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Minerals of base metals
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Tungsten (W) is 19.3 times heavier than water and 1.7 times heavier than lead [688,771]. It is brittle [130,692], making it difficult to work. Tungsten does not occur in nature in its elemental form but is found in 45 minerals with wolframite (iron-manganese tungstate), (Fe,Mn) WO4 and scheelite (calcium tungstate) CaWO4 being the most important economic source of the metal. Tungsten is found in other minerals ferberite (FeWO4), hubnerite (MnWO4).
Metal Recovery Processes
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2017
Irrespective of the techniques (carbon adsorption/IX/SX) employed for the purification of the leach liquors, the purified products are always in the form of concentrated ammoniacal solutions of V, Mo, and W. In ammonical solutions at a pH around 8, vanadium, molybdenum, and tungsten are present as metavandate (V4O124−), molybdate (MoO42−), and tungstate (WO42−) ions. Both ammonium molybdate and tungstate have good solubilities in water. When such solutions are subjected to the process of evaporation crystallization, ammonia is driven off from the solution to form paramolybdate and paratungstate. These para salts are characterized by lower ammonia contents and much less solubilities. As a result, molybdenum and tungsten values crystallize out from the evaporating solutions as ammonium paramolybdate [3(NH4)2O.7 MoO3·4 H2O] and paratungstate [5(NH4)2O.12 WO3. × H2O] salts, respectively. Ammonium metavandate salt itself, on the contrary, has a low solubility and can be crystallized out. During such a crystallization process, care should be taken to avoid formation of decavandate (V10O286−), which is stable at pH 4 to 6.5 and exhibits excellent solubility.44
Internal Corrosion Protection
Published in Mavis Sika Okyere, Corrosion Protection for the Oil and Gas Industry, 2019
An anodic inhibitor acts by forming a protective oxide film on the surface of the metal. It causes a large anodic shift that forces the metallic surface into the passivation region, which reduces the corrosion potential of the material. This entire procedure is sometimes called passivation (Zavenir, 2018). Some examples are chromates, nitrates, molybdate, and tungstate.
Reclamation of tungsten from spent HDS catalyst: a detailed study
Published in Indian Chemical Engineer, 2022
Surjeet Mahalik, A. R. Sheik, Barsha Dash, C. K. Sarangi, K. Sanjay
The HDS spent catalyst was devolatilized at 650°C to remove all oils and organics. The catalyst having tungsten aluminium and nickel in their sulfide form got converted to the corresponding oxide form. The oxidised catalyst was leached with NaOH to get tungsten in the form of water soluble sodium tungstate which is again converted to tungstic acid by acidification. Tungstic acid after roasting forms tungsten trioxide which after H2 reduction gets converted to tungsten metal with 99.97% purity. Nickel was also recovered as Nickel Hydroxide as a by-product. This detailed study is quite useful to extract tungsten from tungsten bearing secondaries.
Enhanced bacterial inhibition and photocatalyzed degradation of industrial contaminants by polyethylene glycol capped PbWO4 nanoparticles
Published in Particulate Science and Technology, 2023
S. Asha, Marwah Bakri, Chadlia El Manna, S. Sasi Florence, V. Sarojini, C. Hentry, M. R. Bindhu
In the last few years, microorganisms have evolved medication resistance due to the alteration in the chromosomes and genetic material. Antibiotic resistance bacteria have emerged as a serious public health concern, prompting a slew of investigations to recreate the current antimicrobial treatments. Helminths, protozoa, fungi, bacteria, rickettsiae, viruses and prions are waterborne pathogens that may cause many diseases (Pitman 2002). The bacterial contamination of drinking water causes more than 80% of diseases (WHO and IWA 2009). The dismissal/deactivation of pathogenic bacteria in the water to defend the water purity is momentous. More than 70% of bacterial infections are tolerable to one/more antibiotics which are usually used to annihilate the infection. These hassles need more growth to fight against new upcoming bacteria. With the biological materials, the nanoparticles lead to the formation of new material with control-specific characteristics such as size, distribution, morphology and surface chemistry (Cao et al. 2021; Safaei et al. 2019). Nanotoxicity is a profound method to analyze the reaction of bacteria when exposed to nanoparticles. This becomes an easier method to inhibit the growth of different pathogenic bacteria. Nowadays the vastly created nanomaterials such as metal oxide nanomaterials have established its efficiency in healing hazardous materials such as chlorinated solvents, microorganisms, pesticides, and mustards. Nano and micro-structured tungstate materials have attracted great interest for their luminescent behavior, structural properties, and potential applications. Lead tungstate (PbWO4), a scintillating crystal, has attracted attention in high-energy physics due to its high density, fast decay time, exciting exciton luminescence, thermo-luminescence, and Raman scattering behavior which include high irradiation damage prevention (Asha et al. 2021). Varies methods can be used to synthesize tungstates including solid-state reaction, sol-gel, solution combustion, solvothermal, hydrothermal, and co-precipitation methods (Lou, Hao, and Cocivera 2002; Bonanni et al. 1998; Phani et al. 2000; Wen et al. 2002). The co-precipitation method is preferred due to its cost-effectiveness, simplicity, softness chemical synthetic methodology, and fastness. This method can work without any particular working conditions and high calcination temperature (Rahimi-Nasrabadi 2017; Rahimi-Nasrabadi et al. 2016; Rahimi-Nasrabadi et al. 2017; Hosseinpour-Mashkani, MahnazMaddahfar, and Sobhani-Nasab 2017). Therefore, these advantages impelled to synthesize co-precipitation based PbWO4 nanoparticles.