Heavy-metal contamination poses a significant global threat to soil environments, underscoring the necessity for effective and sustainable remediation technologies. This review methodically summarizes advances in the field of microbial remediation of heavy metal-contaminated soils, organized around four major dimensions: remediation mechanisms, synergistic technologies, field applications, and future prospects. Firstly, the remediation mechanisms are elucidated, encompassing molecular interactions, cellular adaptation, and community-level cooperative responses. Secondly, the integration of microbes with functional materials and bioelectrochemical systems (BESs) is evaluated, with these materials providing support, electron mediation, and micro-environment regulation that markedly improve remediation efficiency and stability. Moreover, illustrative field cases demonstrate pivotal technological pathways and cost-effectiveness when transitioning from laboratory- to field-scale applications. Finally, emerging frontiers such as synthetic biology-engineered microbes, AI-driven microbial design, circular-economy value recovery, and policy-governance innovations are discussed, proposing essential elements for building a “predictable-controllable-sustainable” microbial remediation platform. This review aims to provide a comprehensive knowledge framework for researchers and to offer decision-making guidance for practitioners and policymakers, thereby advancing microbial remediation toward higher efficiency, reliability, and scalability.

The production process of antimony produces a large amount of solid waste, such as waste rock in mining, tailings in the beneficiation, metallurgical slag in the smelting, and so on. At present, most of these solid wastes are currently in storage, and the storage of a large amount of solid wastes is not only harmful to the local ecological environment but also a waste of resources. In view of this situation, this paper will take antimony tailings and metallurgical slag as examples and summarize them according to their different treatment methods. The comprehensive utilization of antimony tailings is mainly recovering metals by beneficiation and metallurgy and using antimony tailings as building materials and underground filling materials, while the comprehensive utilization method of antimony metallurgical slag is mainly the recovery of valuable metals by pyrometallurgy or hydrometallurgy or the stabilization technology. This paper summarizes the advantages and disadvantages of different treatment methods and puts forward the prospect of future research directions for the treatment of different metallurgical slags and tailings.

In response to the pressing environmental challenges posed by electrolytic manganese residue (EMR) and red mud (RM), this study proposes an innovative cementitious material technology for the synergistic co-utilization of these industrial wastes. By employing steel slag (SS) as a calcium-rich skeleton, the system effectively immobilizes sulfates from EMR and alkalinity from RM, converting hazardous wastes into value-added construction materials. Through orthogonal experimentation, an optimal mix proportion was established—30% RM, 20% EMR, and 50% SS at a water-to-binder ratio of 0.28—which achieved a 28-day compressive strength of 20.40 MPa, meeting relevant industry standards for auxiliary cementitious materials. Microstructural analysis unveiled a multi-stage alkali-sulfate synergistic activation mechanism: (1) the high alkalinity derived from RM rapidly activates the dissolution of aluminosilicate phases in both SS and EMR; (2) sulfate ions released from EMR promote extensive formation of ettringite (AFt), enhancing early-age structural integrity; and (3) calcium ions from SS facilitate the development of a dense C-S-H gel matrix, which serves as the primary binding phase. More profoundly, this process exemplifies a self-stabilizing waste-to-resource conversion mechanism, whereby harmful constituents (sulfates and free alkalis) are constructively incorporated into stable hydration products. This work not only elucidates a coherent scientific framework for the safe and efficient reclamation of multi-source solid wastes, but also demonstrates a scalable and ecologically viable pathway for million-ton-scale valorization of EMR and RM. Furthermore, it presents feasibility insights for the application of high-dosage steel slag-based material systems, thereby unifying significant environmental and economic advantages.

Microbial fuel cells (MFC) have considerable potential in the field of energy production and pollutant treatment. However, a low power generation performance remains a significant bottleneck for MFCs. Biochar and anatase are anticipated to emerge as novel cathode catalytic materials due to their distinctive physicochemical properties and functional group architectures. In this study, biochar was utilized as a support for an anatase cathode to investigate the enhancement of the MFC power generation performance and its environmental impact. The results of the SEM and XPS experiments showed that the biochar-supported anatase composites were successfully prepared. Using the new cathode catalyst, the maximum current density and power density of the MFC reached 164 mA/m² and 10.34 W/m², respectively, which increased by 133% and 265% compared to a graphite cathode (70.51 mA/m² and 2.83 W/m²). The degradation efficiency of Cr (VI) was 3.1 times higher in the biochar-supported anatase MFC than in the graphite cathode. The concentration and pH gradient experiments revealed that the degradation efficiency of Cr (VI) was 97.05% at an initial concentration of 10 mg/L, whereas a pH value of two resulted in a degradation efficiency of 94.275%. The biochar-supported anatase composites avoided anatase agglomeration and provided more active sites, thus accelerating the cathode electron transfer. In this study, natural anatase and biochar were ingeniously combined to fabricate a green and efficient electrode catalyst, offering a novel approach for the preparation of high-performance positive catalysts as well as a sustainable, economical, and environmentally friendly method for Cr (VI) removal in aqueous solutions.

