High efficient adsorption accompanied by in-situ reduction of Cr(VI) removal by rice straw fiber ball coated with polypyrrole

• Published in: Applied surface science 2022-02, Vol.575, p.151583, Article 151583
• Main Authors: Cao, Fengming, Sun, Yanqing, Zhang, Ling, Sun, Jie
• Format: Article
• Language: English
• Subjects: Adsorption; Cr(VI) removal; Mechanism; Polypyrrole; Rice straw fiber ball
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2021.151583

[Display omitted] •PPy-SFB was prepared by in-situ polymerization of pyrrole in presence of waste rice straw.•PPy-SFB showed preferable Cr(VI) adsorption both in static and dynamic adsorption.•The adsorption was monolayer chemisorption, endothermic and spontaneous in nature.•Most of the adsorbed Cr(VI) on PPy-SFB was reduced in situ to the less toxic Cr(III).•Cr resource was recycled as pure Cr2O3 by calcining the Cr(VI) adsorbed PPy-SFB. Rice straw fiber ball coated with polypyrrole (PPy-SFB), a novel adsorbent, was prepared from waste rice straw through in-situ oxidative polymerization of pyrrole monomer. The Cr(VI) adsorption characteristics of PPy-SFB were investigated not only in batch experiments but also in the column experiments, the isothermal models (Langmuir, Freundlich and Temkin), the kinetic models (Pseudo-first-order kinetic, Pseudo-second-order kinetic and Intra-particle diffusion models), and the dynamic models (Adams-Bohart, Thomas and Yoon-Nelson) were used to describe the adsorption behavior. The Cr(VI) removal mechanism of PPy-SFB was revealed by studying the effect of pH on adsorption, testing of Cl−, and analyzing the XPS. The results showed that PPy-SFB could efficiently adsorb and reduce Cr(VI) from water, and the maximum adsorption capacity reached 122.15 mg g−1 at 30 ℃ and pH = 3.0. Adsorption of Cr(VI) by PPy-SFB followed the Langmuir isotherm model, Pseudo-second-order kinetic model and Yoon-Nelson model. The thermodynamic parameters (ΔG0  0 and ΔS0 > 0) indicated that the adsorption process was endothermic and spontaneous in nature. The electrostatic interaction, ion exchange between Cl− and Cr(VI), and reduction of the PPy-SFB surface were attributed to the high efficient removal of Cr(VI). In addition, the adsorbed Cr(VI) was recovered in the form of pure Cr2O3 by simple incineration.