Birnessite-Type MnO₂ Modified Sustainable Biomass Fiber toward Adsorption Removal Heavy Metal Ion from Actual River Aquatic Environment

Abstract

In this work, a novel birnessite-type MnO 2 modified corn husk sustainable biomass fiber (MnO 2 @CHF) adsorbent was fabricated for efficient cadmium (Cd) removal from aquatic environments. MnO 2 @CHF was designed from KMnO 4 hydrothermally treated with corn husk fibers. Various characterization revealed that MnO 2 @CHF possessed the hierarchical structure nanosheets, large specific surface area, and multiple oxygencontaining functional groups. Batch adsorption experimental results indicated that the highest Cd (II) removal rate could be obtained at the optimal conditions of adsorbent amount of 0.200 g/L, adsorption time of 600 min, pH 6.00, and temperature of 40.0 °C. Adsorption isotherm and kinetics results showed that Cd (II) adsorption behavior on MnO 2 @CHF was a monolayer adsorption process and dominated by chemisorption and intraparticle diffusion. The optimum adsorption capacity (Langmuir model) of Cd (II) on MnO 2 @CHF was 23.0 mg/g, which was higher than those of other reported common biomass adsorbent materials. Further investigation indicated that the adsorption of Cd (II) on MnO 2 @CHF involved mainly ion exchange, surface complexation, redox reaction, and electrostatic attraction. Moreover, the maximum Cd (II) removal rate on MnO 2 @CHF from natural river samples (Xicheng Canal) could reach 59.2% during the first cycle test. This study showed that MnO 2 @CHF was an ideal candidate in Cd (II) practical application treatment, providing references for resource utilization of agricultural wastes for heavy metal removal.