ACS Sustainable Resource Management最新文献

The excessive generation and mishandling of waste cooking oil (WCO) necessitate the need for its conversion into specialty resins and polymers for various applications. This work focuses on the development of a biocoating from WCO for paper-based packaging with improved hydrophobicity and moisture barrier properties. WCO was epoxidized and acrylated to form AWCO, subsequently characterized, and modified into a water-based emulsion using a poly(vinyl alcohol) solution. (Aminopropyl)triethoxysilane was grafted in varying proportions to AWCO emulsion to enable cross-linking onto hydroxyl groups of cellulosic paper. The curing process of the coated paper (∼40 gsm coating) was carried out at 130 °C for 5–7 min to ensure complete cross-linking. The coated papers exhibited a water contact angle of greater than 90°, a kit rating of 12/12 along with excellent water retention and oil and ice repellency. Water vapor transmission rate reduction up to ∼129 g/m²·day was achieved by depicting the moisture barrier as well. High glass transition temperatures (T_g) and thermal stabilities of the coatings revealed their suitability for hot food packaging. The coatings most importantly depicted high repulping potential and home compostability, making it a commercially feasible replacement for the existing plastic liners in paper packaging.

One of the wastes that can be considered as a promising secondary raw material is a spent catalyst for cracking petroleum hydrocarbons, containing up to 4 wt % rare earth elements. The work analyzes in detail three methods for recovering lanthanum from leaching solutions of spent catalytic cracking catalysts. Selective precipitation with ammonia solution in the pH ranges of 3.2–6.8 and 6.8–8.2 made it possible to partially separate aluminum and obtain products with a La₂O₃ content of 50.9–51.7 wt %. The sediments contain basic lanthanum salts and their hydrates, complex lanthanum and aluminum salts, and lanthanum and aluminum hydroxides. The La₂O₃ content in the precipitation product with a saturated solution of sodium bicarbonate in the pH range of 4.5–4.7 was 17.6–18.3 wt %. The precipitate is a mixture of hydrated lanthanum carbonate and aluminum hydroxide. As an alternative method for recovering lanthanum compounds, evaporation of a nitric acid leaching solution was considered. Evaporation does not require additional reagents and allows one to obtain a solution of nitric acid at a concentration of 10.8 M for reuse. The residue after evaporation contains at least 80.0 wt % of the liquid phase and after cooling to 30–35 °C is a mixture of hydrated aluminum and lanthanum nitrates. The lanthanum content in the solid residue after evaporation and heat treatment reaches 19.6–20.2 wt %.

Recycling rare earth elements like lanthanum from spent catalysts reduces resource depletion and minimizes waste. This research optimizes environmentally sustainable recovery methods to enhance circular economy practices in industrial applications.

The rare-earth industry plays a promising role in the promotion of low-carbon technologies, which are anticipated as foremost nominees for the development of a green civilization. Among valuable rare-earth elements, neodymium (Nd) is one of the extensively diffused metals in production of high-tech and clean-energy equipment due to its strong and light magnetic properties. China has already acquired a principal place in Nd supply to the global market, becoming a successful competitor with a higher level of utilization capacity in the country to face growing demand. Previous literature has provided some information on substance flow for a few recent years; however, they often fail to interpret better penetration about the current Chinese position of the Nd industry. Therefore, this study attempts to give a detailed examination on the emergence of Nd industry inside the framework of rare-earth utilization and supply with a special emphasis on challenges and prospective. As the frontrunner of rare-earth production, China is responsible for over 95% of the global supply, having a good market for Nd also. It is important to note that recycling Nd plays a crucial role in reducing carbon emissions by lessening the demand for raw material extraction and supporting the growth of green technologies. Finally, it is vital to strengthen the country’s regulations and policies to minimize negative environmental consequences and protect societal values.

Spent automotive catalysts (SACs) are the most important secondary resources for recycling platinum-group metals (PGMs). While accurately determining PGM concentrations in SACs is challenging, it is pivotal for effective recycling. Currently, the main methods for determining the PGM concentration in SACs are direct solid sample analysis and microwave dissolution, which face challenges such as matrix interference and the heterogeneity of samples. This study established a method for determining PGMs in SACs by inductively coupled plasma emission spectroscopy (ICP-OES) after the Cu fire assay, to achieve better detection limits for PGMs. The conditions for Cu fire assay were carefully optimized: under the optimal conditions, the losses of Pt, Pd, and Rh in the slag can be minimized to 5 ± 3, 12 ± 9, and 2 ± 2 μg, respectively. The spectral interference of Cu in determining PGMs was avoided by selecting interference-free emission lines. The established method has excellent analytical performance for Rh, with the detection limits for Pt, Pd, and Rh being 1.3, 13.8, and 0.8 g/t, respectively. The precision evaluated within 11 results of repeated measurements of four different types of real SACs ranged from 0.63% to 3.29%. This method provides a clean and reliable approach for determining trace PGMs in SAC and other solid wastes.

