Recycling and management of waste lead-acid batteries: A mini-review

Toward Direct Regeneration of Spent Lithium-Ion Batteries: A Next-Generation Recycling Method

The popularity of portable electronic devices and electric vehicles has led to the drastically increasing consumption of lithium-ion batteries recently, raising concerns about the disposal and recycling of spent lithium-ion batteries. However, the recycling rate of lithium-ion batteries worldwide at present is extremely low. Many factors limit the promotion of the battery recycling rate: outdated recycling technology is the most critical one. Existing metallurgy-based recycling methods rely on continuous decomposition and extraction steps with high-temperature roasting/acid leaching processes and many chemical reagents. These methods are tedious with worse economic feasibility, and the recycling products are mostly alloys or salts, which can only be used as precursors. To simplify the process and improve the economic benefits, novel recycling methods are in urgent demand, and direct recycling/regeneration is therefore proposed as a next-generation method. Herein, a comprehensive review of the origin, current status, and prospect of direct recycling methods is provided. We have systematically analyzed current recycling methods and summarized their limitations, pointing out the necessity of developing direct recycling methods. A detailed analysis for discussions of the advantages, limitations, and obstacles is conducted. Guidance for future direct recycling methods toward large-scale industrialization as well as green and efficient recycling systems is also provided.

The Air Quality Index (AQI) in historical and analytical perspective a tutorial review

The Air Quality Index (AQI), developed by the United States Environmental Protection Agency (USEPA), has been providing the public with crucial information regarding the status of contamination of the atmosphere for the past 45 years. Prior to introduction of the AQI, only a handful of metropolitan areas reported on air quality, and each region decided on its own metric. The inception of a single AQI helped homogenize the air quality metrics across the nation and indeed served as an important future template for other governmental and regulatory agencies across the world. The formulators had the foresight to recognize that our understanding of air pollution and its effects may change over time, which are likely to change regulatory limits. They used a dynamic framework to define the AQI, such that the broad definition or principle does not need to change with every change in regulatory limits or policy, and the fundamental goal of alerting the public to deleterious air quality is not affected. The establishment of the AQI increased public awareness of the importance of clean air and has helped muster support for air quality and emission regulations. The National Ambient Air Quality Standards (NAAQS) set forth by the USEPA provides acceptable levels of criteria pollutants - namely carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide. A comparison of the actual levels, as compared to the regulatory limits (since the cessation of leaded gasoline, lead is no longer included in the index), are used as the basis for the AQI. As the regulatory limits change, so does the exact evaluation of the AQI, making it a living index. In this paper, we provide a historical overview of the Air Quality Index, the Federal Reference Methods (FRMs) vs. Federal Equivalent Methods (FEMs) for measuring them, and as an illustrative example, we discuss the air quality for Dallas-Ft. Worth, currently the fourth most populous metropolitan region in the United States, vis-a-vis the reported AQI.

Environmental risk assessment near a typical spent lead-acid battery recycling factory in China

In recent years, environmental pollution and public health incidents caused by the recycling of spent lead-acid batteries (LABs) has becoming more frequent, posing potential risk to both the ecological environment and human health. Accurately assessing the environmental risk associated with the recycling of spent LABs is a prerequisite for achieving pollution control. In this study, a spent LABs recycling factory in Chongqing was investigated through on-site investigation, sample analysis. Exposure assessment and health risk assessment were also conducted. The results showed that: firstly, Pb and As concentrations exceeding the standard limit values were found in the environmental air and vegetables near the spent LABs recycling factory. Secondly, exposure assessment results showed that total average daily exposure to hazardous substances for children (3.46 × 10-2 mg/kg) is higher than for adults (4.80 × 10-2 mg/kg). The main exposure pathways for Pb, Cr, Ni, Cu, Zn, and Hg are ingestion of vegetables, while those for Cd, As, and Sb are through inhalation. Thirdly, health risk assessment results indicate that environmental exposure poses unacceptable non-carcinogenic and carcinogenic risk to both adults and children near the spent LABs recycling factory, with children facing higher risk than adults. Pb and As are the main contributors to non-carcinogenic risk, and Ni and As are the main contributors to unacceptable carcinogenic risk. In particular, As, has a greater contribution to total carcinogenic risk index through inhalation than vegetable ingestion. Overall, vegetable ingestion and inhalation are the main exposure pathways for non-carcinogenic and carcinogenic risk. Consequently, future risk assessment should focus on the impact of hazardous substances on children, as well as the health risk associated with ingestion of vegetables and inhalation. Our findings will provide basic information for proposing measures of environmental risk prevention during the recycling of spent LABs, for example, controlling of As in exhaust gas emissions.

