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In this work, cathode materials of spent lithium-ion ternary batteries are recovered and used as metal precursor to prepare multi-metal oxides MnOx(SY) and GdMnO3(SY) via combustion method and sol–gel method, respectively. Furthermore, a series of MnOx(SY)-n and GdMnO3(SY)-n (n = 0.05, 0.10, 1.00, 4.00, n represents the dilute HNO3 concentration) catalysts are fabricated by acid treatment of MnOx(SY) and GdMnO3(SY) samples and catalytic activities of oxygenated VOCs oxidation over all the prepared catalysts are investigated. Catalytic evaluation results show that acid-treated MnOx(SY)-0.10 and GdMnO3(SY)-0.05 samples perform the optimum VOCs removal efficiency respectively, which may be attributed to their obvious enhancement of physicochemical properties. In detail, MnOx(SY)-0.10 and GdMnO3(SY)-0.05 samples exhibit the larger specific surface area, bigger amount of surface high-valence metal ions (Mn4+, Co3+, Ni3+), more abundant adsorbed oxygen species and better low-temperature reducibility, which can play a crucial role in the significant improvement of VOCs oxidation. In situ DRIFTS results imply that the possible main intermediates are -OCO, -COO and -C-O species produced during VOCs oxidation. Possible by-products are further determined via TD/GC–MS analysis.

Supported Pd-Cu NO3− reduction (NO3R) under H2 atmosphere is considered as a promising way to achieve NO3− removal directly in water through converting into N2, which is a harmless product in environment. However, desirable NO3R kinetics and N2 selectivity remain challenges. In this research, 2.5 wt% Cu and 10 wt% Pd are loaded on various oxides supports and combine with electrolytic in-situ H2 generation for NO3R. Pd10%Cu2.5%/TiO2 demonstrates a faster NO3R rate constant than Pd10%Cu2.5%/γ-Al2O3 and even greater than Pd10%Cu2.5%/CeO2. Pd10%Cu2.5%/γ-Al2O3 obtains better N2 selectivity than the other two. Crucially, the oxygen vacancies (VO) existing in TiO2 and CeO2 can reduce the nearby Cu2+ to Cu+, also Cu2+ can attract electrons from Pd0 to form Cu+ on the γ-Al2O3 surface. Verified by experiments and density functional (DFT) calculations, these Cu+ based active sites on the surface of substrates are vital for effective NO3− adsorption and high N2 selectivity.

A selective separation-recovery process based on tuning organic acid was proposed to the resource recycling of spent lithium-ion batteries (LIBs) for the first time. The low-cost preparation of CoFe2O4, reuse of waste acid and recovery of Li can be realized in this process, simultaneously. Li and Co in spent LIBs can be leached efficiently using citric acid as a leaching agent, and separated effectively from leaching solution by tuning oxalic acid content. The results from the characterizations of the prepared CoFe2O4 (CoFe2O4-LIBs) show that it possesses higher ratio of Co(II)/Co(III) and Fe(II)/Fe(III), larger surface specific area and more number of acid sites in comparison with pure CoFe2O4. Besides, CoFe2O4-LIBs was used to activate peroxymonosulfate (PMS) for the degradation of bisphenol A (BPA). Interestingly, its degradation performance is superior to that of pure CoFe2O4 and the related Co-based catalysts. The excellent degradation performance can be maintained in presence of inorganic ions (e.g., C l − , HC O 3 − , H 2 P O 4 − and N O 3 − ) with high concentration or humic acid. Moreover, surface-bound S O 4 ∙ − is considered as the main reactive species for the degradation of BPA. More importantly, CoFe2O4-LIBs can be readily recycled by using an external magnet and own superior ability of regeneration.

