The need to transition to a clean energy economy has received significant global attention in recent years. This has led to pledges by different nations to get to net-zero emissions. For example, the United States targets achieving net-zero emissions by 2050. Of the different strategies for meeting the targets, significant emphasis has been placed on the electrification of transportation systems. This requires advancement in two key components: traction drives and batteries in electric vehicles (EVs). Recycling of the critical metals contained in these components is one aspect of the advancement strategies. Despite several years of research in recycling permanent magnets and batteries, there are still hurdles to overcome towards making a significant impact. 

This talk will, therefore, focus on approaches employed in the recycling of critical metals from permanent magnets in EV traction drives and batteries. It will include a discussion of the key limitations and the opportunities to overcome those. Some innovative approaches developed in the Critical Materials Innovation Hub and Ames National Laboratory will be presented. Particularly, we present the novel acid-free dissolution recycling (ADR) approach for recovering rare earth elements from e-waste. We will also present the newly developed Batteries Recycling and Water Splitting (BRAWS) technology that uses water as the only solvent for recycling Li-ion batteries, uses CO₂ as feedstock and produces green hydrogen as a co-product.

There is growing interest on the utilization of animal by-products and wastes based on sustainability and recycling of natural biomaterials. Animal by-products and wastes mainly refer to skin, bones, and tendons that contain proteins and other macromolecules[1]. Animal raw hides represent a remarkable portion of the weight of sheep (11.0–11.7%), which are abundant sources of epithelial tissue that contains a high concentration of collagen[2]. As the primary ingredients to produce leather products, these raw materials undergo trimming to achieve uniform shapes before commencing the tanning process, which may generate considerable proteinaceous waste[3]. Reportedly, one ton of wet salted hides/skins yields approximately 200kg finished leather along with 350 kg non-tanned solid waste, 250 kg tanned solid waste, and 200 kg wastewater loss[4]. Hence, there remains a considerable of lamb trimming wastes of tannery for the collagen recycle. Plant-based enzymes including papain and bromelain have been utilized for extracting gelatin or collagen from un-tanned bovine trimming waste. Given the potential of ficin enzyme for collagen hydrolysis[5], harnessing this enzyme to extract collagen from discarded sheep trimming waste could be beneficial. In addition, with aided ultrasound, entangled collagen fibrils can be opened then separated, contributing to post-treatment with acids or enzymes as well as reduced extraction periods. 

Based on aided ultrasound technology, the aim of this research is to design a sustainable method for extracting collagen from untreated tannery trimming waste using ficin enzyme derived from ficin leaves. The structural and biochemical characteristics of the extracted collagen from this green method and conventional methods (acetic acid) will be fully discussed.

A simple and effective method for the extraction of collagen from untanned tannery trimming waste using acetic acid and ficin enzyme obtained from ficin leaves was developed in this study. Although acetic acid and ficin enzyme both are effective for the extraction of collagen but enzymatic hydrolysis can extract more collagen than the acid hydrolysis method. Collagen obtained from the enzymatic hydrolysis process maintained its predominant triple helix structure and had amorphousness which was confirmed by the FTIR and XRD analysis. However, the collagen obtained from enzymatic hydrolysis was thermally less stable compared to the collagen obtained by acid hydrolysis. Hence, it can be concluded that ficin enzyme- assisted hydrolysis method can aid in the implementation of circular economy approach in the leather industry by extracting collagen from the trimming waste in an environment-friendly way.
 

