and Electronic Equipment) are generated each year. Giventhe metal content present in electrical waste (e-waste), it is considered to be an urban mine and, if properly treated, can serve as analternative secondary source of metals. Waste printed circuit boards (WPCBs) that constitute approx. 3-5% of WEEE by weight areof particular importance. They contain, on average, 30-40% of metals by weight, with higher purity than in minerals. With environmental and economic benefits in mind, increasing attention is being paid to the development of processes to recover metals and othervaluable materials from WPCBs. The research presented in the article aimed at assessing the usefulness of the biotechnological methodfor leaching of selected metals from e-waste. The results indicate that it is possible to mobilize metals from WPCBs using microorganisms such as Acidithiobacillus ferroxidans bacteria

Synthesis of atomic platinum with high loading on metal-organic sulfide

Synthesis of ultrafine noble metal with sizes down to nanoscale and even atomic scale is of great significance for heterogeneous catalysis. However, the metal loading is usually kept below 2 wt% due to the aggregation tendency at higher metal contents. Herein, by mimicking the multicentered metal sulfur cluster of metalloenzyme, a bioinspired synthesis of isolated noble metal atoms on the metal-organic sulfide (MOS) framework was reported. The sulfur-rich framework featuring [Mo3S7Br6]2− cluster as the building block and dithiol as the linking node was constructed via chemical bonding and employed to support atomic metal species. Remarkably, highly dispersed platinum atoms with a loading amount as high as 18.5 wt% on the underlying sulfur-rich framework could be obtained after reduction. By increasing the number of benzene rings in the dithiol, the pore size and even the wettability of the MOS frameworks could be modulated. The general applicability of the synthesis could also be extended to the synthesis of atomic Pd. Furthermore, the Pt-loaded MOS could serve as the catalyst for selective hydrogenation of phenylacetylene to styrene in both organic solvent and pure water. Density function theory calculation demonstrated that the atomic Pt sites in the sulfur-rich coordination environment could activate H2 molecules and chemoselectively catalyze the semi-hydrogenation of phenylacetylene to styrene through moderately low energy barriers. The metalation of such a versatile MOS framework will shed light on the synthesis of bioinspired catalytic materials with well-defined structures for more diverse applications.

Effects of medical waste incineration fly ash on the promotion of heavy metal chlorination volatilization from incineration residues

High contents of heavy metals and Cl are major challenges for incineration residue disposal. Classification by the Chinese government and the coronavirus disease 2019 pandemic have changed the characteristics of incineration residues, thereby increasing the difficulty of disposal. In this study, medical waste incineration fly ash (MWI FA) was proposed as an additive to promote chlorination volatilization of heavy metals from municipal solid waste incineration fly ash (MSWI FA) and medical waste incineration slag (MWI S). When the mixing ratio of MWI FA to MSWI FA was 1:3, the chlorination volatilization efficiencies of Cu, Zn, Pb, and Cd at 1000 °C for 60 min were 50.2%, 99.4%, 99.7%, and 97.9%, respectively. When MWI FA was mixed with MWI S at a ratio of 1:1, the chlorination volatilization efficiencies of Cu, Zn, Pb, and Cd at 1200 °C for 40 min were 88.9%, 99.7%, 97.3%, and 100%, respectively. Adding MWI FA can replenish Cl in MSWI FA and MWI S while increasing the surface area and forming pore structures by sublimation of NaCl and decomposition of CaSO4, or can reduce the melting point and viscosity by Na2O destroying the glass matrix. Therefore, MWI FA can be co-disposed with MSWI FA and MWI S respectively to enhance the chlorination volatilization of heavy metals.