The construction of composite crystal structure is an effective strategy for developing enhanced functionality and can generally be constructed via two steps. Herein, a series of α@δ-MnO2 catalysts with different α/δ phase ratios are one-pot synthesized using a hydrothermal method; their molar ratio of KMnO4 to MnSO4·H2O was accurately controlled from 2.9 to 3.7. The catalytic results show that all α@δ-MnO2 catalysts exhibit significantly better catalytic performance in oxidizing toluene than single α-MnO2 and δ-MnO2 due to a synergistic effect, in which α@δ-2 with the closest two-phase proportion has the highest activity (T90 = 238 °C under a WHSV of 60,000 mL·g−1·h−1). Various characterization results indicate that α@δ-2 has the largest specific surface area, highest defects, oxygen vacancies, and best low-temperature reducibility among α-MnO2, δ-MnO2, and α@δ-2. Also, the possible reaction pathway for oxidizing toluene over the prepared catalysts is speculated using both TD/GC–MS and in-situ DRIFTS experiments.

In this work, manganese is selectively and efficiently recovered from spent lithium-ion batteries via advanced oxidation by using potassium permanganate and ozone, and the transition metal-doped α-MnO2 and β-MnO2 are one-step prepared for catalytic oxidation of VOCs. The recovery rate of manganese can be approximately 100% while the recovery efficiency of cobalt, nickel, and lithium is less than 15%, 2%, and 1%, respectively. Compared with pure α-MnO2 and β-MnO2, transition metal-doped α-MnO2 and β-MnO2 exhibit better catalytic performance in toluene and formaldehyde removal attributed to their lower crystallinity, more defects, larger specific surface area, more oxygen vacancies, and better low-temperature redox ability. Besides, the introduction of the appropriate proportion of cobalt or nickel into MnO2 can significantly improve its catalytic activity. Furthermore, the TD/GC-MS result indicates that toluene may be oxidized in the sequence of toluene - benzyl alcohol - benzaldehyde-benzoic acid - acetic acid, 2-cyclohexen-1-one, 4-hydroxy-, cyclopent-4-ene-1,3-dione - carbon dioxide. This method provides a route for the resource utilization of spent LIBs and the synthesis of MnO2.

Faced with a large amount of spent lithium-ions batteries from new energy vehicles and portable electronic devices such as personal computers and mobile phones. If they are not treated properly, they would not only result in serious environmental pollution but also lead to the loss of valuable resources like Co and Li. At present, most of researchers mainly focused on the metal recovery via hydrometallurgical and pyrometallurgical method. In this work, manganese-based metal oxides (MnOx(SY), MnOx(MS)) and cobalt-based oxides (CoOx(GS)) are synthesized using manganese and cobalt-based metals recovered from spent ternary, manganate and cobaltate lithium-ion batteries as a precursor, respectively. A series of supported multi-metal oxides were prepared by supporting 10% (wt) of MnOx(SY), MnOx(MS) and CoOx(GS) on CeO2 with different morphologies via impregnation method. The catalytic activities of the metal oxides during the oxidation of 2-ethoxyethyl acetate are investigated. The results obtained show that MnOx(MS)/CeO2-C, MnOx(SY)/CeO2-C and CoOx(GS)/CeO2-P have better catalytic performances due to their excellent physicochemical properties compared to the MnOx(SY), MnOx(MS), CoOx(GS), CeO2-R, CeO2-P, CeO2-C, MnOx(MS)/CeO2-R, MnOx(MS)/CeO2-P, MnOx(SY)/CeO2-R, MnOx(SY)/CeO2-P, CoOx(GS)/CeO2-R, CoOx(GS)/CeO2-C. In-situ diffuse reflectance infrared fourier transform spectroscopy results prove that gaseous O2 plays a vital role in facilitating the complete oxidation of intermediates such as ‒C˭O, ‒COO, ‒C‒O‒C, ‒C‒O into CO2 during 2-ethoxyethyl acetate oxidation. Furthermore, thermal desorption/gas chromatography-mass spectrometer results show that the main by-products obtained during 2-ethoxyethyl acetate oxidation are ethanol,2-methoxy-; ethanol, 2-methoxy-, acetate and acetic acid.