The development of natural fibre biodegradable composites are gaining much attention due to lower environmental impact, driven by the issues with synthetic fiber-based polymer composites manufacture, disposal, and recycling. Nowadays, pineapple leaf fibre (PALF) are playing significant role in composites exhibiting superior performance than other cellulose fibres for a variety of uses in the automotive, biomedical, furniture, and packaging industries, among others. This study examined the combined effects of in-house coupling agent production and pineapple leaf fibre (PALF) loading on the mechanical and thermal characteristics of  biodegradable polymers polylactic acid (PLA) and poly(butylene adipate-co-tere-phthalate) (PBAT), which were manufactured by melt compounding. The PLA grafted with maleic anhydride (MA) (PLA-g-MA) was used as a coupling agent to improve the interfacial adhesion between PLA and PBAT with PALF. The results demonstrated the dependence of thermal stability and tensile properties on the grafting level of MA, and also on the concentrations of PALF. Thus, it could be deduced that combination of PALF at high concentrations (5, 10 and 15 wt%) and PLA-g-MA with high grafting level can significantly improve the thermal stability of PLA and PBAT. On the other hand, at high grafting level, there was an improvement in tensile modulus of biocomposite. The morphological analysis indicated better adhesion between PALF and PLA with PBAT, in composites containing PLA-g-MA with high grafting level. Overall, PLA/PBAT/PALF/PLA-g-MA green composites with improved interfacial adhesion, thermal stability and mechanical properties were successfully optimised to replace non-biodegradable conventional plastics with added advantages of biodegradability.   

The assembly of medium-scale collagen in native tissues promotes excellent performance and multiple functions. The preparation of collagen fibers and fiber bundles from collagen-rich tissues through acid swelling^[1,2] and the utilization of combined chemical and physical treatments have been documented^[3]. Homogenization and grinding were employed to enhance collagen nanofibrillation, albeit with high energy consumption. In this study, two simple and controllable liquid exfoliation methods were used to extract collagen fine structures directly from bovine Achilles tendons. One method utilized a sodium hydroxide (NaOH)/urea water system to extract collagen fibers with diameters ranging from 26~230 nm through freeze-thaw cycles and ultrasound. The other method involved the use of a urea/GuHCl deep eutectic solvent to extract interstitial collagen fibers with diameters ranging from 102~159 nm directly from bovine Achilles tendons. In situ observation under polarized optical microscopy (POM) and molecular dynamics simulations revealed the effects of these two methods on tendon collagen. FTIR results confirmed that these original fibers retained the typical structural characteristics of type I collagen. Subsequently, these extracted collagen fibers were used as building blocks to prepare independent collagen membranes, which exhibited good transparency, strong mechanical properties, excellent barrier performance, and cell compatibility.

The beamhouse plays a pivotal role in leather manufacturing. However, the conventional lime-sulfide system (LSS) used in the beamhouse causes significant environmental pollution due to the extensive use of chemical agents. In recent years, most research has focused on biological treatments, with enzymes emerging as a promising environmentally friendly alternative. In this study, we employed the salt-enzyme system (SES) to utilize MgCl₂-assisted neutral protease to streamline processes and reduce pollution in the beamhouse. Additionally, response surface methodology (RSM) was utilized to optimize the experimental conditions for enhancing unhairing, fiber opening, and bating efficiency. In terms of environmental benefits, compared to LSS, SES exhibits a significant decrease in COD, NH₃-N, and TS by 9.59%, 26.27%, and 76.94%, respectively, highlighting its efficacy as an environmentally sustainable alternative. The environmental impacts of the beamhouse stage (LCA) approach by comparing two scenarios. The results showed that all the environmental significantly lower than those linked to LSS. The utilization of MgCl₂-assisted neutral protease in a one-step beamhouse aligns with the trend of environmentally friendly and green production for the leather industry.

At the present stage, scientists are widely interested in the creation of hybrid (organic-mineral) composite materials [1, 2]. Thus, it is proposed to include silica of biological origin in addition to conventional components in the composition of stoneware and bricks [3, 4]. Since "Ecologization of industry and economy" has been named "the matter of sustainable development of Kazakhstan" by the President of the Republic of Kazakhstan K.-Zh. Tokayev [5], the purpose of the study was to create refractory materials based on an organic-mineral furnace charge that includes silicon-lignohydrocarbon waste.

To obtain new refractories, the base composition (control sample) including refractory clay (59%), chamotte (24%), liquid glass (8.5%), lignosulfonate (2%), magnesium sulfate (4.5%), and aluminum powder (2%) was adopted. New refractories were created using plant waste (PW), as well as liquid products of its processing SiO₂-PW and OC-PW with the respective replacement of chamotte, liquid glass and lignosulfonate in different proportions until complete replacement (100% replacement). In this case, the amount of other components was determined empirically.

