The use of calcium carbonate-enriched clay minerals and diammonium phosphate as novel immobilization agents for mercury remediation: Spectral investigations and field applications

We used calcium carbonate-enriched clay minerals (CECM) and diammonium phosphate (DAP) as immobilization agents for mercury (Hg) immobilization. The effects of CECM, DAP, or both in different amounts and ratios, as well as pH and initial Hg concentrations, on Hg removal from solutions were investigated. The removal mechanism was revealed using transmission electron microscope with energy-dispersive X-ray (TEM-EDX) spectroscopy, and extended X-ray absorption fine structure spectroscopy (EXAFS). The performance of CECM and DAP under field conditions was also studied. The results showed that application of CECM and DAP at a ratio of 50:1 (w/w) removed over 90% of Hg from solutions containing 1.8 μM Hg2+, which was 9- or 2.6-fold higher than solely DAP (