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

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 celcius and pH = 3.0. Adsorption of Cr(VI) by PPy-SFB followed the Langmuir isotherm model, Pseudo-secondorder kinetic model and Yoon-Nelson model. The thermodynamic parameters (Delta G0 0, Delta H0 0 and Delta S0 > 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.

Automated summary

The study revealed that PPy-SFB is an efficient adsorbent for the removal of Cr(VI) from water, with adsorption mechanisms involving electrostatic interactions, ion exchange, and surface reduction. Furthermore, the adsorbed Cr(VI) can be recovered through simple incineration.