Adsorption and Reductive Removal of Hexavalent Chromium from Aqueous Solution by Nanoscale Iron‐modified Dual Surfactants

Abstract In view of the increasingly prominent environmental pollution caused by heavy metals, nanoscale zero‐valent iron was modified by polyethylene glycol and sodium dodecyl benzene sulfonate (PS‐nZVI) and used to treat Cr(VI). The removal rate of Cr(VI) and equilibrium adsorption capacity of PS‐nZVI can reached 92 % and 122.3 mg ⋅ g −1 , respectively, under the conditions of PS‐nZVI 1.0 g ⋅ L −1 , initial Cr(VI) concentration 50 mg ⋅ L −1 , initial pH 5.5, and reaction temperature 298 K. The adsorption process can be described by quasi‐second‐order kinetics and Langmuir isothermal model, and it is characterized by spontaneous endothermy and monolayer surface chemisorption. The mechanism of Cr (VI) removal by PS‐nZVI can be summarized as follows: First, Cr(VI) is adsorbed on the surface of PS‐nZVI by electrostatic attraction. Then, nZVI and Fe(II) reduce Cr(VI) to Cr(III), and themselves are oxidized to Fe(III). Finally, Cr(III) and Fe(III) form (Cr X Fe 1‐X )(OH) 3 or Cr X Fe 1‐X OOH co‐precipitation, which is attached to the PS‐nZVI surface and removed.