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Cadmium ions constitute a major threat to human health and the environment owing to their toxicity, bioaccumulation, and persistence in water bodies, causing renal dysfunction, cancer, and cardiovascular diseases. Hence, this study reports the facile fabrication of a novel sodium iron oxide silicate@amorphous sodium iron silicate product (S1) and its chitosan composite (S1@chitosan) for the high-performance separation of Cd(II) ions from aquatic environments. The Brunauer-Emmett-Teller surface area, total pore volume, and mean pore diameter of S1 were 94.97 m 2 /g, 0.5853 cm 3 /g, and 25.65 nm, respectively, while those for S1@chitosan were 30.94 m 2 /g, 0.09518 cm 3 /g, and 12.31 nm, respectively. The reduction in pore diameter, pore volume, and surface area confirms the successful functionalization of S1 with chitosan, as the chitosan coating partially blocks and fills the pores, reducing the available surface area and porosity. Also, scanning electron microscope (SEM) images revealed an uneven surface morphology for S1 and a more textured and rougher surface for S1@chitosan, supporting the incorporation of chitosan. Besides, energy-dispersive X-ray spectroscopy (EDX) and CHN analyses affirmed the existence of chitosan in the composite through the detection of carbon and nitrogen elements, characteristic of chitosan. The optimum conditions for the removal of Cd(II) ions were determined to be a contact time of 70 min for S1 and 50 min for S1@chitosan, a pH of 7.50, and a temperature of 298 K. The maximum sorption capacities were 284.09 mg/g for S1 and 389.11 mg/g for S1@chitosa. The removal mechanism for S1 primarily involves ion exchange, while S1@chitosan utilizes both ion exchange and complexation through the amino and hydroxyl groups of chitosan. Regeneration using HCl confirmed the effective reusability of both adsorbents over five successive cycles. The adsorption process was found to be chemical, exothermic, and best described by the pseudo-second-order kinetic model and Langmuir isotherm.

Lithium iron silicate （Li2FeSiO4） is capable of affording a much higher capacity than conventional cathodes, and thus, it shows great promise for high-energy battery applications. However, its capacity has often been adversely affected by poor reaction activity due to the extremely low electronic and ionic conductivity of silicates. Here, we for the first time report on a rational engineering strategy towards a highly active Li2FeSiO4 by designing a carbon nanotube （CNT） directed three-dimensional （3D） porous Li2FeSiO4 composite. As the CNT framework enables rapid electron transport, and the rich pores allow efficient electrolyte penetration, this unique 3D Li2FeSiO4-CNT composite exhibits a high capacity of 214 mAh·g^-1 and retains 96% of this value over 40 cycles, thus, outstripping many previously reported Li2FeSiO4-based materials. Kinetic analysis reveals a high Li＋ diffusivity due to coupling of the migration of electrons and ions. This research highlights the potential for engineering 3D porous structure to construct highly efficient electrodes for battery applications.

Iron phosphate-based coating and iron silicate-based coating were used to inhibit the oxidation of sulfide minerals in rainy and submerged environments. The inhibiting effectiveness of coating agents on the oxidation of iron sulfide minerals was investigated using pyrite and rock samples resulting from acid drainage. The film formed with both surface-coating agents was identified by pyrite surface analysis. It was also confirmed that the formation of coatings varies depending on the crystallographic orientation. The inhibitory effects under rainy and submerged conditions were investigated using column experiments. Submerged conditions accelerated deterioration compared to that under rainy conditions. Iron phosphate coating had a significantly better oxidation-inhibitory effect (84.86–98.70%) than iron silicate coating (56.80–92.36%), and at a concentration of 300 mM, H + elution was inhibited by more than 90% throughout the experiment. Furthermore, methods for effective film formation were investigated in terms of producing Fe 3+ ; (1) application of coating agents mixed with oxidant (H 2 O 2 ), (2) application of coating agent after the use of the oxidant. In a rainy environment, applying iron phosphate-based coating using the sequential method showed oxidation inhibition effects for cycles 1–9, whereas applying the mixed material showed effects for cycles 9–13. The use of a surface-coating agent after applying an oxidant did not inhibit oxidation. The surface coating agent and the oxidizing agent should be applied as a mixture to form a film.