To prepare the samples the main components (magnesium sulfate, aluminum powder, refractory clay, and chamotte) were carefully mixed. Lignosulfonate and liquid glass (sample 1, control sample) or their substitutes (SiO₂-PW and OC-PW, sample 2, experimental sample) were added to the resulting mixture. Then PW was added, replacing 10, 50, 60, 100% of chamotte (samples 3-6, experimental samples). From the resulting furnace charge, refractory samples of cylindrical shape measuring 30 × 30 mm were formed in a press mold. The samples were dried in air for 24 hours, followed by drying at a temperature of 150 °C for another 24 hours. The dried samples were then sintered at 950 °C for 1 hour. After sintering, the samples were kept in air until completely cooled; testing was carried out.

The obtained materials were examined by X-ray phase analysis (XRD). To determine optimal composition, heat resistance (number of thermal cycles) was chosen as the starting characteristic. Inspection of the ability of the samples to withstand cyclic temperature changes (heating-cooling) was carried out in a two-stage mode by heating to 960 °C for 40 minutes, followed by cooling in water at a temperature of 15 °C for 3 minutes and in air at a room temperature for 7 minutes until the sample loses 20% or more of its initial mass. Water absorption, bulk density and true density, apparent (open) porosity and true porosity of the samples were also measured.

The presence of the following crystalline phases in almost all (1-3, 6) initial (before sintering) samples was revealed by XRD: quartz, magnesium aluminosilicate, mullite, tridymite, hematite. In addition, the amount of quartz increased in the limit of 56-83 wt.%, and the amount of other phases decreased until they completely disappeared as the chamotte was replaced by the PW component. In samples 4 and 5, among the crystalline phases, only quartz (97-99%) and hematite were found. After sintering the samples at 950 ^оС, an increase in the quartz phase was observed in samples 1, 2, 5, 6. This fact can be viewed as an indicator of the balanced composition of furnace charge in samples 2, 5 and 6, which behaved the same as sample 1 (control sample). In the composition of all the processed samples (after partial destruction), the formation of kaolinite and calcium sulfate hydrate was determined.

Among the experimental samples of refractories obtained using organic secondary raw materials, the best heat resistance (155) is observed in sample 6. It was characterized by the following indicators: water absorption, 41.59%; bulk density, 1.06 g·cm^-3; true density, 1.98 g·cm^-3; apparent (open) porosity, 44.27%; true porosity, 46.11%. Obviously, high heat resistance can be explained by the presence of mullite phase and a high quartz content.

The data provided allow us to characterize the obtained sample as a lightweight refractory material that can find application in construction of vaults, refrigerators, ceiling lining of danger zones of metallurgical units, etc. Further research is needed to study its operational properties.

This research is funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (grant number AP 19677767).

According to archaeological records, there are a number of well-established dating methods. However, there is a lack of identification of specific type of artifacts, especially collagen-based materials with complex structure. Leather cultural relics, one of representative of collagen-based cultural relics, are precious physical historical materials for the study of ancient social history[1-3]. Leather cultural relic is an important carrier for inheriting human civilization and witnessing historical development. Therefore, the research on the identification and aging mechanism of leather cultural relic is of great significance. In this work, with leathers tanned by tara and quebracho as cultural relics model, the pyrolysis characteristics and kinetics of vegetable-tanned leather were investigated by thermogravimetry (TG) analysis at three different heating rates and the pyrolysis products were analyzed by TG coupled with Fourier transform infrared spectrometry and mass spectrometry (TG-FTIR-MS) analysis, whose micro-loss characteristic is in line with the particularity of cultural relics. The pyrolysis kinetics of the untanned sheepskin and vegetable-tanned leathers were investigated by using both methods of modified Kissinger-Akahira-Sunose (MKAS) and Friedman (FR). The gaseous products mainly consist of CH₄, NH₃, H₂O, CO, HNCO, CO₂, and pyrrole. The results were obtained that the appearance of CO and the intensity changes of CH₄ and NH₃ may provide secure and reliable identification of leather tanned by hydrolyzed and condensed tannins. The leather aging mechanism was revealed, and a new identification method was obtained, which might provide an important theoretical basis for the proper preservation and restoration of collagen-based cultural relics.

