Search Results (13)

Soil environments contaminated with heavy metals by typhoon flooding require immediate remediation. High-pressure soil washing using water could be a viable short-term solution for cleaning soil contaminated with heavy metals. Soil washing employing high-pressure generates heavy metal contaminated fine soil and wastewater. This contaminated fine soil cannot be reused without proper treatment because of the high levels of heavy metal contamination. Stabilization was used for immobilizing heavy metals (Cu, Pb) in the contaminated fine soil. The stabilizing agents used for immobilizing heavy metals (Cu, Pb) in the contaminated fine soil included two types of limestone (Ca-LS and Mg-LS) and livestock bone powder (LSBP). The Ca-LS, Mg-LS, and LSBP were applied to the contaminated fine soil at dosages in the range of 2 wt%~10 wt%. Two different particle sizes (-#10 vs. -#20 mesh) and curing times (1 week vs. 4 weeks) were used to compare the effectiveness of the stabilization. Extractions using 0.1 N HCl were conducted to evaluate the stabilization effectiveness. Heavy metal leachability was significantly decreased with higher Ca-LS and LSBP dosages. The LSBP treatment was more effective than the Ca-LS and Mg-LS treatments and the Mg-LS showed the poorest performance. The highest degree of immobilization was attained using a 10 wt% LSBP (-#20 mesh), resulting in an approximate leachability reduction of 99% for Pb and 92% for Cu. The -#20 mesh material and 4 weeks of curing were more effective than the -#10 mesh material and 1 week of curing, respectively. The SEM-EDX results showed that metal precipitates and pyromorphite like phases could be responsible for effective heavy metal immobilization. This study suggests that Ca-LS and LSBP used at an optimum dosage can be effective stabilizing agents for immobilizing Cu and Pb in contaminated fine soils. Full article

Calcium-enriched compounds have great potential in the treatment of heavy-metal contaminated wastewater. Preparing stable basic calcium carbonate (BCC), which is a calcium-enriched compound, and applying it in practice is a great challenge. This work investigated the formation process of hierarchical hydroxyapatite (HAP)/BCC nanocomposites and their adsorption behaviors regarding lead ions (Pb²⁺). The morphology of the HAP/BCC nanocomposite was controlled by the addition of monododecyl phosphate (MDP). The carnation-like HAP/BCC nanocomposite was achieved with the addition of 30 g of MDP. The carnation-like HAP/BCC nanocomposite had a high Pb²⁺ adsorption capacity of 860 mg g⁻¹. The pseudo-second-order and Freundlich model simulation results indicated that the adsorptions of Pb²⁺ on the nanocomposites belonged to the chemisorption and multilayer adsorption processes. The main effective adsorption components for the nanocomposites were calcium-enriched HAP and BCC. Through the Ca²⁺ ions exchanging with Pb²⁺, the HAP and BCC phases were converted to hydroxyl-pyromorphite (Pb-HAP) and hydrocerussite (Pb₃(CO₃)₂(OH)₂), respectively. The carnation-like HAP/BCC nanocomposite has great potential in the treatment of heavy metal ions. This facile method provides a new method for preparing a stable HAP/BCC nanocomposite and applying it in practice. Full article

The 20 minerals encompassing the pascoite family of decavanadate isopolyanion-containing [V₁₀O₂₈]⁶⁻ minerals include a few minerals, such as rakovanite, that have been described as containing a protonated decavanadate anion. Rakovanite was originally assigned the formula Na₃[H₃V₁₀O₂₈]•15H₂O and now is redefined with an ideal formula (NH₄)₃Na₃[V₁₀O₂₈]•12H₂O. Nuclear magnetic resonance (NMR) and particularly ⁵¹V NMR spectroscopy is an informative method used to describe the protonation state and speciation in both solid and solution states of materials in the chemical and life sciences. However, ⁵¹V NMR spectroscopy has not yet been used experimentally to distinguish the protonation state of the decavanadate ion of leaching solutions and thus contributing to the discussion regarding the controversial protonation states of decavanadate ions in gunterite, rakovanite, and nashite. In contrast, the morphology and crystal structure for apatites, vanadinite, pyromorphite, and mimetite was related to ²⁰⁷Pb NMR chemical shifts, assisting in describing the local environments of these minerals. NMR spectroscopy could be a useful method if used in the future for decavanadate-containing minerals. Currently, partial reduction of two Pascoite minerals (caseyite and nashite) is proposed and accordingly could now effectively be investigated using a different magnetic resonance technique, EPR spectroscopy. Full article

