Chromium is a heavy metal used in tanneries, leather industries, electroplating, and metallurgical operations, but improper disposal of waste from these industries leads to environmental contamination. Chromium exists primarily in trivalent and hexavalent forms, with hexavalent chromium (Cr (VI)) being highly toxic. Cr (VI) is carcinogenic, damages fish gills, and negatively impacts crops. Considering these negative impacts of Cr (VI), several physical, chemical, and biological remediation methods have been implemented at contaminated sites, but in most instances, these methods could be uneconomical, highly labor-intensive, and not sustainable. Therefore, a crucial goal is to implement an effective and sustainable remediation technique with consideration of actual site conditions. The aim is to develop a sustainable remediation strategy for a hexavalent chromiumcontaminated site in Ranipet, Tamil Nadu. The comprehensive risk assessment for the site has depicted hazard quotients greater than 1 for both onsite and offsite conditions, indicating the necessity of remediation. To address this, it is suggested to build permeable reactive filters (PRFs) packed with scrap iron filings to reduce Cr (VI) to Cr (III), and succeeding filters with locally produced waste coconut shell biochar to aid in adsorption. The use of waste here aims to eliminate the need to procure any commercially available materials for remediation, completely cutting down the environmental impact of raw material extraction or processing. A continuous chambered set-up packed with contaminated soil and PRFs with biochar and iron filings aided in the decrease of the peak concentration of Cr (VI) by 61 % as compared to a set-up without intervention. Moreover, the outlet concentration after 7 days reduced to 0.08 mg/L, which was 97.6 % less than that in the set-up without intervention.

The exploration of the Moon necessitates sustainable habitat construction. Establishing a permanent base on the Moon requires solutions for challenges such as transportation costs and logistics, driving the emphasis on In-Situ Resource Utilization (ISRU) techniques including Additive Manufacturing. Given the limited availability of regolith on Earth, researchers utilize simulants in laboratory studies to advance technologies essential for future Moon missions. Despite advancements, a comprehensive understanding of the fundamental properties and processing parameters of sintered lunar regolith still needs to be studied, demonstrating the need for further research. Here, we investigated the fundamental properties of lunar regolith simulant material with respect to the stereolithography-based AM process needed for the engineering design of complex items for lunar applications. Material and mechanical characterization of milled and sintered LHS-1 lunar regolith was done. Test specimens, based on ASTM standards, were fabricated from a 70 wt% (48.4 vol %) LHS-1 regolith simulant suspension and sintered up to 1150 degrees C. The compressive, tensile, and flexural strengths were (510.7 +/- 133.8) MPa, (8.0 +/- 0.9) MPa, and (200.3 +/- 49.3) MPa respectively, surpassing values reported in previous studies. These improved mechanical properties are attributed to suspension's powder loading, layer thickness, exposure time, and sintering temperature. A set of regolith physical and mechanical fundamental material properties was built based on laboratory evaluation and prepared for utilization, with the manufacturing of complex-shaped objects demonstrating the technology's capability for engineering design problems.

In the mountainous headwaters of the Colorado River episodic dust deposition from adjacent arid and disturbed landscapes darkens snow and accelerates snowmelt, impacting basin hydrology. Patterns and impacts across the heterogenous landscape cannot be inferred from current in situ observations. To fill this gap daily remotely sensed retrievals of radiative forcing and contribution to melt were analyzed over the MODIS period of record (2001-2023) to quantify spatiotemporal impacts of snow darkening. Each season radiative forcing magnitudes were lowest in early spring and intensified as snowmelt progressed, with interannual variability in timing and magnitude of peak impact. Over the full record, radiative forcing was elevated in the first decade relative to the last decade. Snowmelt was accelerated in all years and impacts were most intense in the central to southern headwaters. The spatiotemporal patterns motivate further study to understand controls on variability and related perturbations to snow water resources.

