Passive Metal Research Articles

FEATURES OF THE INFLUENCE OF VARIOUS FACTORS ON THE QUALITY OF PROTECTIVE AND DECORATIVE CHROME COATINGS

The main features of the widespread use of electrolytic chromium coatings are their high chemical resistance and resistance to mechanical wear even with their small thickness. Practically all metal structures protected by electroplating, including chrome-plated ones, are subject to the corrosion process. The main goal in the electrolytic chrome plating process is to maintain the resistance to mechanical wear of the chromium coating. The positive factors causing the preservation of chrome coatings from corrosion damage are the search for new innovative technologies for obtaining particularly resistant chrome coatings. However, even with the high chemical resistance of chromium, complete corrosion protection of hardware products made of iron cannot be achieved. The reason for this undesirable phenomenon lies in the fact that in a pair of chromium-iron, chromium is the anode. Provided that the coating metal is a cathode, then there are favorable conditions for passivation of the base metal and then the coating can protect the base metal not only mechanically, but also electrochemically. To give protective properties to a chrome coating, a preliminary coating of an iron product with another metal is used – copper, nickel, silver, and then a chrome coating. In such cases, it is possible to give strength to the chrome coating even with a thickness of only about The work is devoted to the selection of methods for creating such a surface of the substrate to obtain chrome coatings of a given thickness, non-porous with good adhesion by electrodeposition.

Efficient activation of sodium percarbonate by hydroxylamine-enhanced zero-valent transition metals for the removal of AZO: performance, free radical generation and mechanism

Azoxystrobin (AZO) fungicides are novel organic pollutants which are stable in water environment. These pollutants can be degraded using low cost zero-valent metals (zero-valent iron (ZVI) and zero-valent copper (ZVC)) to activate sodium percarbonate (SPC), and the introduction of hydroxylamine (HA) can effectively improve the reaction efficiency of this system. According to the experimental results, HA significantly promoted the regeneration of Fe2+ and Cu+ in the decomposed solution of SPC, significantly accelerating the formation of hydroxyl radicals (•OH) and facilitating the degradation of AZO. Under optimal conditions, when pH = 3, the rate of AZO removal by the HA/ZVI/SPC system reached 99.0 % in 15 min, while the HA/ZVC/SPC system required 50 min to reach 99.1 % removal. Both of the tested HA/zero-valent metal/SPC processes produced •OH, carbonate radicals (CO3·-), superoxide radicals (O2·-) and singlet oxygen (1O2), among which, •OH appeared to be the main reactant responsible for AZO removal. Furthermore, it was found that •OH reacted with trace levels of carbonate ions to generate other reactive oxygen species and promote AZO degradation. The addition of HA not only slowed down the surface passivation of zero-valent metals, but also promoted the conversion of high-valent metal ions to low-valent metal ions, resulting in the generation of more reactive oxygen species within the system. In addition, the degradation intermediates were identified by LC-MS analysis and density-functional theory (DFT), allowing the possible AZO degradation pathways to be proposed.

The Correlation Between Wear and Lubricating Film Thickness in the Tribocorrosion of CoCrMo Alloy

Tribocorrosion modelling of passive metals considering the lubrication effect from solution is still not well studied. A lubricated tribocorrosion model for CoCrMo alloy metal-on-metal hip joints has been developed, while the generalization of this model is restricted by Dowson’s empirical correlation. This study explored the correlation between wear of CoCrMo alloy in tribocorrosion and lubricating film thickness. The results showed that the chemical, mechanical and total wear volumes of CoCrMo alloy in tribocorrosion were significantly influenced by the lubrication effect from the solution. Good correlations were obtained between the lubricating film thickness and chemical, mechanical and total wear, respectively. The new chemical and mechanical wear correlations could be used to generalize the current lubricated tribocorrosion model for CoCrMo alloy.

