High Aluminum Content Research Articles

Fly ash-based frit as a sintering aid for ceramic body

Coal fly ash is characterized by high silica and alumina contents, making it suitable as a raw material for alumosilicate ceramics. However, direct use of fly ash reveals obstacles such as high porosity, black core, cracking, and swelling. This work synthesized frit by melting a mixture of fly ash, quartz, limestone, and soda. TG-DSC analysis showed that the glass transition point of the frit occurs at approximately 600 degrees Celsius. Ceramic bodies from raw mixes containing various frit amounts were prepared and characterized. The results showed that with 4% being frit, the firing temperature could be reduced by 30 degrees Celsius, along with decreased water absorption and increased flexural strength. Besides, no swelling, cracks, or black cores occur. These observations indicate that fly ash-based frit is viable a sintering aid in ceramic production.

Effects of clay and fireclay addition on the properties of magnesia–forsterite–spinel refractories synthesized at different firing temperatures

This study investigates the effects of adding clay and fireclay on the physical and mechanical properties of magnesia-based refractories such as contraction, bending strength, bulk density, and apparent porosity. Domestic raw materials were used for the preparation of samples fired at 1350, 1450, and 1550 °C for 2 h. Adding clay exhibited no significant effect on the density and porosity, whereas adding fireclay had a remarkable influence on the shrinkage. Nevertheless, the effects of clay and fireclay on the strength of magnesia were unnoticeable. X-ray diffraction results showed that, after firing, the main phase compositions of the samples with clay addition were periclase and forsterite. Adding fireclay led to the synthesis of magnesite spinel, which can be attributed to the high alumina content. Based on scanning electron microscopy, no liquid phase was formed indicating that the sintering was a solid-state evolution with the synthesis of forsterite.

Exploring the local environment of the engineered nanoclay Mica-4 under hydrothermal conditions using Eu3+ as a luminescent probe

High charge mica Na4Al4Si4Mg6O20F4, Mica-4, is a promising candidate as a filling material to immobilize high-level radioactive waste in deep geological repositories due to its extraordinary adsorption capacity. In contrast to traditional clay materials, the structural composition of this mica, with a high content of aluminum in the tetrahedral sheet, enhances its chemical reactivity, favoring the formation of new crystalline phases under mild hydrothermal conditions, and thus providing a definitive isolation of the radionuclides in the engineered barrier. Moreover, this synthetic clay has some features that allow its use as an optical sensor by doping with luminescent rare earth cations such as Eu3+. In this paper we discuss the local structure of the nanoclay Mica-4 using Eu3+ as a local probe to track the physical and chemical modifications under hydrothermal conditions. For that purpose, a set of hydrothermal experiments has been carried out heating Mica-4 and an aqueous Eu(NO3)3 solution in a stainless steel reactor at different temperatures and times. Optical properties of the as-treated samples were characterized by spectroscopic measurements. The fine peak structure of emission and the relative intensity of different Eu3+ transitions as well as the luminescence lifetime have been correlated with the structure and composition of this nanoclay, and the interaction mechanisms between the lanthanide ions and the clay mineral at different temperatures and times. Special attention has been paid to understanding the role of the aluminum content, which may act as either an aggregating or dispersing agent, in the optical features and reactivity of the system.

Enhancement of 2DEG effective mass in AlN/Al0.78Ga0.22N high electron mobility transistor structure determined by THz optical Hall effect

We report on the free charge carrier properties of a two-dimensional electron gas (2DEG) in an AlN/AlxGa1–xN high electron mobility transistor structure with a high aluminum content (x = 0.78). The 2DEG sheet density Ns=(7.3±0.7)×1012 cm−2, sheet mobility μs=(270±40) cm2/(Vs), sheet resistance Rs=(3200±500) Ω/◻, and effective mass meff=(0.63±0.04)m0 at low temperatures (T=5 K) are determined by terahertz (THz) optical Hall effect measurements. The experimental 2DEG mobility in the channel is found within the expected range, and the sheet carrier density is in good agreement with self-consistent Poisson–Schrödinger calculations. However, a significant increase in the effective mass of 2DEG electrons at low temperatures is found in comparison with the respective value in bulk Al0.78Ga22N (meff=0.334 m0). Possible mechanisms for the enhanced 2DEG effective mass parameter are discussed and quantified using self-consistent Poisson–Schrödinger calculations.

