Unveiling the lithium deintercalation mechanisms in spent lithium-ion batteries via sulfation roasting.

Recovery of valuable metals from spent lithium-ion batteries (LIBs) is of great importance for resource sustainability and environmental protection. This study introduced pyrite ore (FeS2) as an alternative additive to achieve the selective recovery of Li2CO3 from spent LiCoO2 (LCO) batteries. The mechanism study revealed that the sulfation reaction followed two pathways. During the initial stage (550 °C-800 °C), the decomposition and oxidation of FeS2 and the subsequent gas-solid reaction between the resulting SO2 and layered LCO play crucial roles. The sulfation of lithium occurred prior to cobalt, resulting in the disruption of layered structure of LCO and the transformation into tetragonal spinel. In the second stage (over 800 °C), the dominated reactions were the decomposition of orthorhombic cobalt sulfate and its combination with rhombohedral Fe2O3 to form CoFe2O4. The deintercalation of Li from LCO by the substitution of Fe and conversion of Co(III)/Fe(II) into Co3O4/CoFe2O4 were further confirmed by density functional theory (DFT) calculation results. This fundamental understanding of the sulfation reaction facilitated the future development of lithium extraction methods that utilized additives to substantially reduce energy consumption.

Design Strategy of the MnOx Catalyst for SCR of NO with NH3: Mechanism of Lead Poisoning and Improvement Method.

The conventional Mn-based catalysts suffer from lead toxicity and require other transition-metal oxides to enhance their resistance in the selective catalytic reduction of NOx with ammonia (NH3-SCR). Herein, we found that the incorporation of inert silica into pure MnOx effectively improved the Pb resistance. The NOx conversion of the MnOx-SiO2-Pb catalyst was nearly 55% higher than that of the MnOx-Pb catalyst, exhibiting enhanced activity at lower temperatures (150-225 °C). To reveal the essential roles at the molecular level, the types and numbers of surface acidity, nitrate species, and catalytic cycle were established through experimental analysis and theoretical calculations of catalysts. The presence of PbCl2 occupied the active Mn sites, resulting in an obvious decline in the Brønsted acid sites (B-NH4+) and the oxidation performance, and the NH3-SCR cycle was energetically less favorable on the MnOx-Pb catalyst. Conversely, SiO2 played a crucial role in preserving the activity of Mn sites on the MnOx-SiO2-Pb catalyst by preferentially bonding with PbCl2, generating more active intermediates. Significantly, this work provided mechanistic insights into the role of SiO2 in regulating the surface acidity, oxidation performance, and stability of active Mn sites, which is helpful for the design of Mn-based catalysts with high Pb resistance for the NH3-SCR reaction.

Structural tuning of copper sulfide material for sodium-ion batteries.

In this work, single-crystal and twin-crystal copper sulfide materials are constructed in a regulatable and controlled manner. Twin boundaries are engineered into the copper sulphide material to significantly improve its electrochemical performance. The results demonstrate that structure tuning with twin crystals is an effective strategy for enhancing electrochemical reactions, and also sheds light on the design of electrode materials for sodium ion storage.

Unveiling the SO2 Resistance Mechanism of a Nanostructured SiO2(x)@Mn Catalyst for Low-Temperature NH3-SCR of NO.

Low N2 selectivity and SO2 resistance of Mn-based catalysts for removal of NOx at low temperatures by NH3-SCR (selective catalytic reduction) technology are the two main intractable problems. Herein, a novel core-shell-structured SiO2@Mn catalyst with greatly improved N2 selectivity and SO2 resistance was synthesized by using manganese carbonate tailings as raw materials. The specific surface area of the SiO2@Mn catalyst increased from 30.7 to 428.2 m2/g, resulting in a significant enhancement in NH3 adsorption capacity due to the interaction between Mn and Si. Moreover, the N2O formation mechanism, the anti-SO2 poisoning mechanism, and the SCR reaction mechanism were proposed. N2O originated from the reaction of NH3 with O2 and the SCR reaction, as well as from the reaction of NH3 with the chemical oxygen of the catalyst. Regarding improving the SO2 resistance, DFT calculations showed that SO2 was observed to preferentially adsorb onto the surface of SiO2, thus preventing the erosion of active sites. Adding amorphous SiO2 can transform the reaction mechanism from Langmuir-Hinshelwood (L-H) to Eley-Rideal (E-R) by adjusting the formation of nitrate species to produce gaseous NO2. This strategy is expected to assist in designing an effective Mn-based catalyst for low-temperature NH3-SCR of NO.