Passive self-ligating metal brackets: evaluation of torque and slot measurements

New orthodontic bracket designs have been regularly developed. Their clinical performance depends on reliability of measures, among other factors. Objective: The aim of this study was to evaluate slot measures and torque angle of different passive self-ligating metal brackets, while comparing them with measures provided by manufacturers. Material and methods: Five different passive self-ligating metal bracket brands were selected (n = 10 each): Tellus EX, Tellus EX New, Damon Q, Easy Clip and ID-Logical. Bracket slots images were obtained with the aid of Starrett, MV300 Galileo Vision System. For slot digital measurement, Software M3 Metrology Reabout IV was used. Slot measures were evaluated in cervico-occlusal direction (slot height), buccolingual depth (in-out), and bottom-slot inclination (torque angle). Difference between obtained and provided measures was estimated and expressed as a percentage. Data were subjected to descriptive statistical analysis. Results: Most brackets evaluated by the present study revealed variation in both torque angle and slot measures which were confirmed to be greater than those provided by the manufacturer (Easy Clip, Damon Q and Tellus EX), except for two brackets (Tellus EX New and ID-Logical). The latter presented variation within normality with values accepted by ISO standards (± 1 degree and ± 1 mm variation). Conclusion: Most brackets assessed herein (Easy Clip, Damon Q and Tellus EX) presented variation in torque angle and slot measures. Tellus EX New and ID-Logical brackets remained within standards. Better standardization and control should be assumed by manufacturers in order to promote more reliability and predictability of the orthodontic treatment results.

Effect of Cow Bone Addition on the Humification, Heavy Metals Passivation and Fate of Resistance Genes During Swine Manure Composting

Bone meal has been used as economic and effective additive for heavy metals (HMs) pollution remediation due to the distinct components and structures that enable their favorable properties, such as its low cost, high adsorption capacity, acid-base adjustability, and ion-exchange capability. However, no attempt has been made to establish whether cow bone could promote the passivation of HMs and the removal of metal resistance genes (MRGs) and antibiotics resistance genes (ARGs) during the composting process. Two sizes of cow bone (meal (T2) and granule (T3)) were added to investigate their effects on humification, HMs passivation and the abundance of ARGs and MRGs during swine manure composting. Excitation-emission matrix (EEM)-parallel factor analysis showed that the percentage of maximum fluorescence intensity of humic-like substances were higher in T2 (91.82%) than in T3 (88.46%), implying that T2 could promote the humification process compared to T3. In comparison with control (T1), the addition of T2 and T3 could promote the change of exchangeable Cu and reducible Cu into oxidizable Cu, thus reducing the mobility factors (MF) of Cu in T2 and T3 treatments by 10.48% and 6.98%, respectively. In addition, T2 and T3 could increase exchangeable Zn into reducible Zn and oxidizable Zn, thereby reducing the MF of Zn in T2 and T3 treatments by 18.80% and 2.0%, respectively. Quantitative Real-time PCR (qPCR) analysis revealed that the total abundances of MRGs were decreased by 100% in T2 and T3 treatments, and T2 decreased the total relative abundance of ARGs. Furthermore, the relative abundance of ARGs and MRGs had significantly correlated with intI1 and bio-available of Cu and Zn, which was triggered by selective pressure of HMs and horizontal gene transfer. The present study suggested that cow bone meal as additives can be a feasible approach to promote the passivation of HMs and enhance the removal of MGRs and ARGs by decreasing horizontal gene transfer and selective pressure by bioavailable HMs.

Microbial fuel cell-assisted composting yields higher performance on metals passivation, antibiotics degradation, and resistance genes removal

Little scientific evidence on metal passivation, antibiotic degradation and resistance genes removal, is available under autogenetic electrochemical reactions during composting process. This study established microbial fuel cell (MFC)-assisted composting procedure to ascertain the removal performance and detoxification mechanisms involving metals, antibiotics and their resistance genes. Compared to control treatment, the bioavailability of zinc (Zn) and copper (Cu) in MFC-assisted treatment decreased by 7.8% and 26.9%, while the content of tetracycline (TCL) and oxytetracycline (OCL) reduced by 100% and 89%, respectively. Organics mineralization and humification were responsible for 80% and 70% of the variations in metal passivation and antibiotic degradation during composting process. A decrease of 54% was found for tetW gene, while copA gene increased by 42% in MFC-assisted composting treatment. These findings highlight the detoxification mechanisms underlying metal passivation and antibiotic degradation during composting process, and potentially offer valuable insights for environmental source protection and agricultural sustainable development.

