RSC sustainability最新文献

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A graphical abstract is available for this content

Global production of nickel (Ni) and ferronickel (FeNi) alloys, critical to battery materials and stainless steel alloys, is limited to a few countries due to the distribution of laterite ores. To meet the growing demand, an alternative supply of Ni and FeNi alloys needs to be established. Laterite ores result from olivine (Mg_xFe_2−xSiO₄) weathering under tropical conditions, making olivine a promising alternative source to consider; however, the lower Ni concentration of olivine makes it less economical. One approach to lowering the process costs is using waste chemical inputs in place of expensive commodity chemicals. In this study we evaluate the feasibility of using such waste byproducts generated by a demonstration-scale electrochemical marine carbon dioxide removal system to extract Ni from olivine (0.27 wt% Ni) as FeNi alloy. Bipolar membrane electrodialysis (BPMED) technology used for ocean alkalinity enhancement generates acidic, desalinated, and basic streams using seawater and electricity. The acid stream is a waste product, and we show that it is 37% better than equal-strength commercial HCl for leaching of Ni from olivine at room temperature. A small volume of the alkaline product from BPMED is used to increase the pH of the olivine leachate to remove all dissolved silicon and the majority of the dissolved iron, while retaining most of the dissolved Ni (65%) and Mg (84%). This enriched solution is used for Ni recovery via electroplating while the spent electrolyte, rich in Mg, is suitable as an additional source of alkalinity for marine CO₂ removal. We demonstrate the recovery of Ni as a FeNi alloy with an Fe to Ni molar ratio of 1.37 : 1 and evaluate the cost-benefit of the process for various possible scenarios. Preliminary assessment indicates an overall net economic benefit from recovering Ni from olivine using the proposed method and the net benefit is expected to further increase if the overall recovery rate of Ni is improved, the price of the Ni product is increased, and the value of CO₂ credit is included.

Red sanders (Pterocarpus santalinus), an endemic species of Southern India, is highly valued for its heartwood, yet its bark is frequently discarded as waste. The sustainable utilization of underutilized bark offers a promising route to develop bio-based wood preservatives. This study investigates the bio-protective efficacy of Pterocarpus santalinus bark extracts against fungal and termite degradation in plantation timbers. Gravimetric analysis revealed markedly higher yields for aqueous extracts (26.22%) compared to acetone (2.59%) and methanol (1.05%) extracts. Three wood species: rubberwood (Hevea brasiliensis: HB), mango wood (Mangifera indica: MI), and melia wood (Melia dubia: MD) were pressure-impregnated with 3% and 8% extract concentrations for 1 h and 2 h. Retention values in different wood species ranged from 0.94 to 8.81 kg m⁻³, while weight percent gain reached 17.88%, especially in lower-density MD. Acetone extracts conferred the strongest antifungal protection, reducing brown-rot (Oligoporus placentus) mass loss from 46% (control HB) to 11% (HB at 8%), and white-rot (Trametes hirsuta) mass loss from 38% to 11%. A similar phenomenon was seen in MI and MD wood. Termite damage ratings declined from 5.0 (complete failure) in untreated HB and MI to 1.7 and 2.8 post-treatment, and to 0.2 in MD. Leaching resistance improved with higher concentrations and longer impregnation times, while FTIR spectra confirmed the preservation of lignin and hemicellulose associated peaks after fungal tests. SEM confirmed that the extracts form protective barriers into the wood, inhibiting microbial degradation and termite infestation.

A technique combining an extended mechanochemical treatment of biogenic calcium carbonate (bCC) with a one-pot hydrothermal method was used for the first time to prepare nanocrystalline apatite. When calcitic bCC from oyster shell waste was subjected to dry milling for 1 hour (DM) the crystallite size of calcite was decreased from 92 to 14 nm, and the minimum temperature to achieve the complete conversion to apatite (T_min) decreased from 160 °C to 80 °C. In contrast, wet milling (18 h) induced polymorphism and amorphization, yielding calcite, aragonite, and amorphous calcium carbonate, with crystallite sizes of 7 nm for calcite and 13.7 nm for aragonite. The T_min decreased from 160 °C to 40 °C. Both transformations occurred via brushite as an intermediate metastable phase. Kinetic experiments evidenced that DM-bCC transformed faster than WM-bCC at T_min, achieving 98% versus 82% after 4 days, even though the complete transformation took 7 days. Both bCCs and the derived Ap nanoparticles demonstrated cytocompatibility with MS1 endothelial cells and m17.1 ASC murine mesenchymal stem cells. This synthetic approach offers a cost-effective, eco-friendly (without releasing CO₂), sustainable, and scalable (by using already established glass reactor technology rather than costly autoclaves) solution for valorising shells waste.

