Tungsten Recovery from Spent SCR Catalyst Using Alkaline Leaching and Ion Exchange

Abstract

Abstract:The recovery of tungsten (W) from a honeycomb-type spent selective catalytic reduction (SCR) catalyst using an alkaline leaching-ion exchange method was investigated. Spent SCR catalyst mainly consists of TiO 2 and other oxides (6.37% W, 1.57% vanadium (V), and 2.81% silicon (Si), etc.). The ground catalyst was leached at the optimal conditions, as follows: NaOH concentration of 0.3 kg/kg of catalyst, pulp density of 3%, leaching temperature of 70 • C, particle size of −74 µm, and leaching time of 30 min. In this study, the leaching rate values of V and W under the above conditions were 87 wt %, and 91 wt %, respectively. The pregnant solution was then passed through a strong base anion exchange resin (Amberlite IRA900). At high pH conditions, the use of strong base anion exchange resin led to selective loading of divalent WO 4 2− from the solution, because the fraction of two adjacent positively-charged sites on the IRA900 resin was higher and separate from the coexisting VO 4 3− . The adsorbed W could then be eluted with 1 M NaCl + 0.5 M NaOH. The final concentrated W solution had 8.4 g/L of W with 98% purity. The application of this process in industry is expected to have an important impact on the recovery of W from secondary sources of these metals.

Recovery of vanadium and tungsten from waste selective catalytic reduction catalysts by K2CO3 roasting and water leaching followed by CaCl2 precipitation

“…Kim et al (2015) found that the leaching efficiency of W and V can reach values of 99.9% and 86.6%, respectively, at high temperature and pressure. Other researchers obtained similar results at atmospheric pressure (Huo et al 2015;Wu et al 2016). However, large amounts of hydroxides were observed to be needed in these studies.…”

“…However, the lifespan of V 2 O 5 -WO 3 /TiO 2 catalyst is limited by the activity of toxic substances present in flue gas, such as SO 2 , K 2 O, CaO, As 2 O 3 , and HgO (Kong et al 2015;Li et al 2016a, b;Li et al 2018;Nicosia et al 2007;Qi et al 2017;Xu et al 2017;Zhang et al 2014). After several regenerations, these catalysts have been observed to become unable to catalyze NO x SCR (Huo et al 2015;Wu et al 2016). Notably, waste catalysts contain leachable hazardous metals, a trait that contributes to environmental concerns associated with their storage and disposal (Imtiaz et al 2015).…”

Hydrometallurgical Recovery of Cobalt(II) from Spent Industrial Catalysts

“…Several methods are proposed and successfully used in academic and industrial practice. The conventional approaches used in metal reclamation as pyrometallurgy [15] and hydrometallurgy (leaching, ion exchange, extraction) [16][17][18], as well as new methods, include bioleaching [19]. As was mentioned above such methods are applied also in commercial solutions, i.e., the Dutch company Moxba-Metrex [20], the Germany company Nickelhütte Aue GmbH [21], or the Belgian company Sadaci N.V. [22], etc., described in detail in the work [23].…”

A Comparative Study in Vanadium and Tungsten Leaching from Various Sources of SCR Catalysts with Local Difference

“…Furthermore, most of the researches focused on the influence of leaching parameters, such as temperature, time, concentration, liquid/solid ratio, particle size, and stirring speed. Wu et al [8] reported that the leaching efficiency of vanadium (V) and tungsten (W) was optimized at 87% and 91%. Tang et al [9] declared that the leaching efficiency could be as high as 93% for V and 97% for W. Su et al [10] reported that the leaching efficiency was only 66% for V and 49% for W. All these researches were carried out with a specific catalyst, and the leaching rates were quite different among the various researches.…”