Recycling of waste lithium-ion batteries (LIBs) requires metal leaching from the LIB cathode; however, the metal-leaching process is too challenging to be efficient, green, and mild simultaneously. Moreover, the leaching efficiency at mild conditions by green solvents is not high and needs to be improved urgently. Here, deep eutectic solvents (DESs) composed of poly(ethylene glycol) 200 (PEG) and phytic acid (PHA) are designed to leach Co from LIB cathodes with an ultrahigh metalleaching efficiency of 0.987 at a low temperature of 80 °C for 24 h, which is much higher (ca. 0.3) than the efficiency of previously reported DESs. Moreover, the constituents (PEG and PHA) in DESs are low-cost, sustainable, and biodegradable; particularly, PHA is naturally available in legumes, cereals, dried fruits, vegetables, and other fruits, which are also edible by human beings. This work provides a super highly efficient, sustainable, and mild route for metal leaching from LIB cathodes.
Dissolution of the cathode by deep eutectic solvents
(DESs) is
the key and green step to recycle spent lithium-ion batteries (LIBs);
moreover, pollutant removal by adsorbents is the efficient route for
environment protection. However, the couple of dissolving the LIB
cathode and pollutant removal with high sustainability and low cost
has not been reported up to now. Here, we for the first time use cheap
and green DESs to dissolve LIBs for the preparation of magnetic adsorbents
for wastewater treatment and engine oil removal. Results show that
the removal efficiency of wastewater could reach as much as 94.5%.
More importantly, the magnetic adsorbents after removing pollutants
could be easily regenerated by a magnet. In addition to organic dye
removal, the magnetic adsorbent could adsorb 576.75% engine oil. This
work would provide a novel sustainable and cheap strategy for achieving
spent LIB recycle and pollutant removal subsequently with high efficiency.
Fe-based
MOFs (Fe-MOFs) are deemed promising Fenton-like catalysts
due to their well-developed pores and accessible active sites. However,
their inferior catalytic activity, iron leaching, and low H2O2 utilization always hinder their application as Fe-based
MOF catalysts. In this work, we manipulated the structure of Fe-oxo
nodes in MIL-88B(Fe) via a CuI species substitution method,
affording a mixed-valence (Cu-incorporated Fe-MOFs) with highly improved
Fenton-like performance. It is found that the CuI serves
as a shuttle to promote transfer between FeII/FeIII, inducing the formation of a larger amount of stable FeII sites, which was proven by experimental and DFT calculation results.
A linear relationship was observed for the Fenton-like performance
and the amount of CuI species for the catalysts. The corresponding
value of the •OH formation is 2.17 eV for Cu-incorporated
MIL-88B(Fe), which is significantly lower than that of MIL-88B(Fe)
(2.69 eV). Meanwhile, the enriched CuI species suppress
Fe species leaching during the catalytic reaction. The Fe-ion leakage
of 0.4Cu@MIL-88B is very tiny (0.01–0.03 mg/L), significantly
less than that of MIL-88B (2.00–3.02 mg/L). At the same time,
H2O2 utilization for 0.4Cu@ MIL-88B(Fe) is 88%,
which is almost 4.4 times that of pure MIL-88B(Fe). This work provides
insights into the rational design of Fe-MOFs as promising Fenton-like
catalysts for wastewater treatment.
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