For solid waste management and sustainable development, the conversion of waste materials into valuable feedstocks is essential. Keeping in mind the concept of “waste-to-wealth,” we have synthesized value-added microporous graphitic carbon from waste Tecoma leaves, referred to as TA, through a one-step chemical activation process and utilized it for oxygen reduction reactions (ORRs) and capacitive energy storage applications. The transformation of biomass into metal-free porous graphitic carbon having an ORR efficiency comparable to or even better than commercially available Pt/C is critical for renewable energy conversion technologies. The TA-900 sample, synthesized at 900 °C having a high surface area of 1429 m² g^–1, containing 4.41 atom % nitrogen and 4.74 atom % oxygen, demonstrated excellent ORR performance among the synthesized graphitic carbon samples at different temperatures. It showed an onset potential (E_onset) of 1 V and a limiting current density (J_L) of 6.21 mA cm^–2, comparable to 10 wt % Pt/C. Both experimental and theoretical findings suggest that the TA-900 electrocatalyst exhibited a 4e^– transfer mechanism in the electrocatalytic reduction of O₂ to H₂O. Regarding supercapacitor application, TA-900 achieved a high specific capacitance of 546 F g^–1 in acidic and 327 F g^–1 in neutral aqueous electrolyte at a current density of 1 A g^–1 in a three-electrode setup. The TA-900-based symmetrical supercapacitor (SSC) device has remarkable durability, retaining its 84% capacitance retention even after 3000 cycles at 1 A g^–1. It also achieved a notable energy density (33 Wh kg^–1 and 6.60 mWh cm^–3) and a power density (6.20 kW kg^–1 and 1320 mW cm^–3). The findings emphasize that heteroatom-doped TA-900 electrocatalysts synthesized from waste Tecoma leaves will be a promising, affordable alternative to the high-cost Pt/C catalyst used for clean energy conversion.

The Jammu district of the Indian subcontinent has sandy soil that has low water retention, leading to low agricultural produce. This region is also the largest producer and supplier of walnuts, where walnut shells tend to become local agro-industrial waste. The current study deals with the thermochemical treatment of walnut shells using three different atmospheres, i.e., limited oxygen, nitrogen, and vacuum. The walnut shell biochars were tested for water retention capacity and hydraulic conductivity. All the synthesized biochars were then chemically treated with acid or base to increase their water retention capacity. Surface analysis was done using SEM and FTIR and suggested surface modification and hydrophilic functionalization. The highest water retention capacity was observed in untreated biochar synthesized under limited oxygen atmosphere and sodium carbonate treated biochar synthesized under nitrogen and vacuum environments. The increase in water retention can be associated with hydrophilic functionalization and microstructure of the biochar surface, modified by chemical treatment, supported by contact angle measurements. Incorporation of biochar with soil (locally sourced) shows an enhancement in water retention capacity and lowering of hydraulic conductivity. The highest enhancement for water retention was observed to be 11% for the biochar–soil mixture (5%) using sodium carbonate treated vacuum biochar as compared to the control.

Amidst the powerful capabilities of wastewater remediation using ozone nanobubbles (ONBs), the intricate challenge of pH control remains unsolved. To date, an efficient and scalable chemical agent is highly desired to overcome the limiting factor of conventional ozone-based wastewater conversion. This study introduces a sequential system that combines ONBs with adsorption techniques utilizing an eggshell-based adsorbent. The synergistic application of ONBs and adsorption successfully achieved notable removal percentages of 95.05% for turbidity, 96.18% for color at 418 nm, and 61.33% for TDS. In comparison, the individual ONB system showed removal percentages of 94.97%, 95.93%, and 61.97%, while the adsorption alone achieved 34.02, 29.65%, and 16.93%, respectively. Additionally, the combined system effectively neutralized the solution, increasing the pH from 2.67 to 7.14, outperforming both ONBs (pH 2.67) and adsorption (pH 6.89) alone. Our work underscores the efficiency of the system, which not only provides a high removal percentage of pollutants but also secures the required pH levels. This showcases a forward leap in developing environmentally friendly and efficient water treatment technologies.

Chemical recycling of waste plastics into valuable chemical feedstocks, specifically targeting C₃–C₄ gas products and naphtha fraction ranging from C₅–C₉ products, was explored in this study. Our approach involves melting/dispersing polypropylene in a hydrocarbon solvent and decomposing it using a zeolite catalyst. This technique effectively reduces the viscosity of molten plastics, enhances heat transfer, and allows the easy separation of inorganic fillers via filtration. Comprehensive analytical methods are used to identify and differentiate various decomposition products, including aliphatic hydrocarbons, monocyclic and polycyclic aromatics, and heavier hydrocarbons, distinguishing them from those derived from the solvent. The product distribution was thoroughly analyzed using a suite of techniques, including gas chromatography, two-dimensional gas chromatography, distillation gas chromatography, gel permeation chromatography, and thermogravimetric-differential thermal analysis. Our results highlight the effectiveness of using n-hexadecane and zeolite beta, achieving a remarkable 60 wt % yield of naphtha fraction (C₅–C₉) from polypropylene decomposition at 400 °C.

This paper discusses analytical methods adhering to the mass balance approach for the products of plastic decomposition in hydrocarbon solvents.

Developing an effective recycling process for reclaiming valuable metals from lithium-ion batteries is an urgent issue owing to increasing battery waste from electric vehicles. In this study, we developed a leaching method that enables the direct separation of lithium from other critical metals, namely, nickel and cobalt, using a two-phase system that consists of a deep eutectic solvent (DES) and water. The DES consisting of 4,4,4-trifluoro-1-phenyl-1,3-butadione and tri-n-octylphosphine oxide showed the highest leaching performance when combined with water. Several operational parameters, such as the aqueous fraction, solid-liquid ratio, reaction time, and operation temperature, were evaluated. The optimum results in the two-phase direct leaching system were obtained using a 1:1 DES-water ratio and 10 g/L solid-liquid ratio, reacted at 80 °C for 24 h. An in-situ stripping phenomenon was observed, revealing that lithium transferred from the DES phase to the aqueous phase. In the application of black mass leaching, the aqueous phase significantly enhanced Co, Ni, and Mn extraction into the DES phase and thus plays an important role in separating lithium from other metals. The efficiency of direct lithium leaching from the black mass reached 99% within 24 h.