New method for recycling EDTA via formation of EDTA iron(III) sodium salt

NOx and SO2 emissions from combustion of fuels have given significant effects on environmental and human health. Current technique for controlling them by Fe(II) EDTA absorption is highly efficient. The final reaction products mainly include Fe(III) EDTA and S2O6 2-. In our experiment, the invalid absorption solution was oxidized and evaporated, and then the red brown crystal was precipitated and separated from the solution. FTIR revealed that this substance contained EDTA. XRD confirmed that its structure was C10H12N2FeNa•3H2O. All these showed that EDTA was converted into Ethylenediaminetetraacetic acid Fe(III) sodium salt. The product yield was greatly connected with pH value. In the pH range of 3 to 8, the precipitation yield increased firstly and then decreased subsequently due to the acid effect coefficient and the precipitation of Fe(OH)3. The maximum yield reached 78.7% at pH 7.