Effects of Basicity and Al2O3 Content on Viscosity and Crystallization Behavior of Super-High-Alumina Slag

The CaO-SiO2-MgO-Al2O3 slags with high alumina content are widely applied in various pyrometallurgical processes. However, for super-high-alumina slags, especially for those with alumina content of more than 25 wt%, there is a lack of relevant studies about the properties of slag. The melting behavior, viscosity, structural property, and crystallization behavior of high-alumina slag with the fixed MgO content of 11.13 wt% and Al2O3 content from 27.61 wt% to 40 wt% were investigated. The results revealed that the liquidus temperatures and complete solidification temperatures of slag increased with the increasing binary basicity and Al2O3 content. The melting temperature and viscosity of the CaO-SiO2-11.13wt%MgO-Al2O3 slag system increased with the increasing basicity from 0.8 to 1 and Al2O3 content from 27.61 wt% to 40 wt%. The increase in Al2O3 caused the formation of high-crystallinity and high melting point materials in the slag, such as spinel and Åkermanite. A large number of non-uniform phases could quickly crystallize out of the solids present in the slag melt, thereby increasing the slag viscosity and deteriorating the fluidity of the slag.

Effect of Municipal Solid Waste Incineration Fly Ash on the Mechanical Properties and Microstructure of Geopolymer Concrete.

Geopolymers are environmentally friendly materials made from industrial solid waste with high silicon and aluminum contents, and municipal solid waste incineration fly ash (MFA) contains active ingredients such as Si, Al and Ca. According to this fact, a green and low-carbon geopolymer concrete was prepared using MFA as a partial replacement for metakaolin in this study. The mechanical properties of the MFA geopolymer concrete (MFA-GPC) were investigated through a series of experiments, including a compressive strength test, splitting tensile strength test, elastic modulus test and three-point bending fracture test. The effect of the MFA replacement ratio on the microstructure of MFA-GPC was investigated by SEM test, XRD analysis and FTIR analysis. MFA replacement ratios incorporated in GPC were 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40% by replacing metakaolin with equal quality in this study. In addition, toxic leaching tests of MFA and MFA-GPC were performed by ICP-AES to evaluate the safety of MFA-GPC. The results indicated that the mechanical properties of MFA-GPC decreased with the increase of the MFA replacement ratio. Compared with the reference group of GPC without MFA, the maximum reduction rates of the cubic compressive strength, splitting tensile strength, axial compressive strength, elastic modulus, initiation fracture toughness, unstable fracture toughness and fracture energy of MFA-GPC were 83%, 81%, 78%, 93%, 77%, 73% and 61%, respectively. The microstructure of MFA-GPC was porous and carbonized; however, the type of hydrated gel products was still a calcium silicoaluminate-based silicoaluminate gel. Moreover, the leaching content of heavy metals from MFA-GPC was lower than that of the standard limit. In general, the appropriate amount of MFA can be used to prepare GPC, and its mechanical properties can meet the engineering requirements, but the amount of MFA should not be too high.

Thermodynamic substantiation of compositions of silicon aluminium alloys with increased aluminium content in Fe-Si-Al system

