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Currently, various techniques are efficient in eliminating high quantities of fluoride from water, while the deep treatment of a low concentration of fluoridated water is inadequate. In this work, four metallic phosphates were synthesized, including YP, ZrP, CeP, and LaP, to enhance the elimination of fluoride. The X-ray diffractometer data demonstrated that ZrP was amorphous, while CeP, LaP, and YP were highly crystalline. YP had a strong fluoride removal ability in a neutral environment, and ZrP exhibited a superior fluoride adsorption effect in acidic media. The adsorption kinetic results suggested that YP, CeP, and LaP could achieve the adsorption equilibrium within 150 min, which was faster than ZrP. YP had the largest fluoride adsorption capacity fitted by Langmuir of 31.61 mg/g at 298 K, followed by ZrP, which was greater than those of CeP and LaP. All four metallic phosphates showed high selectivity in the interference of competing anions and organics, with YP and ZrP exhibiting superior selectivity than CeP and LaP. The adsorption mechanism was ligand exchange between metallic phosphate particles and fluoride, which was validated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The adsorption rate of metallic phosphates remained essentially stable in five consecutive adsorption–desorption cycles. Overall, metallic phosphates, especially YP and ZrP, have enormous potential in enhancing fluoride removal in the treatment of fluoridated water.

Phosphorite deposits in marine sediments are a long-term sink for an essential nutrient, phosphorus. Here we show that apatite abundance in sediments on the Namibian shelf correlates with the abundance and activity of the giant sulfur bacterium Thiomargarita namibiensis, which suggests that sulfur bacteria drive phosphogenesis. Sediments populated by Thiomargarita showed sharp peaks of pore water phosphate (/=]50 grams of phosphorus per kilogram). Laboratory experiments revealed that under anoxic conditions, Thiomargarita released enough phosphate to account for the precipitation of hydroxyapatite observed in the environment.

Redox transitions of uranium [from U(VI) to U(IV)] in low-temperature sediments govern the mobility of uranium in the environment and the accumulation of uranium in ore bodies, and inform our understanding of Earth’s geochemical history. The molecular-scale mechanistic pathways of these transitions determine the U(IV) products formed, thus influencing uranium isotope fractionation, reoxidation, and transport in sediments. Studies that improve our understanding of these pathways have the potential to substantially advance process understanding across a number of earth sciences disciplines. Detailed mechanistic information regarding uranium redox transitions in field sediments is largely nonexistent, owing to the difficulty of directly observing molecular-scale processes in the subsurface and the compositional/physical complexity of subsurface systems. Here, we present results from an in situ study of uranium redox transitions occurring in aquifer sediments under sulfate-reducing conditions. Based on molecular-scale spectroscopic, pore-scale geochemical, and macroscale aqueous evidence, we propose a biotic–abiotic transition pathway in which biomass-hosted mackinawite (FeS) is an electron source to reduce U(VI) to U(IV), which subsequently reacts with biomass to produce monomeric U(IV) species. A species resembling nanoscale uraninite is also present, implying the operation of at least two redox transition pathways. The presence of multiple pathways in low-temperature sediments unifies apparently contrasting prior observations and helps to explain sustained uranium reduction under disparate biogeochemical conditions. These findings have direct implications for our understanding of uranium bioremediation, ore formation, and global geochemical processes.

In this paper, the inhibition ability of tetrasodium pyrophosphate (TSPP), sodium tripolyphosphate (STPP) and sodium hexametaphosphate (SHMP) to scheelite, fluorite and calcite was predicted by performance calculation and further verified by micro-flotation test. The results of hydrophile lipophilic balance (HLB) calculation, group electronegative calculation and micro-flotation test indicated that the inhibition ability of phosphate to the three minerals increases with the increase of the number of phosphate groups and the order of inhibition ability of the three inorganic phosphates was SHMP > STPP > TSPP. STPP had great potential for flotation separation of scheelite from fluorite and calcite. The order of inhibition ability of STPP against the three calcium-bearing minerals is calcite>fluorite>scheelite. The results of contact angle measurement, adsorption amount measurement, X-ray photoelectron spectroscopy (XPS) analysis and atomic force microscope (AFM) imaging presented that the adsorption of STPP on the fluorite and calcite surface was much larger than that on the scheelite surface. The weak adsorption of STPP on the scheelite hardly influenced the collection of sodium oleate (NaOL). STPP could complex with Ca 2+ on the surface of fluorite and calcite, and hinder the subsequent adsorption of NaOL. The results can provide guiding significance for the flotation of scheelite and the screening of inhibitors for calcium-bearing gangue minerals.