Respirometric Studies on Transpassive Dissolution

Recently, we introduced respirometric methods for real-time monitoring of corrosion, both for atmospheric corrosion [1] and immersion conditions [2]. The approach is based on monitoring the rate of the cathodic reactions with help of different types of sensors; this enables to track the O2 reduction reaction and the H2 evolution reaction simultaneously. The set-ups have been used to study different corrosion scenarios under free corrosion conditions.Even more recently, the respirometric setups were coupled with electrochemistry [3, 4], enabling the corrosion cases to be studied not only at open-circuit conditions but also for potential-controlled systems. With this, it is possible for instance to de-convolute the sum current measured by potentiodynamic polarization curves into different cathodic and anodic partial reaction rates. For passive metal and alloys, transpassive dissolution is being explored, by quantification of the amount of oxygen evolving during transpassive dissolution that typically occurs at potentials above the water stability region (i.e., the net anodic electrical current/charge is a sum of partial currents for oxygen evolution reaction, OER, and for metal oxidation/dissolution). Therefore, a true metal oxidation rate can be determined that is not directly assessable from the electrochemical measurement. Examples will be presented, to illustrate the potential of these techniques to reveal insights into corrosion mechanisms of active and passive metals and alloys.References M. Strebl, M. Bruns, S. Virtanen, Editors’ Choice—Respirometric in Situ Methods for Real-Time Monitoring of Corrosion Rates: Part I. Atmospheric Corrosion, J. Electrochem. Soc. 167 (2020) 21510M.G. Strebl, M.P. Bruns, G. Schulze, S. Virtanen, Respirometric In Situ Methods for Real-Time Monitoring of Corrosion Rates: Part II. Immersion, J. Electrochem. Soc. 168 (2021) 11502M.G. Strebl, M.P. Bruns, S. Virtanen, Coupling Respirometric HER and ORR Monitoring with Electrochemical Measurements, Electrochimica Acta 412 (2022) 140152M.G. Strebl, M. Bruns, S. Virtanen, Respirometric In Situ Methods for Real-Time Monitoring of Corrosion Rates: Part III. Deconvolution of Electrochemical Polarization Curves, J. Electrochem. Soc. 170 (2023) 061503

High Performance Zinc-Based Anodes for Aqueous Zinc Batteries

In the past thirty years, there has been significant development in the search for alternative energy sources such as secondary battery systems. Zinc (fourth-most mined material) has attracted much attention due to its abundance, low-cost, and recyclability. Moreover, as zinc-based batteries can be manufactured with aqueous-based electrolytes that benefits from many advantages of Zn anode, such as low redox potential (-0.76V vs SHE), high theoretical capacity (820mAh/g), and enhanced safety. These features allow for high applicability in large-scale stationary energy storage system. Zinc-based batteries (MnO2/Zinc) have been previously commercialized and are one of the dominant technologies in the primary battery market. However, the alkaline MnO2/Zn battery is not currently considered re-chargeable due to the formation of zinc-dendrites, passivation of Zn metal, and cathode poisoning. In contrast to the alkaline system, the mild acidic system does not suffer from zinc passivation as there is negligible generation of zinc oxide/zinc hydroxide.In this work, we report a proof-of concept work where electrodeposited zinc-based anodes (zinc and zinc-alloys) are used in mild acidic aqueous electrolyte. The study provides a comparison of commercial zinc foil, and electrodeposited zinc/zinc-alloy. The anodes are further analyzed structurally through X-ray diffraction and scanning electron microscopy. To evaluate the feasibility of each anode. further electrochemical characterization was carried out in coin cells as symmetric and full cells. The electrodeposited zinc-based anodes exhibit low electrode polarization (~0.030-0.045V), and more stable cycling performance at 10 mA cm-2 compared to commercial zinc foil. Furthermore, full cells with an electrodeposited zinc or zinc-alloy anode, DTT cathode, in 2M ZnSO4 delivered comparable capacities but higher stability compared to commercial zinc. Consequently, this work points toward a further development for anode materials in rechargeable aqueous zinc batteries for scalable applications.