The construction of a lunar base requires a huge amount of material, which cannot be entirely transported from Earth. Therefore, technologies are needed to build with locally available resources, such as the lunar regolith. One approach is to directly melt the lunar regolith on the surface and under the vacuum condition of the Moon, using laser radiation. In this article, a lunar regolith simulant is laser beam melted to two-dimensional singlelayer-structures using different ambient pressures from 0.05 mbar to 2000 mbar, laser process parameters from 60 W to 100 W laser power, and 1 mm s- 1 to 3 mm s- 1 feed rates. Additionally, the influence of the ambient gas was investigated using argon as an air alternative. The results show that the ambient pressure on the Moon is not negligible when studying the melting processes of lunar regolith on Earth. With decreasing ambient pressure, the appearance of the melted regolith simulant varies from a shiny to a matt surface. At the highest laser energy density, the thickness of a single-layer increases from 2.6 +/- 0.4 mm to 5.3 +/- 0.3 mm and the porosity of the melted regolith increases from 17.2 % to 52.2 % with decreasing ambient pressure. Additionally, mechanical properties are determined using 3-point bending tests. The maximum bending strength decreases by 60 % with the increased ambient pressure from 10 mbar to 2000 mbar. Consequently, the development of in-situ resource utilization technologies, which process the lunar regolith directly on the lunar surface, must consider the ambient pressure on the Moon. Otherwise, the processes will not work as expected from the experiments in Earth-based laboratories.

In today's fast-paced technological era, multifaceted technological advancements in our contemporary lifestyle are surging the use of electronic devices, which are significantly piling e-waste and posing environmental concerns. This stock of e-waste is expected to keep rising up to 50 mt year(-1). Formal recycling of such humongous waste is a major challenge, especially in developing nations. Mishandling of e-waste poses serious threats to human health, soil, and water ecosystem, threatening ecological and environmental sustainability. Complex matrix of resourceful materials comprising valuable metals like gold, silver, and copper, and hazardous substances such as lead, mercury, cadmium, and brominated flame retardants make its judicious management even more crucial. Potential toxic elements such as Pb, Cd, Cr, As, and Hg, as well as plastic/microplastics, nanoparticles are prevalent in components like batteries, cathode ray tubes, circuit boards, glass and plastic components which are known to cause neurological, renal, and developmental damage in humans. Effective and sustainable management of these requires a comprehensive understanding of their sources, environmental behavior, and toxicological impacts. This review explores potential approached for sustainable e-waste recycling (recycling of glass, plastic, rare earth metals, and base metals), and resource recycling through pyrometallurgy, hydrometallurgy, biometallurgy, biohydrometallurgy, bioleaching and biodegradation plastic alongside challenges and prospects.

As the relentless extraction of antimony ore escalates, the incidence of environmental contamination from its residue, known as antimony tailings (AT), has become a frequent occurrence, garnering widespread concern regarding the management of these residues. Presently, the application of AT is predominantly focused within the realms of construction materials and filling materials. However, due to technological constraints, the rate of utilization is minimal, with the majority being confined to tailings ponds, thereby consuming substantial land resources and presenting a looming environmental contamination hazard. This paper introduces, for the first time, the innovative utilization of AT as a primary raw material in the production of lightweight, waterproof, and eco-friendly foamed concrete. The study delves into the mechanical properties, water resistance, and leaching toxicity of the resulting foamed concrete. The findings indicate that the mechanical properties of the foamed concrete exhibit an initial increase followed by a decrease with the increment of AT content. Optimal comprehensive performance is achieved when the AT content reaches 50%, yielding a compressive strength of 28 MPa, a flexural strength of approximately 5 MPa, a dry density of 110 kg/m3, a wet density of 158 kg/m3, a void index of 1.25, and a softening coefficient of 0.89 after 28 days of standard curing. Furthermore, it is observed that cement and fly ash significantly enhance the solidification of toxic and harmful elements present in AT. This research substantiates the viability of crafting sustainable, environmentally benign, and waterproof foamed concrete by leveraging AT from multiple perspectives.

Phosphogypsum (PG), an industrial solid waste produced from the wet phosphoric acid process, has seriously damaged the ecological environment. Its comprehensive utilization rate needs to be improved urgently. In this paper, the chemical enhancement effect of solid waste PG on expansive soil, known as engineering cancer, was investigated through systematic macroscopic and microscopic experiments. The positive and negative environmental impacts of the PG modifier were also comprehensively analyzed. Laboratory soil test results show that PG mixed with expansive soil can change the consistency limit of expansive soil, effectively increase the soil strength by 2-3 times and reduce the expansion of expansive soil to 62%. Therefore, it can be considered to be applied to the improvement of expansive soil roadbed. However, when the dosage is too high, it may be affected by the dissolution of PG, and the improvement effect is relatively decreased. The optimal dosage of PG is 15%. XRD, XRF, SEM and MIP microcosmic tests show that the mineral composition, element content and porosity of the expansive soil have changed after the addition of PG. Its microstructure is much tighter. Through TCLP test, the environmental effects of heavy metals caused by resource utilization of PG modified expansive soil were evaluated. In this study, only Cr element exceeded 2.6% slightly when the content of PG was 25%. The analysis found that the engineering properties of expansive soil were effectively improved, resulting in the effective solidification of heavy metals in PG.

