Hydrous Aluminum Research Articles

Adsorption of methyl blue, dichromate, and copper on ettringite under various pH values

Ettringite is a hydrous calcium aluminum sulfate mineral present in cement. In this study, ettringite was synthesized via co-precipitation to remove methyl blue, dichromate, and copper ions from solutions with various pH values. The synthesized ettringite was characterized using scanning electron microscopy, X-ray photoelectron spectrometry, Fourier transform infrared spectroscopy, zeta potential analysis, and the Brunauer–Emmett–Teller method. Equilibrium adsorption experiments were performed using methyl blue and dichromate at pH values ranging from 5 to 11. To avoid precipitation, equilibrium adsorption experiments were performed on copper ions in solutions with pH values of 3, 4, and 5. The adsorption kinetics experiments for each contaminant were performed at pH 5. The results showed that ettringite was successfully synthesized, and calcite might have precipitated during the synthesis process. The point of zero charge was at pH 8.6. The maximum adsorption capacities for methyl blue, dichromate, and copper ions at pH 5 were 406, 321, and 365 mg/g, respectively. The adsorption kinetics fitted the pseudo-second-order model well. The properties of the contaminants affect their equilibrium and rate constants. Ion exchange is regarded as the primary adsorption mechanism, whereas the other mechanisms include complexation, hydrogen bonding, surface precipitation, π-interaction, and van der Waals forces. This study revealed a new adsorbent, ettringite, for the removal of contaminants from wastewater, which is a promising alternative adsorbent that can be used under specific conditions.

Effect of Iron Ore and Copper Ore Tailings on Engineering Properties and Hydration Products of Sustainable Cement Mortar

Abstract The prohibition of river sand mining has drawn the attention of researchers in finding practicable alternatives. In the approach of finding these alternatives, it is essential to ensure minimal or zero impairment to the ecological balance, which can be mainly attained by making use of industrial waste/byproducts. The wastes from the mining industry are the major contributors in causing impairment to the environment, and their influence on the stability of mortars on using as fine aggregates needs to be systematically investigated with the view of long-term performance concerns. Thus, the present study explores the applicability of mine tailings and finding the optimum dosage in cement mortars by investigating the engineering properties and microstructure development with the aid of qualitative and quantitative analysis associated with hydration products. The studies confirm that the increased consumption of portlandite for secondary hydration reactions followed by the additional formation of calcium silicate hydrate (CSH) and calcium aluminum silicate hydrate (CASH) phases in mine tailing-based mortars helped in achieving a quality microstructure. These additional formations of CSH and CASH phases are also confirmed through Fourier transform infrared spectroscopy by identifying the shift of Si-O-Si stretching vibration bands toward a lower wavenumber. The lowering of calcium/silicate atomic ratio and increased formation of mineralogical compounds related to CSH and CASH in x-ray diffraction patterns also confirms the same. Gismondine, chabazite, and hillebrandite are the additional phases formed and found to take part in refining the pore structure. This enhanced performance of mine tailing mortars was also verified with the aid of a modified Andreasen and Andersen particle packing model. The formation of high-quality microstructure is reflected in the hardened properties of optimized cement mortar in the proportion of 20 % for iron ore tailing and 30 % for copper ore tailing.

Modified trichrome stain for faster and improved detection of intestinal protozoan parasites.

Permanent stains such as trichrome have better sensitivity but are time-consuming and the fixative includes toxic mercuric chloride. Thus, a newer modification was tested and found to be a superior, faster and safer staining technique for intestinal parasitic detection. Our study lasted 9 months and a single stool sample was collected from each enrolled patient. We evaluated classical trichrome (T1 - using Schaudinn fixative) with newer modifications, which involved different fixatives with mordant combinations (T2 - acetic acid + hydrated aluminium sulphate, T3 - citric acid + copper sulphate hydrate). Conventional PCR targeting Entamoeba histolytica, Giardia lamblia and Cryptosporidium spp. was taken as the reference. Out of 175 stool samples, 25.1% protozoa were identified by wet mount, 24% by each T1 and T2, 25.7% by T3. Statistically, T3 and T2 had higher sensitivity as compared to T1 and wet mount when PCR was used as reference.