A priority direction of ferrous metallurgy development is to increase in output of the high quality metal and metal products of new assortment. One of the methods to improve a quality of steels is to involve of complex alloys based on aluminum, silicon, manganese, etc. for their output. They are necessary as deoxidizing agents and alloying additives. This paper considers the possibility of the thermodynamic substantiation of the aluminum solubility in the ferrosilicon-aluminum complex alloy (FeSiAl) on the basis of their phase diagrams using the osmotic coefficient of the Bjerrum-Guggenheim. Methodology used is based on the theoretical studies of the phase equilibria using the Bjerrum-Guggenheim concept. It includes a set of computer programs in C# language (C sharp) designed to evaluate a deviation scope of properties of a real system from the ideal one. Criterion for evaluation is an osmotic coefficient of the Bjerrum-Guggenheim. The pattern of change in an osmotic coefficient of the Bjerrum-Guggenheim on the ratio of activity of components in the ideal liquid and solid phases (positive Фi <1 or negative Фi >1) under the boundary forming conditions of crystallization regions of phases related to the melting ferrosilicon-aluminum processes is a direct proof of the possibility to use it as a metal reducing agent. The calculated mathematical dependences of the osmotic coefficient of the Bjerrum-Guggenheim permit us to determine the crystallization temperature of the ferrosilicon-aluminum alloy. The alloying process with rich aluminum content is observed at this temperature. The dependence diagrams of an osmotic coefficient of the Bjerrum-Guggenheim of a crystallizing component on the ratio of its activity in the liquid and solid phases demonstrated that a temperature rise leads to strong negative deviations in silicon properties, and thus to its good mixability in the melt with iron and aluminum. Compositions of silicon-aluminum alloys with high aluminum content in the ferrosilicon-aluminum complex alloy (FeSiAl) were determined on the basis of their phase diagrams using the osmotic coefficient of the Bjerrum-Guggenheim with iron content of 12-37%, aluminum 20-25% and silicon 68-38%. The received theoretical results permit to determine conditions which give the maximum possible aluminum assimilation with the ferrosilicon-aluminum melts supplied from the high-ash coal in the melting process of this metal in the ore-thermal furnaces. Thus it is a direct method to develop the output technology of the complex alloys.

Aluminum sulphate-assisted stepwise dealumination of OSDA-free low-silica chabazite for methanol-to-olefin reaction

The synthesis of chabazite (CHA) aluminosilicate without organic structure-directing agent (OSDA) is a green process, but producing the CHA zeolite with excess acid sites, structural instability and limited applications due to a high aluminum content. Therefore, it is meaningful to develop an effective dealumination method to partially remove the framework aluminum atoms from the OSDA-free low-silica CHA zeolite. A novel stepwise dealumination and stabilization strategy through the subsequent treatment of Al2(SO4)3, H2O, HNO3 and NH4F was developed, which not only increased the Si/Al ratio from 2.4 to 5.0, but also stabilized the framework structure. Simultaneously, the removal of Al atoms optimized the acidity, introduced mesopores into the CHA framework and enhanced the diffusion property. Compared with low-silica CHA, the obtained high-silica CHA zeolite displayed attractive catalytic performance in methanol-to-olefin (MTO) reaction, showing a methanol conversion above 80% for more than 360 min with a maximum selectivity of 87% for low olefins (C2= - C4=).

Assessment of Potentially Toxic Elements in the Urban Soil and Plants of Kirkuk City in Iraq

Kirkuk city is known for its industrial activities, especially oil and cement production, as well as its road traffic. The aim of this study was to assess potentially toxic elements (PTEs) in the soil and plants from urban areas by measuring pollution indices and estimating the effect that this pollution has on the environment. Leaf and soil samples were taken from 10 different locations in Kirkuk. These samples were pre-treated using the acid digestion method and concentrations of 12 elements were determined using inductively coupled plasma mass spectrometry (ICP-MS). The results indicate a high content of aluminum and magnesium (mg/kg) in the soil samples from all study sites. For leaf samples, the results showed a moderate to low amount of magnesium and aluminum. Based on our results, the PTE concentrations were found in the following order—Mg > Al > Ni > Cu > Cr > Pb > Co > As > Se > Cd > Hg > Ti—in leaf samples from all 10 study sites. However, in the soil samples, PTE concentrations were in the following order—Mg > Al > Cr > Ni > Cu > Pb > Co > As > Se > Ti > Cd > Hg—from all study sites. Pollution indices showed a moderate level of contamination of Pb, Cd, and Ni, and a high level of contamination of As and Hg in plant and soil samples from all study sites in Kirkuk city.

Groundwater Pollution Model and Diffusion Law in Ordovician Limestone Aquifer Owe to Abandoned Red Mud Tailing Pit

