Al Hydroxide Research Articles

Prime-boost immunization with inactivated human adenovirus type 55 combined with an adjuvant enhances neutralizing antibody responses in mice

BackgroundHuman adenovirus type 55 (hAd55) infection can lead to acute respiratory diseases that often present with severe symptoms. Despite its persistent prevalence in military camps and communities, there are no commercially available vaccines or vaccine candidates undergoing clinical evaluation; therefore, there is an urgent need to address this. In this study, we evaluated the immunogenicity of inactivated hAd55 isolates and investigated the effects of adjuvants and various immunization intervals.Methods and resultsTo select a vaccine candidate, four hAd55 strains (6–9, 6–15 (AFMRI 41014), 28–48 (AFMRI 41013), and 12–164 (AFMRI 41012)) were isolated from infected patients in military camps. Sequence analysis revealed no variation in the coding regions of structural proteins, including pentons, hexons, and fibers. Immunization with inactivated hAd55 isolates elicited robust hAd55-specific binding and neutralizing antibody responses in mice, with adjuvants, particularly alum hydroxide (AH), enhancing antibody titers. Co-immunization with AH also induced hAd14-specific neutralizing antibody responses but did not induce hAd11-specific neutralizing antibody responses. Notably, booster immunization administered at a four-week interval resulted in superior immune responses compared with shorter immunization intervals.ConclusionsPrime-boost immunization with the inactivated hAd55 isolate and an AH adjuvant shows promise as a potential approach for preventing hAd55-induced respiratory disease. Further research is needed to evaluate the efficacy and safety of these vaccine candidates in preventing hAd55-associated respiratory illnesses.

Organic-mineral colloids regulate the migration and fractionation of rare earth elements in groundwater systems impacted by ion-adsorption deposits mining in South China

Ion-adsorption rare earth element (REE) deposits distributed in the subtropics provide a rich global source of REEs, but in situ injection of REEs extractant into the mine can result in leachate being leaked into the surrounding groundwater systems. Due to the lack of understanding of REE speciation distribution, particularly colloidal characteristics in a mining area, the risks of REEs migration caused by in situ leaching of ion-adsorption REE deposits has not been concerned. Here, ultrafiltration and asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4-ICP-MS) were integrated to characterize the size and composition of REEs in leachate and groundwater from mining catchments in South China. Results show that REEs were associated with four fractions: 1) the <1 kDa fraction including dissolved REEs; 2) the 1 – 100 kDa nano-colloidal fraction containing organic compounds; 3) the 100 kDa – 220 nm fine colloids including organic-mineral (Fe, Mn and Al (oxy)hydroxides and clay minerals); 4) the >220 nm coarse colloids and acid soluble particles (ASPs) comprising minerals. Influenced by the ion exchange effect of in situ leaching, REEs in leachate were mostly dissolved (79 %). The pH of the groundwater far from the mine site was increased (5.8 – 7.3), the fine organic-mineral colloids (46 % – 80 %) were the main vectors of transport for REEs. Further analysis by AF4 revealed that the fine colloids can be divided into mineral-rich (F1, 100 kDa – 120 nm) and organic matter-rich (F2, 120 – 220 nm) populations. The main colloids associated with REEs shifted from F1 (64 % ∼ 76 %) to F2 (50 % ∼ 52 %) away from the mining area. For F1 and F2, the metal/C molar ratio decreased away from the mining area and middle to heavy REE enrichment was presented. According to the REE fractionation, organic matter was the predominant component capable of binding REEs in fine colloids. Overall, our results indicate that REEs in the groundwater system shifted from the dissolved to the colloidal phase in a catchment affected by in situ leaching, and organic-mineral colloids play an important role in facilitating the migration of REEs.

