Jianzhong Zheng

Iron oxides play an important role in regulating global biogeochemical cycles, yet how their physicochemical properties influence community structure, function, and assembly remains poorly understood. Here, we investigated the effects of four representative iron oxides—ferrihydrite (Fh), goethite (Gt), haematite (Ht), and magnetite (Mt)—serving as terminal electron acceptors on microbial communities enriched from activated sludge. Metagenomic profiling revealed mineral‐dependent divergence in community composition and functional potential. The communities developed on amorphous Fh demonstrated low microbial diversity and were heavily dominated by Pseudomonas _A. In contrast, the communities associated with crystalline oxides (Gt and Ht) maintained intermediate diversity. Notably, the Mt. communities exhibited a more polycentric structure, possessing the highest richness and evenness, alongside a significant enrichment of Geobacter . Methane was detected in crystalline‐oxide systems but remained below detection in Fh systems. Mineralogical analyses revealed substantial Fe(III) reduction and secondary mineral formation across treatments. Null‐model analysis of pairwise turnover supports mineral‐associated community turnover while highlighting that the relative contributions of selection versus undominated processes vary among minerals. Overall, these findings demonstrate that iron oxide identity is associated with differences in anaerobic community structure and biogeochemical outcomes.

Gallium is a critical metal for high-tech industries, with its global demand surging in recent years. Currently, approximately 90% of primary gallium is extracted from Bayer liquor. Chelating resins such as amidoxime sorbents are widely adopted commercial materials for this purpose. However, gallium recovery from such highly caustic media remains a formidable challenge, as gallium is present at low concentrations while aluminate ions are hundreds of times more abundant, and the medium is rich in competing vanadate ions and humic substances. These interfering components impede both adsorption and desorption cycles, leading to a progressive decline in resin performance and a subsequent increase in operational costs. In recent years, functionalized carbon-based materials have gained significant traction. This growing interest is motivated by the carbon-based materials’ exceptional chemical resilience across both acidic and alkaline environments, tunable surface chemistry, and facile re-functionalization. This mini-review synthesizes recent progress in functionalized carbon-based materials for gallium recovery, with a particular emphasis on their adsorption performance and mechanistic insights. At the end of the paper, major challenges and research gaps are identified, and future research directions are proposed.

Facing the severe environmental challenge of massive red mud (RM) stockpiles, iron extraction research is accelerating from traditional pyrometallurgy and other conventional processes toward green low-carbon, multi-source synergistic, and total-component high-value utilization approaches—a transition that continues to evolve. This review systematically examines three frontiers: green reduction technologies, synergistic valorization via waste-treating-waste, and integrated cascading strategies for total-component high-value utilization. Evaluation focuses on the principles, advantages, and challenges of biomass reduction, hydrogen metallurgy, selective flocculation, advanced heating techniques, co-processing with other solid wastes, and multi-metal cascading extraction. Evidence suggests that future RM iron extraction technology lies in establishing cross-industry circular economy networks, transforming RM from a singular waste into a resource hub linking aluminum, steel, and construction industries to maximize environmental and economic benefits.

The development of effective materials for uranium extraction from seawater is vital for advancing sustainable energy solutions. However, the efficient recovery of uranium from seawater presents significant challenges due to its extremely low concentration, the presence of competing ions, and the complex marine environment. To address these issues, various materials such as inorganic and organic sorbents, chelating resins, nanostructured sorbents, and composite materials have been explored. More recently, the functionalization of carbon-based materials for enhanced adsorption properties has attracted much interest because of their high specific surface area, excellent chemical and thermal stability, and tunable porosity. These materials include activated carbon, graphene oxide, biochar, carbon cloths, carbon nanotubes, and carbon aerogels. The enhancement of carbonaceous materials is typically achieved through surface functionalization with chelating groups and the synthesis of composite materials that integrate other high-performance sorbents. This review aims to summarize the work of these functionalized carbon materials, focusing on their adsorption capacity, selectivity, and durability for uranium adsorption. This is followed by a discussion on the binding mechanisms of uranium with major chelating functional groups grafted on carbonaceous sorbents. Finally, an outlook for future research is suggested. We hope that this review will be helpful to researchers engaged in related studies.

A facile method was employed to impregnate activated carbon, a commonly used water treatment medium, with nanostructured magnesium oxide for fluoride removal. Batch adsorption tests were conducted to evaluate the adsorption performance of the nanostructured magnesia-impregnated activated carbon (nMgO@AC) for fluoride removal. The results demonstrated that this composite material exhibited a good adsorption capacity, with a maximum equilibrium uptake of approximately 121.1 mg/g for fluoride. Kinetic studies revealed that the adsorption process followed the pseudo-second-order adsorption kinetic model, reaching equilibrium in about 100 min. Within the initial pH range of 3 to 11, the adsorption efficiency of nMgO@AC for fluoride remained above 95%, indicating that the initial solution pH had a minimal effect on the material’s fluoride removal capability. The adsorption mechanism was elucidated by characterizing the material properties before and after adsorption using SEM, TEM, XRD and XPS. Initially, magnesium oxide reacted with water and rapidly transformed into magnesium hydroxide. Subsequently, a ligand exchange occurred between the hydroxide groups in magnesium hydroxide and fluoride ions in the aqueous solution, resulting in the effective removal of fluoride. The findings of this study suggest that nanostructured magnesia-impregnated activated carbon holds significant potential for the treatment of fluoride-containing wastewater, particularly for highly alkaline wastewater.

Interfacial free energy is a quantitative basis for explaining and predicting interfacial behavior that is ubiquitous in nature. The contact angle (CA) method can determine the surface free energy (γ) as well as Lifshitz-van der Waals (γ^LW) and Lewis acid/base (γ⁺/γ^-) components of a solid material from its CAs with a set of known test liquids according to the extended Young-Dupré equation. However, the reliability of the "known" parameters of the test liquids is questioned due to the long-neglected surface roughness effect during calibration of the liquids. This study proposed a simple and practicable two-step approach to correct the energy parameters of several test liquids by incorporating Wenzel's surface roughness relationship into CA measurement. Step 1: water and two apolar liquids (diiodomethane and α-bromonaphthalene) were used as benchmarks to calibrate the surface roughness and energy parameters of two reference solids [apolar poly(tetrafluoroethylene) and monopolar poly(methyl methacrylate)], and step 2: the reference solids were used to calibrate any other test liquids by solving the energy parameters from their CAs in the extended Young-Dupré-Wenzel model. Monte Carlo simulation was used to evaluate error transmission and robustness of the model solutions. The obtained energy parameters (γ^LW/γ⁺/γ^-) of four test liquids (dimethyl sulfoxide, formamide, ethylene glycol, and glycerol) are 28.01/13.68/4.67, 34.95/3.53/37.62, 26.26/7.51/15.74, and 32.99/9.24/26.02 mJ/m², respectively, and different from the literature values. The liquids were applied to characterize an example solid surface with true γ^LW/γ⁺/γ^- values of 28.00/1.00/8.00 mJ/m² and a roughness index (r) of 1.60. Without correction of the liquid parameters, the calculated surface energy, hydration energy, and hydrophobic attraction energy of the solid sample can deviate by 50, 13, and 27%, respectively. This proves the necessity of correcting parameters of the test liquids before they can be used in CA and interfacial energy studies in the presence of surface roughness.