The Spanish cement sector must adapt its production model to a green economy model. This study focuses on the use of new secondary main constituents (SMCs) suitable for a cement plant that specializes in sulfate-resistant (SR) cement production, defining a framework of technical conditions for their usage and their economic and environmental feasibility. Low-calcium-carbonate-content albero, steel slags, and iron silicate were the tested SMCs; however, they are not currently permitted in cement manufacture. CEM I 42.5 R-SR 3 (type I-SR) was mixed with 5%, 20%, and 30% of these new SMCs. XRF, XRD, leaching and other chemical tests, setting, and hardening tests were performed with no significant issues. Albero is the best option, on the whole, because of the following characteristics: availability, >100 Mt; proximity, 3 km; and acceptable compressive strength level. However, black slag cement with 30% SMC after 28 days shows the best performance, with a compressive strength of 41.3 MPa compared to 35.3 MPa for albero cement and 56.5 MPa for the type I-SR reference. Albero and steel slag at 30% content are the best option according to the cost savings of 32% (−31.5 EUR/t and −31.6 EUR/t, respectively) compared to the type I-SR reference. Regarding the carbon footprint, albero and steel slag at 30% content have the least impact, showing a 31% reduction (−254.8 kg CO2/t and −255.2 kg CO2/t, respectively) compared to the type I-SR reference. The studied SMCs meet the analytical conditions and—with the corresponding regulatory changes—offer potential cost savings for SR cement production, exhibiting a competitive advantage.

A significant source of copper losses from pyrometallurgical copper extraction is attributed to dissolved and entrained copper in discarded slag. Entrained copper can be recovered via pyrometallurgical slag cleaning in a settling furnace, where the slag viscosity and copper droplet size distribution (CDSD) are critical parameters. Reduced copper losses suggest improved raw material efficiency, and the slag becomes a more environmentally safe byproduct. In this study, iron silicate slags from a smelting furnace are industrially CaO modified in a fuming furnace to contain a CaO content between 8 and 18 wt.%. The viscosity of slags with and without CaO modifications is evaluated in the temperature range from 1423 to 1723 K. The influences of the CaO modifications on the CDSD, slag matrix copper content, and total copper content were determined. The results show that the slag viscosity decreases with increasing CaO concentrations in the slag. In addition, the copper content decreases in the slag phase, and the CDSD shifts to contain relatively larger droplets. The effect of CaO slag modification reveals a linear relationship between the overall copper recovery and viscosity, which increased from 63 to 88% when the viscosity in the respective batch was 0.51 and 0.25 Pa·s. Graphical Abstract

Pyrometallurgical copper production is associated with high slag rates, typically ranging from 2.2 to 3.0 tons of slag per ton produced copper. Therefore, slag valorization is necessary to maintain a resource-efficient operation. An attractive application for these iron silicate slags is as supplementary cementitious materials (SCMs), which effectively lowers the CO 2 emissions per ton of concrete. Although utilizing iron silicate slags as SCMs has been studied in previous work, the scientific literature has limited data on the isolated effect of composition on the inherent reactivity in cementitious systems. In particular, no reports on the impact of the FeO/SiO 2 ratio have been presented in previous publications. Therefore, the present study aimed to isolate this parameter in a synthetic FeO–SiO 2 –Al 2 O 3 –CaO–MgO–Cr 2 O 3 system. Since the amorphous content is a pertinent parameter for SCMs, a hot-stage confocal laser scanning microscope was utilized to assess the crystallization behavior at continuous cooling conditions. Furthermore, high-temperature rheological experiments were conducted to measure the viscosities of the slags in relation to the crystallization behavior. The experiments highlighted that depolymerizing the slag by increasing the FeO/SiO 2 ratio poses increased demands on the cooling rate to avoid crystallization, which was consistent with the rheological data on the impact of temperature on structural changes in the slags. Furthermore, Rapid Reliable Relevant (R3) isothermal calorimeter experiments, assessing the inherent reactivity as an SCM, showed that increasing FeO/SiO 2 ratios improves early reactivity at the expense of seven-day reactivity, i.e., a balance between the degree of polymerization and contribution of silicon to the reactions. Graphical Abstract

Granulated iron silicate slag, a by-product of pyrometallurgical copper extraction, has excellent properties for construction applications. Slag modification with CaO enhances the application properties regarding pozzolanic reactivity, potentially extending slag use in the future. The slags’ short-term leaching behavior has already been investigated with promising results, while the long-term leaching effects are less studied. Therefore, this study aims to determine the long-term leaching effects on CaO-modified iron silicate slags. The CaO-modifications were conducted during full-scale slag treatment operation. The slags were characterized and leached, and the remaining slags were investigated regarding the formation of secondary phases. The long-term leaching of main and trace elements was determined over 30 days using a dynamic leaching method corresponding to an extended time period. The leaching tests showed increased leaching of the main slag elements (Si, Ca). Zn and Cu showed peak leaching after four days of leaching, and the leaching of As and Sb decreased with the increasing CaO content in the samples. After dynamic leaching, secondary phases formed on the Cu-containing inclusions on the sample surfaces. Independent of the CaO content, the leaching of Cu was increased when subjected to external acidic and oxidating conditions using static pH titration at pH 5 in dilute nitric acid.

