Search for: All records

Antimony (Sb) plays an important role in functional oxides: antimony trioxide (Sb₂O₃) is widely used in flame-retardant polymers and as a catalyst in PET, while oxidized Sb species and Sb-doped oxides enable electroceramic and oxide-electronic technologies. As a critical material with geographically concentrated supply, the United States is fully import-dependent and vulnerable to supply disruption. Here we map Sb mass flows in the U.S. economy, emphasizing the chemical forms that govern fate and recovery (Sb₂O₃ in plastics, Sb(III)/Sb(V) in aqueous phases, Sb⁰ in alloys). While lead-acid batteries achieve high recycling rates, large quantities of Sb₂O₃ in flame-retardant plastics and WEEE, and Sb embedded in discarded PET, enter landfilling and incineration, representing underutilized secondary reservoirs. We review recovery pathways for these streams, including supercritical water processing, solvometallurgy, hydrothermal/alkaline sulfide systems, and capture from ash and leachates, and outline policy and infrastructure actions to strengthen Sb oxide circularity and supply resilience. 

With diminishing availability of high-quality phosphate rock and increasing supply uncertainties, improving phosphorus (P) recovery, recycling, and waste reduction has become critical for sustaining agricultural production. We developed an integrated P cycling and soil dynamics model to quantify 7 circular strategies for reducing mineral P demand in the United States, using data for 91 major crops and 20 livestock types across 3,142 counties from 1866 to 2050. We show that soil residual P reuse has the largest potential to reduce mineral P demand in the United States. By 2023, total soil P stocks had accumulated to 99 Tg, equivalent to approximately 68% of mineral P inputs over 1866–2023. For 2024–2050, projections under various socioeconomic scenarios indicate that soil residual P reuse alone could potentially supply approximately 2.4 to 5.1 times projected US mineral P demand, with substantial residual P stocks accumulated in both cropland and pastureland soils. Recycling from sewage sludge and livestock and crop by-products could collectively offset an additional approximately 0.5 to 1.0 times mineral P demand, while food waste reduction could reduce requirements by approximately 0.3 times. Spatial analyses further highlight a mismatch between circular P availability and cropland P demand, with high mineral P avoidance potential concentrated in the South and West, but relatively low ratios of circular P supply to projected mineral P demand across most counties in the Midwest. These findings provide spatially explicit and decision-relevant insights into how circular P strategies can enhance the stability and resilience of US food systems under future resource constraints. 

Abstract Potassium sodium niobate, i.e., K_0.5Na_0.5NbO₃or KNN, is an important lead (Pb)-free, perovskite-structured, piezoelectric ceramic composition. KNN is typically synthesized by solid-state reaction of the unary alkali carbonates, i.e., K₂CO₃and Na₂CO₃, with Nb₂O₅at high temperatures. It is well known that this reaction can result in chemically inhomogeneous powders and ceramics, which can have deleterious effects on key physical properties. In this work, we demonstrate that substantial improvements in chemical homogeneity of KNN are achieved by initially pre-reacting the unary carbonates to form the binary carbonate KNaCO₃, and then subsequently reacting KNaCO₃with Nb₂O₅to form KNN. The binary carbonate, KNaCO₃, is a distinct compound with a unique structure relative to the unary carbonates. In contrast with the unary carbonates, the consumption of KNaCO₃during the reaction to form KNN facilitates the balanced incorporation of K⁺and Na⁺into the growing KNN phase, leading to improved chemical homogeneity. Key methods include in situ X-ray diffraction (XRD) during thermal treatment, scaled-up batch processing in a muffle furnace, and Williamson–Hall analysis of XRD patterns to determine changes in microstrain due to chemical homogeneity. 

Abstract Potassium carbonate (K₂CO₃) and sodium carbonate (Na₂CO₃) are useful inorganic alkali salts with a multitude of uses, although both can be unstable at room temperature. The focus of this work was to react these two unary carbonates together to form KNaCO₃single crystals, and to determine the structure of the resulting crystals. The symmetry of the crystals was assigned to the monoclinic space groupC2/c(No. 15), with lattice parameters (Ǻ) of 5.4546(7), 9.462(1), 6.1282(7), andβ = 95.209(4). The K and Na are located on fully occupied, symmetry-unique atomic positions. The phase evolution of K₂CO₃and Na₂CO₃to form KNaCO₃was also examined using in situ high temperature X-ray diffraction. The final compound in both single crystal and powder form was found to be stable over time at room temperature. 

To address wicked problems, particularly in sustainability, interdisciplinary solutions that bridge science and society are essential. These solutions inevitably require the involvement of diverse stakeholders. However, the field of stakeholder engagement includes a wide range of approaches, and there is no universally agreed-upon set of standard practices for engagement, particularly in wicked problem contexts. This article addresses this gap by connecting scientific knowledge on stakeholder engagement with an exploration of its challenges, drawing from both the broader literature and the authors’ own experiences in sustainability contexts. In particular, this article first identifies and briefly reviews 6 key steps and best practices for stakeholder engagement, and then discusses challenges and lessons learned from engaging stakeholders in the context of phosphorus sustainability largely within U.S. contexts. Phosphorus sustainability is a valuable case study due to its vital role in supporting global agriculture and societal functioning, while also contributing to environmental challenges caused by excess runoff, among other issues. Reflecting on both best practices and our own experiences, we identify 3 key challenges to engaging stakeholders in phosphorus sustainability: (i) managing the inherent tensions between breadth and depth of engagement, (ii) difficulties in evaluating the collective impact of engagement, and (iii) building sufficient capacity in carrying out engagement. To address these limitations, we highlight lessons we have learned in our own engagement efforts and provide recommendations for future research on stakeholder engagement, particularly in the context of wicked sustainability problems. 

The solid-state synthesis of perovskite BiFeO3 has been a topic of interest for decades. Many studies have reported challenges in the synthesis of BiFeO3 from starting oxides of Bi2O3 and Fe2O3, mainly associated with the development of persistent secondary phases such as Bi25FeO39 (sillenite) and Bi2Fe4O9 (mullite). These secondary phases are thought to be a consequence of unreacted Fe-rich and Bi-rich regions, that is, incomplete interdiffusion. In the present work, in situ high-temperature X-ray diffraction is used to demonstrate that Bi2O3 first reacts with Fe2O3 to form sillenite Bi25FeO39, which then reacts with the remaining Fe2O3 to form BiFeO3. Therefore, the synthesis of perovskite BiFeO3 is shown to occur via a two-step reaction sequence with Bi25FeO39 as an intermediate compound. Because Bi25FeO39 and the γ-Bi2O3 phase are isostructural, it is difficult to discriminate them solely from X-ray diffraction. Evidence is presented for the existence of the intermediate sillenite Bi25FeO39 using quenching experiments, comparisons between Bi2O3 behavior by itself and in the presence of Fe2O3, and crystal structure examination. With this new information, a proposed reaction pathway from the starting oxides to the product is presented.