Dissolution Of Zn Research Articles

Cadmium geochemistry and groundwater pollution status evaluation using indexing and spatial analysis for Keffe community and Environs Sokoto Basin, North Western Nigeria

Representative groundwater samples were collected from the Kaffe community and environs to evaluate the concentrations and geochemical constraints for mobilizing cadmium (Cd) and selected heavy metals. Field-based in-situ measurements of physicochemical parameters were combined with Atomic Absorption Spectrophotometer analysis of dissolved elemental concentrations. Pollution indices (i.e. heavy metal pollution index; HPI, heavy metal evaluation index; HEI, contamination degree; Cd, metal index; MI, synthetic pollution index; SPI, ecological risk index; ERI and Nemerow index; NI) evaluations highlighted the levels of heavy metals in the groundwater. Cadmium and iron (Fe) concentrations exceeded the recommended limits in 97% of the analysed samples, with an average pH of 6.3. Strong positive correlations were observed between cadmium and the computed pollution indices (p 0.774 to p 0.100), suggesting significant Cd pollution of the groundwater. Components analysis grouped Cd, Fe, and the pollution indices in the first PC. This was favourably compared to the correlation analysis result. Cluster analysis categorized Cd, Zn and pH in the first cluster consistent with the suggested dissolution and enrichment of Cd and Zn in the groundwater under similar geochemical conditions. The study area is medium and moderately polluted based on HPI, HEI, Cd, and NI.

Effect of Zn interlayer on friction stir butt welding of A1100 and SUS316L stainless steel

The effect of Zn interlayer on the microstructure and mechanical properties of dissimilar A1100 and SUS316L friction stir welded (FSW) butt joints was investigated. The results showed that Zn could improve the joint’s tensile strength. However, a complete dissolution of the Zn interlayer was necessary to achieve a sound joint. During the FSW process, the stirring action of the tool dispersed the Zn into the A1100 matrix forming a solid solution of Zn. A direct relationship was found between the tool rotational speed and the Zn dissolution rate. Also, the addition of Zn inhibited the Al–Fe IMCs growth, which played a positive role in the obtained tensile strength.

Nanostructuring Matters: Stabilization of Electrocatalytic Oxygen Evolution Reaction Activity of ZnCo2O4 by Zinc Leaching

Despite the enormous attention paid to cobalt oxide materials as efficient water splitting electrocatalysts, a deep understanding of their activity discrepancy is still elusive. In this work, we showed that stabilization of the internally generated oxygen evolution reaction (OER) active phase (oxyhydroxide) is crucial for ZnCo2O4 electrocatalysts. A systematic evaluation of the bulk and nanostructured ZnCo2O4 system concomitant with nanostructured Co3O4 showed that leaching of Zn is the driving force behind the near-surface transformation to the oxyhydroxide phase. The relative contribution to this near-surface reconstruction was found to be surface-sensitive. The electrochemical observations combined with Raman and impedance spectroscopy revealed that the good catalytic activity could be attributed to the formation of the cobalt oxyhydroxide phase, which was created by the dissolution of Zn from the nanostructured surface. Moreover, this study sheds light on previous contradicting postulates regarding the discrepancy of the OER activity of ZnCo2O4. Our finding regarding the formation of the OER active phase in spinel Zn-Co oxide will motivate researchers to focus more on the near-surface reconstruction behavior of cobalt-based oxide electrocatalysts in the future.

Electrochemical Growth of Ag/Zn Alloys from Zinc Process Solutions and Their Dealloying Behavior