Mineral exploration generates a significant amount of waste, whose improper disposal can cause adverse environmental impacts. This work investigates the use of mining waste in the manufacture of interlocking paving blocks, with the aim of promoting sustainability in civil construction and reducing environmental liabilities. For this purpose, the waste was processed through gravimetric separation methods, using a shaking table and Humphrey spiral, aiming to separate the sand from the iron contained in the waste. Gravimetric methods are based on the difference in density between minerals to promote separation. The shaking table, a device that uses vibratory movements combined with a water flow, separates particles according to their density and size. In this process, heavier particles, such as iron, are directed to one end, while lighter particles, such as sand, are collected at the other end. The Humphrey spiral, in turn, uses the centrifugal force generated by the spiral flow to separate particles of different densities, with the sand being collected on the outer parts of the spiral. After separation, the resulting sand was analyzed for its granulometry through sieving. This process involves passing the sand through a series of sieves with different openings, classifying the particles according to their size. Adequate granulometry is crucial to ensure the quality of interlocking blocks, directly influencing their strength and durability. The processed sand was then used in the production of interlocking paving blocks, employing a vibratory press. This equipment compacts the mixture of sand, cement, and water, forming high-density, high-strength blocks. Interlocking blocks are a sustainable and efficient alternative for paving, offering ease of installation and maintenance, as well as allowing rainwater drainage. To evaluate the quality of the produced blocks, standard compressive strength tests were carried out. These tests consist of subjecting the blocks to compressive forces until rupture occurs, measuring the maximum strength supported. The interlocking blocks manufactured with the processed waste sand achieved a compressive strength of 25 MPa, meeting the normative requirements for paving. The results demonstrate that it is feasible to use mining waste, properly processed, in the manufacture of interlocking paving blocks, contributing to the reduction of environmental impacts and promoting sustainability in civil construction. The application of gravimetric separation methods proved effective in obtaining sand of adequate quality, and the produced blocks showed satisfactory performance in compressive strength tests. This study reinforces the importance of innovative solutions for the management of mining waste, promoting material recycling and the circular economy. Furthermore, the use of waste in civil construction can represent an economically viable alternative, reducing costs with raw materials and minimizing the environmental liabilities associated with mining.

The leather industry produces footwear, leather textiles, technical leather, and leather for haberdashery. The main auxiliary chemicals are compounds of trivalent and hexavalent chromium. Stabilization of appropriately treated natural hide, as a by-product of slaughterhouses, is carried out with 80% complex compounds of trivalent chromium, which creates strong coordination bonds with peptide groups of the skin protein - collagen, and thus achieves the desired useful properties of stabilized raw hide - leather. However, the use of chromium also carries risks. In relation to the shoes that we wear, it is important that the shoe material contains only trivalent chromium. According to standards, the maximum content of Cr VI in footwear is 3 ppm and 50 ppm Cr III of leachable chromium. Our contribution looks at both valences of chromium, the conditions under which trivalent chromium is oxidized to its toxic hexavalent form, and its relationship to the footwear and to our health.

Collagen is a naturally occurring polymer with unique triple helical structure, which is the main structural component of leather [1]. The thermal stability of leather has important implications for practical applications and is affected by many factors. In the present work, the effect of re-tanning and fat-liquoring, two important post-tanning operations [2], on thermal degradation behaviors, kinetics and mechanisms of chrome-tanned leather (CTL) was investigated by using thermogravimetry (TG) and TG-Fourier transform infrared (TG-FTIR). The activation energy (Ea) values for the thermal degradation of chrome-tanned, re-tanned and fat-liquored leathers at different conversions were calculated using modified Kissinger-Akahira-Sunose (MKAS) method [3]. It was found that the average value of Ea decreased after re-tanning and fat-liquoring operations. The thermal degradation mechanism was predicted and compared based on single-step and multi-step reaction models with the combination of isoconversional and master plots methods. The results suggested that a two-parallel-reaction model could match the An model better than single-step one. TG-FTIR results showed that CO2, H2O, NH3 and pyrrole were main evolved gaseous products during CTL thermal degradation and confirmed an enhancement of gas release after re-tanning and fat-liquoring operations.

