Ellen M. Moon

The efficient processing of fine mineral particles remains a major challenge in the minerals beneficiation industry, primarily due to poor particle settling and low flotation recovery, which result from their limited attachment to air bubbles during froth flotation. In this study, a 4-arm star block polymer p(MeO2MA-co-OEGMA)-b-qDMAEMA (4A-MOQ) was designed and subsequently synthesized via RAFT polymerization and investigated for its dual role in quartz flocculation and selective flotation. The polymer consists of a poly(ethylene glycol)-based segment and a cationic quaternized DMAEMA block, enabling strong interactions with negatively charged quartz surfaces. Owing to its amphiphilic structure, the multiarm polymer self-assembled into cationic micelles in aqueous solutions, with the critical micelle concentration (CMC) of around 6.8 mg/L and a hydrodynamic diameter of approximately 60 nm. Adsorption studies using total organic carbon (TOC) analysis confirmed the adsorption of polymer onto the quartz surface, while ζ-potential measurements revealed effective charge neutralization. Turbidity analysis and settling tests were carried out to demonstrate the effective flocculation performance of the polymer within the dosage range of 0.4–0.8 mg/g, while the in situ particle and aggregate size analysis using a BlazeMetrics probe further confirmed the increase in chord lengths following the addition of the polymer. In reverse flotation experiments, the multiarm polymer acted as an effective collector for quartz over a broad range of pH while maintaining low recovery for hematite, demonstrating pronounced selectivity toward quartz and achieving approximately 80% recovery and 84% quartz grade, with hematite recovery below 20%. The enhanced flotation recovery of quartz was attributed to the adsorption of cationic polymer on the mineral surface, improving the hydrophobicity of the mineral to promote particle-bubble attachment. Overall, this work highlights the scope of controlled polymer architectures as dual-functional reagents, providing opportunities for the design of advanced materials in mineral processing.

Background: Water authorities commonly use vulnerability assessments to evaluate asset bushfire risk for large or key facilities; however, this traditional approach ignores the vast array of distributed component assets (e.g. pipes, air valves, etc.). Aims: To address this, a new risk criticality model was developed to correlate geographic information system (GIS)-referenced bushfire intensity data with water distribution asset data to determine risk criticality for each component asset. Methods: Fire agencies and water operators were consulted to incorporate the available GIS-referenced bushfire behaviour and water network asset data. During this consultation, asset risk consequence ratings were established as a reference source from which GIS software iteratively quantified asset critical bushfire risk. Key results: The model successfully demonstrated its application through a case study providing the water operator with enhanced risk assessment and planning data, and highlighting its capacity to inform and strengthen bushfire risk management. Conclusions: The model provides the water sector with a practical tool, aligned to their risk appetite, which can be periodically updated as new fire behaviour and water asset data becomes available. Implications: The framework developed for water assets also demonstrated its adaptability and potential for application by other utilities and represents a significant step towards informed climate resilient design.

Flash droughts are marked by a rapid decline in soil moisture and sudden shifts in land-atmosphere interactions, posing concerns for hydrology, agriculture and water resource management in India. Limited understanding remains of how these events vary across India’s climatic regions and what drives their onset and development. This study examines flash drought characteristics across seven Koppen-Geiger climate zones of India over 1960-2023. The Monsoon season (June-September) is the critical period, with the highest frequency in the tropical Monsoon (Am) and humid subtropical (Cwa) regions. A significant increasing trend in intensification is observed across the arid steppe (Aw) and tundra (ET) zones, indicating more rapid soil moisture depletion under changing climate conditions. Contrasts in dominant drivers emerge across climate zones. In the Cwa region, flash droughts are primarily influenced by precipitation deficits combined with wind and radiation-related factors, highlighting moisture deficits and atmospheric interactions. In contrast, the Am region shows stronger influence of atmospheric energy demand, with potential evapotranspiration, temperature, and wind interactions playing prominent roles, alongside humidity and radiation coupling. Decadal analysis indicates changing flash drought drivers, with atmospheric demand becoming more influential in recent decades, particularly in the Cwa region. Flash droughts are rarely controlled by a single factor and result from combined moisture availability and atmospheric energy conditions. Overall, these findings support region-specific early warning systems, water management, and climate-resilient agricultural strategies.