Co-application of Aspergillus niger (A. niger) and phosphate rocks (PR) has been practiced by environmentalists for lead (Pb) remediation. The secretion of organic acid by A. niger usually dominates the dissolution of PR and Pb immobilization. In this study, two types of PR (fluorapatite (FAp) and phosphogypsum (PG)) were investigated in Pb remediation by A. niger under three different forms of nitrogen (ammonium, nitrate, and urea). Our results reveal that the formation of pyromorphite and lead oxalate contributed to Pb removal by the combination of A. niger with FAp and PG. PG showed a significant capability for Pb remediation compared with FAP, over 94% of Pb vs. 50%. Compared with nitrate and urea, ammonium significantly decreased Pb cation concentrations from 1500 mg/L to 0.4 mg/L. Due to ammonium containing sulfate, the lead sulfate formed also contributed to Pb removal. However, nitrate stimulated A. niger to secrete more oxalic acid (~1400 mg/L) than ammonium and urea (~200 mg/L), which can form insoluble lead oxalate. These insoluble minerals can reduce the availability of removed Pb. Despite the efficacy of both ammonium and nitrate for Pb remediation, our findings suggest that nitrate is the primary candidate in this regard due to high oxalic acid secretion. Full article

The current study is the first comprehensive investigation of the polychromy of Palmyrene funerary portraits. It presents the technical examinations of six portraits (ca. 150–250 CE) from the collection of the Ny Carlsberg Glyptotek, illustrating the marvellous splendour of the cultural heritage of ancient Palmyra. The six portraits were examined with various analytical methods, including microscopy, ultraviolet-induced visible fluorescence imaging and visible light-induced infrared luminescence imaging, X-ray fluorescence spectroscopy, scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Finally, two samples were collected for liquid chromatography–tandem mass spectrometry to obtain the amino acid sequence information. Various pigments were detected in the polychromy including lapis lazuli, pyromorphite, mimetite, yellow ochre, red ochre, a red lake, lead carbonate, zinc oxide, bone black, and charcoal black. The proteinaceous binding medium was identified as collagen-based and possibly also keratin-based animal glue. The examinations of the Palmyrene portraits in the Ny Carlsberg Glyptotek have proven that these artefacts, despite their current uniform, white appearance, originally presented themselves in a wealth of colours. This is illustrated by the digital reconstructions carried out of two of the examined portraits, which show how the original painting of these portraits would have given them an entirely different expression from what we see today. Full article

We describe occurrences of platinum-group minerals (PGM) and an uncommon mineral enriched in Cl, and provide a brief review of Cl-bearing minerals associated with basic–ultrabasic complexes. An unusual phosphohedyphane-like phase (~30 µm), close to CaPb₄(PO₄)₃Cl, occurs in one of the PGM-bearing veins of massive sulfides in the Monchepluton layered complex, Kola Peninsula, Russia. These veins consist of varying amounts of pyrrhotite, pentlandite, chalcopyrite, pyrite and accessory grains of galena; they are fairly abundant in the heavy-mineral concentrate, as are small (<0.1 mm) grains of PGM: michenerite, sperrylite, Bi-enriched members of the merenskyite–moncheite series and kotulskite, also rich in Bi. The PGE mineralization is attributed to a low-temperature deposition at the hydrothermal stage. The pyromorphite–phosphohedyphane solid solution likely formed as a secondary phase under conditions of a progressive build-up of oxygen fugacity via oxidation reactions of a precursor grain of galena and involving Ca, as an incompatible component of the sulfides, in a medium of residual fluid enriched in Cl. Full article

