The effect of pH, calcium, phosphate and humic acid on cadmium availability and speciation in artificial groundwater

The interface between the ions in groundwater affects the biogeochemical behaviour of metal, and metal bioremediate by bacteria. Therefore, this study was aimed to predict the influence of pH, calcium, phosphate and humic acid on cadmium availability in artificial groundwater (AGW). Speciation and the thermodynamic calculation (MINTEQ program) were used to predict this in AGW theoretically. In results, cadmium availability diminished with an increase in pH, increase of calcium concentration and the addition of phosphate and humic acid of AGW. According to MINTEQ program, cadmium binds to some cations leaving fewer free cadmium ions available in AGW such as CdHCO₃ ⁺, Cd(SO₄)₂ ^2-, CdCl⁺, CdHPO₄, HA1-Cd, FA1-Cd, FA2-Cd, and HA2-Cd. It is suggested though that pH in AGW is maintained at pH 4.00 for best availability of cadmium and bioremediate by bacteria. (paper)