Flash droughts are marked by a rapid decline in soil moisture and sudden shifts in land–atmosphere interactions, emerging as a serious concern for hydrology, agriculture, and water resource management in India. Despite their growing relevance, there is still limited understanding of how these events vary across India’s diverse climatic regions and what drives their onset and development. In this study, we examine flash drought characteristics across seven Koppen Geiger climate zones of India over the period 1960-2023. Results show that the Monsoon season (June, July, August and September) is the most critical period for flash drought occurrence, with the highest frequency observed in the tropical Monsoon (Am) and humid subtropical (Cwa) regions. There is also a significant increasing trend in the rate of flash drought intensification across the arid steppe (Aw) and tundra (ET) zones, suggesting more rapid soil moisture depletion under changing climate conditions in recent years. Importantly, clear contrasts emerge in the dominant drivers across climate zones. In the Cwa region, flash droughts are primarily influenced by precipitation deficits in combination with wind and radiation related factors which highlights the role of moisture deficit and its interaction with atmospheric conditions. In contrast, the Am region shows a stronger influence of atmospheric energy demand driven processes, where factors like potential evapotranspiration, temperature and wind interactions play a more prominent role, along with contributions from humidity and radiation coupling. The decadal analysis also suggests that the factors driving flash droughts have been changing over time with atmospheric demand becoming more influential in recent decades, especially in the Cwa region. It is also evident that these events are rarely controlled by a single factor, instead they typically result from the combined effects of moisture availability and atmospheric energy conditions. Overall, this study highlights clear climate-specific patterns and key driving factors of flash droughts in India. These insights can support the development of more effective, region-specific early warning systems, as well as improved water management and climate-resilient agricultural strategies.

With the depletion of high-grade ores and increasing demand for critical minerals, more efficient and sustainable mineral processing methods are needed. The loss of valuable fine mineral particles to tailings due to inefficient recovery by traditional flotation remains a critical challenge. In this research, novel emulsion binders were developed and evaluated for a rapid agglomeration approach to enhance the capture of fine hydrophobic particles below the optimal flotation size range. High Internal Phase (HIP) water-in-oil (w/o) emulsions stabilised by four novel polyethylene glycol-based amphiphilic polymers synthesised via RAFT polymerisation were tested for agglomeration and recovery of naturally hydrophobic talc particles (mean size 17.5 µm) using a 100 – 180 µm sieve system. Benchmark comparisons were performed using HIP traditional emulsions stabilised with Span® 80 (sorbitan monooleate), a previously reported poly(N-isopropyl acrylamide) (PNIPAM) block copolymer surfactant, and plain kerosene oil. One polymer was further explored, stabilising emulsions containing 0.12 volume fraction of kerosene oil and up to 88 vol.% of 3 wt% NaCl aqueous solution, with polymer concentrations of 0.5 - 2.5 wt%. These binders (in 5-25 g doses) were evaluated in rapid agglomeration experiments, while plain oil was limited to 6 g. The novel binders outperformed the benchmarks overall, achieving over 90 wt% particle recovery and reducing the organic liquid requirement up to 10-fold compared to plain oil. Additionally, emulsions aged for 28 days retained good agglomeration capability, particularly at higher polymer concentrations. These results demonstrate the potential of polymer-stabilised HIP emulsions to improve fine mineral processing.

Graphical abstract showing activated carbon from municipal garden waste used in long-term column filtration of reservoir water, promoting biofilm formation and enhancing NOM removal, resulting in improved effluent quality across different carbon media. This is the first research to investigate the conversion potential of garden-waste-based activated carbon (SAC) into biological activated carbon (BAC) for water treatment. Five identical columns containing different carbon media were operated with reservoir water for eight months to compare the performance of natural organic matter (NOM) removal. Effluent chemistry was monitored regularly, and three distinct phases were observed across the operational period for all carbon media. From days 1 to ∼65, ∼65 to 146, and 146 onwards, phases can be defined as the development phase, the breakthrough phase, and the equilibrium phase, respectively. Conversion of activated carbon (AC) into BAC was demonstrated by the steady removal of dissolved organic carbon (DOC) during the equilibrium phase, biofilm formation on the AC media, and was visualized. Seeding with pre-established BAC did not enhance column stabilization time. Despite having lower initial DOC removal, SAC ultimately showed a similar removal efficiency (37.5%) to commercial AC by the end of the experiment, particularly for NOM with a molecular weight below 3,000 Da. Therefore, the results suggest SAC as an effective medium for biological filtration and this finding may open up a promising approach for water utilities to provide affordable services through the re-use of municipal garden waste.

