A porous biochar supported nanoscale zero-valent iron material highly efficient for the simultaneous remediation of cadmium and lead contaminated soil

•Immobilization of metals by BC-nZVI process was superior to that of BC or nZVI.•Immobilization of Cd or Pb was inhibited with addition of 2,4-dichlorophenol.•Cd and Pb availability decreased, whereas soil pH and organic matter increased.•Stable metals speices such as CdCO3, Cd(OH)2, PbCO3 and Pb(OH)2 were formed.•Mechanism for the simultaneous immobilization of Cd and Pb in soil was proposed.