Sustainable and efficient leaching of tungsten in ammoniacal ammonium carbonate solution from the sulfuric acid converted product of scheelite

Abstract

To directly obtain solution of (NH4)2WO4 instead of Na2WO4 is the key for developing a cleaner technology of ammonium paratungstate production. In this paper, ammoniacal ammon iu m carbonate solution was adopted for leaching tungsten from the converted product, a mixture of H2WO4 and CaSO4 obtained by treating scheelite with sulfuric acid. The research indicates that tungsten can be efficiently extracted in form of ammonium tungstate solution with WO3 leaching yield of > 99.5% under moderate leaching conditions. The WO3 leaching yield is influenced by the transformation of calciu m sulfate to calcium carbonate due to forming CaWO4 through the secondary reaction between CaSO4 and (NH4)2WO4, whereas an excess (NH4)2CO3 (≥ 0.64 mol/L) can suppress the secondary reaction by facilitating the transformation. Additionally, the consumed ammonium carbonate can be recovered by treating the leaching residue with ammonium sulfate solution at above 70 o C. This work presents a cleaner and sustainable technique for producing ammonium paratungstate, with circulating the leaching reagents and bypassing the conversion of Na2WO4 to (NH4)2WO4.

Low-Energy Feasibility for Leaching an Indigenous Scheelite Ore for Industrial Applications

“…This was followed by adding 10 g/L of the < 75 µm scheelite smallest particle size to the reactor and the contents were thoroughly stirred. After a specific duration, the resultant solution was filtered, water-washed, and oven-dried at 40 °C for 24 h. The fraction of ore reacted in the leachant was calculated from the difference between the mass of the reacted and unreacted at various contact times after respective drying [7,23,24]. For a better understanding of the nature of the unreacted species, the residual product at optimal leaching conditions (2.5 mol/L HCl, 70 °C, < 75 µm, 120 min) was accordingly analyzed by X-ray diffraction (XRD) using PHILIP PW 1800 X-ray diffraction with Cu Kα 1 (0.154 nm) radiation graduated at 40 kV and 55 mA, Scanning electron microscopy (SEM) with NanoSEM 230, and Energy dispersive spectroscopy (EDS) with an oxford X-max EDS detector using INCA software, respectively.…”

“…For a better understanding of the nature of the unreacted species, the residual product at optimal leaching conditions (2.5 mol/L HCl, 70 °C, < 75 µm, 120 min) was accordingly analyzed by X-ray diffraction (XRD) using PHILIP PW 1800 X-ray diffraction with Cu Kα 1 (0.154 nm) radiation graduated at 40 kV and 55 mA, Scanning electron microscopy (SEM) with NanoSEM 230, and Energy dispersive spectroscopy (EDS) with an oxford X-max EDS detector using INCA software, respectively. Also, the dissolution kinetics mechanism for the scheelite ore dissolution was determined by appropriate shrinking core models (SCM) [7,23,25].…”

Electrodialytic removal of tungsten and arsenic from secondary mine resources — Deep eutectic solvents enhancement

“…Additionally, tuning the water content and composition of DES can change their properties, favoring their versatility for several applications. Through the use of strong acids, as sulfuric and nitric acids, the yields in metals extraction could achieve up to 97% (Gong et al, 2019;Pena-Pereira and Namieśnik, 2014;Shen et al, 2018). However, their negative impacts are also widely recognized (Shen et al, 2019).…”

Sustainable and Efficient Recovery of Tungsten from Wolframite in a Sulfuric Acid and Phosphoric Acid Mixed System

“…However, with the increasingly strict requirements of environmental protection in recent years, the price of a NaOH leaching reagent from the high-pollution chlor-alkali industry remains at a high level. In addition, the problem of sodium wastewater discharge has not been solved: 20–100 tons of sodium salt wastewater is discharged per ton of ammonium paratungstate (APT) production. , In addition, the alkali leaching residue has been listed as a hazardous solid waste in China . Thus, use of the traditional alkali autoclaving method is untenable.…”

“…In addition, the problem of sodium wastewater discharge has not been solved: 20−100 tons of sodium salt wastewater is discharged per ton of ammonium paratungstate (APT) production. 15,16 In addition, the alkali leaching residue has been listed as a hazardous solid waste in China. 17 Thus, use of the traditional alkali autoclaving method is untenable.…”