Self-Assembled Monolayers of a Fluorinated Phosphonic Acid as a Protective Coating on Aluminum

Aluminum (Al) placed in hot water (HW) at 90 °C is roughened due to its reaction with water, forming Al hydroxide and Al oxide, as well as releasing hydrogen gas. The roughened surface is thus hydrophilic and possesses a hugely increased surface area, which can be useful in applications requiring hydrophilicity and increased surface area, such as atmospheric moisture harvesting. On the other hand, when using HW to roughen specified areas of an Al substrate, ways to protect the other areas from HW attacks are necessary. We demonstrated that self-assembled monolayers (SAMs) of a fluorinated phosphonic acid (FPA, CF3(CF2)13(CH2)2P(=O)(OH)2) derivatized on the native oxide of an Al film protected the underneath metal substrate from HW attack. The intact wettability and surface morphology of FPA-derivatized Al subjected to HW treatment were examined using contact angle measurement, and scanning electron microscopy and atomic force microscopy, respectively. Moreover, the surface and interface chemistry of FPA-derivatized Al before and after HW treatment were investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS), verifying that the FPA SAMs were intact upon HW treatment. The ToF-SIMS results therefore explained, on the molecular level, why HW treatment did not affect the underneath Al at all. FPA derivatization is thus expected to be developed as a patterning method for the formation of hydrophilic and hydrophobic areas on Al when combined with HW treatment.

Enhanced removal of fluoride from groundwater using biosynthetic hydroxyapatite modified by bimetallic (La–Fe or La–Al) hydroxides

Long-term exposure to groundwater contaminated with excessive fluoride (F−) can cause irreversible damage to ecosystems and human health. It is necessary for searching economical and reliable solutions to eliminate excess F− within aquatic environments. Herein, the doping technique was applied to modify the biosynthetic hydroxyapatite, and the maximum defluoridation efficiency (90.37%) was obtained in the La@HAP system. The introduction of Fe and Al species prominently reduced the dosage of La species while ensuring the ideal defluoridation effect. At optimal conditions (preparation parameters: biosynthetic time 12 h, pH 7.0, and dosage of La–Fe and La–Al 2 mM; operation parameters: pH 7.0, dosage 0.3 g L−1, and F− content 3.0 mg L−1), the average defluoridation efficiencies of La–Fe@HAP and La–Al@HAP reached 63.42% and 79.79%, respectively. Kinetic results indicated that the F− adsorption on both bimetallic composite adsorbents was better fitted with the pseudo-second-order model, and a higher initial F− content inhibited the reaction rate. Compared with La–Fe@HAP, La–Al@HAP exhibited lower sensitivity to coexisting anions and humic acid, and higher selectivity to F−. Electrostatic interaction and ligand exchange were the main mechanisms for enhancing the adsorption properties of biosynthetic hydroxyapatite, and F− removal was principally depended on the La species (La > Al > Fe). This study provides inspiration for saving the usage of rare earth metals and designing high-performance and low-cost adsorbents with low pH dependence.

New insight into the interaction between maleic anhydride grafted polypropylene and aluminum foil converted with trivalent chromate: An experimental and DFT study

The good adhesion between layers of aluminum (Al)/polymer composite is necessary for the safety of lithium-ion batteries. The Al foil was converted with environmentally friendly trivalent chromate [Cr(III)] to enhance its adhesive strength with the inner adhesive layer. The morphology, composition and adhesive strength with maleic anhydride grafted polypropylene (mPP) of different Cr-converted Al foils were studied. The Cr conversion coating mainly consists of metal oxides and hydroxides and the interfacial adhesion strength is enhanced by 93 % through Cr(III) conversion treatment. The effect of Cr conversion on the acid-base characteristics on the Al was determined through contact angle measurement. The results reveal that Cr conversion increases the acidity of the Al surface. The bonding mechanism at the interface was further studied fundamentally. To study the reaction at the interface mPP/Al foils, a coating-evaporation technique was utilized to fabricate a nano-thick mPP layer on the Al foils. The morphology and thickness of the mPP coating on the substrate were analyzed using atomic force microscopy and the interfacial reaction was characterized through attenuated total reflection-Fourier Transform Infrared Spectroscopy. The bonding mechanism at the molecular level was further investigated by quantum chemical calculations based on density function theory. The results of theoretical calculations further indicate that the strength of the interfacial interaction between mPP and Cr oxides and hydroxides is stronger than that between mPP and Al oxides and hydroxides.