Magnesium (Mg) and its alloys are lightweight as well as biocompatible and possess a high strength-to-weight ratio, making them suitable for many industries, including aerospace, automobile, and medical. The major challenge is their high susceptibility to corrosion, thereby limiting their usability. The considerably lower reduction potential of Mg compared to other metals makes it vulnerable to galvanic coupling. The oxide layer on Mg offers little corrosion resistance because of its high porosity, inhomogeneity, and fragility. Chemical conversion coatings (CCs) belong to a distinct class because of underlying chemical reactions, which are fundamentally different from other types of coating. Typically, a CC acts as an intermediate sandwich layer between the base metal and an aesthetic paint. Although chromate CCs offer superior performance compared to phosphate CCs, yet still they release carcinogenic hexavalent chromium ions (Cr 6+ ); therefore, their use is prohibited in most European nations under the Registration, Evaluation, Authorization and Restriction of Chemicals legislation framework. Phosphate-based CCs are a cost-effective and environment-friendly alternative. Accordingly, this review primarily focuses on different types of phosphate-based CCs, such as zinc, calcium, Mg, vanadium, manganese, and permanganate. It discusses their mechanisms, current status, pre-treatment practices, and the influence of various parameters—such as pH, temperature, immersion time, and bath composition—on the coating performance. Some challenges associated with phosphate CCs and future research directions are also elaborated.

Electrical asymmetric-fow feld-fow fractionation (EAF4) is a new and interesting analytical technique recently proposed for the characterization of metallic nanoparticles (NPs). It has the potential to simultaneously provide relevant information about size and electrical parameters, such as electrophoretic mobility (µ) and zeta-potential (?), of individual NP populations in an online instrumental setup with an array of detectors. However, several chemical and instrumental conditions involved in this technique are defnitely infuential, and only few applications have been proposed until now. In the present work, an EAF4 system has been used with diferent detectors, ultraviolet–visible (UV–vis), multi-angle light scattering (MALS), and inductively coupled plasma with triple quadrupole mass spectrometry (ICP-TQ-MS) for the characterization of gold, silver, and platinum NPs with both citrate and phosphate coatings. The behavior of NPs has been studied in terms of retention time and signal intensity under both positive and negative current with results depending on the coating. Carrier composition, particularly ionic strength, was found to be critical to achieve satisfactory recoveries and a reliable measurement of electrical parameters. Dynamic light scattering (DLS) has been used as a comparative technique for these parameters. The NovaChem surfactant mix (0.01%) showed a quantitative recovery (93±1%) of the membrane, but the carrier had to be modifed by increasing the ionic strength with 200 µM of Na2CO3 to achieve consistent µ values. However, ? was one order of magnitude lower in EAF4-UV–vis-MALS than in DLS, probably due to diferent electric processes in the channel. From a practical point of view, EAF4 technique is still in its infancy and further studies are necessary for a robust implementation in the characterization of NPs.

