Recovery of vanadium and tungsten from spent selective catalytic reduction catalyst by alkaline pressure leaching

Abstract

Improving the efficiency of precious metal recovery from spent Selective Catalytic Reduction (SCR) catalyst provides economic benefits and promises sustainable use of resources. Here we demonstrate highly efficient alkaline pressure leaching method for the extraction of vanadium (V) and tungsten (W) from spent SCR catalyst. We analyzed the effects of experimental parameters such as the stirring speed, leaching agent concentration, leaching temperature, liquid-to-solid ratio, and leaching time. The Box-Behnken design of experiments and the response surface methodology have been employed to understand the impact of the leaching parameters and the impact of their interactions on the leaching rate of V and W. The results showed that the leaching agent concentration significantly promoted the recovery of V and W; the influence of the reaction temperature and leaching time moderately increased the leaching rate of the metals. Moreover, the efficiency of the alkaline pressure leaching technique was determined by the interactions between leaching time and reaction temperature, and the relationships between reaction temperature and leaching agent concentration. By using the response surface methodology, the optimal leaching conditions were found that the leaching agent concentration was 4.75 mol×L-1, the leaching temperature was 190 °C, and the reaction time was 44.5 min, and the predicted values of V and W leaching rates were 95.76% and 98.36%, respectively. Based on the excellent fitting between modeling and experimental results demonstrated in this work, we conclude that our study can shed light on the development of highly efficient and sustainable metal recovery strategies for practical applications.

Prevalence of Post-Traumatic Stress Disorder (PTSD) in University Students during the COVID-19 Pandemic: A Meta-Analysis Attending SDG 3 and 4 of the 2030 Agenda

“…We found no significant differences in the prevalence of PTSD between men and women. Our results are, thus, not consistent with other findings in the general population and in other adult cohorts, which indicate that women are at increased risk for PTSD [22,[62][63][64][65][66][67], including during the COVID-19 pandemic [20]. Some studies suggest that women are at a higher risk of PTSD than men because of gender inequality and discrimination [68][69][70], genetic predisposition and hormonal influences, and individual gender roles [71].…”

“…Several studies have shown that pandemics, natural disasters, and other loss-of-life events are associated with increased PTSD among students [17][18][19][20]. Research among university students suggests that vicarious traumatization [21] via media coverage of COVID-19 [22,23] may have caused some cases of PTSD. In fact, a systematic review of general population studies found that there was more PTSD during the COVID-19 pandemic among young people than among the older population [20].…”

Phase Equilibria and Phase Diagram of the Quaternary NaOH–Na3VO4–Na2WO4–H2O System at 278.15 K to 353.15 K

“…Spent SCR catalysts are increasingly generated from corresponding industrial sectors , and are gaining more attention given their very high concentration of strategic as well as base metals like vanadium, tungsten, and titanium . The spent SCR catalyst is subjected to recycling through an integrated hydrometallurgical route , to recover the valuable metal and simultaneously address the resulting global environmental issues …”

“…The use of a selective catalytic reduction (SCR) catalyst has become the most effective means of reducing nitrogen oxide (NO x ) emissions from stationary segments around the world because of strengthened regulatory trends and emerging environmental issues. − The most widely used SCR catalyst, the V 2 O 5 –WO 3 /TiO 2 system, , contains a considerable amount of valuable metals (7–10 wt % of WO 3 , 0.5–1.5 wt % V 2 O 5 , and 70–80 wt % TiO 2 ) . This system shows excellent catalytic properties, such as a wide operating temperature window and high denitration rate …”

Sequential recovery orocesses of tungsten from hubnerite mineral concentrate of Qash Amir mineralized quartz veins, South Eastern Desert, Egypt

“…Alternately, alkali leaching (NaOH or Na2CO3) is widely used to process tungsten concentrates under high temperature and pressure conditions (Hairunnisha et al, 2007;Zhao et al, 2011;Liu et al, 2020). Na2CO3 is the most cited reactant in the literature (Paulino et al, 2012).…”