Long‐term atmospheric corrosion rates of Zn55Al‐coated steel

AbstractHot‐dip Zn55Al‐coated steel samples have been exposed for up to 6 years at 11 different weathering sites, including marine, marine‐industrial, acid‐rain and dry atmospheres. From the mass loss measurements, Zn55Al metallic coating showed globally long‐term good corrosion resistance in all weathering conditions compared with hot‐dip Zn‐0.2Al‐coated steel (Z). Yet, weaker performance was observed on Zn55Al in high SO2 polluted atmosphere, particularly when combined with seawater aerosols. This is explained by a more acidic surface condition linked to high SO2. Although the extent of corrosion in this phase was different at the different sites, the final corrosion products formed after 6 years were rather similar at all sites. This consists of hydrous aluminium sulphate or hydrous aluminium hydroxy sulphate and, probably also a smaller amount of sulphate‐containing zinc corrosion products or Al/Zn products.

Improving the strength of metakaolin-lime based binder

Pozzolanic reaction of low-calcium metakaolin (MK) with calcium hydroxide (CH) at ambient temperature in the presence of water forms a series of hydrated phases such as tetracalcium aluminate hydrate (C4AH13), calcium silicate hydrate (C-S-H) and calcium aluminum silicate hydrate (stratlingite - C2ASH8). Stratlingite is the main crystalline phase and is responsible for the strength of the binder. Tetracalcium aluminate hydrate (C4AH13) is carbonated upon contact with air or converted to hemicarboaluminate and/or monocarboaluminate if the system contains excess carbonate phases (calcite or calcareous aggregates). However, the calcium aluminate hydrates formed after the reaction of MK with lime lose their strength over time due to their instability. Especially in a high humidity environment where there is no carbonation, the presence of both stratlingite and (CH) in the binder creates weak phases called katoite (Ca3Al2(SiO4)(OH)8) and can reduce the mechanical strength and durability. On the other hand, it has been determined that using chemical activators to increase the pozzolanic reactivity is the most feasible method, although it increases the cost of the material. In this study, it is aimed to eliminate the phases that cause katoite formation and improve the performance of the binder by using alkaline hydroxide solution in a mixture of metakaolin and slaked lime, similar to the pore solution caused by hydrated cement. For this aim, the effect of sodium carbonate (N-Na2CO3), quicklime (C-CaO) and calcite (CC-CaCO3) on the (CH-Ca(OH)2) activated metakaolin system is investigated through the experimental campaign. The preparation of the mixtures is done by the novel one-part mixing method.

Legacy sediment as a potential source of orthophosphate: Preliminary conceptual and geochemical models for the Susquehanna River, Chesapeake Bay watershed, USA

Nutrient pollution from agriculture and urban areas plus acid mine drainage (AMD) from legacy coal mines are primary causes of water-quality impairment in the Susquehanna River, which is the predominant source of freshwater and nutrients entering the Chesapeake Bay. Recent increases in the delivery of dissolved orthophosphate (PO4) from the river to the bay may be linked to long-term increases in pH, decreased acidity of precipitation, and decreased acidity, iron, and aluminum loading from widespread AMD. Since the 1950s, baseline pH increased from ~6.5 to ~8 in the West Branch and “North Branch” of the Susquehanna River, which drain bituminous and anthracite coalfields of Pennsylvania. A current baseline pH of ~8 and daily maxima exceeding 9 have been documented along the lower Susquehanna River. In response to improved river quality, bioavailable PO4 now may be released into solution from legacy sediment that has filled major impoundments in lower reaches of the river. At typical pH (5–8) of natural water, aqueous PO4 species tend to be adsorbed by hydrous iron, aluminum, and manganese oxides that coat soil and sediment particles; however, PO4 may be substantially desorbed at pH >8. We created a geochemical model that simulates equilibrium aqueous/solid distributions of PO4 as pH and other solution characteristics change. Considering current conditions in the lower Susquehanna River, the model demonstrates potential for extensive release of adsorbed PO4 at pH >8. Empirical data from laboratory experiments corroborate model results. The transfer of PO4 into the water column may increase algae growth, which removes CO2 and drives pH to higher values, facilitating additional PO4 release and exacerbating the potential for harmful algal blooms. Thus, legacy sediment is a currently unquantified source of PO4 that warrants consideration by resource managers and programs collaborating to reduce phosphorus loads to the bay and similar settings worldwide.