Red mud is a strong alkaline solid waste pollutant produced in the process of aluminum smelting, which causes great pollution to the regional groundwater environment due to its high content of fluorine and aluminum and high concentration of strong alkali. In this study, fluoride ion was selected as the model contaminant, and a numerical model of the groundwater flow field and solute transport was developed using GMS software to simulate and analyze the migration patterns of fluoride contaminants caused by the red mud pit for the fractured karst geohydrological conditions. The results demonstrated that the groundwater model and flow pattern were mainly controlled by atmospheric precipitation recharge, given flow boundary conditions and leakage of rivers and drains. When the concentration of fluorine pollutants in the red mud yard was 60.0 mg/L, the maximum migration distance of F− in the groundwater of the ordovician limestone aquifer was 473, 1160, 1595 and 1750 m after 1, 5, 10 and 15 years of bottom leakage, and the additional transport distances were 687, 435 and 155 m every 5 years, respectively. The range of F− pollution plume was 0.37 km2, 1.15 km2, 1.95 km2 and 2.14 km2, respectively and the range of newly added pollution plume was 0.78 km2, 0.80 km2 and 0.19 km2, respectively, every five years. Both indicated that with the extension of time, the migration and diffusion rate of pollutants slow down, and the diffusion volume increased first and then decreased. The F− pollution plume spread from the red mud pit to the northeast, which was consistent with the flow of groundwater. The high-concentration pollution plume was mainly distributed in the Ordovician limestone fractured aquifer in the northeast. This study revealed the migration law of red mud pollutants, and provided a scientific decision-making basis for the prevention and control of red mud groundwater pollution in the future.

PROSPECTS FOR CREATING SURFACE LAYERS OF DETA-LEU WITH INCREASED TRIBOLOGICAL CHARACTERISTICS USING GAS-DYNAMIC FILLING

The article presents the results of the analysis of antifriction materials based on tin and lead, copper, aluminum, plastics. The advantages and disadvantages of one or another antifriction material, as well as the possibility of their application on the surface of parts by the method of cold gas-dynamic spraying, are shown. The use of liquid and solid anti-friction materials as lubricating oils is considered. Considerable attention has been paid to materials with the same crystal structure as graphite, now known as two-dimensional (2D) materials. Among these 2D materials, the most studied materials are MoS2 and a carbon-based compound, including graphite and graphene. The scheme of interaction of sliding surfaces is considered, including wear, molecular deformation, adhesion, thermal effect and the environment. Analysis of anti-friction materials showed that their application to the surface of parts can be carried out using the process of cold gas-dynamic spraying. The article shows a diagram and type of installation for cold gas-dynamic spraying of antifriction surface layers. For the research, copper-graphite powder with a particle size of 10,7 – 80,8 microns was used. Using the application "Maso central characteristics" of the software "Compass-3D", the mass of the deposited figure as a continuous material for copper-graphite coatings, with a density of ρ1 = 0,0086454 g / mm3, and the porosity of the deposited figure were determined. In the course of the study, it was found that, in comparison with the substrate material AA7075, the sliding friction coefficient was reduced by 47% - 62% for the copper-graphite surface layer. To obtain composite coatings, a mechanical mixture of A30-01 aluminum powder and C01-00 copper was used. The dependences of the coefficients of sputtering of copper and aluminum on the mass content of aluminum in the sprayed mixture at an initial concentration of aluminum of less than 66% are found. The copper deposition rate is higher than the aluminum deposition rate. Both monotonically increase with increasing aluminum concentration until it reaches 61%. At high concentrations of aluminum (more than 66%), the coefficients of deposition of copper, aluminum and their mixtures coincide.

Fabrication method, dielectric properties, and electromagnetic absorption performance of high alumina fly ash-based ceramic composites

Mullite-Al2O3-SiC composites were in-situ synthesized through carbothermal reduction reaction of fly ash (FA) with a high alumina content and activated carbon (AC). The effects of sintering temperature, holding time, and amount of AC on the β-SiC yield, microstructure, dielectric properties, and electromagnetic (EM) absorption performance of the composites in the 2–18 GHz frequency range were studied. The results show that increasing the AC improves the porosities of the composites, with the highest porosity of 56.17% observed. The β-SiC yield varies considerably as the sintering parameters were altered, with a maximum yield of 23% achieved under conditions of 12 wt% AC, 1400 °C sintering temperature, and 3 h holding time. With a thickness of 3.5 mm, this composite has excellent EM absorption performance, exhibiting a minimum reflection loss (RLmin) of -51.55 dB at 7.60 GHz. Significantly, the maximum effective absorption bandwidth (EAB) reaches 3.39 GHz when the thickness is 3.0 mm. These results demonstrate that the composite prepared under ideal conditions can absorb 99.99% of the waves passing through it. Because of the interfacial polarization, conductive loss, and impedance matching of the heterostructure, the synthesized mullite-Al2O3-SiC composites with densities ranging from 1.43 g/cm3 to 1.62 g/cm3 demonstrate outstanding EM attenuation capabilities. Therefore, this study presents a remarkable way of utilizing fly ash to fabricate inexpensive, functional ceramic materials for EM absorption applications.