Shooting ranges are among the major anthropogenic sources of Pb contamination in soils worldwide. Once they have reached the soil, bullet residues can have different fates according to the characteristics of the soil environment, leading to the formation of different Pb weathering products whose stability is crucial for Pb accessibility to soil biota. In this study, Pb availability in a former polluted shooting range was investigated with a combination of conventional soil analyses, X-ray microanalyses and assays with the bio-indicator earthworm Eisenia andrei. Chemical extractions evidenced a rather low mobility of soil Pb, while micro-X-ray fluorescence spectroscopy (µXRF) and scanning electron microscopy coupled with microanalysis (SEM-EDX) showed the formation of a weathering crust around Pb-containing bullet slivers dispersed within the soil. Such crusts consisted of a mixture of orthophosphates, including the highly insoluble Cl-pyromorphite. Furthermore, no acute toxicity effects and low Pb concentration values were measured in earthworm tissues (94.9 mg kg⁻¹) and coelom fluids (794 µg L⁻¹) after 28 days of exposure to the polluted soil. These results allow us to assume that most of the Pb in the shooting range soil underwent stabilization processes promoted by phosphatic fertilization. The soil was in fact used for agriculture after being dismissed for firing activities. Such a combined approach can be applied to study Pb bioavailability in other shooting ranges or, more generally, in soils heavily polluted with Pb. Full article

Specialist bacteria can synthesize nanoparticles from various metal ions in solution. Metal recovery with high efficiency can be achieved by metal-tolerant microorganisms that proliferate in a concentrated metal solution. In this study, we isolated bacteria (Pseudomonas sp. strain KKY-29) from a bacterial library collected from water near an abandoned mine in Komatsu City, Ishikawa Prefecture, Japan. KKY-29 was maintained in nutrient medium with lead acetate and synthesized hydrocerussite and pyromorphite nanoparticles inside the cell; KKY-29 also survived nanoparticle synthesis. Quantitative PCR analysis of genes related to phosphate metabolism showed that KKY-29 decomposed organic phosphorus to synthesize lead phosphate. KKY-29 also deposited various metal ions and synthesized metal nanoparticles when incubated in various metal salt solutions other than lead. The present study considers the development of biotechnology to recover lead as an economically valuable material. Full article

Lead (Pb) solubility is commonly limited by dissolution–precipitation reactions of secondary mineral phases in contaminated soils and water. In the research described here, Pb solubility and free Pb²⁺ ion activities were measured following the precipitation of Pb minerals from aqueous solutions containing sulfate or carbonate in a 1:5 mole ratio in the absence and presence of phosphate over the pH range 4.0–9.0. Using X-ray diffraction and Fourier-transform infrared spectroscopic analysis, we identified anglesite formed in sulfate-containing solutions at low pH. At higher pH, Pb carbonate and carbonate-sulfate minerals, hydrocerussite and leadhillite, were formed in preference to anglesite. Precipitates formed in the Pb-carbonate systems over the pH range of 6 to 9 were composed of cerussite and hydrocerussite, with the latter favored only at the highest pH investigated. The addition of phosphate into the Pb-sulfate and Pb-carbonate systems resulted in the precipitation of Pb₃(PO₄)₂ and structurally related pyromorphite minerals and prevented Pb sulfate and carbonate mineral formation. Phosphate increased the efficiency of Pb removal from solution and decreased free Pb²⁺ ion activity, causing over 99.9% of Pb to be precipitated. Free Pb²⁺ ion activities measured using the ion-selective electrode revealed lower values than predicted from thermodynamic constants, indicating that the precipitated minerals may have lower K_SP values than generally reported in thermodynamic databases. Conversely, dissolved Pb was frequently greater than predicted based on a speciation model using accepted thermodynamic constants for Pb ion-pair formation in solution. The tendency of the thermodynamic models to underestimate Pb solubility while overestimating free Pb²⁺ activity in these systems, at least in the higher pH range, indicates that soluble Pb ion-pair formation constants and K_SP values need correction in the models. Full article

Farmed urban soils often bear legacies of historic contamination from anthropogenic and industrial sources. Soils from seven community farms in Newark, New Jersey (NJ), USA, were analyzed to determine the concentration and speciation of lead (Pb) depending on garden location and cultivation status. Samples were evaluated using single-step 1 M nitric acid (HNO₃) and Tessier sequential extractions in combination with X-ray absorption fine structure spectroscopy (XAFS) analysis. Single-step extractable Pb concentration ranged from 22 to 830 mg kg⁻¹, with 21% of samples reporting concentrations of Pb > 400 mg kg⁻¹, which is the NJ Department of Environmental Protection (NJDEP) limit for residential soils. Sequential extractions indicated lowest Pb concentrations in the exchangeable fraction (0–211 mg kg⁻¹), with highest concentrations (0–3002 mg kg⁻¹) in the oxidizable and reducible fractions. For samples with Pb > 400 mg kg⁻¹, Pb distribution was mostly uniform in particle size fractions of <0.125–1 mm, with slightly higher Pb concentrations in the <0.125 mm fraction. XAFS analysis confirmed that Pb was predominantly associated with pyromorphite, iron–manganese oxides and organic matter. Overall results showed that lowest concentrations of Pb are detected in raised beds, whereas uncultivated native soil and parking lot samples had highest values of Pb. As most of the Pb is associated with reducible and oxidizable soil fractions, there is a lower risk of mobility and bioavailability. However, Pb exposure through ingestion and inhalation pathways is still of concern when directly handling the soil. With increasing interest in urban farming in cities across the USA, this study highlights the need for awareness of soil contaminants and the utility of coupled macroscopic and molecular-scale geochemical techniques to understand the distribution and speciation of soil Pb. Full article