Incongruent dissolution of silicates and its impact on the environment: an example of a talc mine

The paper analyzes the process of incongruent dissolution of silicates taking place in close proximity to a talc mine. The chemical and phase composition as well as the concentrations and mobility of potentially toxic elements (PTE) in research material with varying levels of weathering were determined using instrumental (XRF, XRD) and chemical methods (extractions: BCR, aqua regia, water leaching, 0.05 M EDTA). It was demonstrated that the predominant minerals in the weathering crust include weathering-resistant minerals (i.e. quartz and muscovite) and secondary minerals (kaolinite, illite and interstratified minerals, vermiculite/chlorite) and that the predominant processes are hydrolysis and oxidation. The weathering process has an impact on the complexity of the chemical and mineral composition and the diverse structure of the weathering crust. A layer of Fe and Al oxides and hydroxides forms in the upper part of the weathering crust, while the amount of silica decreases. Low-mobility elements (i.e. Si, Al and Fe) react on the phase separation surface, causing the formation of clay minerals (i.e. vermiculite, montmorillonite) or Al and Fe hydroxides (e.g. goethite). The duration of weathering causes an increase in the content of PTEs in solid materials: multifold in the case of Cr (15), Ba (9), Pb (7), Zn (6) and considerably lower in the case of V (1.3), Sr (0.8) and Co (0.4). It was demonstrated that PTEs co-occur in several chemical fractions in the weathering crust and that the highest share of their total concentration are cations incorporated in the crystal lattice of minerals and bound by strong crystalline bonds (F4 46%). The lowest share was observed for the reducible fraction (9%) and the share of the oxidizable fraction was 29% The most mobile cations connected by the weakest bonds comprised only 16% of the total concentration. Based on the content of the readily soluble fraction of PTEs, it was concluded that the degree of weathering does not increase the environmental risk, but actually reduces it for Cr, Cr and Pb. The obtained Ecological Risk Index (ERI) values indicate that the ecological risk associated with the elements tested is low for the entire area, which means that natural weathering processes do not have any impact on environmental pollution.

New clues to the mechanism in controlling arsenic leaching from flash copper smelter flue dusts by using X-ray absorption spectroscopy

This paper characterizes the leaching of the toxic element (As) and other elements (Cu, Pb, Zn, Fe, Al, Cd, Mg, K, Ca, Mn, Co, Ni, Mo, Bi, and Sb) from the fresh and washed copper smelter flue dusts (FDs) over a wide pH range (3–12) based on the batch pH-static leaching experiment in combination with geochemical modeling. Furthermore, the leaching control mechanism of As was also explored on a microscale by using an X-ray absorption spectroscopy. Results revealed that the leached concentration of As showed a strong pH dependency, resulting in “L-shaped” leaching curves, similar to the leaching of Cu and Zn, whose leaching contents decreased dramatically with the increase of pH values. It should be noted that a partial of As was also released at the alkali conditions, especially from the washed FDs. Arsenic phases in the leachate were modeled by Visual MINTEQA 3.1 incorporated adsorption to Fe/Al hydroxides. The results were well in line with the actual leached content of As and showed that H3AsO3 is prevailing in the leachates at the pH range of 3–11, and AsO3- 4 is the dominant species in the alkali condition (pH = 12). Furthermore, the decreasing mineralogical composition of arsenolite and koritnigite in the washed FDs indicated that the above two arsenic-bearing phases primarily accounted for its release. According to the EXAFS analysis, ferric arsenates with a poorly crystalline scorodite structure in the raw FDs are important arsenic carriers, which could easily convert into crystalline scorodite at low pH. Furthermore, secondary Al hydroxides also have the potential to retain arsenate by forming a bidentate complex. Thus, As3+ species are the major resources for arsenic release from FDs and should be taken a crucial consideration when assessing its environmental risk. In contrast, arsenate was easily fixed by converting it into crystalline scorodite or adsorbing it onto Al hydroxides. This work may have important implications for the development of new eco-friendly technologies to reclaim valuable elements from the copper smelter flue dusts.