Forest fire mobilization and uptake of metals by biota temporarily exacerbates impacts of legacy mining

While wildfires are a natural occurrence and ecosystems have evolved with fire, a changing climate is extending the wildfire season increasing the number, size and severity of fires in the western United States. In 2018, wildfire consumed 30% more area in the Western United States than the average ten years prior, and 76% more area than the average twenty years ago. These recent wildfires have impacted communities in the southwestern Rocky Mountains. In 2018, the 416 Fire, burned over 21,000 ha of public and private lands in southwestern Colorado. The 416 Fire is uniquely located in a legacy mine region in Colorado. The fire occurred in the Animas River watershed, which was already recovering from impacts of the Gold King Mine release of 2015. Three years of water quality monitoring after the 416 Fire have demonstrated elevated total and dissolved metal concentrations downstream of the burn area in Hermosa Creek and the Animas River. Following high-intensity rainstorm events, concentrations of metals such as aluminum, cadmium, iron, lead, manganese and zinc were significantly higher compared to pre-fire conditions in the burned watershed, and several metals often exceeded water quality standards for aquatic life. Macroinvertebrate monitoring in the Animas River and the main fire-impacted tributary indicate substantially altered insect communities. Macroinvertebrate tissue samples, with high concentrations of aluminum, iron, lead and nickel provide evidence that metals observed in the water column of fire-impacted streams were transferred to the benthic communities. In contrast, algae tissue from below the fire did not have elevated metals. High sediment volumes with absorbed metals from mineral rich and mined hillsides were transported to the streams and their aquatic ecosystems after the fire. Results from this study highlight the post-fire mobilization of naturally occurring metals to streams that already experience elevated metals from legacy mines, and will help in development of mitigation efforts in downstream communities.

Effect of Mechanical Activation of Al-Ti-B Powder Mixture on Phase Composition and Structure of Al-TiB2 Composite Materials Obtained by Self-Propagating High-Temperature Synthesis (SHS).

In this study, we successfully obtained Al-TiB2 composite materials using self-propagating high-temperature synthesis and preliminary mechanical activation of the initial Al-(Ti + 2B) powder mixture with a high aluminum content (70 wt.%). We investigated the possibility of controlling the structure of synthesis products, in particular, the size and shape of ceramic particles. We examined the effects of the mechanical activation of the initial powder mixture on the structure and particle size of titanium diboride in the synthesis products. We proposed a mechanism of structure formation in the synthesis products obtained by SHS using the method of preliminary mechanical activation of the initial mixture. We found that mechanical activation for 60-180 s led to the formation of isolated TiB2 particles of prolate and irregular shape. The average particle size of TiB2 in the synthesis products was 0.77 (after 60 s of mechanical activation) and 1.5 µm (after 180 s of mechanical activation), respectively. An increase in the duration of mechanical activation to 900 s led to the formation of an island (skeletal) structure, in which there were interconnected aggregates and isolated particles of titanium diboride. The average size of these particles was 4.3 µm.

Alkali-Activated Materials with Pre-Treated Municipal Solid Waste Incinerator Bottom Ash

This study presents the results of an experimental campaign on the use of municipal solid waste incinerator bottom ash (MIBA) and fly ash (FA) as precursors for the production of alkali-activated materials. MIBA was subjected to a pre-treatment stage in response to two issues: high metallic aluminum content, which reacts in a high pH solution, releasing hydrogen; and low amorphous content of silica-, aluminum- and calcium-bearing phases, which translates into a limited formation of reaction products. The proposed pre-treatment stage oxidizes most of the metallic aluminum fraction and compensates for the low reactivity of the material via the formation of additional reactants. Different combinations of MIBA and FA were tried—mass-based ratios of 0/100, 25/75, 50/50, 75/25, and 100/0 for MIBA/FA. Two mix designs of the alkaline activator with sodium hydroxide and sodium silicate were evaluated by varying the Na2O/binder and SiO2/Na2O ratios. These mortars were tested in the fresh and hardened state. The results showed that the pre-treatment stage was effective at stabilizing the dimensional variation of MIBA. Despite the lower reactivity of MIBA, mortars with 50/50 of MIBA/FA presented a maximum 28-day compressive strength of 25.2 MPa, higher than the 5.7 MPa of mortars made with MIBA only.