Investigation of the Passivation Reaction of Li Metal in Liquid Electrolytes Using Microcalorimetry

The demand for energy storages with high energy density and long lifetime is growing rapidly. Using lithium metal as an anode would maximize the energy density of lithium batteries by having an anode-free system in the discharged state. Lithium-ion batteries can undergo several thousand cycles using liquid electrolytes with low capacity losses and very low safety risks. Passivation of lithium metal and the uncontrolled formation of lithium dendrites has so far prevented the large-scale commercialization of lithium-metal batteries with liquid electrolytes. Understanding the passivation reactions and formation of the solid electrolyte interphase in of lithium metal in liquid electrolytes is crucial to increase the longevity and safety of this system. In this study, we present experimental results on the lithium metal liquid interfaces for next-generation lithium batteries utilizing isothermal microcalorimetry.The experimental setup involved the investigation of coin cells at a symmetrical lithium metal cell and lithium-copper (Li-Cu) half-cell level. Two baseline electrolytes were employed, including a carbonate (EC:EMC 3:7 wt%, 1M LiPF6) and an ether-based- formulation (LiFSI:DME:TTE 1:1.2:3 molar), supplemented with fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives. Those coin cells were investigated at various current densities ranging from 0.5 to 5 mA/cm² at a constant cyclic capacity throughput of 5 mAh/cm².Our results reveal insights into the thermodynamic behavior and stability of lithium metal interfaces in different electrolyte environments and for different current densities. The calorimetric measurements provide the additional information on the heat flow associated with plating and stripping processes, shedding light on the kinetics of lithium deposition and dissolution. Furthermore, we systematically investigated the influence of electrolyte composition, including the presence of FEC and VC additives, on the interfacial properties and passivation reactions of lithium metal. In symmetrical lithium metal cells, we observed distinct heat signatures corresponding to the coulombic efficiency (CE) in Li-Cu half cells. The addition of FEC and VC additives exhibited pronounced effects on the suppression of irreversible passivated lithium depositions and the enhancement of stability at high current rates.Our results highlight the importance of electrolyte composition in the behavior of lithium metal/liquid electrolyte interfaces. The comprehensive understanding gained from these experiments provides a basis for testing new electrolyte compositions with additional insight over conventional testing methods.

(Invited) Low Contact Resistance on Buried Interfaces in Oxide Thin-Film Transistors by Selective-Area Reduction Using Hydrogenation Catalyst Electrode

As the focus on amorphous oxide semiconductor (AOS) in memory applications deepens, there is a push for higher packing densities and more efficient read-write efficiencies, leading to increasingly complex AOS transistor structures with dimensions scaled down to the nanometer size. In pursuit of high density for AOS-based dynamic random-access memory (DRAM), 3D-stacked vertical IGZO transistor devices have been employed, wherein the contact interfaces of these vertical devices are buried and located internally within the device, and these vertical or buried interfaces are prone to causing contact issues. However, conventional methods to addressing contact resistance in thin-film transistors (TFTs) used for flat-panel displays are not applicable to buried interfaces. The development of novel methods to resolve this issue is a current challenge for the future development of complex structured AOS memory devices.In this work, the contact resistance of a-IGZO TFT was reduced by three orders of magnitude by utilizing hydrogenation catalyst electrodes for a selective area reduction reaction at the interface and constructing a hydrogen transfer pathway1. The key to effective hydrogenation on the internally buried interface is the selection of the optimal catalyst metal electrode and passivation materials that satisfy the following requirements. 1) High hydrogen diffusion rate and moderate hydrogen solubility for reversible hydrogen transfer. 2) Catalytic hydrogen dissociation to highly active H0 atoms on/in the metal electrode for low-temperature reaction [Fig. 1(a)]. 3) Dense oxide passivation layer with hydrogen tolerant electronic structure to hydrogen, in which a shallower CBM than the charge transition level of E(H+/H−), to isolate the effective channel from hydrogen. Pd was selected as the best electrode for this strategy owing to its flexible lattice and unique properties of hydrogen permeability without brittleness to hydrogen. Also, amorphous Zn–Si–O (ZSO x ), which can be easily deposited by sputtering, was used as the passivation layer.Detection through hard X-ray photoelectron spectroscopy indicates that the high reactivity of H0 reduces metal oxides at the interface, forming a metallic interface layer. Fig. 1(b) shows the hydrogen annealing condition dependence of the contact resistance and effective channel length deviation estimated by TLM measurements. By optimizing hydrogen annealing conditions, the company succeeded in achieving both a small effective channel length deviation of ~40 nm and contact resistance that was reduced by approximately three orders of magnitude. The field-effect mobility was enhanced from 3.2 to ~20 cm2 V–1 s–1 as a consequent effect of the improved contact resistance. Furthermore, as shown in Fig. 1(c), the prepared a-IGZO TFTs also demonstrated excellent bias-stability, further proving the reliability of using catalytic electrodes and hydrogen tolerant passivation layer in the process.