Effect of pretreatment on the interfacial bonding strength between modified polyolefin and aluminum foil treated with trivalent chromium chemical conversion: Experimental, quantum chemical calculations and molecular dynamics simulation

Good adhesive strength and joint durability are necessary for aluminum (Al)/polymer laminated film for lithium-ion battery packages. A pretreatment method involving alkaline degreasing followed by acid pickling was employed to treat the Al foil surface to facilitate the deposition of trivalent chromium [Cr(III)] conversion coating on the surface. The adhesive strength between propylene-based elastomer grafted glycidyl methacrylate (GMA-g-PBE) and Cr(III)-converted Al foil pretreated with 0.5 M HF pickling was 51% higher than Cr(III)-converted Al foil without pretreatment. Moreover, the effect of different pretreatments on the interfacial bond strength of GMA-g-PBE/Cr(III)-converted Al foil was studied from macroscopic to microscopic perspectives. The results indicate that the pretreatment of 0.5 M HF pickling results in complete coverage of the Cr(III) compounds and the formation of a thicker Cr(III) conversion coating on the Al foil compared to other pretreatments. A higher content of Cr(III) compounds results in an increased surface free energy of Cr(III)-converted Al foil, improving the wettability of adhesive melt on the substrate and enhancing the adhesion strength. Moreover, quantum chemical calculations and molecular dynamics simulations were used to investigate the interface bonding mechanism, and the results indicate that GMA in the adhesive exhibits a higher binding energy with Cr(III) oxides and hydroxides compared to Al oxides and hydroxides.

Alumina production: Historical development, issues, and solutions. Part 1

This study focuses on documenting the historical stages of aluminium and alumina production prior to the transition to a modern industry structure, involving the Hall-Héroult electrometallurgical process, and their technical significance for the contemporary metallurgical complex. It highlights the significance of these stages in the development of scientific knowledge related to alumina, aluminium, and their production technology when using chemical methods for obtaining metallic aluminium. The analysis includes aspects, such as classification, technical evaluation of the processes, and the raw material base. It is shown that the formation of scientific knowledge regarding alumina and aluminium is mainly associated with the practical need for using alum and, to some extent, clay minerals. Since the commencement of deliberate research into methods for aluminium production in its elemental state and virtually until the 1890s, aluminium was primarily produced using the metallothermal methods pioneered by Henri St. Clair Deville and his colleagues due to the high thermodynamic stability of aluminium compounds and the absence of affordable energy sources. It was found that from 1854 to 1890, the production of aluminium by chemical method was associated with the use of sodium aluminium chloride (NaCl·AlCl3), natural cryolite, or synthesised fluoride salts. Available technical reagents (aluminium sulphate, ammonia alum, and aluminium hydroxide), along with natural raw materials (cryolite, bauxite, and clay), were used as source materials in this period. The extraction and processing of bauxite were primarily associated with the production of alum and aluminium sulphate consumed by light industry. Although the demand for pure aluminium oxide was limited during the metallothermic production of aluminium, the driving force behind the advancement of modern technologies for alumina production was the demand for chemical products. This demand led to the development of technology for processing bauxite, which forms the foundation of the metallurgical complex in aluminium production using the Hall-Héroult electrometallurgical method.

From nickel waste solution to hydrogen storage alloys – An excellent example of circular economy implementation

In light of the need to protect the environment from hazardous heavy metals, waste management is becoming not just a proposal but a necessity for the reduction of wastewater toxicity and, additionally, a value-added substitute for processes of extracting raw materials from primary sources. This article demonstrates the feasibility of using critical and hazardous element as Ni(II) from industrial nickel waste solutions to produce hydrogen storage alloys (HSA), perfectly fulfilling the circular economy assumptions. The hydrometallurgical process proposed for the preparation of the Ni-containing electrolyte (NiE) from the waste solution included the following stages: diffusion dialysis, Cr(III) and Al(III) hydroxide precipitation, extraction to separate Co(II) from Ni(II), and the organic phase regeneration by Co(II) stripping with dialysate. The raffinate after extraction performed as NiE (∼10–15 g/dm3 Ni(II), 0.1 g/dm3 Co(II)) for the preparation of HSA. However, to improve the quality of Ni deposit on NiCo foam or steel plates, NiE should be modified with an ammonia solution (to pH ∼ 12). A better voltammetric characteristic of the modified electrodes (25–30 percentage points higher peaks resulting from NaBH4 electrooxidation), compared to those unmodified was reported. It was proven that the electroactive materials obtained showed high catalytic performance for the borohydride oxidation reaction.