Small artificial waterbodies such as farm dams are recognized as important sources of anthropogenic emissions. Carbon dioxide (CO ₂ ) fluxes from farm dams are highly variable across spatial scales, with sites acting as sources or sinks based on single daytime measurements. However, diel variations are an overlooked source of temporal variability in CO _2, complicating upscaling efforts. To provide a more accurate estimate of the CO ₂ source‐sink status of farm dams, four irrigation dams were monitored for dissolved CO ₂ at half‐hourly intervals over a five‐month period in 2021–2022. Carbon dioxide concentrations were undersaturated between 12% and 37% of the measurements, indicating a dominance of CO ₂ production over consumption when considering diel cycles and seasonal patterns. Carbon dioxide was consistently lower during daytime and early night periods compared with late‐night and exhibited large diel shifts up to 57–99 μM. Diel CO ₂ amplitude was driven primarily by metabolic controls, as revealed by strong correlations with dissolved oxygen and temperature, except for one irrigation dam which indicated CO ₂ variation was driven by external inputs. Spatial variability based on previously acquired data (inter‐dam coefficient of variation (CV) 105%) was higher than diel (CV 34%–54%) and seasonal (CV 13%–29%) variability. However, if only daytime CO ₂ measurements are considered, total CO ₂ emissions over the study period would be underestimated by between 11% and 148%, demonstrating the consequence of not including diel variation. Future refinements of upscaled farm dam CO ₂ emission estimates will require more geographically dispersed studies that feature diel measurements to constrain uncertainty in these highly variable systems.

This study explores use of unmodified biochar as a novel sustainable stabiliser for water-in-oil (w/o) Pickering emulsions for oil agglomeration of fine minerals. While previous studies used chemically modified biochar and petroleum-based oils, this work employs pristine wheat straw biochar pyrolysed at 550 °C and 700 °C and canola oil as a green alternative, minimising costs, and environmental impacts. Eight biochar-based Pickering emulsions (BbPE) were developed with dispersed to continuous phase ratio 2:3, and particle concentration of 0.5, 1, 3, and 5 wt.%. Emulsion stability assessment was conducted using optical and confocal microscopy, sedimentation and accelerated sedimentation methods. Among eight emulsions, the most stable emulsion was used for oil agglomeration of talc, demonstrating its application in recovery of fine minerals. Emulsion stability increased with biochar pyrolysis temperature, and biochar particle concentration however, decreased with reducing hydrophobicity of the biochar particles. Wheat straw biochar pyrolysed at 700 °C can generate Pickering emulsions that remain stable for more than a month, with water droplet size of 10 to 200 µm. Oil agglomeration with BbPE showed higher recovery and formation of larger talc agglomerates compared to w/o emulsions made with a typical surfactant. The high stability of these emulsions coupled with improved mineral agglomeration makes biochar a promising material as an alternative to traditional w/o emulsions on a large scale. This coupled with the biodegradable nature of canola oil, carbon sequestration potential of biochar and its co-benefits to soil health gives this sustainable Pickering stabiliser a promising future in multiphase separation processes.

This study explores use of unmodified biochar as a novel sustainable stabiliser for water-in-oil (w/o) Pickering emulsions for oil agglomeration of fine minerals. While previous studies used chemically modified biochar and petroleum-based oils, this work employs pristine wheat straw biochar pyrolysed at 550 °C and 700 °C and canola oil as a green alternative, minimising costs, and environmental impacts. Eight biochar-based Pickering emulsions (BbPE) were developed with dispersed to continuous phase ratio 2:3, and particle concentration of 0.5, 1, 3, and 5 wt.%. Emulsion stability assessment was conducted using optical and confocal microscopy, sedimentation and accelerated sedimentation methods. Among eight emulsions, the most stable emulsion was used for oil agglomeration of talc, demonstrating its application in recovery of fine minerals. Emulsion stability increased with biochar pyrolysis temperature, and biochar particle concentration however, decreased with reducing hydrophobicity of the biochar particles. Wheat straw biochar pyrolysed at 700 °C can generate Pickering emulsions that remain stable for more than a month, with water droplet size of 10 to 200 µm. Oil agglomeration with BbPE showed higher recovery and formation of larger talc agglomerates compared to w/o emulsions made with a typical surfactant. The high stability of these emulsions coupled with improved mineral agglomeration makes biochar a promising material as an alternative to traditional w/o emulsions on a large scale. This coupled with the biodegradable nature of canola oil, carbon sequestration potential of biochar and its co-benefits to soil health gives this sustainable Pickering stabiliser a promising future in multiphase separation processes.