Phosphogypsum (PG) is an industrial solid waste containing a large number of pollutants, and its surface stockpile has a potentially negative impact on the environment nearby. The PG-based cemented backfill can solve the problem to a great extent. However, the negative environmental impact might be transferred into the underground when PG-based cemented backfill is filled into tunnels of mine, which is still an open question. This paper studies the change of pollutant concentrations in the leachate of PG-based backfill. The results show that the pH value of the leachate tends to be neutral with time. Before backfilling, the phosphate concentration supernatant of PG solution is 3979 mg/L, and it decreases to 1.3 mg/L when PG is made into backfilling material. In the prolonged store underground, the phosphate concentration decreases to about 0.3 mg/L. On the other hand, the concentrations of Zn, Fe, Cr, Mn, Ba, As and other elements in the leachate significantly decrease in the leachate after being cemented. Some F and Pb can dissolve in the leachate indicates that the dissolution migration mechanism and the F, P solidication technology need to be further studied. In conclusion, compared to PG surface stockpile, PG-based cemented backfill can well solidify/stabilize the harmful pollutants in PG, which could be a promising industrial process for PG disposal.
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