Recycling of phosphogypsum and clay by-products from phosphate mines for sustainable alkali-activated construction materials

This work investigated the recycling the large quantities of phosphogypsum, generated by phosphoric acid plants, by exploring its potential use as a precursor in alkali-activated materials. The alkali-activation involved using phosphogypsum and calcined clays as precursors and an alkaline activator. The compressive strength of elaborated materials was evaluated after 28 days of curing. Additionally, various techniques were used to characterize the diverse samples. The results demonstrated the effectiveness of the alkaline activation process to induce the formation of Calcium Aluminum Silicate Hydrate and Sodium Aluminum Silicate Hydrate gels in the elaborated samples. The samples with 22.4% phosphogypsum, 11.28 M NaOH, and a liquid/solid ratio of 0.86 presented the maximum compressive strength of 27.3 MPa as they presented a more dense and less porous structure. The Toxicity Characteristic Leaching Procedure test showed no release of harmful substances. These findings suggest that phosphogypsum could be recycled in alkali-activation technology in the construction industry.

Synthesis of zeolite and aluminum-modified zeolite from lake sediment for simultaneous immobilization of cationic and anionic pollutants in lakes

Aiming at the development of ecologically safe and environmentally friendly materials to immobilize both anionic and cationic pollutants in eutrophic lakes, we have attempted to synthesize zeolites and aluminum-modified zeolites (AMZs) from four lake sediments by a fusion-assisted hydrothermal method. Characterization by X-ray fluorescence spectrometry, X-ray diffraction analysis, Fourier-transform infrared spectrometry, scanning electron microscopy, and specific surface area measurements confirmed that zeolites including Na–X, Na–P1, and hydroxysodalite were successfully synthesized, and the AMZs composed of zeolite and amorphous hydrous aluminum oxide were formed. The cation-exchange capacity (representing the ability to adsorb cationic pollutants) and the phosphate adsorptive capacity (representing the ability to adsorb anionic pollutants) of zeolites (204.3–305.7 cmol/kg and 9.3–16.3 mgP/g, respectively) and AMZs (105.7–309.2 cmol/kg and 26.8–38.9 mgP/g, respectively) were much higher than those of the original lake sediments (3.7–6.4 cmol/kg and 0.5–1.7 mgP/g, respectively). Incubation of sediment in lake water under anoxic conditions, which are commonly encountered at the beds of eutrophic lakes, triggered substantial release of phosphorus, iron, manganese, and ammonium, but amendment with AMZ significantly reduced the concentrations of these pollutants in the overlying water. Our findings demonstrated that zeolite and AMZ synthesized from lake sediments may be applied as suitable materials for the remediation of eutrophic lakes.

Comparative study of the photooxidation of arsenite mediated by dissolved and mineral-associated humic acid under light irradiation

The photochemical processes of dissolved humic acid and its potential contribution to As(III) oxidation in natural water has received considerable attention. However, the role of mineral-humic complexes in As(III) conversion is rarely studied. Herein, two simulated mineral-humic complexes were prepared by coating humic acid on hydrous aluminum oxide, HA@HAO, or montmorillonite, HA@SWy, respectively, and batch experiments at circumneutral pH were performed under light irradiation. Our findings showed that the light-assisted oxidation of As(III) increased with increasing fractions of organic carbon in mineral-humic complexes, and As(III) photooxidation with HA@HAO or HA@SWy was up to 18.2 or 3.5-fold higher compared to that measured in the presence of equivalent amount of free HA, respectively. The reactive triplet state of HA and hydroxyl radicals in HA@HAO and HA@SWy system made a primary contribution to As(III) oxidation under irradiation. The results indicated that mineral-humic complexes have dual roles, an adsorbent and a photosensitizer, to promote As(III) access to reactive intermediates at the particle surfaces. This process was important for As(III) conversion in paddy water as colloidal particles, composed of both minerals and HA, could greatly promote As(III) oxidation and As(V) immobilization. This study provides a previously overlooked, important mechanism of As(III) phototransformation mediated by mineral-associated humic acid in natural environment.