Mars is increasingly considered for colonization by virtue of its Earth-like conditions and potential to harbor life. Responding to challenges of the Martian environment and the complexity of transporting resources from Earth, this study develops a novel geopolymer-based high-performance Martian concrete (HPMC) using Martian soil simulant. The optimal simulant addition, ranging from 30% to 70% of the total mass of the binders, was explored to optimize both the performance of HPMC and its cost-effectiveness. Additionally, the effects of temperature (-20 degrees C-40 degrees C) and atmospheric (ambient and carbonated) curing conditions, as well as steel fibre addition, were investigated on its long-term compressive and microstructural performance. Optimal results showed that HPMC with 50% regolith simulant achieved the best 7-day compressive strength (62.8 MPa) and the remarkable efficiency improvement, a result of ideal chemical ratios and effective geopolymerization reaction. Under various temperature conditions, sub-zero temperatures (-20 degrees C and 0 degrees C) diminished strength due to reduced aluminosilicate dissolution and gel formation. In contrast, specimens cured at 40 degrees C and 20 degrees C, respectively, showed superior early and long-term strengths, with the 40 degrees C potential for moisture loss related shrinkage cracking and reduced geopolymerization. Regarding the atmospheric environment, carbonation curing and steel fibre addition both improved the matrix compactness and compressive strength, with carbon-cured fibre-reinforced HPMC achieving 98.3 MPa after 60 days. However, long-term exposure to high levels of CO2 eventually reduced the fibres' toughening effect and caused visible damages on steel fibres.

Establishing a permanent, self-sufficient habitat for humans on planetary bodies is critical for successful space exploration. In-situ resource utilisation (ISRU) of locally available resources offers the possibility of an energy-efficient and cost-effective approach. This paper considers the high-temperature processing of molten lunar regolith under conditions which represent the lunar environment, namely low gravity, low temperature, and negligible atmospheric pressure. The rheological properties of the low-titanium lunar mare regolith simulant JSC-1A are measured using concentric cylinder rheometry and these results are used to explore the influence of viscosity on processing operations involving the flow of molten regolith for fabricating construction components on the Moon surface. These include the delivery of molten regolith within an extrusion-based 3D printing technique and the ingress of molten regolith into porous structures. The energy and power required to establish and maintain sufficiently high temperatures for the regolith to remain in the liquid state are also considered and discussed in the context of lunar construction.

Non-technical summary To address the issues of declining groundwater levels and the degradation of soil ecological functions caused by open-pit coal mining in China. Based on theoretical analysis, laboratory experiments, on-site monitoring, mathematical modeling, and other means, the concept of coal ecological protection mining of 'damage reduction mining, three-dimensional protection, systematic restoration' is proposed. The mining concept has achieved remarkable ecological restoration effects, leading the scientific and technological progress of safe, efficient and green mining in open-pit coal mines. Technical summary The mechanism of damage propagation among 'rock-soil-water' ecological elements in open-pit coal mining was revealed. Adopting comprehensive damage-reducing mining technology throughout the entire stripping process, mining and drainage, shengli open-pit coal mine has doubled its production capacity, and reduced the land excavation and damage by 60 mu/year, reduced the mining area by 1,128 mu, and raised the groundwater level by 2.6-6 m, and the ecological restoration of the drainage field was advanced by more than 1 year. Adopting the three-dimensional water storage technology involves underground reservoirs, aquifer reconstruction, and near-surface distributed water storage units, baorixile open-pit mine has built the world's first open-pit underground water reservoir, with a water storage capacity of 1.22 million m(3), and the speed of groundwater level restoration has been increased by more than 70%. By adopting the systematic restoration technology of geomorphology-soil-vegetation in the discharge site, the soil water content in the demonstration area has been increased by 52%, the survival rate of plants has been increased by 34%, and the vegetation coverage has been increased by more than 40%. Social media summary Damage-reducing mining and systematic ecological restoration in open-pit coal mining are essential for the safe, efficient and green development of coal.