Effect of Phosphogypsum Released Solution on Soil and Aquifer Water

Abstract

This paper reports the interaction between natural environment and phosphogypsum free solution hereafter named industrial effluent. It is a strongly acid solution containing some heavy metals and fluorides (F^–). Two components of the receiving environment were considered, ground sediments and Jeffara aquifer water (Tunisia Gabes area). The selection of these two components is linked particularly to their basic character and their phase's differences (liquid and solid). In fact, the considered soil is slightly carbonated and Jeffara aquifer water is slightly basic. In addition, the soil is constituted of various sizes solid particles and could constitute well adsorbent to metal ions existing in phosphogypsum free solution. This effluent contains many ions such as Cd²⁺ and F^– which may react with natural environment after first contact. The experimental study was conducted at room temperature and variable pH to highlight the partition of considered ions between the liquid phase (effluent), the sediment and the potential newly formed solid phase (co-precipitation). This work shows particularly the precipitation of a solid phase identified as CaF². It contributes first of all to F^– decrease and then to Cd²⁺ partial removal from industrial effluent which becomes roughly neutral. Consequently it is expected that the effect of this effluent on natural environment will be horizontally restricted and with no vertical expansion due to pH neutralization and ions species retention.