Acid-free extraction of valuable metal elements from spent lithium-ion batteries using waste copperas.

A large amount of hazardous spent lithium-ion batteries (LIBs) is produced every year. Recovery of valuable metals from spent LIBs is significant to achieve environmental protection and alleviate resource shortages. In this study, a green and facile process for recovery of valuable metals from spent LIBs by waste copperas was proposed. The effects of heat treatment parameters on recovery efficiency of valuable metals and the redox mechanism were studied systematically through phase transformation behavior and valence transition. At low temperature (≤460 °C), copperas reacted with lithium on the outer layer of LIBs preferentially, but the reduction of transition metals was limited. As the temperature rose to 460-700 °C, the extraction efficiency of valuable metals was greatly enhanced due to the generation of SO2, and the gas-solid reaction proceeded much fast than the solid-solid reaction. In the final stage (≥700 °C), the main reactions were the thermal decomposition of soluble sulfates and the combination of decomposed oxides with Fe2O3 to form insoluble spinel. Under the optimum roasting conditions, i.e., at a copperas/LIBs mass ratio of 4.5, and a roasting temperature of 650 °C and roasting time of 120 min, the leaching efficiencies of Li, Ni, Co and Mn were 99.94%, 99.2%, 99.5% and 99.65%, respectively. The results showed that valuable metals can be selectively and efficiently extracted from the complex cathode materials by water leaching. This study used waste copperas as an aid to recover metals and provided an alternative technical route for green recycling of spent LIBs.

A novel strategy for efficient utilization of manganese tailings: High SO2 resistance SCR catalyst preparation and faujasite zeolite synthesis.

Herein, a core-shell structure SiO2@Mn catalyst was successfully synthesized from manganese tailings for NO removal through selective catalytic reduction with ammonia at low temperature. In the presence of 10 % H2O and 100 ppm SO2, the SiO2@Mn catalyst exhibited excellent catalytic activity of 85 % NO conversion at 225 °C. This special core-shell was constructed by inert nano-SiO2 particles, which grew and encapsulated on the surface of manganese oxide, inhibiting the reaction between SO2 with MnOx and thus improving the SO2 resistance. Furthermore, a filter residue was generated in the process of catalysts preparation. Under proper hydrothermal conditions, the residue comprising of Si, Al, and O was used to synthesize high-crystallinity X-type zeolite. This process fully utilized manganese tailings and inspired for Mn-based catalysts design and X-type zeolite preparation, realizing the dual benefits of atmosphere purification and solid waste disposal.

Constructing C-O bridged CeO2/g-C3N4 S-scheme heterojunction for methyl orange photodegradation：Experimental and theoretical calculation.

Owing to its feasibility, efficiency in light-harvesting and effectiveness in the interfacial charge transfer between two n-type semiconductors, constructing heterojunction photocatalysts have been identified as an effective way for enhancing the photocatalytic properties. In this research, a C-O bridged CeO2/g-C3N4 (cCN) Step-scheme (S-scheme) heterojunction photocatalyst was constructed successfully. Under visible light irradiation, the cCN heterojunction exhibited the photocatalytic degradation efficiency of methyl orange, which was about 4.5 and 1.5 times higher than that of pristine CeO2 and CN, respectively. The DFT calculations, XPS and FTIR analyses demonstrated the formation of C-O linkages. And the calculations of work functions revealed the electrons would flow from g-C3N4 to CeO2 due to the difference in Fermi levels, resulting in the production of internal electric fields. Benefiting from the C-O bond and internal electric field, the photo-induced holes in the valence band of g-C3N4 and the photo-induced electrons from conduction band of CeO2 would be recombined when exposed to visible light irradiation, while leaving the electrons with higher redox potential in the conduction band of g-C3N4. This collaboration accelerated the separation and transfer rate of photo-generated electron-hole pairs, which promoted the generation of superoxide radical (•O2-) and improved the photocatalytic activity.

In situ deposition of 0D CeO2 quantum dots on Fe2O3-containing solid waste NH3-SCR catalyst: Enhancing redox and NH3 adsorption ability.