Efficient removal of para arsanilic acid with Ca-Al-Fe composite: Performances and mechanisms

Para arsanilic acid (p-ASA) as the one of the sources of highly toxic and carcinogenic inorganic arsenic is frequently excreted into the aqueous systems, raising serious environmental hazards and human health risks. Thus, it is compelling to develop techniques that can realize high efficiency of p-ASA removal while being cost effective. Here, a ternary composite material Ca-Al-Fe was designed via facile mechanochemistry and low-temperature calcination on the mixture of inexpensive and readily available Ca(OH)2, C6H9AlO6 and FeC2O4. The results showed that the resulting Ca-Al-Fe composite was capable of achieving a preferable p-ASA adsorption from water with high adsorption capacity (41.23 mg/g), fast kinetic (30 min), long-term stability and reusability on account of the interfacial synergetic effect between ternary composite components. Furthermore, the mechanism investigation demonstrated that, in the preparation stage, CO2 was liberated by the decomposition of FeC2O4, leading to a favorable porous structure and the formation of CaCO3. In the adsorption stage, the hydrolysis of generated CaCO3 enabled the continuous release of OH–, which induced in situ formation of high reactive Fe and Al hydroxides by Al3+ and Fe3+ to adsorb p-ASA by hydrogen bond and coordination interactions. The current work provides a new insight and direction for the development of high-performance metal composite materials.

The geochemical processes affecting the mobility of Cu, Pb, Zn during phytostabilization on sulfidic mine tailings revealed by a greenhouse study

Sulfidic mine tailings have the potential to release toxic metals into the surrounding environment. Phytostabilization can stabilize these toxic metals in the rhizosphere, providing a sustainable method for mine reclamation. However, previous research has not examined the inorganic geochemical processes in the rhizosphere that are significant for controlling acid mine drainage. Therefore, a greenhouse study was conducted to explore the geochemical processes affecting the mobility of Cu, Pb, and Zn through the establishment of phytostabilization on sulfidic mine tailings. The mineralogy of substrates before and after experiments and the changes in metal concentrations and pH of the drainage were analyzed. The results showed that at the end of the experiments, pH of pot substrates with plants became acidic (pH ranging from 2.59 to 3.77), the concentrations of Cu, Pb, and Zn in the drainage increased (up to 20.14 mg/L of Cu, 2.28 mg/L of Pb, and 3199.87 mg/L of Zn), leading to the generation of acid mine drainage. It was concluded that, in addition to the sulfide oxidation, two other acidification processes played a role: the decomposition of organic matter and the release of roots exudates, in decreasing pH and increasing metal concentrations in the drainage from amended tailings. The acidity in the rhizosphere was neutralized sequentially through the following geochemical processes: (1) dissolution of carbonates, (2) dissolution of Al&Fe (oxy)hydroxide, and (3) silicates weathering. The long-term reliability of phytostabilization can be achieved by re-applying amendments to initiate these neutralization processes. This research has filled the research gap regarding the geochemical mechanisms controlling the migration of metals in the rhizosphere during phytostabilization with two grass species (Pascopyrum and Lolium multiflorum). It provides a valuable reference for designers and engineers when considering metal immobilization in sulfidic mine tailings through the technique of phytostabilization during mine reclamation and closure stage.