Effect of Low-CTE Oxide-Dispersion-Strengthened Bond Coats on Columnar-Structured YSZ Coatings

Thermal barrier coatings (TBCs) are commonly used to protect gas turbine components from high temperatures and oxidation. Such coatings consist of ceramic top coats and metallic bond coats. The mismatch in thermal expansion of the top coat, the bond coat and the component material is one main factor leading to the failure of the coating system. Columnar-structured top coats offer an enhanced tolerance to the strain during thermal cycling. On a flat bond coated surface, these TBCs reach higher thermal cycling performance. However, on rough surfaces, as used for thermal spray coatings, the performance of these thermal barrier coatings seems to be restricted or even stays below the performance of atmospheric-plasma-sprayed (APS) thermal barrier coatings. This low performance is linked to out-of-plane stresses at the interface between the top coat and the bond coat. In this study, a thin additional oxide-dispersion-strengthened (ODS) bond coat with high alumina content provides a reduced mismatch of the coefficient of thermal expansion (CTE) between the top coat and the bond coat. Columnar suspension plasma sprayed (SPS), yttria-stabilized zirconia (YSZ) TBCs were combined with low-CTE ODS bond coats. The behavior of these TBCs was characterized with respect to thermal cycling performance and degradation in a burner-rig facility. The comparison showed an up-to-four-fold increase in the performance of the new system.

Maternal offloading of arsenic and other trace elements in Peruvian fur seals

AbstractThe maternal transfer of 15 elements was examined in Peruvian fur seal (Arctocephalus australis) dam and pup paired vibrissae (whiskers), serum, and milk samples collected from 2009 to 2019. Pup vibrissae, grown in utero, represented gestational transfer, while milk represented lactational transfer. Element concentrations, except arsenic, were highest in vibrissae compared to serum and milk for both dams and pups. Mean arsenic concentrations in pup vibrissae (0.44 μg/g) and milk (0.41 μg/g) were twice as high as dam vibrissae concentrations (0.19 μg/g) and nearly ten times higher than dam (0.06 μg/g) and pup serum (0.04 μg/g) concentrations. Mean arsenic concentrations from 2011 to 2019 increased in dam vibrissae (0.026 μg/g to 0.262 μg/g) and milk (0.361 μg/g to 0.484 μg/g). Pup vibrissae had significantly higher concentrations for 11 of the 15 elements analyzed compared to dam vibrissae, suggesting that element transfer is occurring through recent exposure and remobilization of elements from dam body stores. Potentially high concentrations of aluminum, arsenic, copper, and lead in pup tissues may impact their survival and population health. The impact of regional mining activities can contribute to elevated trace elements through runoff and pose a possible threat to local marine environments.

Aluminum Bioaccumulation in Reed Canary Grass (Phalaris arundinacea L.) from Rivers in Southwestern Poland.

This study aimed to determine aluminum levels in reed canary grass Phalaris arundinacea L.) in rivers in southwestern Poland—Bystrzyca, Strzegomka, and Nysa Szalona, together with their tributaries. The samples were collected in spring and autumn 2015–2018. The highest amounts of aluminum were recorded in the Nysa Szalona, and the lowest in the Bystrzyca. During the four-year cycle of studies, the highest values were recorded in the last year, and the lowest in the first year. The highest amounts of aluminum were found in all three rivers in the lowland tributaries. In the main rivers, higher amounts of aluminum were found at the mouth of the Nysa Szalona and Strzegomka reservoirs, while the opposite situation was found for the Bystrzyca. Higher aluminum contents were recorded in autumn than in spring, and the values of BCFW (aluminum bioaccumulation factor in relation to water) and BCFB (aluminum bioaccumulation factor in relation to bottom sediments) coefficients were also higher. The MPI (metal pollution index) was arranged in a series: Bystrzyca < Strzegomka < Nysa Szalona, while the degree of pollution was high for Bystrzyca and very high for the other two rivers. The variability in Al levels may be attributed to pollution level in the catchments, but also to successive modernization works carried out in the beds of the main rivers and their tributaries. All these works were carried out in a variable way and often covered only a fragment of the riverbed; therefore, the consequences of activity may have been visible in the catchment but not necessarily in the same vegetation cycles.