Crystallization of C-S-H and C-A-S-H in artificial seawater at ambient temperature

Calcium silicate hydrate (C-S-H) or calcium aluminum silicate hydrate (C-A-S-H) are the primary binding phases of Portland and blended cementitious systems. This study investigated the effect of seawater on the crystallization of C-S-H and C-A-S-H with different Al dosages and pH conditions up to 90 days of curing using different experimental techniques. The results showed that the gel phases converted to the crystalline phase, which is known as tobermorite, after 56 days of exposure to seawater under ambient temperature and pressure. It was also observed that relatively low pH (8.2– 10) and Al content within a specific range aided the crystallization of the tobermorite from the gel phase. However, at a high dosage of Al, katoite was observed to precipitate instead of tobermorite. The hydrothermally synthesized tobermorite in different pH conditions and Al-contents also confirmed the role of pH and Al on the crystallization of this phase.

A Review: Progress in Molecular Dynamics Simulation of Portland Cement (Geopolymer)—Based Composites and the Interface between These Matrices and Reinforced Material

Molecular dynamics (MD) is an important method for studying the molecular and atomic scale of cement (geopolymer)-based composites which provides an effective method for the optimal design of cementitious materials. In this paper, the research progress of MD simulation in Portland cement and geopolymer-based materials is discussed in detail, including molecular structure models of calcium silicate hydrate, calcium aluminosilicate hydrate, sodium aluminum silicate hydrate gel, and auxiliary experimental techniques. The basic mechanical properties of calcium silicate hydrate, calcium aluminosilicate hydrate and sodium aluminum silicate hydrate in Portland cement-based materials (CBM) and geopolymer-based materials are reviewed. In addition, the dynamic simulation of the interface between CBM and reinforcement materials such as rebar, synthetic fibers, plant fibers and nanoparticles is also discussed. Through the macroscopic experimental results of cement (geopolymer)-based materials and the performance analysis of an MD microscopic model, MD helps to better explain the macroscopic properties of materials, and can quickly and conveniently analyze the mechanical properties, transport properties and interface properties of composite materials, so as to improve the fine design of cement (geopolymer)-based materials. Existing structural models and force fields are affected by environment and time, and MD simulation shows great differences in application range and characterization ability. It is necessary to further study and reveal the internal mechanism for improving concrete performance through a large number of experiments and MD simulation, and lay a theoretical foundation for preparing the next generation of (super) high-performance concrete.

Removal of arsenic from contaminated soils by combining tartaric acid with dithionite: An efficient composite washing agent

In the context of the increasing global problem of arsenic (As) contamination in soils, an efficient remediation method is urgently needed to alleviate it. In this study, a composite washing agent consisting of 0.2 mol L−1 dithionite and 0.05 mol L−1 tartaric acid (TA) in a 1:1 mixing volume ratio was prepared and used in the remediation of arsenic-contaminated soils. The results showed that the removal efficiency of arsenic was 62.47% in soil 1 at a concentration of 134 mg kg−1 and 70.08% in soil 2 at a concentration of 70 mg kg−1. Dithionite achieved greater release of the arsenic associated with amorphous hydrous oxides of iron and aluminium (F3) and arsenic associated with crystalline hydrous oxides of iron and aluminium (F4) forms of arsenic by the reductive dissolution of iron oxides, while also reducing Fe3+. TA released some arsenic in the specifically adsorbed (F2) and F3 forms through acidic effects. The mechanism of arsenic removal from the composite washing agent was found to be a synergistic effect between dithionite and TA. The TA complexation formed Fe-TA complexes with Fe2+ in solution, preventing the formation of new iron mineral phases and reducing the readsorption or precipitation of arsenic to the soil surface. Meanwhile, the formation of Fe-TA complexes kept the iron oxides dissolved, allowing more iron oxide-bound arsenic (F3 +F4) to be released. This study showed that combining TA with dithionite is a promising technology for remediating arsenic-contaminated soils because of its high efficiency.