Release of labile Si from forest and agricultural soils

Despite the importance of silicon (Si) as benefecial nutrient for many plants, including economically-important cereals, the reactivity of various Si pools in soils (silicate minerals, amorphous compounds, phytoliths, organic litter) is not fully quantified which does not allow predicting the capacity of agricultural or forested soil to provide soluble Si to soil porewaters where it can be used by plants. Towards better understanding of factors controlling bioavailable Si in soils, here we quantified the release rate of Si from several pairs of French forest and agricultural topsoils, developed on calcareous or loess parent material. We used mixed-flow and column reactors, in acetate and carbonate buffers and distilled water, at various pH (4–8) and time of reaction (day to month).The rate of Si release from soil (RSi) exceeded that of crystalline clay minerals by 1–2 orders of magnitude, being 5–10 times lower than that of various allophanes. The rates were weakly dependent on pH (compared to clays or phytoliths) and varied from 5 × 10−7 to 2 × 10−6 mol/gsoil/day at 4 < pH ≤ 8. In terms of Si reactivity, four studied soil groups followed the order: “calcaric cambisols ≈ hypereutric cambisols ≥ luvisols ≥ albeluvisol”. Calcaric and hypereutric cambisols as well as luvisols exhibited a weak decrease of RSi with pH increase. The rate of Si release from albeluvisol increased 2 times with a pH increase from 4 to 8. There was no measurable difference in RSi between agricultural and forest soils.The pool of labile Si in forest soils was quantified via soil column flow-through experiments. The breakthrough curves of Si demonstrated high concentrations (1.6–5.7 mg/L) over first several hours of reaction in the soil column. The water leachable Si pool ranged from 0.04 to 0.08 mg Si gsoil−1, corresponding to labile Si stock in the 0–20 cm soil of 80–160 kg ha−1. These values can meet the annual requirements of plants in forests and cultivated soils. The pool of labile Si correlated (RPearson > 0.90; p < 0.05) with Si associated with amorphous Fe and Al compounds and soluble bioavailable Si extracted using CaCl2 method, but negatively correlated with total Si content in soils and Si of phytoliths. The main pools of soil labile Si could be allophanes, organo-Fe-Al-Si compounds and adsorbed forms of Si onto Fe and Al hydroxides. We hypothesize that, because of low sensibility of RSi to type of soil and fluid pH, the majority of soils regulate Si release at some ‘universal’ rate which is further reflected in relatively narrow range of riverine Si concentrations and export fluxes across the world. Therefore, the modeling of chemical weathering and element export flux in the watersheds should incorporate the experimentally measured reactivity of the whole soil rather than individual constituting primary or secondary minerals.

Advanced electrocoagulation using aluminum electrodes supported by persulfate for the treatment of a high-strength wastewater

In this study, the treatment of leachate nanofiltration (NF) concentrate, which is high-strength wastewater, by advanced electrocoagulation (EC) was investigated. The EC process, in which aluminum electrodes were used, was enhanced by persulfate (PS) addition (EC-PS). First, the control experiments were conducted then the operating parameters of the process were optimized by the Box-Behnken design. Process variables were PS dose, applied current, initial pH, and reaction time while chemical oxygen demand (COD), total organic carbon (TOC), UV254, and color removal were the system responses. COD, TOC, UV254, and color removal efficiencies by the validation studies performed under optimized conditions (PS dose: 0.590 g/L; applied current: 0.710 A; initial pH: 5, and reaction time: 31.4 min) were 62.6%, 54.3%, 74.2%, and 88.0%, respectively. Based on the degree of effect on COD and TOC removal, statistical analysis parameters can be listed as linear, quadratic, and interactive from higher to lower one. The linear parameters can be listed as initial pH, applied current, reaction time, and PS dose according to the level of their effect on removal efficiencies. Quenching experiments showed that sulfate and hydroxyl radicals work together in the process while hydroxyl radicals were more effective. The specific energy consumption and total cost of the process under optimized operating conditions were 1.90 kWh/kg COD and 1.40 $/m3 respectively. By obtaining the spectrum of the sludge formed under optimum process conditions by Fourier Transform Infrared Spectroscopy analysis, the characteristics of the sludge were determined and Al hydroxides and hydrocarbons were present in the sludge.

Aluminum hydroxide exposure induces neurodevelopmental impairment in hESC-derived cerebral organoids

