State-of-the-art advances in enhancement strategies for iron sulfide mineral-mediated autotrophic denitrification.

As a low-carbon strategy for nitrate removal, iron sulfide mineral-mediated autotrophic denitrification (ISAD) has attracted increasing attention, but its dense crystal structures and continuously evolving surface states often result in limited electron accessibility, complex intermediate formation, and pronounced variability in reported performance. To alleviate these shortcomings, diverse enhancement strategies are proposed. However, research in this field remains fragmented, resulting to persistent mechanistic ambiguities and engineering uncertainty. To narrow the gap, this review provides a critical synthesis of ISAD by examining reaction pathways, microbe-mineral interactions, and enhancement strategies from material and process perspectives. Rather than treating mineral reactivity, microbial activity, and reactor configuration as independent factors, the comprehensive analysis reveals that many inconsistencies across existing studies arise from neglecting the time-dependent co-evolution of mineral surfaces, electron transfer processes, and microbial functional organization. By reframing ISAD as a dynamically evolving mineral-microbe-reactor coupled redox system, this review clarifies the mechanistic origins of performance instability and identifies critical bottlenecks that constrain long-term reliability. Overall, the insights synthesized herein highlight that bridging the gap between laboratory demonstrations and practical application requires a shift toward systems-level understanding and design, enabling ISAD to progress toward predictable, resilient, and scalable nitrogen removal in complex real-world wastewater environments.