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  • Tailings have accumulated into large mounds
    Tailings pond
    Tailings have accumulated into large mounds
  • All-solid-waste sinter-free blocks prepared using geopolymer cementitious materials and solid waste aggregates.
    Sinter-free paving bricks made entirely from solid waste
    All-solid-waste sinter-free blocks prepared using geopolymer cementitious materials and solid waste aggregates.
The utilization of solid waste resources is the only way for the sustainable development of the building materials industry!
Mine Rehabilitation
The primary goals of mine reclamation are to eliminate geological hazards, curtail the diffusion of contaminants, and reestablish ecological systems. Within this framework, the harmless disposal and resource-efficient utilization of tailings constitute critical components.
I. Harmless Disposal of Tailings Slag for Pit Backfilling

Heavy Metal Solidification/Stabilization

Technical Principle: By mixing chemical agents (solidifiers) with tailings slag, heavy metal ions are converted into insoluble compounds to block their migration.

Key Steps:

Pretreatment: Screen the tailings slag to remove large particle impurities;

Agent Addition:

Inorganic solidifiers: Cement, fly ash (forming a silicate network to encapsulate heavy metals);

Organic solidifiers: Sulfides (e.g., Na₂S), phosphates (generating precipitates such as Pb₃(PO₄)₂);

New materials: Geopolymers (with better acid and alkali resistance than cement).

Mixing and Curing: Control the moisture content (15-20%) and cure for more than 7 days to form a solidified body.

Engineering Solidification for Pit Backfilling

Layered Compaction: The filling thickness of each layer is ≤ 0.5m, and mechanical compaction is performed to achieve a compactness of > 90% to prevent collapse.

Anti-seepage Barrier: Lay an HDPE membrane (2mm thick) + bentonite cushion (GCL) at the pit bottom to block the downward seepage of heavy metals;

The side walls are protected with shotcrete (thickness 10-15cm).

Monitoring System: Embed leachate collection pipes + water quality sensors (to monitor pH and heavy metal concentrations in real time).

II. Core Work for Greening of Tailings Ponds

Substrate Improvement

Physical improvement: Cover with 30-50 cm of soil (or mix foreign soil with tailings slag at a 1:1 ratio) and incorporate straw/sludge (to increase organic matter).

Chemical improvement: Add quicklime (to adjust pH to 6.5-7.5); apply passivators (hydroxyapatite to passivate cadmium, zeolite to adsorb arsenic).

Vegetation Reconstruction

Selection of pioneer plants: For example, heavy metal-accumulating plants to absorb/fix pollutants; barren-tolerant herbs to quickly cover the surface; nitrogen-fixing shrubs to improve soil fertility.

Planting techniques:

Hydroseeding: Mix substrate + seeds + binder and spray (for areas with a slope > 30°);

Ecological blankets: Cover with coconut fiber blankets to retain water (suitable for arid regions).

Water-Fertilizer System and Long-Term Management

Micro-irrigation system: Lay drip irrigation tapes, combined with slow-release fertilizers (N-P₂O₅-K₂O = 15-15-15).

Ecological monitoring: Test the heavy metal content in vegetation quarterly (e.g., arsenic in Pteris vittata leaves should be < 100 mg/kg) to prevent pollution spread.

III. Key Risk Control Points

Prevention of Secondary Release of Heavy Metals:

Before greening, it is necessary to ensure that the pH of tailings slag is > 6.0 (to avoid heavy metal leaching by acid water);

Vegetation shall be incinerated after harvesting (with ashes disposed of in safe landfills).

Guarantee of Slope Stability:

When the slope is > 35°, lattice beams + anchor bolts shall be installed for support;

Deep-rooted shrubs (such as Caragana korshinskii) shall be planted to reinforce the soil layer.

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