The co-contamination of manganese ions (Mn²⁺) and ammonia nitrogen (NH₄⁺) caused by the stockpiling of manganese residue poses a serious threat to the ecological environment. In this study, a series of the composite was prepared from red mud, bentonite, and corn straw via oxygen-limited pyrolysis. The effects of pyrolysis temperature and raw material ratio on the material properties were investigated, and the synergistic remediation performance of the composites for Mn²⁺ and NH₄⁺ in manganese residue-contaminated soil was evaluated through a 180-day soil column experiment. The results showed that the composite prepared with a raw material ratio of 1:1:1 at a pyrolysis temperature of 700 °C exhibited the largest specific surface area and the most developed pore structure, achieving a Mn²⁺ removal rate of 92.72% ± 0.85% in aqueous solution. In the soil column experiment, the material prepared at 700 °C gave the highest immobilization rate for soil Mn²⁺ (96.22% ± 0.5%), whereas the combined addition of materials prepared at 700 °C and 500 °C achieved the best removal efficiency for NH₄⁺ (99.33% ± 0.23%). Mechanistic studies revealed that the stabilization of Mn²⁺ is primarily attributable to alkaline precipitation and mineral lattice solid solution induced by the composite, leading to the formation of stable spinel phases (e.g., (Fe,Mn)₃O₄) and insoluble manganese phosphate-carbonate salts. The removal of NH₄⁺ is proposed to proceed via adsorptive enrichment by the porous structure and Fe⁰-mediated Fenton-like catalytic oxidation, ultimately converting NH₄⁺ to N₂ gas. The 180-day monitoring results demonstrated that the remediation effect continuously increased over time, indicating good long-term stability of the composite. This study provides an efficient, low-cost functional material derived from solid waste for the remediation of manganese residue-contaminated soil and offers a theoretical basis for the synergistic resource utilization of multiple solid wastes.

Tantalum and niobium are critical strategic rare refractory metals; however, most associated tantalum–niobium resources are characterized by ultra-low grade, finely disseminated grains, and severe argillization, which causes pronounced slime coating of gangue mica on valuable mineral surfaces and impedes efficient recovery via gravity separation. In this study, an innovative beneficiation route combining sodium silicate pre-dispersion conditioning with shaking-table gravity separation was proposed to recover a spodumene-dominant pegmatitic lithium ore containing trace associated Nb–Ta minerals, with mica as the major slime-forming gangue. Process mineralogy analysis revealed that the raw ore has a total (Nb,Ta)₂O₅ grade of only 0.019%, with the main valuable minerals being columbite-(Mn), columbite–tantalite, and tantalite, whereas layered mica minerals constitute the primary argillization gangue that readily generates micro-fine slimes smaller than 5 μm. Single-factor tests demonstrated that the optimal grinding fineness was 84.4% passing 200 mesh, and the optimal feed pulp density for gravity separation was 28.6%. Adjusting pulp concentration alone, without a dispersant, yielded a Nb₂O₅ concentrate grade of merely 0.144%, as severe slime coating greatly limited separation selectivity. Following the introduction of sodium silicate for pre-dispersion, the separation performance improved markedly at the optimal dosage of 300 g/t: the concentrate Nb₂O₅ grade reached 1.28% (8-fold higher than the blank test), and the Ta₂O₅ grade increased to 0.47% (85-fold higher than the blank test). Multi-scale characterization, including zeta potential measurements, ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), was employed to elucidate the dispersion mechanism of sodium silicate. The results confirmed that sodium silicate undergoes selective chemisorption on mica surfaces by forming Si–O–Al bonds with surface Al–OH active sites, which substantially increases electrostatic repulsion between mineral particles and eliminates mica slime coating on tantalum–niobium minerals. In contrast, sodium silicate exhibits only weak physical adsorption on tantalum–niobium mineral surfaces, with no evident chemical bonding. This work provides a low-cost, eco-friendly pretreatment–gravity separation coupling technology for the efficient enrichment of argillized ultra-low-grade tantalum–niobium associated ores and offers theoretical guidance for the green utilization of complex tantalum–niobium tailings and low-grade mineral resources.