Tissue-related disorders continue to present critical clinical challenges due to their limited self-repair abilities and rising global incidence. Conventional grafting techniques and implant materials are suffering from significant drawbacks, including immune rejection, donor site morbidity, and lack of bioactivity. Herein, this study explores the development of a smart, biomimetic scaffold that combines a piezoelectric polymer polyvinylidene fluoride (PVDF) with a demineralized extracellular matrix derived from fish scales. The demineralization process effectively removes heavy metal contaminants while preserving the collagen-rich matrix, making it suitable for scaffold applications. PVDF, known for its biocompatibility, flexibility, and electroactive properties, was electrospun at varying concentrations to achieve nanofibrous membranes with tailored anisotropic and electromechanical characteristics. These PVDF nanofibers were layered onto D-FS to create hybrid scaffolds that mimic the hierarchical architecture and dynamic responsiveness of native skeletal tissues. Based on SEM and FTIR analyses, 12% w/v PVDF demonstrated uniform fiber distribution with minimal bead formation. Physico-chemical analyses confirmed its enhanced crystallinity and structural alignment, while electrical assessments demonstrated adequate piezoelectric performance under mechanical stimulation, including device fabrication. Biological evaluations, including the MTT assay, hemolysis analysis, LIVE–DEAD staining, and protein adsorption study, were conducted; the results indicate that C-FS exhibits cytotoxicity, whereas D-FS does not. This work presents a promising strategy for the development of next-generation tissue engineering scaffolds with the potential to eliminate the need for secondary surgeries.

In between mechanical and chemical recycling, the recycling by dissolution/precipitation method has emerged as an economically and sustainably viable solution. This work addresses the challenges of this recycling method, particularly those related to the complex and diverse composition representative of polymers feedstocks from sorting centers, from an analytical perspective. We used various analytical tools, ranging from off-line chromatography coupled with high resolution mass spectrometry (LC-HRMS) to in situ spectroscopy, as well as thermal and fractionation analysis, to deeply characterize the plastic feedstocks at different stages of the recycling process. LC-HRMS and thermal gradient interaction chromatography (TGIC) provide valuable insights into the composition of market-available plastics feedstocks and the efficiency of sorting center operations. In situ NIR and Raman spectroscopy allowed real-time monitoring of the dissolution step to ensure complete dissolution, as well as the precipitation step to ensure effective polymer/additive separation. Ex situ attenuated total reflectance infrared spectroscopy (ATR-IR), differential scanning calorimetry (DSC), high temperature size exclusion chromatography (HT-SEC), and LC-HRMS confirmed that the recovered polymer after recycling maintained its properties while removing a fraction of additives. Also, we show that substitution of fossil-based solvents like xylene and decalin is possible by more responsible solvents like amyl acetate or cyclohexanone with comparable dissolution and additives removal performances.

Polyurethane plastics are essential in many consumer and commercial products such as insulation, furniture, automotive interiors, and clothing. Pathways for producing polyurethane from microalgae offer an opportunity to reduce greenhouse gas emissions and other environmental impacts and can incorporate processes that avoid the use of toxic isocyanates typically used in conventional polyurethane production processes. In this study, the greenhouse gas emissions, fossil energy, and water consumption of biobased polyurethane and biobased non-isocyanate polyurethane were evaluated via life-cycle analysis using the R&D Greenhouse Gases, Regulated Emissions, and Energy Use in Technologies model. Microalgae-based polyurethane foam was found to achieve greenhouse gas emission reductions of up to 79% compared with conventional polyurethane foam production. The greenhouse gas reductions for the non-isocyanate microalgae polyurethane pathway are slightly lower at 58% compared with conventional polyurethane foam. However, it offers additional benefits by reducing toxicity potential compared to the isocyanate polyurethane pathway. The analysis also included a biorefinery-level analysis to evaluate the impact of incorporating polyurethane production into fuel-processing microalgae biorefineries. The sensitivity analyses conducted in this study reveal that improved algae cultivation strategies can lead to decreases of up to 127% and 80% in GHG emissions from the baseline process of Bio-PU and Bio-NIPU, respectively. Likewise, implementation of renewable electricity can result in up to 128% and 74% lower GHG emissions compared to the baseline production of Bio-PU and Bio-NIPU, respectively. Finally, the analysis evaluated different coproduct handling methods including displacement and allocation (based on mass, energy, and market-value). The results suggest that it is important to consider both the displacement and allocation methods as these led to significant differences in the environmental impacts.

Water eutrophication caused by excess nutrients can be addressed by applying layered double hydroxide (LDH) materials. The LDH structure is based on positively charged layers and negatively charged counterions between the layers, or solvent molecules, which are optimal for phosphate removal. The M²⁺ : M³⁺ molar ratio and the synthesis method employed affect LDH properties. LDH materials are synthesized using co-precipitation, urea hydrolysis, hydrothermal treatment, and sol–gel methods. The phosphate adsorption performance of different LDH materials is compared, focusing on Al, Fe, and La, as well as Zn, Mg, and Ca. The role of LDH composites is highlighted. Different optimization parameters, including dosage, contact time, pH, initial concentration, reusability, temperature, and the influence of co-existing ions, are discussed. Interactions such as electrostatic attraction (ES), ion exchange (IX), ligand exchange (LX), ligand complexation (LC), surface complexation (SC), hydrogen bonding (HB), and π–π appear to be the main mechanisms of phosphate adsorption by LDHs. Thus, the need for low-cost and efficient systems for phosphate recycling underscores the promise of tunable LDH composition for selective phosphate adsorption as LDH materials have demonstrated sustained performance, verifiable regeneration, successful real-world piloting, scalable supply, and regulatory standards consistent with the circular economy.

Correction for “Green initiatives for the synthesis of polyamide monomers: precision fermentation using engineered Corynebacterium glutamicum and extraction of purified 5-aminovaleric acid (5AVA) and putrescine” by Keerthi Sasikumar et al., RSC Sustainability, 2025, https://doi.org/10.1039/d5su00799b.