Simultaneous Passivation and Removal of Heavy Metals in the Compost of Agricultural Waste and Sediment by the Enhanced Migration of Liquid Media

Simultaneous Passivation and Removal of Heavy Metals in the Compost of Agricultural Waste and Sediment by the Enhanced Migration of Liquid Media

Investigation of resistive switching behavior driven by active and passive electrodes in MoO2–MoS2 core shell nanowire memristors

Memristive devices based on layered materials have the potential to enable low power electronics with ultra-fast operations toward the development of next generation memory and computing technologies. Memristor performance and switching behavior crucially depend on the switching matrix and on the type of electrodes used. In this work, we investigate the effect of different electrodes in 1D MoO2–MoS2 core shell nanowire memristors by highlighting their role in achieving distinct switching behavior. Analog and digital resistive switching are realized with carbon based passive (multi-layer graphene and multiwall carbon nanotube) and 3D active metal (silver and nickel) electrodes, respectively. Temperature dependent electrical transport studies of the conducting filament down to cryogenic temperatures reveal its semiconducting and metallic nature for passive and active top electrodes, respectively. These investigations shed light on the physics of the filament formation and provide a knob to design and develop the memristors with specific switching characteristics for desired end uses.

Poly-γ-glutamic acid chelates chromium (III) and copper (II), alleviating their toxicity in cucumber and affecting rhizosphere bacterial community assembly

The accumulation of chromium (Cr) and copper (Cu) in soil during industrialization and modernization poses an extreme threat to crops. Poly-γ-glutamic acid (γ-PGA) has the potential to stabilize heavy metals in soil through chelation because of the numerous carboxyl groups in its side chain. The rhizosphere microbiome contributes to plant detoxification by participating in heavy metal passivation. However, it is still unclear whether γ-PGA can alleviate the toxicity of Cr and Cu to plants and whether this effect is associated with changes in the rhizosphere microbiome assembly. Here, we found that γ-PGA application significantly reduced the content of Cr or Cu in cucumber plants by 67.45%–86.77% and 94.67%-98.21, respectively, and alleviated the oxidative stress of Cr or Cu to plants. Moreover, γ-PGA significantly increased the biomass of cucumber fruits in the plot experiment by 13.5% and 25.3% under Cr and Cu stress, respectively. The content of Cr or Cu in the cucumber fruit was below limits of detection, in contrast to the 31.23 mg/kg Cr or 9.86 mg/kg Cu detected in the no-γ-PGA treatment. γ-PGA effectively chelated Cr and Cu in vitro, and less than 30% of their chelates were degraded in 20 weeks, suggesting the strong stability of these chelates. γ-PGA significantly altered the rhizosphere bacterial community composition of cucumber by enriching phyla Gemmatimonadota, Acidobacteriota and Firmicutes, and genera Gemmatimonas and Stenotrophomonas, which potentially involved in reducing the mobility of Cr and Cu in soils. Furthermore, γ-PGA significantly enriched taxa assigned to plant growth-promoting bacteria (PGPB). Together, our results suggest that γ-PGA can reduce the Cr and Cu contents in cucumber, and this process is strongly associated with the chelation capacity of γ-PGA and its effects on rhizosphere microbiome composition. These results highlight the exciting potential to use γ-PGA for the remediation of heavy metal-contaminated soils.