Structure, Antiferroelectricity and Energy-Storage Performance of Lead Hafnate in a Wide Temperature Range

Lead hafnate (PbHfO₃) has attracted a lot of renewed interest due to its potential as antiferroelectric (AFE) material for energy storage. However, its room temperature (RT) energy-storage performance has not been well established and no reports on the energy-storage feature of its high-temperature intermediate phase (IM) are available. In this work, high-quality PbHfO₃ ceramics were prepared via the solid-state synthesis route. Based on high-temperature X-ray diffraction data, the IM of PbHfO₃ was found to be orthorhombic, Imma space group, with antiparallel alignment of Pb²⁺ ions along the [001]_cubic directions. The polarization-electric field (P-E) relation of PbHfO₃ is displayed at RT as well as in the temperature range of the IM. A typical AFE loop revealed an optimal recoverable energy-storage density (W_rec) of 2.7 J/cm³, which is 286% higher than the reported data with an efficiency (η) of 65% at 235 kV/cm at RT. A relatively high W_rec value of 0.7 J/cm³ was found at 190 °C with an η of 89% at 65 kV/cm. These results demonstrate that PbHfO₃ is a prototypical AFE from RT up to 200 °C, making it a suitable material for energy-storage applications in a wide temperature range.

Valorisation of spent tire rubber as carbon adsorbents for Pb(II) and W(VI) in the framework of a Circular Economy

Spent tire rubber-derived chars and their corresponding H3PO4 and CO2-activated chars were used as adsorbents in the recovery of Pb(II) ion and (W(VI)) oxyanion from synthetic solutions. The developed chars (both raw and activated) were thoroughly characterized to have insight about their textural and surface chemistry properties. H3PO4-activated chars presented lower surface areas than the raw chars and an acidic surface chemistry which affected the performance of these samples as they showed the lowest removals of the metallic ions. On the other hand, CO2-activated chars presented increased surface areas and increased mineral content compared to the raw chars, having presented higher uptake capacities for both Pb(II) (103-116 mg/g) and W(VI) (27-31 mg/g) ions. Cation exchange with Ca, Mg and Zn ions was appointed as a mechanism for Pb removal, as well as surface precipitation in the form of hydrocerussite (Pb3(CO3)2(OH)2). W(VI) adsorption might have been ruled by strong electrostatic attractions between the negatively charged tungstate species and the highly positively charged carbons' surface.The results shown in this work allow concluding that the valorisation of spent tire rubber through pyrolysis and the subsequent activation of the obtained chars is an alternative and a feasible option to generate adsorbent materials with a high uptake capacity of critical metallic elements.

Toward High-Energy-Density Aqueous Lithium-Ion Batteries Using Silver Nanowires as Current Collectors

The lack of suitable lightweight current collectors is one of the primary obstacles preventing the energy density of aqueous lithium-ion batteries (ALIBs) from becoming competitive. Using silver nanowire (AgNW) films as current collectors and a molecular crowding electrolyte, we herein report the fabrication of ALIBs with relatively good energy densities. In the 2 m LiTFSI-94% PEG-6% H₂O solution, the AgNW films with a sheet resistance of less than 1.0 ohm/square exhibited an electrochemical stability window as broad as 3.8 V. The LiMn₂O₄//Li₄Ti₅O₁₂ ALIBs using AgNW films as the current collectors demonstrated an initial energy density of 70 Wh/kg weighed by the total mass of the cathode and anode, which retained 89.1% after 50 cycles.

