Efficient removal of Pb(ii) and Cr(vi) from acidic wastewater using porous thiophosphoryl polyethyleneimine

Removing heavy metal ions from acidic mine wastewater is a big challenge. In this paper, a novel porous thiophosphoryl polyethyleneimine (TPEI) adsorbent was designed for removing Pb(ii) and Cr(vi) from acidic wastewater. The optimum adsorption pH value of TPEI for Pb(ii) and Cr(vi) is 3 and 2, respectively. At 298 K, the maximum adsorption capacity for Pb(ii) and Cr(vi) is 421.9 mg g(-1) and 191.04 mg g(-1), respectively. The adsorption equilibrium time of Pb(ii) and Cr(vi) is 25 min and 10 min, respectively. The adsorption of Pb(ii) and Cr(vi) both conform to the pseudo-second-order model and the Langmuir isotherm model. The adsorption mechanism of Pb(ii) depends on the chelation interaction, while Cr(vi) depends on the electrostatic interaction. The regeneration test shows that the adsorbent is stable and reusable. This study provides a new strategy for the purification of acidic heavy metal wastewater.