Supercritical Carbon Dioxide Chelating-extraction of Trace Heavy Metal from Calcium Lactate

Supercritical CO2 chelating-extraction was applied to remove heavy metal matter such as Pb, As and Hg from calcium lactate, and the effect of process parameters on removal efficiency were investigated including chelating agent, ethanol (as a modifier), temperature, extraction pressure and time. The results showed that the removal efficiency of trace heavy metals is obviously different from chelating agent, modifier and extraction time, thus the concentration of modifier and extraction pressure give little influence. The extraction process was optimized to get the condition of a temperature of 323.15K, a pressure of 20MPa, an extraction time of 90min, a supercritical CO2 fluid flow rate of 13l/h and 2% of the chelating agent mixtures combined with tetrabutyl bromide and sodium diethyldithiocarbamate (DDC). The maximum yield of Pb, As and Hg can reach 88.41%, 78.57% and 86.21%, respectively.