Triangular Intuitionistic Fuzzy Aggregating and Ranking Function Approach for the Rating of Battery ‘End-of-Life’ Handling Alternatives

The increased adoption of intermittent renewable sources in the energy sector has also increased the use of battery storage systems. However, the negative impact which the improper disposal of batteries has on the environment has stirred debates on its sustainability. To ensure the proper disposal of battery waste, there is a need to identify and rank the most preferred battery ‘end-of-life’ handling alternatives. This paper focuses on identifying the most preferred ‘end-of-life’ handling alternatives for batteries using a modified triangular intuitionistic fuzzy aggregating and ranking function (TIFARF) model. To test the proposed modified TIFARF model, opinions from experts in the Nigerian renewable energy sector were collected, and the results show that the most preferred alternative is incineration, with a closeness coefficient of 0.130, while the least preferred alternative is recycling, whose closeness coefficient is 0.112. The results are an indication of a lack of facilities needed for the proper recycling of battery remains after their lifetime; if adequate facilities are available, the opinion of experts may be biased towards other alternatives. Future studies should focus on more battery ‘end-of-life’ handling alternatives and on countries with adequate facilities that can be used to manage batteries at the end of their lifespan.

Long-term continuous and real-time in situ monitoring of Pb(II) toxic contaminants in wastewater using solid-state ion selective membrane (S-ISM) Pb and pH auto-correction assembly

Lead (Pb) contaminants in wastewater have inhibited microbial activities and thus exerted high energy consumption in wastewater treatment plants (WWTPs). Current Pb monitoring has been conducted ex situ and off line, unable to affect real-time proactive control and operation. This study targets the crucial challenge of better and faster Pb monitoring by developing novel mm-sized screen-printed solid-state ion-selective membrane (S-ISM) Pb sensors with low-cost, high accuracy and long-term durability and that enable real-time in situ monitoring of Pb(II) ion contamination down to low concentrations (15 ppb-960 ppb) in wastewater. An innovative pH auto-correction data-driven model was built to overcome the inextricable pH inferences on Pb(II) ISM sensors in wastewater. Electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) analysis showed (3,4-ethylenedioxythiophene, EDOT) deposited onto the mm-sized screen-printed carbon electrodes using electropolymerization effectively alleviated the interferences from dissolved oxygen and improved long-term stability in wastewater. Monte Carlo simulation of the nitrification process predicted that real-time, and high accurate in situ monitoring of Pb(II) in wastewater and swift feedback control could save ∼53 % of energy consumption by alleviating the errors from pH and DO impacts in WWTPs.

Novel Bioderived Composites from Wastes

The recycling and reuse of solid wastes can be considered important challenges for civil and environmental applications in the frame of a more sustainable model of development and the consumption of new resources and energy [...].

Lead recovery from spent lead acid battery paste by hydrometallurgical conversion and thermal degradation

Spent lead paste is the main component in lead-acid batteries reaching end of life. It contains about 55% lead sulphate and 35% lead dioxide, as well as minor amounts of lead oxide. It is necessary to recycle spent lead paste with minimal pollution and low energy consumption instead of the conventional smelting method. In this study, a novel approach involving hydrometallurgical desulphurisation and thermal degradation is developed to recover lead as PbO products from spent lead acid batteries. First, the desulphurisation effects and phase compositions of products with different transforming agents were compared, and the optimum conditions using (NH₄)₂CO₃ as a transforming agent were determined. And then, the thermal degradation processes of both precursors lead carbonate and lead dioxide were investigated to prepare α-PbO, Pb₃O₄, and β-PbO products in argon and air atmospheres, respectively. Both the desulphurisation precursors and the calcination products were characterised by thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The results showed that the lead oxide products were prepared, including α-PbO at 450°C in argon, Pb₃O₄ and β-PbO at 480°C and 620°C in air, respectively.

