UTILIZATION OF PHOSPHOGYPSUM FOR BACKFILLING, WAY TO RELIEVE ITS ENVIRONMENTAL IMPACT

Intensive mining and ore processing activities concerning phosphate ores have generated billions of tons of phosphogypsum (PG) throughout world. Even in China, it is estimated that more than 200 million tons of PG waste have been disposed at tailing dumps which distributed in almost every provinces. And the amount will increase by 20 million tons annually. However, there is still little usage of them. They are just stockpiled in waste repositories. Under the action of several physicochemical mechanisms, toxic and radioactive elements contained in the wastes are mobilized, migrate to the surroundings and cause severe and widespread contamination to air, soils, surface and ground waters. This has sparked criticism from citizens concerned, and leads to high cost of treatment and compensation each year. In this paper, pilot study was conducted to improve the PG as backfilling material by adding fly ash and cement in Kaiyang Phosphorus Mine. Specimens with different blending ratio of the three compounds were tested with INSTRON testing system to obtain the best blending ratio, with which the compounding PG had the needed strength for underground backfilling. Then, the corresponding filling system was developed to transmit the backfilling material into stopes. By this way, 100,000 tons of PG was changed from waste into valuable backfilling material annually. Two years' application and monitoring prove that utilization of PG for backfilling is one of the most promising ways to relieve the environmental impact of PG tailing and bring its role into play to the maximum extent.