From spent alkaline batteries to ZnxMn3−xO4 by a hydrometallurgical route: synthesis and characterization

Transformation of Graphite Recovered from Batteries into Functionalized Graphene-Based Sorbents and Application to Gas Desulfurization

The recycling and recovery of value-added secondary raw materials such as spent Zn/C batteries is crucial to reduce the environmental impact of wastes and to achieve cost-effective and sustainable processing technologies. The aim of this work is to fabricate reduced graphene oxide (rGO)-based sorbents with a desulfurization capability using recycled graphite from spent Zn/C batteries as raw material. Recycled graphite was obtained from a black mass recovered from the dismantling of spent batteries by a hydrometallurgical process. Graphene oxide (GO) obtained by the Tour's method was comparable to that obtained from pure graphite. rGO-based sorbents were prepared by doping obtained GO with NiO and ZnO precursors by a hydrothermal route with a final annealing step. Recycled graphite along with the obtained GO, intermediate (rGO-NiO-ZnO) and final composites (rGO-NiO-ZnO-400) were characterized by Wavelength Dispersive X-ray Fluorescence (WDXRF) and X-ray diffraction (XRD) that corroborated the removal of metal impurities from the starting material as well as the presence of NiO- and ZnO-doped reduced graphene oxide. The performance of the prepared composites was evaluated by sulfidation tests under different conditions. The results revealed that the proposed rGO-NiO-ZnO composite present a desulfurization capability similar to that of commercial sorbents which constitutes a competitive alternative to syngas cleaning.

Studies of Selective Recovery of Zinc and Manganese from Alkaline Batteries Scrap by Leaching and Precipitation

Recovery of zinc and manganese from scrapped alkaline batteries were carried out in the following way: leaching in H₂SO₄ and selective precipitation of zinc and manganese by alkalization/neutralization. As a result of non-selective leaching, 95.6-99.7% Zn was leached and 83.7-99.3% Mn was leached. A critical technological parameter is the liquid/solid treatment (l/s) ratio, which should be at least 20 mL∙g^-1. Selective leaching, which allows the leaching of zinc only, takes place with a leaching yield of 84.8-98.5% Zn, with minimal manganese co-leaching, 0.7-12.3%. The optimal H₂SO₄ concentration is 0.25 mol∙L^-1. Precipitation of zinc and manganese from the solution after non-selective leaching, with the use of NaOH at pH = 13, and then with H₂SO₄ to pH = 9, turned out to be ineffective: the manganese concentrate contained 19.9 wt.% Zn and zinc concentrate, and 21.46 wt.% Mn. Better selectivity results were obtained if zinc was precipitated from the solution after selective leaching: at pH = 6.5, 90% of Zn precipitated, and only 2% manganese. Moreover, the obtained concentrate contained over 90% of ZnO. The precipitation of zinc with sodium phosphate and sodium carbonate is non-selective, despite its relatively high efficiency: up to 93.70% of Zn and 4.48-93.18% of Mn and up to 95.22% of Zn and 19.55-99.71% Mn, respectively for Na₃PO₄ and Na₂CO₃. Recovered zinc and manganese compounds could have commercial values with suitable refining processes.

Obtaining and Characterization of Highly Crystalline Recycled Graphites from Different Types of Spent Batteries

Spent batteries recycling is an important way to obtain low-cost graphite. Nevertheless, the obtaining of crystalline graphite with a rather low density of defects is required for many applications. In the present work, high-quality graphites have been obtained from different kinds of spent batteries. Black masses from spent alkaline batteries (batteries black masses, BBM), and lithium-ion batteries from smartphones (smartphone black masses, SBM) and electric and/or hybrid vehicles (lithium-ion black masses, LBM) were used as starting materials. A hydrometallurgical process was then used to obtain recycled graphites by acidic leaching. Different leaching conditions were used depending on the type of the initial black mass. The final solids were characterized by a wide set of complementary techniques. The performance as Li ion batteries anode of the sample with better structural quality was assessed.

Photocatalytic Activity of Zn x Mn3-x O4 Oxides and ZnO Prepared From Spent Alkaline Batteries

Oxides with Zn x Mn3-xO4 stoichiometries and ZnO were synthesized from the "black mass" material recovered from spent alkaline batteries. The oxides were characterized by XRF, XRD with Rietveld refinement, SEM, and TEM methods. Optical characterization included diffuse reflectance (DRS) and photoluminescence (PL) measurements. ZnO presented a clear band edge in the UV region, and PL signals were detected. The Zn/Mn oxides showed strong absorption in the UV region and a continuous absorption band in the Vis-IR regions. There is a non-detected PL signal due to excited charges being trapped on sub-band energy states and/or transfer by non-radiative paths. Photocatalytic activity under both irradiation conditions was evaluated using the resazurin dye test, terephthalic acid fluorescence probe method, and NOx air purification evaluation. In the three photoactivity tests, ZnO performed well under both UV and Vis irradiation, whereas no evidence of any appreciable photocatalytic activity was observed for the Zn/Mn oxides. The results are discussed in terms of the findings of previously reported optical measurements.

Energy efficient electrodes for lithium-ion batteries: Recovered and processed from spent primary batteries

In an attempt to develop low cost, energy efficient and advanced electrode material for lithium-ion batteries (LIBs), waste-to-wealth derived as well as value added spent battery materials as potential alternatives assume paramount importance. By combining the low lithiation potential advantages, one can arrive at energy efficient electrodes bestowed with cost effective and eco-friendly benefits required for practical LIB applications. In the present study, Zn and Mn-salts along with C were successfully extracted from the spent zinc carbon batteries through a simple and efficient hydrometallurgy approach and decomposed thermally to obtain ZnMn₂O₄ at 350 °C for 12 h and 450 °C for 3 h. Further, C-ZnMn₂O₄ nanocomposites were prepared and demonstrated for appreciable electrochemical performance in LIB assembly. Our results show that C-ZnMn₂O₄ composites prepared at 350 °C and 450 °C demonstrate better performance than pristine ZnMn₂O₄ anode due to the improved electronic conductivity rendered by the added carbon obtained from spent primary battery. In particular, C-ZnMn₂O₄ at 350 °C @12 h exhibits appreciable electrochemical performance by showing a stable and higher capacity of 600 mAhg^-1 at a current density of 50 mAg^-1 in the voltage range of 0.01-3.0 V and qualifies it as a better performing cost-effective anode for LIBs.