This study investigates the sustainable preparation of Ag/Zn alloys from a simulated zinc process solution (20 ppm Ag, 65 g/L Zn, and 10 g/L H2SO4) via electrodeposition-redox replacement (EDRR) and the electrochemical dealloying behavior of the Ag/Zn alloys. Results indicate that Ag/Zn deposits with diverse compositions and microstructures can be obtained at room temperature without any complexing agents, simply by varying EDRR parameters like deposition time, deposition potential, and redox replacement time. Two types of Ag/Zn intermetallics (Zn0.96Ag0.04 and Ag0.76Zn0.24) were identified by the combination of X-ray diffraction (XRD) and anodic linear sweep voltammetry. Mass-transfer limitations have significant effects on the growth process, and a nucleation-growth mechanism from Ag/Zn particles into dendrites with increased EDRR cycles is introduced: with EDRR parameters favoring mass-transfer limitations (higher overpotentials, longer deposition times, and shorter redox replacement times), a more dendritic morphology of Ag/Zn alloys is achieved. The selective dissolution of Zn (i.e. dealloying) allowed the formation of silver-rich surfaces with an enhanced surface plasmon resonance behavior, which can be readily tuned by EDRR and dealloying parameters. These results highlight the significant potential of the EDRR-dealloying route to produce different types of Ag/Zn alloys and optically functional materials directly from base metal process solutions.

Flooding and drainage induced abiotic reactions control metal solubility in soil of a contaminated industrial site

Intense industrialization has led to the increasing leaching risk of metals into groundwater at heavily polluted industrial sites. However, metal dissolution in polluted industrial soils has been neither fully investigated nor quantified before. In this study, the dissolution of Zn, Ni, and Cu in soil from a heavily contaminated industrial site during a flooding-drainage period was investigated by sequential extraction, geochemical modelling, and X-ray absorption near edge structure spectroscopy. The results showed a steady decrease in metal solubility during both reduction and oxidation stages. During reduction, with limited decrease in Eh (>100 mV), formation of carbonate precipitates rather than sulfide precipitates and adsorption on soil solids was responsible for Zn and Ni dissolution, whereas bound to soil organic matter (SOM) and iron oxides dominated Cu dissolution, due to its lower concentration and higher affinity to SOM and iron oxides compared to Zn and Ni. During oxidation, the acidity caused by ferrous oxidation was buffered by calcite dissolution, while metal precipitation ceased and adsorption on soil surface controlled metal solubility. The metal solubility and speciation during the flooding-drainage process were quantitatively predicted by geochemical model. The findings demonstrate that due to high metal concentrations and weak microbial effect in the industrial soil, metal release was largely regulated by abiotic reactions rather than biotic reactions, which is somehow different from that of the wetland or rice field soils.

Highly Efficient, Dendrite‐Free Zinc Electrodeposition in Mild Aqueous Zinc‐Ion Batteries through Indium‐Based Substrates

AbstractQuasi‐neutral aqueous zinc‐ion (Zn‐ion) batteries are nowadays among the most promising energy storage devices for smart‐grid applications. However, their practical use remains hindered by the low Zn electrodeposition efficiency at the negative electrode, which is especially reduced due to the parasitic evolution of gaseous hydrogen. Indium is a non‐toxic metal showing poor hydrogen evolution kinetics, but it is also very expensive. Therefore, an optimized mixture of bismuth and indium particles has been used as the substrate for the Zn electrodeposition and dissolution reaction to increase its reversibility and its efficiency in a quasi‐neutral ZnSO4 solution. This strategy not only allowed to prolong the cycle life of a full Zn‐ion cell of 10 times at 0.5 C due to the suppression of the hydrogen evolution reaction, as proved by the operando DEMS analysis, but also led to very homogeneous zinc deposits over prolonged cycling at realistic charge and current densities.

Selective dissolution during acid pickling of aluminum alloys by element-resolved electrochemistry

The surface reactivity and the elemental dissolution of a high-strength aerospace alloy (AA7449-T651) during acid pickling was investigated with element-resolved electrochemistry (AESEC). The results demonstrated a sequential dissolution of Mg, Al, Zn and Cu, following the order of their respective galvanic reactivity in common acid pickling solutions. The enrichment of Cu during pickling with the H2SO4 solution was observed. The effect of oxidizing solution components HNO3 and Fe(III) on Cu dissolution were investigated using an experimental Evans diagram approach.

Unlocking the Allometric Growth and Dissolution of Zn Anodes at Initial Nucleation and an Early Stage with Atomic Force Microscopy.