Pyromorphite is one of the important end member lead apatites that has potential applications in environment remediation. The thermal behavior of natural pyromorphite, Pb₁₀(PO₄)₆Cl₂, has been investigated up to 1373 K at room-pressure using a powder X-ray diffraction device equipped with a heating system. Pyromorphite experiences melting and decomposing at 1373 K into lead phosphate (Pb₃(PO₄)₂), and lead dioxide (PbO₂) with reaction with air. The fit of the temperature–volume data yields a linear volume expansion coefficient α_V = 4.5 (±0.02) × 10⁻⁵ K⁻¹. The linear expansion coefficients for lattice parameters present the anisotropic thermal expansibility, i.e., α_a = (±0.06) × 10⁻⁵ K⁻¹ and α_c = 2.2 (±0.06) × 10⁻⁵ K⁻¹. We looked into the crystal chemistry and proposed an expression to quantitatively evaluate the structural evolution of pyromorphite upon high temperature by calculating the twist angle of the Pb(1)O₆ metaprism, which decreases at elevated temperatures. A distinct drop of the twist angle was observed at ~1100–1200 K, which might be a sign for the phase transition to a low symmetric subgroup. The variation of the twist angle is more sensitive than that of the unit cell; therefore, it can be applied to monitor the structural and phase changes of apatite group materials in general. Full article

Five lead-arsenate apatites (mimetites)-Pb₅(AsO₄)₃X—where X denotes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and hydroxide (OH)—were synthesized via precipitation from aqueous solutions. The crystal structures were determined through Rietveld refinement of powder synchrotron X-ray data. All the compounds crystallized in the hexagonal class symmetry (space group P6₃/m). The Rietveld refinement indicated that mimetite-Cl, -Br, -I, and -OH had an anion deficiency at position X. Substitution of halogens in a mimetite structure brought about systematic changes in unit-cell parameters, interatomic distances, and metaprism twist angles φ, proportional to the substituted halogen’s ionic radius. Mimetite-OH did not follow the linear correlations determined within the series. Twist angle φ, a useful device for monitoring changes in apatite topology, ranged from 20.34° for mimetite-F to 11.42° for mimetite-I. The geometric method has been proposed for determining the diameter of hexagonal channels hosting halogens in apatites. A comparison of the results with halogenated pyromorphites showed similar systematic trends: the substitutions in mimetites have comparable effect on the interatomic distances as in their phosphorous analogues. Full article

Soluble lead (Pb) can be immobilized in pure systems as pyromorphite through the addition of phosphorus (P) sources; however, uncertainties remain in natural systems. Knowledge of point zero charge (PZC) is important to predict the ionization of functional groups and their interaction with metal species in solution. This study utilized Pb- and As-contaminated soils to determine the combined effect of pH with respect to PZC and different rates of P-application on pyromorphite formation as well as Pb and arsenic (As) bioaccessibility as impacted by speciation changes. Solution chemistry analysis along with synchrotron-based Pb- and As-speciation as well as bioaccessibility treatment effect ratios (TERs) were conducted. Results indicated no significant effect of PZC on pyromorphite formation in P-amended soils; however, the TER_Pb appeared significantly lower at pH > pH_PZC and higher at pH < pH_PZC (α = 0.05). In contrast, the TER_As was significantly higher at pH > pH_PZC compared to the other two treatments for the tested soils. The lack of conversion of soil Pb to pyromorphite may be attributed to several reasons including the presence of highly stable minerals, such as plumbojarosite, limiting soluble Pb availability to react with phosphates, high Fe and S content in IKS, high organic matter in BO, and high Ca content in NW. Full article