As NOx has been turning into a crucial environmental problem, NH3-SCR technology with relatively simple device, reliable operation and low secondary pollution, has become a widely used commercial and mature de-nitration technology. However, some weaknesses restricted the further application of commercialized V2O5-WO3/TiO2 NH3-SCR catalysts, while Fe2O3-based catalysts have received much attention due to their high thermal stability, passable N2 selectivity and low cost. In this study, Fe2O3-containing solid waste derived from Zn extraction process of electric arc furnace dust was exploited as the base material for catalyst preparing. Owing to the complementary and synergistic effect of CeO2 and Fe2O3, 0D CeO2 quantum dots (CeQDs) with fully-exposed active sites, large specific surface area, and rapid charge transfer have been introduced and deposited onto Fe2O3-containing solid waste nanorods. The in-situ deposition of CeQDs led to the admirable enhancement in NH3-SCR catalytic activity, N2 selectivity and SO2 tolerance of the extremely low-cost Fe2O3 catalyst. Comprehensive characterizations and DFT calculations describing the adsorption of O2 and NH3 were applied to analyze the catalyst structure and further investigate the detailed relationship between structural properties and activity as well as reaction mechanism. This work provides new insights for the high-value utilization of iron-containing solid waste and a practical reference for boosting the performance of NH3-SCR catalysts by introducing quantum dots.

Different lead species deactivation on Mn-Ce activated carbon supported catalyst for low-temperature SCR of NO with NH3: Comparison of PbCl2, Pb (NO3)2 and PbSO4.

Due to the accumulation of heavy metal compounds produced by the sintering process in steel industry, the catalysts used for low-temperature selective catalytic reduction of NO with NH3 (NH3-SCR) might be seriously deactivated. In this work, the deactivation effect of PbCl2, Pb(NO3)2, and PbSO4 on Mn-Ce activated carbon supported catalyst for low-temperature NH3-SCR of NO was investigated and compared. Poisoned catalysts were provided by impregnating fresh catalysts with Pb(NO3)2, PbSO4 and PbCl2 aqueous solutions, respectively. Deactivation could be observed on the poisoned samples, and the deactivation degree was following PbCl2 > PbSO4 > Pb(NO3)2. The catalytic activities of all samples were tested, and the physicochemical properties of fresh and poisoned catalysts were assessed. PbCl2 caused the most severe deactivation of the catalyst, owing to its poor redox property and surface acidity. Cl- could also react with Mn active sites to form -O-Mn-Cl bonds, resulting in additional acid sites, although these newly generated sites were not reactive in NH3-SCR reaction process. PbSO4 exhibited moderate poisoning effect due to the addition of SO42-, which created new Brønsted acid sites, facilitating the NH3 adsorption and NO reduction. Pb(NO3)2 had the least poisoning impact on the catalyst due to the NO3-, promoting the NH3 activation. The in situ DRIFTS results revealed that NH3-SCR reaction over all samples was governed by Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanism, and did not change due to the lead poisoning. Finally, a possible mechanistic model for different lead salts poisoning over Mn-Ce/AC catalyst was proposed.

Influence of phosphorus on the NH3-SCR performance of CeO2-TiO2 catalyst for NOx removal from co-incineration flue gas of domestic waste and municipal sludge.

Domestic waste and municipal sludge are two major solid hazardous substances generated from human daily life. Co-incineration technology is regarded as an effective method for the treatment of them. However, the emitted NOx-containing exhaust with high content of phosphorus should purified strictly. CeO2-TiO2 is a promising catalyst for removal of NOx by NH3-SCR technology, but the effect of phosphorous in the exhaust is ambiguous. Therefore, the effect of phosphorus on NH3-SCR performance and physicochemical properties of CeO2-TiO2 catalyst was investigated in our present work. It was found that phosphorus decreased the NH3-SCR activity below 300 °C. Interestingly, it suppressed the formation of NOx and N2O caused by NH3 over-oxidation above 300 °C. The reason might be that phosphorus induced Ti4+ to migrate from CeO2-TiO2 solid solution and form crystalline TiO2, which led to the destruction of Ti-O-Ce structure in the catalyst. So, the transfer of electrons between Ti and Ce ions, the relative contents of Ce3+, and surface adsorbed oxygen, as well as the redox performance were limited, which further inhibited the over-oxidation of NH3. In addition, phosphorus weakened the NH3 adsorption on Lewis acid sites and the adsorption performance of NO + O2, while increased the Brønsted acid sites. Finally, the reaction mechanism over CeO2-TiO2 catalyst did not change after introducing phosphorus, L-H and E-R mechanisms co-existed on the surface of the catalysts.