Zn anodes have gained intensive attention for their environmental-friendliness and high volumetric capacity but are limited by their severe dendrite formation. Understanding the initial nucleation behavior is critical for manipulating the uniform deposition of Zn. Herein, the allometric growth and dissolution of Zn in the initial nucleation and early stages are visualized with in situ atomic force microscopy in aqueous ZnCl2 electrolytes. Zn nuclei grow via a horizontal radial direction and dissolve reversibly in a top-down process. The critical nucleation radius and density are dependent on the electrolyte concentration of ZnCl2, namely, the initial nucleus size is proportional to the ratio of surface free energy between deposited Zn and the electrolyte and overpotentials for Zn electrodeposition, and the density is inversely proportional to the cube of this ratio. This investigation provides guidelines for regulating uniform metal electrodeposition and yields benefits for the development of anode-free batteries.

Root Reason for the Failure of a Practical Zn-Ni Battery: Shape Changing Caused by Uneven Current Distribution and Zn Dissolution.

In recent years, with the increasing application of lithium-ion batteries in energy storage devices, fire accidents caused by lithium-ion batteries have become more frequent and have arisen wide concern. Due to the safety of aqueous electrolyte, aqueous Zn-based batteries have attracted vast attention, among which Zn-Ni batteries stand out by virtue of their excellent rate performance and environmental friendliness. However, poor cycling life limits the application of Zn-Ni batteries. To figure out the main cause, a failure analysis of a practical Zn-Ni battery has been carried out. During the cycling of the Zn-Ni battery, the evolution of gas, the shape changing, and the aggregation of additive and binder of Zn anode can be observed. Combined with the finite element analysis, we finally reveal that the key factor of battery failure is the shape changing of the Zn anode caused by uneven current distribution and the dissolution of Zn. The shape changing of the Zn anode reduces the effective surface area of anode and increases the possibility of dead Zn, which makes the battery unable to discharge even in the presence of a large amount of Zn. These findings are helpful to deepen the understanding of the working and failure mechanisms of the Zn anode and provide effective guidance for subsequent research.

Direct and pulsed current electrodeposition of Zn-Mn coatings from additive-free chloride electrolytes for improved corrosion resistance

Electrodeposited Zn-Mn alloy coatings are known to provide excellent corrosion resistance to steel due to their ability to form compact corrosion products when exposed to corrosive media. However, obtaining good quality coatings using conventional direct current (DC) electrodeposition from additive free baths is challenging. Pulsed current (PC) deposition has been reported for various Zn based alloy systems to obtain coatings with superior corrosion resistance properties. In this work, Zn-Mn coatings containing up to 9.2 wt. % Mn were electrodeposited on steel from additive-free chloride electrolytes using both DC and PC electrodeposition. Cyclic voltammetry, potentiostatic measurements, Hull cell experiments and SEM-EDS studies indicated good quality DC deposited Zn-Mn coatings in the current density range of 40-60 mA cm−2 with clustered plate morphology at low and cauliflower morphology at higher current densities. PC deposited coatings showed increased Mn contents and improved corrosion rates. The coating deposited at a low duty cycle and a high frequency showed a fine and compact microstructure with the highest Mn content of 9.2 wt. %. XRD studies showed a complete change in phase composition from a monophasic η-Zn-Mn coating with DC to a monophasic ε-Zn-Mn with PC deposition. Electrochemical impedance analysis revealed porous corrosion products in DC coating, whereas the PC coating formed a compact corrosion product which inhibited the dissolution of Zn and Mn, thus providing higher resistance to corrosion. XRD analysis of the samples after corrosion confirmed the presence of zinc hydroxy chloride (ZHC) as a corrosion product. In summary, PC electrodeposited Zn-Mn coatings provided superior corrosion resistance than those obtained through DC.

Catalytic Effect of Graphite Promoting Zn Dissolution from Sphalerite using a Leptospirillum ferrooxidans Dominated Mixed Culture

In this study, the effect of graphite on sphalerite dissolution was investigated using a Leptospirillum ferrooxidans (L. ferrooxidans) dominated meso-acidophilic bacterial consortium. Results of the studies indicated that Zn dissolution enhanced from 18.75% (in control tests) to 78.46% (using L. ferrooxidans) without graphite in the system (the conventional approach). Addition of graphite further improved sphalerite bio-oxidation up to 10%, i.e., from 78.46 to 87.83% indicating bio-catalytic effect and possible galvanic interaction between sphalerite and graphite. Through the conventional route, the system’s pH eventually lowered from 1.8 to 1.4 and ORP increased from 300 to 700 mV. In presence of graphite, the pH lowered to nearly 1.0 and ORP reached 600 mV. This indicated efficient bacterial activity and stabilized leaching conditions in both cases. Analytical characterization studies through XRD and SEM-EDAX indicated the presence of sulfur and K-type jarosite (KFe3+ 3(OH)6(SO4)2), ascribed to the passivation layers formed during sphalerite bioleaching.

