Pyrophosphate coupling with chelant-enhanced soil flushing of field contaminated soils for heavy metal extraction

► Metal extraction was mainly influenced by the initial metal distribution in soils. ► Metal extraction was less influenced by the flushing duration. ► EDDS-to-metal molar ratio was less crucial in affecting metal extraction. ► The extraction rate of Ni by EDTA and EDDS was time dependent. ► Na4P2O7 promoted mineral dissolution which enhanced metal extraction.