Aluminum (Al) has been classified as a cumulative environmental pollutant that endangers human health. There is increasing evidence to suggest the toxic effects of Al, but the specific action on human brain development remains unclear. Al hydroxide (Al(OH)3), the most common vaccine adjuvant, is the major source of Al and poses risks to the environment and early childhood neurodevelopment. In this study, we explored the neurotoxic effect of 5 μg/ml or 25 μg/ml Al(OH)3 for six days on neurogenesis by utilizing human cerebral organoids from human embryonic stem cells (hESCs). We found that early Al(OH)3 exposure in organoids caused a reduction in the size, deficits in basal neural progenitor cell (NPC) proliferation, and premature neuron differentiation in a time and dose-dependent manner. Transcriptomes analysis revealed a markedly altered Hippo-YAP1 signaling pathway in Al(OH)3 exposed cerebral organoid, uncovering a novel mechanism for Al(OH)3-induced detrimental to neurogenesis during human cortical development. We further identified that Al(OH)3 exposure at day 90 mainly decreased the production of outer radial glia-like cells(oRGs) but promoted NPC toward astrocyte differentiation. Taken together, we established a tractable experimental model to facilitate a better understanding of the impact and mechanism of Al(OH)3 exposure on human brain development.

Phosphorus Recovery from Eutrophic Lake Water Using Al/Fe Micro-Electrolysis

Phosphorus (P) is a critical and nonrenewable resource. P crisis threatens future global food security, while P-induced eutrophication is damaging aquatic ecosystems. In eutrophic lakes, P is often heavily concentrated in algae-accumulated zones, creating “P reserves” for reuse. In this study, P was harvested from eutrophic lake water using Al/Fe micro-electrolysis and the stability of the harvested P was tested through anoxia incubation. The results showed that, compared with Fe micro-electrolysis, Al micro-electrolysis was more effective at co-harvesting dissolved and particulate P, and the yields were stable under anoxia conditions, making them suitable as slow-release P fertilizers. At 15 V, the P harvesting efficiency of Al micro-electrolysis was 2.68 times higher than that of Fe micro-electrolysis. This could be attributed to the powerful netting–bridging of amorphous Al hydroxides, which favor floatation separation and thereby P harvesting. Under anoxia, the transformation of Fe species caused P release from Fe micro-electrolysis yields, potentially enhancing P loss through leaching if the yields are used as soil P fertilizers. This study provides a promising strategy for P resource recycling from eutrophic lakes, which may be beneficial to the restoration of lake ecosystems and mitigation of the P crisis.

The subhorizon Ofh as a prospective geoindicator of temperate soil quality in relation to selected trace elements and PAHs: a review

Soils, next to vegetation, are one of the most popular indicators in environmental quality studies. The response of soil to air pollution is less complex than the response of vegetation. In soils, mainly in their upper layers, the deposition of compounds may occur almost undisturbed; therefore, results of chemical analyses are readily used in the assessment of changes caused by natural processes and anthropogenic activities. In a temperate climate zone, the outermost layer of forest soils is formed by an organic horizon (O), which comprises two basic subhorizons, of which the organic fermentative-humic subhorizon (Ofh) is recognized as the most noteworthy. The subhorizon Ofh encompasses partially and fully decomposed organic matter (humic and fulvic acids, humins), as well as Fe, Mn, and Al oxides and hydroxides, forming a characteristic tangled mat. The structure pattern of this subhorizon is responsible for the higher concentrations of elements and organic compounds, which are immobilized through sorption, complexation, or precipitation. Some previous studies have shown that the subhorizon Ofh has enhanced accumulative properties in comparison to the remaining subjacent soil horizons. Results derived from soil studies in the Holy Cross Mountains (south-central Poland) have also revealed that this subhorizon is mainly enriched in polycyclic aromatic compounds (polycyclic aromatic hydrocarbons) and some trace elements (Hg, Cd, Cu, Pb, and Zn). This could make the subhorizon Ofh a potential geoindicator of soil quality in relation to these compounds over the temperate climate zone. However, further study on this issue is needed to confirm its application in environmental monitoring.

A single application of fertilizer can affect semi-natural grassland vegetation over half a century.