Nutritional and phytochemical compositions and their interrelationship in succulent pods of pigeonpea (Cajanus cajan [L.] Millsp.)

Malnutrition remains one of the major human health issues affecting millions of people in sub-Saharan Africa (SSA). Hence, the objective of this study was to quantify the nutritional and phytochemical compositions of immature pods of pigeonpea genotypes to select promising lines with unique nutritional quality for production and cultivar development. Seven preliminarily tested and identified pigeonpea genotypes were grown under field conditions using a randomized complete block design with three replicates to quantify the nutritional and phytochemical contents in the immature pods. Significant (P ≤ 0.01) genotype effect was detected for the assessed nutritional and phytochemical compositions. Relatively higher contents of iron (15.53 mg/100g), zinc (1.59 mg/100g), magnesium (114.60 mg/100g) and total flavonoid (8.47 mg CE/g) were present in genotype Ilonga_14m1 ICEAP-0054. Higher compositions of beta-carotene (2.84 mg/100g), total phenolics (20.42 mg GAE/g), and vitamin-C (95.84 mg/100g) were detected in genotypes, Mali ICEAP-00046, PigeonP-3018 and Kiboko ICEAP-00932, respectively. Cluster analysis allocated the tested genotypes into three main groups. Significant (P ≤ 0.05) positive correlations were recorded among the assessed nutritional and phytochemical compositions that will allow direct and indirect selection of the evaluated genotypes for nutritional and phytochemical quality improvement. The principal component analysis resolved four components that cumulatively explained 76.85% of the total genetic variation in nutritional and phytochemical compositions among the tested genotypes of pigeonpea. Genotype PigeonP-3021 exhibited high levels of beta-carotene and vitamin C, while Kiboko ICEAP-00932 and PigeonP-3018 had high contents of aluminium, iron, phosphorus and total phenolics. Genotype Ilonga_14m1 ICEAP-0054 had high compositions of zinc, potassium, magnesium, copper and calcium. Unique pigeonpea genotypes (i.e., PigeonP-3021, Kiboko ICEAP-00932, and PigeonP-3018) were identified for quality breeding or direct production with promising nutrient profiles for food and nutrition security.

Recovery of iron from high-iron red mud using suspension magnetization roasting and magnetic separation

• Suspension magnetization roasting and magnetic separation process treat red mud effectively. • Alumogoethite [Al x Fe (1- x ) ]OOH transformed into Fe-Al spinel phase Fe(Al,Fe) 2 O 4 . • Al-containing magnetite combined part of Fe(Al, Fe) 2 O 4 enter into the iron concentrate. • The saturation magnetization and specific magnetic susceptibility are enhanced via magnetization roasting. An innovative suspension magnetization roasting followed by magnetic separation process was developed to recover iron from high-iron red mud (HIRM), and the effects of roasting temperature, roasting time, CO concentration and grinding fineness on the recovery of iron were investigated. Under the optimized conditions, determined to be a roasting temperature of 560 ℃, reaction time of 15 min, CO concentration of 30% and total gas-flow rate of 500 mL/min, an iron concentrate assaying 55.44 wt% Fe with an iron recovery of 89.34% was prepared by magnetic separation. X-ray diffraction, chemical phase analysis, vibrating sample magnetometer, and scanning electron microscope were employed to assess the characteristics of red mud, roasted sample and magnetic separation products. The hematite in the red mud was transformed into magnetite during the suspension magnetization roasting, thus the magnetism was significantly enhanced. While, the alumogoethite was transformed into Fe-Al spinel phase Fe(Al,Fe) 2 O 4 , and entered the magnetic concentrate along with the magnetite. In addition, some fine-grained alumina particles were also easy to be wrapped by magnetic agglomerates and entered the magnetic concentrate, resulting in high aluminum content in the iron concentrate.