Mechanisms of heavy metal-induced rhizosphere changes and crop metabolic evolution: The role of carbon materials

To investigate the effects of modified carbon-based materials on soil environmental remediation and crop physiological regulation, this research relied on rice pots with lead (Pb) and cadmium (Cd) composite contamination. Dolomite, montmorillonite, attapulgite and sepiolite modified biochar with different doses have been developed to explore the mechanisms on heavy metal passivation, nutrient improvement, microbial activation, and crop growth. The results indicated that the modified materials effectively reduced heavy metal bioavailability and accumulation in plant tissues through adsorption complexation. Specifically, under montmorillonite and sepiolite modified treatments, the Grains-Pb content significantly decreased by 29.23–30.31% and 27.49–30.58%, compared to the control group (CK). Meantime, carbon-based materials increased available nutrient levels, providing a biological substrate for soil microorganisms metabolism. The content of ammonium nitrogen (NH4+-N) and available phosphorus (AP) in different proportions of montmorillonite modified biochar increased by 10.99–13.98% and 55.76–77.86%, respectively, compared to CK. Furthermore, sepiolite modified biochar enhanced bacterial community diversity, significantly improving the tolerance and resistance of bacterial communities such as Proteobacteria and Acidobacteria to heavy metals. Meanwhile, carbon-based materials enhanced community stability and network complexity, improving microbial stress resistance to adverse environments. In summary, montmorillonite and sepiolite modified biochar regulated microbial community interaction mechanisms by mitigating the physiological toxicity of heavy metals. This process enhanced soil available nutrients and ecological function stability, which had significant implications for improving crop growth and quality.

The improvement in methane production, nutrient removal, and heavy metal passivation during anaerobic digestion of chicken manure: The role of modified porous materials

The improvement in methane production, nutrient removal, and heavy metal passivation during anaerobic digestion of chicken manure: The role of modified porous materials

Effect of natural aging on biochar physicochemical property and mobility of Cd (II).

This project utilized both field experiment and laboratory analyses to address the gap in understanding regarding the alterations in properties and functions of biochar, and the impact of heavy metal passivation in soil over long-term natural field aging. The study aimed to examine the changes in the physical and chemical characteristics of biochar over an extended period of natural aging. Additionally, it sought to analyze the impact and mechanisms of biochar in reducing of the harmful effects of the heavy metal cadmium (Cd) during the aging process. Both original and aged biochar conformed to the pseudo-second-order kinetics model and the Langmuir model. The aging process enhanced the adsorption of Cd by biochar and mitigated the leaching of Cd2+ into the soil. These findings provide a scientific basis for evaluating biochar's environmental behavior and its potential use in the remediation of soil contaminated with heavy metals.

Co-hydrothermal carbonization of lignocellulosic biomass and swine manure: Optimal parameters for enhanced nutrient reclamation, carbon sequestration, and heavy metals passivation

