A novel application of phosphogypsum: Treatment of a diamond mine\'s slimes tailings

Abstract

Premier Mine\'s current slimes dam is nearing the end of its operational life. This is aggravated by a large volume of poor quality
water in the dam which is not being recycled back into the process. The poor quality water is the result of a stable colloidal suspension formed from the dominant clay species present in the kimberlitic ore body.
The main objective of this test work was to clarify the water to improve the quality for reuse. Phosphogypsum has been identified as an alternative coagulant to clarify the slimes dam water at a relatively low cost. Laboratory- and plant-scale test work was done to investigate the optimum gypsum dosage, as well as to determine the most suitable application technique. The test work showed that gypsum can successfully destabilise the colloidal suspension. However, poor settling rates were achieved. This improved when the gypsum was added in a slurry form in two stages. The addition of flocculants to aid in settling
did not have the desired effect, with resultant high consumption and operating costs.
Toxicity tests indicated no lethality to Daphnia organisms and showed a positive growth in the algae test. The establishment
of a monitoring programme will assist in determining the long-term effects of gypsum on the environment.

Water SA Vol.32 (4) 2006: pp.489-497