The recycling of spent LiFePO 4 batteries has received extensive attention due to its environmental impact and economic benefit. In the pretreatment process of spent LiFePO 4 batteries, the separation of active materials and current collectors determines the difficulty of the recovery process and product quality. In this work, a facile and efficient pretreatment process is first proposed. After only freezing the electrode pieces and immersing them in boiling water, LiFePO 4 materials were peeled from the Al foil. Then, after roasting under an inert atmosphere and sieving, all the cathode and anode active materials were easily and efficiently separated from the Al and Cu foils. The active materials were subjected to acid leaching, and the leaching solution was further used to prepare FePO 4 and Li 2 CO 3 . Finally, the battery-grade FePO 4 and Li 2 CO 3 were used to re-synthesize LiFePO 4 /C via the carbon thermal reduction method. The discharge capacities of re-synthesized LiFePO 4 /C cathode were 144.2, 139.0, 133.2, 125.5, and 110.5 mA·h·g −1 at rates of 0.1, 0.5, 1, 2, and 5 C, which satisfies the requirement for middle-end LiFePO 4 batteries. The whole process is environmental and has great potential for industrial-scale recycling of spent lithium-ion batteries.

Bioactive glasses (BGs) are especially useful materials in soft and bone tissue engineering and even in dentistry. They can be the solution to many medical problems, and they have a huge role in the healing processes of bone fractures. Interestingly, they can also promote skin regeneration and wound healing. Bioactive glasses are able to attach to the bone tissues and form an apatite layer which further initiates the biomineralization process. The formed intermediate apatite layer makes a connection between the hard tissue and the bioactive glass material which results in faster healing without any complications or side effects. This review paper summarizes the most recent advancement in the preparation of diverse types of BGs, such as silicate-, borate- and phosphate-based bioactive glasses. We discuss their physical, chemical, and mechanical properties detailing how they affect their biological performances. In order to get a deeper insight into the state-of-the-art in this area, we also consider their medical applications, such as bone regeneration, wound care, and dental/bone implant coatings.

Biomaterials are in use for the replacement and reconstruction of several tissues and organs as treatment and enhancement. Metallic, organic, and composites are some of the common materials currently in practice. Metallic materials contribute a big share of their mechanical strength and resistance to corrosion properties, while organic polymeric materials stand high due to their biocompatibility, biodegradability, and natural availability. To enhance the biocompatibility of these metals and alloys, coatings are frequently applied. Organic polymeric materials and ceramics are extensively utilized for this purpose due to their outstanding characteristics of biocompatibility and biodegradability. Hydroxyapatite (HAp) is the material from the ceramic class which is an ultimate candidate for coating on these metals for biomedical applications. HAp possesses similar chemical and structural characteristics to normal human bone. Due to the bioactivity and biocompatibility of HAp, it is used for bone implants for regenerating bone tissues. This review covers an extensive study of the development of HAp coatings specifically for the orthopaedic applications that include different coating techniques and the process parameters of these coating techniques. Additionally, the future direction and challenges have been also discussed briefly in this review, including the coating of HAp in combination with other calcium magnesium phosphates that occur naturally in human bone.

Although azurite is one of the most important copper oxide minerals, the recovery of this mineral via sulfidization-xanthate flotation is typically unsatisfactory. The present work demonstrated the enhanced sulfidization of azurite surfaces using ammonia phosphate ((NH 4 ) 3 PO 4 ) together with Na 2 S, based on micro-flotation experiments, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, contact angle measurements, Fourier-transform infrared (FT-IR) spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. Micro-flotation experiments showed that the floatability of azurite was increased following the simultaneous addition of (NH 4 ) 3 PO 4 and Na 2 S. ToF-SIMS and XPS analyses demonstrated the formation of a high content of S species on the azurite surface and an increase in the number of Cu(I) species after exposure to (NH 4 ) 3 PO 4 and Na 2 S, compared with the azurite-Na 2 S system. The zeta potential of azurite particles was negatively shifted and the contact angle on the azurite surface was increased with the addition of (NH 4 ) 3 PO 4 prior to Na 2 S. These results indicate that treatment with (NH 4 ) 3 PO 4 enhances the sulfidization of azurite surfaces, which in turn promotes xanthate attachment. FT-IR and UV-Vis analyses confirmed that the addition of (NH 4 ) 3 PO 4 increased the adsorption of xanthate with reducing the consumption of xanthate during the azurite flotation process. Thus, (NH 4 ) 3 PO 4 has a beneficial effect on the sulfidization flotation of azurite.