Trace Element and Isotope Systematics in Vent Fluids and Sulphides From Maka Volcano, North Eastern Lau Spreading Centre: Insights Into Three-Component Fluid Mixing

Back-arc spreading centres and related volcanic structures are known for their intense hydrothermal activity. The axial volcanic edifice of Maka at the North Eastern Lau Spreading Centre is such an example, where fluids of distinct composition are emitted at the Maka hydrothermal field (HF) and at Maka South in 1,525–1,543 m water depth. At Maka HF black smoker-type fluids are actively discharged at temperatures of 329°C and are characterized by low pH values (2.79–3.03) and a depletion in Mg (5.5 mmol/kg) and SO4 (0.5 mmol/L) relative to seawater. High metal (e.g., Fe up to ∼6 mmol/kg) and rare Earth element (REE) contents in the fluids, are indicative for a rock-buffered hydrothermal system at low water/rock ratios (2–3). At Maka South, venting of white smoke with temperatures up to 301°C occurs at chimneys and flanges. Measured pH values range from 4.53 to 5.42 and Mg (31.0 mmol/kg), SO4 (8.2 mmol/L), Cl (309 mmol/kg), Br (0.50 mmol/kg) and Na (230 mmol/kg) are depleted compared to seawater, whereas metals like Li and Mn are typically enriched together with H2S. We propose a three-component mixing model with respect to the fluid composition at Maka South including seawater, a boiling-induced low-Cl vapour and a black smoker-type fluid similar to that of Maka HF, which is also preserved by the trace element signature of hydrothermal pyrite. At Maka South, high As/Co (>10–100) and Sb/Pb (>0.1) in pyrite are suggested to be related to a boiling-induced element fractionation between vapour (As, Sb) and liquid (Co, Pb). By contrast, lower As/Co (<100) and a tendency to higher Co/Ni values in pyrite from Maka HF likely reflect the black smoker-type fluid. The Se/Ge ratio in pyrite provides evidence for fluid-seawater mixing, where lower values (<10) are the result of a seawater contribution at the seafloor or during fluid upflow. Sulphur and Pb isotopes in hydrothermal sulphides indicate a common metal (loid) source at the two vent sites by host rock leaching in the reaction zone, as also reflected by the REE patterns in the vent fluids.

The Effect of Endophytic Talaromyces pinophilus on Growth, Absorption and Accumulation of Heavy Metals of Triticum aestivum Grown on Sandy Soil Amended by Sewage Sludge.

Sewage sludge improves agricultural soil and plant growth, but there are risks associated with its use, including high heavy metal content. In this study, experiments were carried out to investigate the role of endophytic Talaromyces pinophilus MW695526 on the growth of Triticum aestivum cultivated in soil amended with sewage sludge and its phytoremediation ability. T. pinophilus could produce gibberellic acid (GA) and stimulate T. aestivum to accumulate GA. The results showed that inoculation with T. pinophilus boosted plant growth criteria, photosynthetic pigments, osmolytes (soluble proteins, soluble sugars and total amino acids), enzymatic antioxidants (catalase, superoxide dismutase and peroxidase), K, Ca and Mg. On the other hand, it reduced Na, Na/K ratio, Cd, Ni, Cu and Zn in the growth media as well as in the shoot and root of T. aestivum. The results suggest that endophytic T. pinophilus can work as a barrier to reduce the absorption of heavy metals in T. aestivum cultivated in soil amended with sewage sludge.

Influence of water leaching on alkali-induced slagging properties of biomass straw

Deposition or slagging problem caused by the alkali metal species is one of the major obstacles to utilize biomass fuel in combustion and gasification plant. The paper mainly studies the effect of water leaching on alkali-induced slagging properties of corn straw and rice straw. The original mineral form of alkali elements in biomass straw was studied with comparison of low temperature ash of biomass before and after water leaching. The release and transformation of alkali compounds in biomass straw at different temperatures during heating were analyzed with combination of the XRD result of the heated biomass and the chemical composition of the digested samples. The result shows that the potassium in corn and rice straw mainly exists in the form of KNO3, KClO4, K2SO4 and KAlSi3O8, in which KNO3, K2SO4 and KClO4 is mostly removed in water leaching. The fusion temperatures increased after water leaching, especially for rice straw ash, which is a typical sample that the basic compounds are mainly potassium-containing compounds. The decrease of potassium content with temperature in the original corn and rice was because the potassium-containing minerals decomposed and escaped at 25−1000°C. The release of potassium in the range of 400−800°C significantly reduced for corn and rice straw after water leaching, but the potassium content will still decrease above 800°C. The decrease of magnesium content in corn with increasing temperature may be due to the volatilization of magnesium oxide under the action of carbon reduction. For fuels with high alkali metal content after water leaching, the residual alkali metal will still escape and cause deposition or slagging in the furnace, especially in the temperature range above 800°C.