An Extrinsic Faradaic Layer on CuSn for High-Performance Electrocatalytic CO 2 Reduction

An Extrinsic Faradaic Layer on CuSn for High-Performance Electrocatalytic CO ₂ Reduction

One-step, low temperature synthesis of reduced graphene oxide decorated with ZnO nanocrystals using galvanized iron steel scrap

Production of a ZnO–rGO composite, using a novel one-pot method consisting in continuously flowing argon into a GO aqueous suspension heated at 80 °C, in the presence of galvanized iron steel scrap is presented. FTIR shows the complete disappearance of GO functional groups and only the C=C band remained, indicating extensive GO reduction. Raman spectra indicated sp2 character increase after reaction and the presence of the E2h mode of ZnO. SEM showed submicron crystals identified by XRD as ZnO in the hexagonal phase, while TEM images indicate ZnO nanoparticles decorate mainly the rGO borders. Optical band gap of 3.5 eV corresponding to ZnO, and optical transitions at 4.1 and 5.5 eV related with n → π and π → π* were observed. Electrochemical characterization by cyclic voltammetry shows an specific capacitance of 4.7 F g−1 at a scan rate of 5 mVs−1, which drops to ca. 0.8 F g−1 at 200 mVs−1. By electrochemical impedance spectroscopy, the relaxation time was ca. 5 ms. The proposed mechanism for the materials‘ synthesis includes Zn dissolution from scrap, galvanic displacement of oxygen moieties at the GO sheet, Zn deposition onto the carbon surface, and further oxidation and growth of ZnO nanocrystals.

Effect of ZnO nanoparticles on Zn, Cu, and Pb dissolution in a green bioretention system for urban stormwater remediation

Stormwater runoff from urban and suburban areas can carry hazardous pollutants directly into aquatic ecosystems. These pollutants, such as metals, nutrients, aromatic hydrocarbons, pesticides, and pharmaceuticals, are very toxic to aquatic organisms. Recently, significant amounts of zinc oxide engineered nanoparticles (ZnO-NPs) have been detected in urban stormwater and its bioretention systems. This raises concerns about a potential increase of stormwater toxicity and reduced performance of the treatment infrastructures. To tackle these issues, we developed a simple, low-cost bioretention system to remediate stormwater and retain ZnO-NPs. This system retained up to 73% Zn, 66% Cu, and >99% Pb. However, the removal efficiency for Pb was lower after adding ZnO-NPs to the system, possibly due to the remobilization of Pb phosphates. The effect of ZnO-NPs on stormwater toxicity and metal accumulation in wetland plants was also evaluated.

Uptake and Translocation of Mesoporous SiO2-Coated ZnO Nanoparticles to Solanum lycopersicum Following Foliar Application.

Nanoparticles composed of ZnO encapsulated in a mesoporous SiO2 shell (nZnO@SiO2) with a primary particle diameter of ∼70 nm were synthesized for delivery of Zn, a micronutrient, by foliar uptake. Compared to the rapid dissolution of bare nZnO (90% Zn dissolution after 4 h) in a model plant media (pH = 5), nZnO@SiO2 released Zn more slowly (40% Zn dissolution after 3 weeks), thus enabling sustained Zn delivery over a longer period. nZnO@SiO2, nZnO, and ZnCl2 were exposed to Solanum lycopersicum by dosing 40 μg of Zn micronutrient (in a 20 μL suspension) on a single leaf. No Zn uptake was observed for the nZnO treatment after 2 days. Comparable amounts of Zn uptake were observed 2 days after ZnCl2 (15.5 ± 2.4 μg Zn) and nZnO@SiO2 (11.4 ± 2.2 μg Zn) dosing. Single particle inductively coupled plasma mass spectrometry revealed that for foliar applied nZnO@SiO2, almost all of the Zn translocated to upper leaves and the stem were in nanoparticulate form. Our results suggest that the SiO2 shell enhances the uptake of ZnO nanoparticles in Solanum lycopersicum. Sustained and controlled micronutrient delivery in plants through foliar application will reduce fertilizer, energy, and water use.