ROLE OF KAOLIN ON FRUIT QUALITY MANAGEMENT

Kaolin is a white, soft, flexible clay, is a fine-grained plate-like material frequently referred to as “China Clay.” kaolin consists of ‘alumina octahedral sheets’ and ‘silica tetrahedral sheets’ stacked alternatively, chemically is a “Hydrous aluminium silicate” (Al2Si205(OH)4). It is used in ceramic products like white wares, spread the fruit with an even layer of film, adds strength to fiber glass and alter insect or pathogen behaviour. It has numerous applications in horticulture to overcome adverse conditions of plants such as summer stress, fruit cracking, sun burn, pests and diseases and improve water use efficiency with better fruit quality. Kaolin is boon to the farmer as it is helpful in mitigating biotic and abiotic stresses of plant, reduces the use of agrochemicals and improve yield and quality of the produce.

Influence of Geochemical Fractionation of Fulvic Acid on its Spectral Characteristics and its Protection Against Copper Toxicity to Daphnia magna.

Dissolved copper (Cu) can contribute to toxicity in aquatic systems impacted by acid mine drainage (AMD), and its bioavailability is influenced by aqueous complexation with organic ligands that predominantly include fulvic acids (FAs). Because the geochemical fractionation of FAs that accompanies sorption to hydrous aluminum oxides (HAOs) and hydrous iron oxides (HFOs) can alter Cu complexation with FA, we investigated FAs isolated from three categories of water (pristine, AMD, and in situ-fractionated mixtures of pristine and AMD collected at stream confluences) in three mining-impacted alpine watersheds in central Colorado, USA. We also conducted geochemical fractionation of field-collected FAs and Suwannee River FAs by precipitating HAOs and HFOs in the laboratory. Spectral properties of the FAs (e.g., UV-VIS absorbance) were altered by geochemical fractionation, and in acute toxicity tests with an aquatic invertebrate (Daphnia magna) Cu was more toxic in the presence of in situ- and laboratory-fractionated FAs (median effect concentration [EC50] 19-50 µg Cu L-1 ) than in the presence of nonfractionated FAs (EC50 48-146 µg Cu L-1 ). After adjusting for the strain-specific sensitivity of our D. magna, we improved the accuracy of Biotic Ligand Model predictions of Cu EC50 values for AMD-related FAs by using an "effective dissolved organic carbon" based on spectral properties that account for among-FA differences in protectiveness against Cu toxicity. However, some differences remained between predicted and measured EC50 values, especially for FAs from AMD-related waters that might contain important metal-binding moieties not accounted for by our measured spectral indices. Environ Toxicol Chem 2023;42:449-462. © 2022 SETAC.

Environmental risk assessment of the contamination of river water and sediments from the Bor mining area, East Serbia―Secondary Cu enrichment at the reservoir site

AbstractThe study area is within the Bor copper mining region, Eastern Serbia, where wastewaters from the Bor metallurgical/smelting facilities have caused serious copper (Cu) and arsenic (As) contamination to the Timok river system. The operating conditions at smelting facilities control the pH of the river waters, resulting in highly acidic waters in 2019 than 2015. This study compares the mobility of Cu and As and risk assessment of river water contamination during both years as well as assessing the risks of riverbed sediments contamination and investigating the origins of Cu and As pollution. In the river system, As generally existed as a particulate species in the entire study area during both years and was widely removed from river waters by sorption onto the hydrous ferric oxides (HFO), whereas dissolved Cu was removed from river waters only at neutral pH conditions with hydrous aluminum oxides (HAO) and HFO at the downstream reservoir site of Timok River. Despite the similarity in Cu mobility during both years, the lower pH of river waters in 2019 than 2015 enabled dissolved Cu species to be transported farther downstream, resulting in a higher level of river water pollution. The contamination factor (CF), used to estimate levels of sediment pollution, had higher values for Cu and As compared to Zn, Pb, Co, and Ni. The CF values of Cu were the highest in sediments near the Bor metallurgical/smelting facilities and at downstream reservoir site, whereas the CF values of As were generally high in the entire research field. Additionally, the ecological risk potential (Er) values of Cu were the highest in sediments of the Bor River and Timok River, reflecting an enrichment of Cu at these sites. Finally, a clarification on the origin of Cu pollution and risks of mobilization was inferred from the sequential extraction test. The predominant Cu species in sediments of the upstream region were oxidizable and residual, hosted by copper sulfides originating from the flotation tailings, suggesting a relatively low risk of Cu release from these sediments. However, at the downstream site (especially reservoir sediments), the contribution of acid‐soluble Cu was 34.8%, suggesting a higher risk of Cu release. The highest contributions of acid‐soluble and reducible Cu (18%) at the reservoir site were promoted by the effective settlement of Cu‐sorbing HAO and HFO. The Cu contents of these two fractions were 0.86 wt%, almost three times higher than that of Cu ore in Veliki Krivelj open pit mine.

