Swift development of electric vehicle (EV) absolutely produces enormous amounts of spent EV Li-ion batteries (LIBs), hence more studies should be performed to seek cheap, efficient, safe and ...eco-friendly ways for the recovery of spent EV LIBs. In this work, release of valuable Li, Co, Mn and Ni from three typical spent EV LIBs cathode LiFePO4, LiMn2O4 and LiNixCoyMn1-x-yO2 by bioleaching at 1% pulp density was explored for the first time. The results showed the maximum extraction efficiency of Li occurred in the sulfur–At system, indicating that Li release was due to acid solution by biogenic H2SO4; whereas the mixed energy source-mixed culture system harvested the highest dissolution yield for Co, Ni and Mn than other systems, suggesting these metals were mobilized by a combined work of Fe2+ reduction and acid dissolution. Moreover, a non-contact mechanism accounted for Li extraction, while a contact mechanism between the cathodes and cells was essential for mobilization of Co, Ni and Mn. Due to the enhancement effect in cell growth, pH adjustment greatly improved bioleaching performance, an average extraction efficiency of 4 valuable metals from the resistant LiNixCoyMn1−x−yO2 reached more than 95%, especially the release efficiencies of Co and Ni rose from 43.5% to 96% and from 38.3% to 97%, respectively. The rather high extraction efficiencies of the valuable metals suggest that the cheap autotrophic bioleaching is capable of recovery of the spent EV LIBs.
•Bioleaching efficiently released Li and Mn from EV LIBs, but poor with Co and Ni.•pH adjustment evidently improved bioleaching performance, especially Co and Ni.•Li release was due to solution by biogenic H2SO4 based on indirect mechanism.•Release of Co, Mn, Ni was due to co-work of Fe2+ reduction and acid dissolution.•Direct contact between cathodes and cells was needed for release of Co, Ni and Mn.
The bioleaching mechanism of Co and Li from spent lithium-ion batteries by mixed culture of sulfur-oxidizing and iron-oxidizing bacteria was investigated. It was found that the highest release of Li ...occurred at the lowest pH of 1.54 with elemental sulfur as an energy source, the lowest occurred at the highest pH of 1.69 with FeS
2. In contrast, the highest release of Co occurred at higher pH and varied ORP with S
+
FeS
2, the lowest occurred at almost unchanged ORP with S. It is suggested that acid dissolution is the main mechanism for Li bioleaching independent of energy matters types, however, apart from acid dissolution, Fe
2+ catalyzed reduction takes part in the bioleaching process as well. Co
2+ was released by acid dissolution after insoluble Co
3+ was reduced into soluble Co
2+ by Fe
2+ in both FeS
2 and FeS
2
+
S systems. The proposed bioleaching mechanism mentioned above was confirmed by the further results obtained from the experiments of bioprocess-stimulated chemical leaching and from the changes in structure and component of bioleaching residues characterized by XPS, SEM and EDX.
•Bioleaching behavior of spent LIBs at pulp density (PD) of 1–4% was explored.•Great decline in leaching efficiency was observed for Co/Li with increase in PD.•Maximum leach yield of 89% for Li and ...72% for Co was reach by process control.•Bioleaching has greater potential than chemical leaching based on thermodynamics.•Product layer diffusion model described best bioleaching behavior of Co and Li.
Release of Co and Li from spent lithium ion batteries (LIBs) by bioleaching has attracted growing attentions. However, the pulp density was only 1% or lower, meaning that a huge quantity of media was required for bioleaching. In this work, bioleaching behavior of the spent LIBs at pulp densities ranging from 1% to 4% was investigated and process controls to improve bioleaching performance at pulp density of 2% were explored. The results showed that the pulp density exerted a considerable influence on leaching performance of Co and Li. The bioleaching efficiency decreased respectively from 52% to 10% for Co and from 80% to 37% for Li when pulp density rose from 1% to 4%. However, the maximum extraction efficiency of 89% for Li and 72% for Co was obtained at pulp density of 2% by process controls. Bioleaching of the spent LIBs has much greater potential to occur than traditional chemical leaching based on thermodynamics analysis. The product layer diffusion model described best bioleaching behavior of Co and Li.
Extraction of manganese from electrolytic manganese residues using bioleaching was investigated in this paper. The maximum extraction efficiency of Mn was 93% by sulfur-oxidizing bacteria at 4.0
g/l ...sulfur after bioleaching of 9
days, while the maximum extraction efficiency of Mn was 81% by pyrite-leaching bacteria at 4.0
g/l pyrite. The series bioleaching first by sulfur-oxidizing bacteria and followed by pyrite-leaching bacteria evidently promoted the extraction of manganese, witnessing the maximum extraction efficiency of 98.1%. In the case of sulfur-oxidizing bacteria, the strong dissolution of bio-generated sulfuric acid resulted in extraction of soluble Mn
2+, while both the Fe
2+ catalyzed reduction of Mn
4+ and weak acidic dissolution of Mn
2+ accounted for the extraction of manganese with pyrite-leaching bacteria. The chemical simulation of bioleaching process further confirmed that the acid dissolution of Mn
2+ and Fe
2+ catalyzed reduction of Mn
4+ were the bioleaching mechanisms involved for Mn extraction from electrolytic manganese residues.
