A new strategy for efficient removal of Cd(II) and Pb(II) by porous and high-capacity N-doped carbon aerogels microspheres

•NCA and CA were obtained through phase reaction polymerization and carbonization.•Three isotherm models were applied to interpret the adsorption process.•DFT calculations confirm that N doping is beneficial to lead adsorption.•A mixing mechanism including physical and chemical adsorption was proposed. Many Industrial effluents contain high concentrations of Cd(II) and Pb(II), which are serious problems for causing threat to human health. Adsorption has drawn considerable attention owing to its high efficiency and easy operation. In this paper, nanoscale nitrogen-doped aerogel microspheres (NCA) was synthesised through polymerization of phenolic resin and melamine in an emulsion suspension system. Factors influencing the adsorption properties of NCA and carbon aerogels microspheres (CA) toward Cd(II) and Pb(II) ions were studied, namely, pH, adsorbent content, initial Cd(II) and Pb(II) concentrations, and contact time. Furthermore, three models isotherm including Langmuir, Freundlich, and Sipss and three kinetic models were used in interpreting the adsorption process. NCA exhibited an excellent adsorption property and maximum removal capacity of 935.56 mg·g−1 for Pb(II) and 282.07 mg·g−1 for Cd(II). Results from XPS analysis implied that the amount of Pb absorbed by NCA was higher than that of CA mainly because of the complexing effect of nitrogen-containing functional groups on Pb(II). Furthermore, density functional theory (DFT) calculations confirm that N doping is beneficial to Pb(II) adsorption. These results suggested that NCA can be used as an adsorbent for the removal of Cd(II) and Pb(II) from industrial effluents.