Fe-Al binary composite filled dialysis membrane tubes (DMT-HFAO): a modified method for assessment of phosphate desorption from aqueous and soil solutions.

Phosphorus (P) limits plant growth particularly in strongly acidic soils due to P fixation. P availability to a plant is a functional concept of time rather than a measurable quantity. Therefore, a method that can estimate P availability over time is required. This research work was intended to synthesize a nanocomposite material that can monitor soil P desorption kinetics. To this effect, a binary sorbent system filled in a dialysis membrane tube was developed. Accordingly, calcined and amorphous powder samples of Fe-Al binary mixed oxides were synthesized by a gel-evaporation method and characterized by XRD, FTIR, TGA-DTA, SEM-EDX and BET techniques. The performance, as a phosphate sink, of crystalline hydrous ferric aluminum oxide (HFAO) and hydrous amorphous ferric aluminum oxide (HAFAO) each filled in a dialysis membrane tube (DMT) was evaluated. A single hydrated ferric oxide (HFO) suspension filled in dialysis membrane tubes (DMT) designated DMT-HFO was used as a benchmark. For the aqueous system, the sorption capacity of the DMT-HFAO was found to be 260% (mg mg-1 phosphate) whereas the amorphous congener (DMT-HAFAO) was approximately 200% (mg mg-1 phosphate) times that of DMT-HFO during the 24 h equilibration. For the soil solution system, the phosphate desorbed by the DMT-HFAO was about 520% (mg mg-1 phosphate) compared with a single system, DMT-HFO, in 168 h. For the desorption experiment carried out with soil solution, the data fitted fairly well with first order kinetics for both sorbents (R2 = 0.946-0.998), the amount adsorbed by DMT-HFAO being greater than DMT-HFO. The soil data fitted an intra-particle diffusion model fairly well for both sorbents (R2 = 0.98-0.992) with rate constants, kp, following the order: DMT-HFAO > DMT-HAFAO > DMT-HFO. The DMT-HFAO approach also showed better fit to the two component first order model (R2 = 0.994 & 0.997) indicating that the modified method has promising potential for a long-term phosphate desorption kinetics study from soil, the implication of which is important both from agricultural and environmental perspectives. However, correlation of the P adsorbed by this sink method with actual plant P uptake in various soils should be carried out to validate the universality of this technique.

Barnyard grass (Echinochloa crus-galli L.) as a candidate plant for phytoremediation of arsenic from arsenic-amended and industrially polluted soils

The potentiality of barnyard grass for remediation of arsenic (As)-contaminated soil has been reported in several research works. However, the phytoremediation ability of barnyard grass from industrially polluted multimetal-contaminated soil in comparison to As-amended soil needs to be elucidated. This work investigated the As remediation potentiality of barnyard grass from As-amended and industrially polluted soils, and the fractionation of As was done in soils with plants and without plants grown. The result showed that at the highest As level in the soil, barnyard grass accumulated the highest amount of As in both the root (414.81 mg kg-1) and shoot (114.12 mg kg-1). However, barnyard grass produced the highest amount of biomass in industrially polluted soil that resulted in the highest amount of As uptake. Moreover, barnyard grass also accumulated lead (Pb) and chromium (Cr) from industrially polluted soil. The bioaccumulation factor (BF) of As was >1 in As-amended soil in all the treatments as well as in industrially polluted soil. Fractionation of As in post-harvest soil revealed that compared to soil without plants grown, As in the soil was reduced from residual As (F5); As associated with well-crystallized hydrous oxides of iron (Fe) and aluminum (Al) (F4); As associated with amorphous and poorly crystallized hydrous oxides of Fe and Al (F3), whereas a slight increase was found in non-specifically sorbed As (F1) and specifically sorbed As (F2) due to the plant’s effect. The slight increase in the concentration of As in F1 and F2 fractions contributed to the bioavailable forms of As in the rhizosphere and sustained As concentration for further plant uptake. The maximum plant growth and highest uptake of As in the industrially polluted soil revealed the potentiality of barnyard grass for remediation of multimetal-polluted soil.

