Abstract
The enormous amount of spent catalysts generated worldwide may pose a risk to the environment because of their high load of metals, including vanadium. The latter may be mobilized and released to the environment if managed improperly. Moreover, the catalysts could be considered as secondary resources rather than waste. This study aimed at the efficient extraction of vanadium from spent desulfurization catalyst (SDC) from a sulfuric acid production plant. The raw SDC and the post-extraction residues were characterized in terms of their chemical and phase composition. The metal mobility from the materials was examined with both single-step and multi-step extractions. The environmental risk assessment was performed using sequential extraction. The study revealed that both tested methods (citric acid leaching and bioleaching with Acidithiobacillus thiooxidans) enable the extraction of nearly 96% of V from SDC with a simultaneous reduction of metal mobility. However, the bacterial treatment was found more suitable. The leached residue was mostly (> 90%) composed of SiO2, which makes it a potential candidate for application in construction (e.g., concrete mixtures) after additional examinations. The study highlights the need to develop a metal extraction process for SDC in a way that metal-free residue could be a final product.
Highlights
Having a high-quality living environment is of great importance for humans
The results of phase analysis by X-ray diffraction (XRD) (Fig. 2a) showed that the main phase in the raw spent desulfurization catalyst (SDC) sample was SiO2 in the form of cristobalite or tridymite, which is typically used as a porous support phase
The last two phases corresponded to potassium pyro-sulfo-vanadate, doped on the porous surface of the catalyst
Summary
Having a high-quality living environment is of great importance for humans. industrial development deteriorates the environment, which can lead to harmful effects on living organisms, including humans (Mikoda et al 2017). The spent catalysts generated worldwide include 700,000 to 900,000 tons of spent fluid catalytic cracking (FCC) residues (Muddanna and Baral 2019); up to 200,000 tons of catalyst from petroleum industry (Pathak et al 2018); up to 40,000 tons of catalyst from sulfuric acid production (Nikiforova et al 2017); and up to 38,000 tons of selective catalytic reduction (SCR) waste in China itself (Dai et al 2018). These numbers force researchers to find comprehensive methods of economic and environmentfriendly use of catalysts
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