Restoration of species-rich semi-natural grassland requires not only a seed source but also appropriate soil properties. In Europe, approximately 10 years are required for the properties of fertilized soils to reach suitable conditions and be considered successfully restored. However, restoration may require additional time in Japan because heavier precipitation causes leaching of basic cations from soils, resulting in soil acidification; volcanic ejecta also forms active Al and Fe hydroxides with high phosphate sorption. Within this context, we aimed to answer the following questions: i) whether and how the impacts of fertilization remain in the soil properties after half a century in Japan; and ii) how fertilization affects the restoration of semi-natural grasslands in Japan. We investigated the vegetation and soil properties of a Zoysia japonica pasture improved half a century ago with a single application of fertilizer and an adjacent semi-natural grassland (native pasture) in Japan, and found the following: (1) the two pastures had similar dominance of Z. japonica, but differed in the species composition; (2) the improved pasture exhibited lower species richness than the native pasture; (3) soil nutrients, including N, P, K, Mg, and Ca, were higher in the improved pasture than in the native pasture; and (4) many chemical properties of the soils were associated with species composition; namely, the vegetation on nutrient-rich soil had more alien species and fewer native species. We conclude that a single dose of fertilization can affect soil properties in semi-natural grasslands over half a century in Japan, leading to species loss and changing the species composition. We suggest that fertilized soils under grazing in Japan may require more than half a century to restore the nutrients to suitable levels for the establishment of a species-diverse grassland.

Experimental insights into the formation of secondary minerals in acid mine drainage-polluted karst rivers and their effects on element migration

Acid mine drainage (AMD) threatens the water quality and safety of karst river water (KRW), and the formation of secondary iron or aluminum-bearing minerals during the mixing of AMD with KRW plays a crucial role in the migration of elements. However, the variations in the mineralogical, morphological and elemental compositions of secondary minerals and their influences on the migration of elements during AMD–KRW mixing have not been systematically studied. In this study, we mixed different proportions of AMD and KRW in a laboratory experiment to simulate seasonal hydrological conditions in a river to understand the major and trace elemental distributions in the mixed water and in precipitates and we discuss the formation process for the secondary minerals. The results showed that AMD can lead to a decrease in pH and DO and an increase in heavy metals and rare earth elements (REEs) in KRW. With the biological or chemical oxidation of Fe2+, Fe3+ combines with SO42− to form schwertmannite or hydrolyzes to form Fe(OH)3(s) and FeOOH(s), accompanied by the formation of amorphous Al hydroxide, resulting in a decrease in pH and an increase in Eh. Schwertmannite had strong adsorption and coprecipitation effects on Mn, Cr, Cu and As, so the adsorption and coprecipitation effects of schwertmannite on REEs were inhibited, while the migration of REEs were mainly affected by Al hydroxides. Therefore, after the AMD mixes with KRW, it not only causes severe water and sediment pollution but also adsorbs and enriches high concentrations of heavy metals in the secondary minerals formed during the mixing process, creating a major ecological hazard that requires further attention.

SO42−, Cl−, Br−, and TDS removal by semi continuous electrocoagulation reactor using rotating anode

In this study, the simultaneous removal of SO 4 2 − , Cl − , Br − , and TDS from saline lake water was investigated using an emerging electrocoagulation (EC) reactor in a batch and a semi-continuous electrocoagulation mode (batch recirculation system). The possibility of the EC process in salt removal and sludge production were evaluated. The EC continuous reactor with rotating anode was used and the effect of the impeller plate anode was validated. Several variables were estimated to set the optimum operating conditions for a batch system. The effects of variables such as rotation speed (rpm), retention time (min), recirculation flow rate, current density (mA/cm 2 ), inter space distance (mm), pH solution, and continuous flow system were optimized. These operational parameters were set at 75 rpm, 10 min, 4 L/min, 2 mA/cm 2 , pH 8, 1 cm 2 , and 0.25 L/min, respectively. Statistical analyses were performed to determine the optimal EC conditions. The results revealed that the maximum removal efficiency of SO 4 2 − , Cl − , Br − , and TDS were 90.2%, 93.4%, 90.8%, and 92.3%, respectively. Electrical energy, aluminum consumption, chemical reagents, and sludge production were calculated to achieve an operating cost per m 3 of $0.1766. The sludge and treated water were characterized, and the mechanism of the EC technology was assessed. The results revealed that treated water with the use of the EC process was very efficient, with a low overall consumption cost. • SO 4 2 − , Cl − , Br − , and TDS are limited via physical adsorption with Al hydroxides. • Impeller plates of rotating anodes were used. • EC rotation speed, retention time, pH, and current density were the key parameters. • The EC technology revealed efficiency in saline water treatment.