Kinetic investigation of galvanic dissolution of ZnS and PbS with FeS2 from hydrothermal sulfides in seawater

Sulfide mineral dissolution is an important reaction controlling geochemical and environmental chemical processes in aqueous environments. In this study, we quantitatively evaluated the kinetic influence of galvanic interactions between different sulfide minerals on their dissolution in seawater. Four hydrothermal sulfides with different amounts of Fe disulfide minerals (pyrite) were reacted with artificial seawater for 144 h, and the dissolution rates of Zn and Pb were determined by an extraction method. The Zn dissolution rates from samples with high Fe/Zn molar ratios (>0.26) were 1.3–1.5 × 10−10 mol m−2 s−1; approximately one order of magnitude higher than those of samples with low Fe/Zn molar ratios (<0.002; 1.6–1.8 × 10−11 mol m−2 s−1). The Pb dissolution rates from a sample with high Fe disulfide were approximately nine orders of magnitude higher (8.4× 10−10 mol m−2 s−1) than reference data of the single galena dissolution rate (8.9 × 10−19 mol m−2 s−1). The higher solubility of PbSO4 than PbS and PbCO3 could explain the intense release of Pb from the other samples. These results and mineralogical observations with X-ray diffraction, X-ray photoelectron spectroscopy, and electron probe micro-analysis of sulfide mineral particulates provide evidence for the selective dissolution of anodic sulfide minerals (e.g., sphalerite and galena) at a higher reaction rate than cathodic sulfide minerals of Fe disulfide (e.g., pyrite).

Electrochemical preparation of porous ZnCuNi by electrodeposition in ethaline deep eutectic solvent followed by anodic or cathodic dealloying in alkaline aqueous solutions for higher nitrate reduction activity

Abstract Electrodeposition of zinc-rich ternary ZnCuNi alloys were potentiostatically studied from an Ethaline deep eutectic solvent (DES) (having a molar ratio of 1:2 choline chloride-ethylene glycol) containing ZnCl2, CuCl2 and NiCl2. Voltammetry was conducted to understand the cathodic deposition and anodic stripping occurred in this system as a function of potential before the deposition of the ternary alloys. Selective anodic dissolution of Zn from the as-deposited alloys in a NaOH aqueous solution produced porous structures; however, Cu was also dissolved from the alloys if the alloys are overoxidized. Alternatively, porous structures were also produced via cathodic dealloying of the Zn when the as-deposited alloy was subjected to the electroreduction of NaNO3. When used as electrode, both kinds of porous structure showed enhanced activities towards nitrate reduction. Because the cathodic dealloying did not consume Cu, the electrodes produced by cathodic dealloying exhibited activity and stability superior to the electrodes produced by anodic dealloying. More importantly, because the dealloying process and electrode activation could be simultaneously achieved in one step during the cathodic electrolysis of nitrate, the term “self-enhancing electrode formed by in-situ cathodic dealloying” was used in this study. The XPS analysis indicated that Ni-rich surfaces of ZnCuNi electrodes were produced with the anodic dealloying in contrast to the Cu-rich surfaces produced with the cathodic dealloying. This study demonstrates a facile approach to control the electrode surface compositions in dealloying zinc alloys. Although the application of the porous electrodes prepared in this study was tested for electroreduction of nitrate, this approach can be extended to the electrocatalysis of other systems.