Recycled Expanded Polystyrene as Lightweight Aggregate for Environmentally Sustainable Cement Conglomerates

In the present work the rheological, thermo-mechanical, microstructural, and wetting characteristics of cement mortars with recycled expanded polystyrene (EPS) were analyzed. The samples were prepared after partial/total replacement of the conventional sand aggregate with EPS having different grain size and size distribution. Lightness and thermal insulation were relevant features for all the bare EPS composites, despite the mechanical strengths. Specifically, EPS based mortars were characterized by higher thermal insulation with respect to the sand reference due to the lower specific mass of the specimens mainly associated with the low density of the aggregates and also to the spaces at the EPS/cement paste interfaces. Interesting results in terms of low thermal conductivity and high mechanical resistances were obtained in the case of sand-EPS mixtures although characterized by only 50% in volume of the organic aggregate. Moreover, sand-based mortars showed hydrophilicity (low WCA) and high water penetration, whereas the presence of EPS in the cement composites led to a reduction of the absorption of water especially on the bulk of the composites. Specifically, mortars with EPS in the 2-4 mm and 4-6 mm bead size range showed the best results in term of hydrophobicity (high WCA) and no water penetration in the inner surface, due to low surface energy of the organic aggregate together with a good particle distribution. This was indicative of cohesion between the ligand and the polystyrene as observed in the microstructural detections. Such a property is likely to be correlated to the observed good workability of this type of mortar and to its low tendency to segregation compared to the other EPS containing specimens. These lightweight thermo-insulating composites can be considered environmentally sustainable materials because they are prepared with no pre-treated secondary raw materials and can be used for indoor applications.

Assessment of Leaching Characteristics of Solidified Products Containing Secondary Alkaline Lead Slag

Reuse of waste is one of the main principles of sustainable development and circular economy. Secondary alkaline lead slag is a hazardous waste generated in the recycling process of lead-acid batteries that may be suitable in construction materials. The environmental impact of the use of lead slag as a partial replacement of fine aggregates in the cement-based stabilization/solidification (S/S) process for the preparation of concrete was studied in this paper. Solidified products containing 10%, 15%, 20%, and 25% slag were laboratory tested by unconfined compressive strength (UCS) analyses and the Toxicity Characteristic Leaching Procedure (TCLP). At the same time, the leachability of toxic elements from solidified products with a high percent of slag was evaluated under environmental conditions for during one year. The results of the UCS and TCLP indicated that utilization of this type of slag in cement-based applications may be justified with its controlled addition. However, the described application of the slag was disputed due to the high release of As under high alkaline environmental conditions. Eh-pH analyses and the geochemical modeling using the software PHREEQC were evaluated, as well as the mechanism of pollutant (Pb, As) immobilization (precipitation, adsorption) as a function of pH conditions.

Identification of management strategies and generation factors for spent lead acid battery recovery plant wastes in Turkey

The recovery of spent or waste lead acid batteries is important both for the management of lead input to the environment and to meet the lead demand of the market in a more energy and cost effective manner than primary production. As an important producer of lead acid batteries for the Middle Eastern and Eastern European market, Turkey seems to meet 22%-52% of its total lead demand by waste lead acid battery recovery. In this study, the wastes from Turkish waste lead acid battery recovery plants are identified and management strategies that are both technically sufficient and economically feasible for each of these wastes are complied. Furthermore, ranges of the amount of each waste generated per mass of final lead produced in these plants are estimated. Some of the most significantly generated wastes are lead containing dusts, wash water treatment sludges and slags from smelting furnaces with generation rates between 5-250, 1-150 and 5-100 kg t^-1 of product lead, respectively. Many of these can be fed back to the recovery process inside the plants except a subset of slags that are called 'final slag' and have low (5%-6%) lead content. Final slags can either be recovered for the production of cement, road-filling materials or abrasives proven that they are in a non-leachable, stable state or should be stored at hazardous waste landfills. For improved environmental performance, newly emerging techniques that eliminate the generation of such slags are also discussed and suggested.

