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It might be of practical significance to recover different metals from the already complicated waste spent lithium-ion battery (LIB) stream by simplified recycling processes. This study is, therefore, focused on the exploration of a simplified process for the simultaneous recovery of different metals from waste cathode materials of mixed types of spent LIBs. It is discovered that the leaching agent phosphoric acid demonstrates natural repulsion for Fe, while valuable metals such as Ni, Co, Mn, and Li can be completely dissolved under optimized leaching conditions, indicating a coupling reaction of selective leaching and precipitating for valuable metals and iron, respectively. Characterization results indicate valuable metal-enriched solution and pure FePO4 in leaching solution and residue, respectively. Kinetics and dynamics studies suggest that the leaching of valuable metals is co-controlled by chemical reaction and internal diffusion, accompanying a spontaneous formation of FePO4. Then, new cathode materials LiFePO4 and LiNi1/3Co1/3Mn1/3O2 with sound electrochemical performances can be re-fabricated from leaching residues and lixivium, respectively, and phosphoric acid can be regenerated during the co-precipitating of valuable metals. This entire recycling process can be a highly selective, closed-loop and simplified alternative for recycling different metals from the current most complicated waste LIB stream. [ABSTRACT FROM AUTHOR]

In this work, a new gas diffusion electrode (GDE) of carbon nanotube/graphitic carbon nitride (CNT/g-C3N4) was prepared, which enables the substantially improved production of H2O2 (up to 1083.54 mg L−1) compared to generation without g-C3N4 (400 mg L−1). Characterized by TEM, XRD and XPS, the synthesized g-C3N4 was proved to be a thin layer sheet with low defects. Important cathode manufacturing parameters including the mass ratio of CNTs to g-C3N4 were optimized, and the dependence of H2O2 generation on pH, current density, aeration rate and performance stability were investigated. Further explored by linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) analysis, the presence of g-C3N4 was found to accelerate the electron transfer rate, benefit the oxygen surface reaction, which contributed to the enhanced performance for H2O2 production. Finally, such a CNT/g-C3N4 cathode demonstrated effectiveness for the degradation of alizarin yellow R (AYR) by electro-Fenton (EF), photo-Fenton (PF) and photoelectron-Fenton (PEF) processes. AYR was degraded completely, and 94.8% of the organic carbon was removed, which is more than 5 times the amount removed using PF degradation only. And during the PEF degradation process of AYR, electro- and photocatalysis support and optimize each other, which produces a substantial synergistic effect, proving great potential for practical application in organic wastewater treatment. [ABSTRACT FROM AUTHOR]

A new graphite felt cathode loaded with carbon nanotubes (CNTs) was developed. The resulting electrode showed a very high generation rate of H2O2 (10.73 mg h−1 cm−2) at a relatively low electric energy consumption (6.90 kW h kg−1). These features improved the in situ production of H2O2 by about 20 folds when an optimized ratio of CNTs to carbon black mass (3 : 2) was used. Several manufacturing parameters like the ratio and loads of CNTs were optimized. Also, factors influencing the electro-generated H2O2, such as pH and current density, were investigated. Examination of H2O2 electro-generation mechanisms indicated that some cathode features would accelerate the oxygen reduction reaction (ORR) activity and enhance the electrochemical behavior during H2O2 production. The removal rate of diclofenac by electro-Fenton (EF) using a CNT loaded cathode reached over 99% within 30 min. The total organic carbon (TOC) removal of diclofenac approached 91.71% at 180 min, which was over 4 folds higher than that obtained with the unloaded electrode (19.05%). LC-MS analyses allowed building a possible mechanism and a degradation pathway of diclofenac. In terms of stability, the CNT loaded electrode revealed excellent stability as the removal of TOC was maintained at 87.4% of the original response after ten runs. Such CNT loaded cathodes with efficient and significantly enhanced H2O2 production offer efficient and low energy consumption degradation of organic pollutants by EF. [ABSTRACT FROM AUTHOR]

This work set out to study the effects of cadmium (Cd) in sediments on the antioxidant enzyme activities in the digestive gland of Asian clam Corbicula fluminea and to explore the potential for applying these responses to evaluate the Cd-contaminated sediment. Additionally, diffusive gradients in thin-films (DGT) technique was used to predict the response of its antioxidant defense system. The sediments, collected from Taihu Lake, were spiked with Cd at different concentrations (0.72, 0.91, 1.62, 2.59, 11.2, 20.4 and 40.6 mg kg(-1), dry weight). Asian clam was cultivated for 28 days. Concentrations of Cd in the body of Asian clam had a good relationship with concentrations of Cd in overlying water and sediments, as measured by DGT. Cd affected these biochemical parameters significantly, especially for superoxide (SOD), peroxidase (POD) and glutathione (GSH), which began to show higher sensitivity and have a significant difference in low dosage (0.91 mg Cd kg(-1)) compared with blank. Contents of MDA and MT, which were induced by Cd, increased with the increasing Cd concentration in sediments and reached peak values at 11.2 and 20.4 mg kg(-1), respectively, after 28 days exposure. All of these results suggested that biochemical responses cooperated in detoxifying and maintaining cellular metabolic homeostasis. The R(2) of regression analysis between the contents of MT and the concentrations of Cd measured by DGT, in sediments and soft body were 0.71, 0.94 and 0.88 after 28 days exposure. This suggested that DGT measurement could predict the response of MT. Cd accumulation, GSH and MT were indispensable biomarkers and the MDA content and DGT appeared to be promising biomarkers. The results clearly indicated that Cd could induce oxidative stress in the digestive gland of Asian clam. The combination of biomonitors with DGT can obtain different information about Cd bioavailability and confirm the significance of applying a suite of biomarkers rather than a selective index to assess the sublethal effect. It also offered theoretical methods for the prediction of sediment Cd pollution.