Entrapment of nano-ZnO into alginate/polyvinyl alcohol beads with different crosslinking ions for fertilizer applications

Zinc oxide nanoparticles (nano-ZnO) are attractive as fertilizer materials but high concentrations may negatively affect the environment. To reduce their dispersion in the environment we entrapped nano-ZnO in biodegradable polymer beads consisting of alginate and polyvinyl alcohol (PVA). The alginate/PVA/ZnO beads were prepared via ionotropic gelation using two different crosslinking ions (Ca2+ and Zn2+), and the effect of alginate crosslinking ion and PVA content on bead structure, water absorption, water retention and zinc release was investigated. The pure CaAlg and ZnAlg beads demonstrated a poor water absorption and retention, which were strongly enhanced by the incorporation of PVA into the beads. The continuous Zn release was measured in a sand column, and it was found that the Zn-crosslinked beads rapidly released high concentrations of Zn followed by a more gradual Zn release, whereas Ca alginates showed only a gradual Zn release. The Zn dissolution kinetics could be tuned by the crosslinking ion composition. The prepared nano-ZnO-containing alginate/PVA beads may be attractive for Zn fertilizer applications under water-limited conditions.

The effect of zinc shape on its corrosion mitigation as an anode in aqueous Zn/MnO2 battery

• Developing of Zn powder and dust electrode for aqueous Zn/MnO 2 battery. • Zn powder with grain sizes >500 µm attenuate its corrosion and dissolution in NH 4 Cl solution. • Assembling of Zn powder or dust (anode) with electrolytic (EMD) or nanostructured (NMD) MnO 2 (cathode) in Zn/MnO 2 cell. • Zn powder (>500 µm)/NMD cell yields a highest output voltage of 1.646 V. • Specific energy (109.722 mWh/g) and the lowest voltage drop of 0.7% after 2 h of discharge. This work gives an insight into how zinc (Zn) anode in the Zn/MnO 2 batteries is corroded depending on its shape (in the form of powder or dust), and how such shape can play a role to attenuate the Zn corrosion and dissolution during an electrochemical process. Indeed, the corrosion of Zn anodes in powder and dust shape was investigated in ammonium chloride aqueous NH 4 Cl solution using open circuit potential (OCP) plot, linear polarization (LP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) methods. The electrodes were also observed by scanning electron microscopy (SEM) and analyzed using X-ray diffraction (XRD). The results show that the corrosion rate significantly depends on Zn grain size and surface area. In addition, the SEM observations showed clearly some corrosion features on the surface of Zn grains. Furthermore, the XRD analysis confirms the formation of a corrosion layer constituted of ZnO and adsorbed Zn(NH 3 ) 2 Cl 2 molecules. These electrodes, with two distinct shapes, were used as anodes in assembled Zn/MnO 2 batteries with two types of MnO 2 cathode namely nanostructured manganese dioxide (NMD) and electrolytic manganese dioxide (EMD). Discharge tests showed high performance for Zn/MnO 2 cell based on Zn powder (>500 µm) as anode and NMD as a cathode in NH 4 Cl electrolyte, with an output voltage of 1.65 V and specific energy of 109.72 mWh/g after 2 h under 1 mA. Moreover, this cell is the most stable with a voltage drop as low as 0.7% after 2 h of continuous discharge. Such results demonstrate that the assembled Zn/MnO 2 can be used for low cost and high-performance battery with a specific structure and shape of both anode and cathode materials.

Organic acid leaching was an efficient approach for detoxification of metal-containing plant incineration ash.

Metal-containing plant incineration ash (MPIA), which was the by-product for metal extraction from soil by phytoextraction process, contains various kinds of heavy metal that have post potential risk to the environment. This study investigated the leaching efficiency and metal redistribution of MPIA using organic acid as leaching agents. The MPIA before and after leaching was characterized using the toxicity characteristic leaching procedure (TCPL) test, X-ray diffraction, scanning electronic microscopy, and Fourier transform infrared spectroscopy. The results showed that all tested organic acids resulted in the dissolution of metals, especially 1 mol L-1 citric acid leaching achieved for the dissolution efficiency of 84% Mn, 87.01% Cd, 66.97% Zn, and 55.83% Pb. During leaching progress, the synergetic of chelation and acid soluble action accelerated the metal release and redistribution, and the dissolution of Mn, Zn, Pb, and Cd fit best to the shrinking core model of chemical control. Meanwhile, the leaching residue reached the regulatory standard. Thus, organic acid leaching may be a feasible strategy for detoxification of MPIA.