Natural Clays as Adsorbents for the Removal of Heavy Metals from Phosphogypsum

Abstract

AbstractIn this paper, we report current problematic issues of environment—health interactions in the context of phosphogypsum storage. Tunisia suffers from pollution problem mainly from the Tunisian Chemical Group. Phosphogypsum is the by-product of the manufacture of phosphoric acid, resulting from the sulfuric attack of a natural calcium phosphate ore. On the environmental front, crude phosphogypsum is likely to release heavy metals and radio-elements into the water and into the atmosphere, which poses serious problems. Several researchers have shown that a variety of materials of natural or biological origin are characterized by their ability to fix significant amounts of heavy metals, taking the example of clays that have been the subject of various studies for various applications such as adsorption. Chemical analysis of phosphogypsum waste indicated a high concentration of heavy metals, particularly Cd and Cr. On the other hand, radioactivity study indicated that the Ur and Th levels were acceptable and not dangerous to human health. Column experiments with clay give positive and encouraging results, as the Haidoudi and Romana clay deposits showed the capacity to absorb the extractable metals in the phosphogypsum waste. The natural clays from Gabes area, Tunisia, turned out to be an effective natural adsorbent for capturing metals from phosphogypsum waste and can be effectively used for the treatment of contaminated wastewaters in the environment.KeywordsPhosphogypsumStorageClay depositsAdsorptionHeavy metalsColumns