Leather manufacturing is increasingly prioritizing environmentally friendly processes, emphasizing clean production to reduce environmental impacts [1-3]. The present work was focused to explore the application of an α-amylase/neutral protease system (ANS) in a simplified one-step process for unhairing, fiber opening, and bating to replace the traditional, chemically beamhouse of lime-sulfide system (LSS). With response surface methodology (RSM), a mathematical model was established to optimize operational conditions, with the concentrations of 0.3 wt.% α-amylase and 0.5 wt.% neutral protease at 28.4℃ for 16.6 hours. The effectiveness of the process on unhairing and fiber opening was studied through scanning electron microscopy (SEM), and the impact on bating was evaluated by the removal rates of carbohydrate and proteoglycan. The leather produced using the optimized ANS exhibited comparable physical properties to those traditionally processed, with higher hydrothermal shrinkage temperature and better softness. Environmentally, the optimized ANS process achieved significant reductions in pollutants, more than 90% of chemical oxygen demand (COD), NH₃-N, and Cl^-, and 73.91% of total solids (TS) by. An economic analysis further revealed a direct cost savings of 30.98% with the ANS of that with the LSS, alongside indirect benefits of enhanced production efficiency and simplified wastewater treatment. Notably, the one-step enzymatic beamhouse substantially decreases the electricity and water usage, potentially reducing the greenhouse gas emissions by 44.6%. The ANS is proposed to be a sustainable and cost-effective alternative for leather manufacturing with environmentally friendly practices.

Mineral exploration generates a significant amount of waste, whose improper disposal can cause adverse environmental impacts. This work investigates the use of mining waste processed by gravimetric separation methods, aiming at the production of sustainable construction materials and the elimination of dams, pits, and dry stacks. The waste was subjected to separation processes using a shaking table and a Humphrey spiral, with the objective of separating the clay, sand, and iron contained in the residual material. 

Gravimetric methods are based on the difference in density between minerals to promote separation. The shaking table uses vibratory movements combined with a water flow to separate particles according to their density and size. In this process, heavier particles, such as iron, are directed to one end, while lighter particles, such as sand and clay, are collected at the other end. The Humphrey spiral, in turn, uses the centrifugal force generated by the spiral flow to separate particles of different densities, collecting the sand in the outer parts of the spiral and the clay in the intermediate areas. 

After separation, the resulting sand was analyzed for its granulometry through sieving. This process involves passing the sand through a series of sieves with different openings, classifying the particles according to their size. Adequate granulometry is crucial to ensure the quality of interlocking blocks, directly influencing their strength and durability. 

The processed sand was then used in the production of interlocking paving blocks, employing a vibratory press. This equipment compacts the mixture of sand, cement, and water, forming high-density and high-strength blocks. Interlocking blocks are a sustainable and efficient alternative for paving, offering ease of installation and maintenance, as well as allowing rainwater drainage. 

To evaluate the quality of the produced blocks, standard compressive strength tests were carried out. These tests consist of subjecting the blocks to compressive forces until rupture occurs, measuring the maximum strength supported. The interlocking blocks manufactured with the processed waste sand achieved a compressive strength of 14,87 MPa, meeting the normative requirements for paving.

In addition to using sand, the separated clay was used in the manufacture of soil-cement blocks for building construction. The clay was mixed with soil and cement, compacted in specific molds, and cured to achieve adequate strength for civil construction. These soilcement blocks offer advantages in terms of sustainability and cost-benefit, contributing to more ecological constructions. 

The iron separated from the waste was pelletized to supply the metallurgical industry. Pelletization involves agglomerating iron fines into pellets, which are then used as raw material in steel production. This process not only adds value to mining waste but also reduces the need for virgin iron ore extraction, promoting sustainability in the metallurgical industry. 

The results of this study demonstrate the feasibility of using processed mining waste in the production of sustainable construction materials and supplying the metallurgical industry. The application of gravimetric separation methods proved effective in obtaining materials of adequate quality, and the manufactured products showed satisfactory performance in strength tests. This study reinforces the importance of innovative solutions for mining waste management, promoting material recycling and the circular economy, eliminating the need for dams, pits, and dry stacks.