Impact of Low Molecular Weight Organic Acids on Soil Phosphorus Release and Availability to Wheat

ABSTRACT Phosphorus (P) use efficiency (FPUE) is very low due to fixation of P with the hydrous oxides of iron and aluminum in acid soils and calcium in neutral to calcareous soil. The roots of wheat (Triticum aestivum) excrete low molecular weight organic acids (LMWOAs) to increase P bioavailability in P-deficient soil through acidification, chelation, and exchange mechanisms. However, the amount of LMWOAs excreted in the rhizosphere is small, and they undergo rapid microbial degradation. The present study was undertaken by applying different levels of LMWOAs and phosphorus to the soil followed by sowing of wheat seeds to learn the impact of applying LMWOAs, especially oxalic (OA) and citric acid (CA), on the yield and FPUE of wheat. The results showed that application of P fertilizer along with OA and CA significantly increased the Olsen P concentration in soil and in turn increased P uptake, FPUE, and yields of wheat. Application of OA @ 15 mg kg−1 recorded 20% (±0.22%) and 30% (±0.55%) higher grain and straw yield, respectively, over control and was more effective than CA. Among LMWOAs, application of OA @ 15 mg kg−1 was more effective than CA. Therefore, the application of OA has the potential to reduce the excess application of phosphorus and its buildup in soils and cause eutrophication of water bodies.

Waste glass as a precursor in alkali‐activated materials: Mechanical, durability, and microstructural properties

AbstractThe long‐term characteristics and durability of alkali‐activated mortars based on waste glass are crucial to better understand their performance in aggressive environments. In this regard, the performance of waste glass as a building material and its characteristics such as mechanical (compressive, flexural, and tensile strengths), durability (chloride migration coefficient, sulfate resistance, and drying shrinkage), and microstructural properties [x‐ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) with energy dispersive x‐ray analysis (SEM/EDX)] were evaluated. For this purpose, the specimens with different amounts of silica modulus and Na2O content were prepared. The specimens were cured at 95°C for 20 h and then kept at a relative humidity of 50% at room temperature until testing. The specimen with 10% Na2O and a silica modulus of 1.5 demonstrated the highest compressive, flexural, and tensile strengths. The specimens illustrated a lower chloride migration coefficient and lower expansion than the Portland cement one. By increasing both silica modulus and Na2O contents, the drying shrinkage of the specimens increased due to the presence of more free water. The microstructural results indicated that amorphous gels such as sodium aluminum silicate hydrate (N‐A‐S‐H) and sodium (calcium) silicate aluminum hydrate [N‐(C)‐A‐S‐H] were formed. The results of this study signify the utilization possibility of waste glass as an eco‐friendly material with desirable characteristics.

On the possibility to modify the CsAlSi5O12/CsAlSi2O6 ratio during the thermal transformation of Cs-clinoptilolite

Clinoptilolite is a natural zeolite employed in Cs+ removal, and its cesium form transforms, by heating, into a matrix composed mainly by CsAlSi5O12 (CAS) with smaller quantities of glass and CsAlSi2O6 (pollucite). Both crystalline compounds were proposed as host for 137Cs, albeit pollucite is considered superior. This work shows how, by mixing Cs-clinoptilolite and amorphous hydrated aluminum hydroxide (L), it is possible to modify the solid-state transformation of the zeolite and favor the crystallization of pollucite over CAS. Cs-clinoptilolite, L and several mixtures of the two materials were preliminary subjected to thermal and XRD analyses. Muffle treatments of 32 h at 1200 °C and 8 h at 1300 °C, followed by Q-XRD analyses, were performed on some materials. Unlike CAS, pollucite always crystallized. The greater the quantity of L in the mixture, the lower the ratio between the quantities of CAS and pollucite formed. In the range 1200–1300 °C, the CAS/pollucite ratio decreases with temperature. Al2O3-polymorphs (mainly corundum) and glass were ubiquitous in the fired mixtures, whereas mullite was not. By varying the content of L in the mixture, the distribution of cesium among the Cs-bearing phases varied, and for some compositions most of the cesium was trapped inside pollucite.