Photosynthetic MICP: A sustainable pathway for soil remediation in coal tailings

Coal tailings, a byproduct of mining activities, pose severe threats to ecosystem health due to structural degradation and poor water retention. Herein, this study proposed a photosynthetic microbially induced carbonate precipitation strategy driven by the synergistic interaction of Chlorella sorokiniana FK and Bacillus sp. QX4 to rehabilitate coal tailings soil. Photosynthetic biomineralization effectively aggregates dispersed coal tailing particles, enhancing the content of water-stable macroaggregates by 128 % following five cycles of dry-wet alternation. This process also results in a 14 % increase in average weight diameter, doubles the calcium-bound organic carbon content, reduces water evaporation by 47.9 %, and decreases surface crack proportion by 64 %. Ca²⁺ and extracellular polymeric substances are key regulators of CaCO₃ nucleation and particle binding with the cation-π bonds they form being the primary mechanism for increasing the stability of the coal tailing macroaggregate composite structure. This urea-free method significantly enhances aggregate stability and water retention capacity, offering a sustainable strategy for the functional soil transformation of coal tailings. This holds significant implications for the ecological restoration of mining-affected areas.