Lead acid battery recycling for the twenty-first century

There is a growing need to develop novel processes to recover lead from end-of-life lead-acid batteries, due to increasing energy costs of pyrometallurgical lead recovery, the resulting CO2 emissions and the catastrophic health implications of lead exposure from lead-to-air emissions. To address these issues, we are developing an iono-metallurgical process, aiming to displace the pyrometallurgical process that has dominated lead production for millennia. The proposed process involves the dissolution of Pb salts into the deep eutectic solvent (DES) Ethaline 200, a liquid formed when a 1 : 2 molar ratio of choline chloride and ethylene glycol are mixed together. Once dissolved, the Pb can be recovered through electrodeposition and the liquid can then be recycled for further Pb recycling. Firstly, DESs are being used to dissolve the lead compounds (PbCO3, PbO, PbO2 and PbSO4) involved and their solubilities measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The resulting Pb2+ species are then reduced and electrodeposited as elemental lead at the cathode of an electrochemical cell; cyclic voltammetry and chronoamperometry are being used to determine the electrodeposition behaviour and mechanism. The electrodeposited films were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We discuss the implications and opportunities of such processes.

Toward sustainable and systematic recycling of spent rechargeable batteries

A comprehensive and novel view on battery recycling is provided in terms of the science and technology, engineering, and policy.

Spent lead-acid battery recycling in China - A review and sustainable analyses on mass flow of lead

Lead is classified to be one of the top heavy metal pollutants in China. The corresponding environmental issues especially during the management of spent lead-acid battery have already caused significant public awareness and concern. This research gives a brief overview on the recycling situation based on an investigation of the lead industry in China and also the development of technologies for spent lead-acid batteries. The main principles and research focuses of different technologies including pyrometallurgy, hydrometallurgy and greener technologies are summarized and compared. Subsequently, the circulability of lead based on the entire life cycle analyses of lead-acid battery is calculated. By considering different recycling schemes, the recycling situation of spent lead-acid battery in China can be understood semi-quantitatively. According to this research, 30% of the primary lead production can be shut down that the lead production can still ensure consecutive life cycle operation of lead-acid battery, if proper management of the spent lead-acid battery is implemented according to current lead industry situation in China. This research provides a methodology on the view of lead circulability in the whole life cycle of a specific product and is aiming to contribute more quantitative guidelines for efficient organization of lead industry in China.

Utilization of two agrowastes for adsorption and removal of methylene blue: kinetics and isotherm studies

Fresh water streams contaminated with synthetic dye-containing effluents pose a threat to aquatic and human life either by preventing aquatic photosynthesis or by entering into the food chain. Adsorptive removal of such dyes with potent biosorbents is an important technique to reduce bioaccumulation and biomagnifications of the dyes in human life. We report use of betel nut (BN) husk and banana peel (BP), two most abundant ligno-cellulosic wastes, as efficient adsorbents for the removal of the basic dye methylene blue (MB). The adsorption by BN and BP was consistently high over wide ranges of pH and temperature, suggesting their dye removal potential in diverse conditions. Physico-chemical studies, e.g. scanning electron microscopy and Fourier transform-infrared spectroscopy studies, revealed changes in surface topology and functional moieties of BN and BP post adsorption, implying dye interaction with the biomass surface. The dye adsorption in both cases followed pseudo-second-order kinetics. While adsorption of MB by BN was better fitted with the Temkin isotherm model, adsorption with BP followed both Langmuir and Freundlich isotherm models. Our studies concluded that both adsorbents efficiently remove MB from its aqueous solution with BP proved to be marginally superior to BN.