The zinc in the fayalite slag of copper smelters, in which Zn-containing raw materials are used, is mainly found to be in oxidic phases, such as glassy iron silicate. During the slag water granulation process, the molten slag is heated, whereby the granulated slag achieves varying granulation temperatures. Therefore, in this study, we aimed to characterize and assess the leaching behavior of a synthesized Fe-saturated (FeX,Zn(1−X))2SiO4 system to understand the dependance of the zinc leaching behavior on the parameters of the ZnO content (1–10 wt.%) and granulation temperature (1300 or 1400 °C). It was found that the Zn leaching increased with the increasing Zn content and granulation temperature, using both batch and static pH leaching methods. Zn leaching was further increased at pH 5 using diluted nitric acid under oxidation conditions. Among the oxides in the samples—fayalite, spinel, and glass—glass was found to contribute to Zn leaching, owing to its weathering during pH-titration.

This study conducts low-vacuum sulfidation to form a sulfidation layer on the serpentinite-derived magnesium iron silicate, thereby enhancing its electrochemical properties. Results show (Mg,Fe)2SiO4 calcined at 900 °C has the best crystallinity, and the cubic FeS2 is synthesized on the surface of the orthorhombic magnesium iron silicate (MFS). Two distinct charge plateaus can be distinguished during the first charge process, and the discharge capacities increased significantly. This study confirms that the surface FeS2 layer provides extra ion pathways, allowing more lithium/magnesium ions to be extracted and inserted in the serpentinite-derived magnesium iron silicate. Accordingly, the serpentinite electrode boasts straightforward exploitation with low-cost advantages and potential.

Waste materials are often available without cost, making them economically viable sources for the production of nanoadsorbents. This can significantly reduce the overall cost of manufacturing and contribute to cost-effective waste management strategies. Hence, in this study, canned beans and rice husk wastes were employed as sources of iron and silicon, respectively, for facile and low-cost hydrothermal synthesis of novel sodium iron silicate/sodium iron oxide silicate nanostructures. The nanostructures, which were produced after 6, 12, 18, and 24 hrs, were abbreviated as N6, N12, N18, and N24, respectively. The average crystal size of the N6, N12, N18, and N24 nanostructures is 15.23, 25.64, 40.21, and 42.87 nm, respectively. Additionally, the BET surface area of the N6, N12, N18, and N24 nanostructures is 71.57, 48.25, 32.92, and 32.19 m 2 /g, respectively. The produced nanostructures were utilized for the efficient removal of Cd(II) ions from aqueous media. The maximum adsorption capacity of the N6, N12, N18, and N24 samples towards Cd(II) ions is 248.76, 207.47, 182.82, and 173.61 mg/g, respectively. The removal efficiency of Cd(II) ions from 100 mL of a 150 mg/L solution using 0.05 g of nanostructures increased with raising pH from 2.5 to 6.5. The removal efficiency of Cd(II) ions by the N6, N12, N18, and N24 samples at pH 6.5 is 80.96, 66.99, 58.49, and 55.72 %, respectively. Also, the removal efficiency of Cd(II) ions from 100 mL of a 150 mg/L solution using 0.05 g of nanostructures increased with raising the contact time from 5 to 30 min due to the availability of adsorption sites. The removal efficiency of Cd(II) ions by the N6, N12, N18, and N24 samples after 30 min is 80.45, 66.32, 57.68, and 55.08 %, respectively. The removal efficiency of Cd(II) ions from 100 mL of a 150 mg/L solution using 0.05 g of nanostructures decreased with raising the solution temperature from 298 to 328 K. Besides, the removal efficiency of Cd(II) ions decreased with raising the concentration from 50 to 250 mg/L. The pseudo-second-order kinetic model and Langmuir isotherm are the best equations for describing the adsorption of Cd(II) ions by the synthesized nanostructures. The adsorption of Cd(II) ions by the synthesized nanostructures is spontaneous, exothermic, and chemical. The synthesized nanostructures were renewed and used multiple times to remove Cd(II) ions without losing their efficiency.