Using Iron Tailings for Phosphate Removal in Cemented Phosphogypsum (PG) Backfill
Ying Shi1, Xiaolin Wang1, Zixuan Qing1
1School of Resources and Safety Engineering, Central South University, Changsha 410083, China.
Materials (Basel, Switzerland)
|December 11, 2022
Summary
Adding iron tailings (ITs) to phosphogypsum (PG) backfill effectively controls phosphate emissions. This solid waste addition rapidly reduces phosphate levels and enhances backfill strength, immobilizing pollutants long-term.
Area of Science:
- Environmental Engineering
- Materials Science
- Waste Management
Background:
- Phosphate pollution is a significant environmental concern, necessitating effective emission control strategies.
- Phosphogypsum (PG), a byproduct of phosphate production, contains substantial residual phosphate, posing challenges for its reuse.
- Recycling PG as cemented backfill can lead to phosphate emissions into surrounding water bodies.
Purpose of the Study:
- To investigate the efficacy of adding iron tailings (ITs) to PG backfill for controlling phosphate emissions.
- To assess the impact of ITs on the phosphate adsorption characteristics and mechanical properties of PG backfill.
- To evaluate the long-term phosphate immobilization potential of IT-amended PG backfill.
Main Methods:
- Preparation of cemented backfill slurry incorporating PG and varying percentages of ITs.
- Phosphate concentration analysis in bleeding water and leachates using standard methods.
- Adsorption experiments to determine phosphate adsorption mechanisms (Langmuir and pseudo-second-order models).
- Unconfined compressive strength (UCS) testing to evaluate backfill mechanical properties.
- Toxic leaching tests on cured backfill samples.
Main Results:
- ITs addition rapidly reduced phosphate concentration in backfill slurry to below the discharge standard (<0.5 mg/L) within 15 minutes.
- Phosphate adsorption by ITs followed Langmuir and pseudo-second-order models, indicating monolayer chemical adsorption.
- The addition of 20% ITs increased the UCS of PG backfill from 1.08 MPa to 1.33 MPa.
- Phosphate concentration in leachates from 28-day cured backfill remained below 0.02 mg/L.
Conclusions:
- Iron tailings effectively accelerate phosphate removal and control emissions from phosphogypsum cemented backfill.
- ITs act as an effective adsorbent for phosphate, with adsorption governed by chemical processes.
- Incorporating ITs not only mitigates phosphate pollution but also enhances the mechanical strength and long-term stability of the backfill material.
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