Hydrochar, the primary product of hydrothermal carbonization (HTC) of wet organic waste, is recognized as a versatile, carbon-abundant material with diverse applications. However, optimizing its performance for specific uses remains challenging. Therefore, this study introduced a co-HTC process involving carbon-rich lignocellulosic materials and ash-rich livestock manure [i.e., Zanthoxylum bungeanum branch residue (ZB) and swine manure (SM), respectively]. The impacts of HTC temperature (i.e., 180 °C, 220 °C, and 240 °C) and mass ratios (i.e., 1:0, 7:3, 5:5, 3:7, and 0:1) on hydrochar properties (e.g., pH, EC, nutrient contents, heavy metal content and availability, chemical stability, etc) and the characteristics of process water were evaluated. Results reveal that co-HTC dramatically improved the quality of hydrochars compared with that derived from a single feedstock. Notably, the ZB:SM ratio had a more substantial impact on total nutrient content, carbon stability, and heavy metal accumulation and mobility. Additionally, the synergistic effects of ZB and SM were greatly dependent on the HTC temperature. By adjusting the feedstock mass ratio and HTC temperature, a highly-functionalized hydrochar can be produced. For example, hydrochars produced at 240 °C with a 7:3 ZB to SM ratio (HC240-7) is optimal for degraded soil amendment, enhancing carbon sequestration and nutrient supplementation. Results from this study could provide valuable insights for improving waste management through HTC and expanding the environmental and agricultural application of hydrochar.

Optimizing feedstock organic composition to regulate humification and heavy metal passivation during solid-state anaerobic digestion

This study uncovered the impacts of feedstock organic composition, comprising proteins, lignocellulose, and lipids, on humification and passivation of heavy metals (HMs) in solid-state anaerobic digestion (SSAD). Mantel tests and partial least squares structural equation modeling (PLS-SEM) results revealed that copper (Cu) and zinc (Zn) passivation predominantly occurred through complexation with humic acid (HA). In contrast, lead (Pb) and chromium (Cr) passivation were pH-dependent as influenced by substrate conditions in SSAD. Increasing protein content in the feedstock facilitated lignocellulose biodegradation to enhance HA formation, and thus augmenting Cu and Zn passivation. Furthermore, the improved biodegradation of organic components elevated the substrate pH, further enhancing Pb and Cr passivation. Such improvement was notable when the protein: lignocellulose: lipid ratio of feedstock was regulated to 4.1:3.7:2.2, which increased HA contents to 35.25% and pH to 9 to enhance the passivation of Cu, Pb, and Cr by 0.48%, 52.0%, and 17.9%, respectively.

Effect of Rice Biochar on Typical Cadmium, Lead and Zinc Form in Contaminated Soil in Northwest Guizhou Province, China

This study was conducted in Hezhang County, Bijie City, Guizhou Province. The soil in the zinc smelting area has been contaminated with cadmium, lead, and zinc. Therefore, these elements are the focus of this research. Rice husk biochar was used as the passivation material. The Fourier infrared spectrum was utilized to study the biochar’s morphology, element content, mineral composition, structure, and surface functional groups. Moreover, the physical and chemical properties of the biochar were analyzed to explore its passivation effect. Biochar is beneficial in the cleaning of cadmium, lead, and zinc minerals and can be used for the passivation of heavy metals in contaminated soil. This study aims to understand the detailed mechanism behind this process and provide experimental data and ideas for pollution control. The results indicate that the biochar contains many functional groups, including -OH, C-H, C-O, C=O, C=C, and C-O-C. It also consists of a significant quantity of potassium salt, calcite, and quartz. Biochar has a noticeable pore structure, and as the pyrolysis temperature increases, the pore structure becomes more developed and thinner, with a smooth surface. The main minerals in the soil are quartz, mica, zeolite, illite, and chlorite. The aromatic degree of biochar increased with pyrolysis temperature. In contrast, the aromatic degree and polarity first increased and then decreased. The 0.2-0.45 mm biochar exhibited the best passivation effect on cadmium, lead, and zinc.

Bone aluminum accumulation in the current era.

In the last few years, evidence from the Brazilian Registry of Bone Biopsy (REBRABO) has pointed out a high incidence of aluminum (Al) accumulation in the bones of patients with CKD under dialysis. This surprising finding does not appear to be merely a passive metal accumulation, as prospective data from REBRABO suggest that the presence of Al in bone may be independently associated with major adverse cardiovascular events. This information contrasts with the perception of epidemiologic control of this condition around the world. In this opinion paper, we discussed why the diagnosis of Al accumulation in bone is not reported in other parts of the world. We also discuss a range of possibilities to understand why bone Al accumulation still occurs, not as a classical syndrome with systemic signs of intoxication, as occurred it has in the past.