Abstract
Waste copper-containing paint residue (WCPR) represents a typical hazardous waste containing both toxic organic substances and toxic heavy metals, but there are few reports on the recycling ...of heavy metals. The recovery of Cu from WCPR by H2SO4 leaching–extraction–stripping has the advantages of eco-friendliness, simplicity of operation, and high value-added product. The results show that under the optimal conditions, the leaching rate of Cu in WCPR is 94.31% (18.02 g/L), while the extraction and stripping rates of Cu in the leaching solution are 99.46 and 95.32%, respectively. Due to the high concentration of Cu2+ with fewer impurities in the stripping solution, the stripping solution is heated, evaporated, cooled, and crystallized to successfully produce high-purity dark blue CuSO4 crystal, accomplishing the high-value recycling of Cu in WCPR. In addition, the leach residue of WCPR contains acrylic resin and SiO2, which can be used in cement kilns for incineration, thus realizing the overall recycling and utilization of WCPR.
•Strong adhesion of cells to the spent EV LIBs occurs, mediated by added EPS.•EPS produce aggregates with higher hydrophilicity/surface energy to favour bioleaching.•EPS adsorb both Fe3+ and Fe2+ to ...concentrate the Fe2+/Fe3+ cycle inside the aggregate.•EPS raise the potential and lower the resistance to boost electron movement inside the aggregate.•A unique contact reductive mechanism triggered by enriched Fe2+ was suggested.
As a fairly new concept, the recovery of valuable metals from urban mining by using bioleaching has become a hotspot. However, the function of extracellular polymeric substances (EPS) in the bioleaching of urban mining gains little attention. The current study used spent EV LIBs to represent urban mining products and systematically explored the function and role of EPS in the attachment of cells to the cathodes, formation of aggregates (cell-EPS-cathode), variation in the electrical and surface properties of the aggregates, concentration of both Fe2+ and Fe3+ surrounding the aggregates, electron transfer inside the aggregates and metals released from the aggregates. The results indicated that a strong adhesion of cells to the cathodes occurs mediated by EPS via both hydrophobic force as a main role and electrostatic force as a minor role. Second, the EPS not only adsorb Fe3+ but also more strongly adsorb Fe2+ to concentrate the Fe2+/Fe3+ cycle inside the aggregates, witnessing stronger reductive attack on the high valence state of metals as a contact reductive mechanism. Third, the retention or addition of EPS elevated the electronic potential and reduced the electronic resistance to lift the corrosion electric current, thereby boosting the electron transfer and metal dissolution.
► Bioleaching was used for extraction of valuable Zn and Mn from the spent batteries at high pulp densities. ► Bioleaching dynamics of both Zn and Mn under different pulp densities were compared. ► ...Reasons for decrease of bioleaching efficiency at high pulp densities were unveiled. ► Feasible measures for improving efficiency at high pulp density of 4% were proposed. ► Extraction yields of 100% for Zn and 89% for Mn at 4% of pulp density were attained.
The reasons for decline of bioleaching efficiency of Zn and Mn from spent batteries at high pulp densities were analyzed; the measures for improving bioleaching efficiency were investigated. The results showed that extraction efficiency of Zn dropped from 100% at 1% of pulp density to 29.9% at 8% of pulp density, with Mn from 94% to only 2.5%. It was almost the linear reduction of the activity of the sulfur-oxidizing bacteria with increase of pulp density that witnessed declined bioleaching efficiency of Zn; it was the complete inactivation of the iron-oxidizing bacteria at 2% of pulp density or higher that witnessed declined bioleaching dose of Mn. By means of reducing initial pH value of leaching media, increasing concentration of energy matters and exogenous acid adjustment of media during bioleaching, the maximum extraction efficiency of almost 100% for Zn and 89% for Mn at 4% of pulp density was attained, respectively.
The development of visible-light-responsive photocatalysts with high efficiency, stability, and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this ...work, the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35-2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions was carried out for the first time. The huge amount of biogenic S
and inherent extracellular proteins (EPs) secreted by SRB are important components of rapid extracellular biosynthesis. The ternary ZnCdS QDs at different molar ratios of Zn
and Cd
from 15:1 to 1:1 were monodisperse spheres with good crystallinity and average crystallite size of 6.12 nm, independent of the molar ratio of Cd
to Zn
. All the ZnCdS QDs had remarkable photocatalytic activity and stability for hydrogen evolution under visible light, without noble metal cocatalysts. Especially, ZnCdS QDs at Zn/Cd = 3:1 showed the highest H
production activity of 3.752 mmol·h
·g
. This excellent performance was due to the high absorption of visible light, the high specific surface area, and the lower recombination rate between photoexcited electrons and holes. The adhered inherent EPs on the ZnCdS QDs slowed down the photocorrosion and improved the stability in photocatalytic hydrogen evolution. This study provides a new direction for solar hydrogen production.
In this paper bioaccumulation of Cu-complex reactive dye by growing pellets of
Penicillium oxalicum and its mechanism was investigated. Shaking flasks experiment showed that 99.7% of dye removal at ...400 mg/l was attained after 48 h contact. Column reactor experiment showed that air lift ferment tower was a suitable reactor for both pellets formation and dye bioaccumulation. Repeated inoculation of the dye-loaded pellets accelerated dye bioaccumulation, leading to complete dye removal within 12 h. Dye initially was adsorbed on surface of cell, followed by penetration into cytoplasm. During bioaccumulation, mycelium expanded unevenly and thickened locally in diameter, generating a chain of spindles along the mycelium. In addition, the cell walls grew loose and thickened remarkably, being 4–5 folds as thick as the control one. The loose cell wall may offer both dye accumulation space and route way for dye to enter cytoplasm. There were certain unknown active matters in cytoplasm, which played an important role in dye accumulation. Desorption experiments suggested that electrostatic attraction was mainly attributed to the dye bioaccumulation.
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