Mechanisms of the Reductive Immobilization of Hexavalent Chromium by Wheat Straw Biochar

• Author / Creator

  Cossio Kohler, Manuel G

• Biochar has received significant attention as an innovative sorbent for treating heavy metal contamination due to its high surface reactivity and sorption capacity, ease of manufacture and low production cost. Most studies involving chromium removal from solution by biochar have focused on removal rates and extent, which largely ignores the mechanisms of sorption and electron transfer that occur during Cr immobilization. For this reason, a comprehensive Cr-biochar study that couples adsorption and reduction kinetics to spectroscopic data to elucidate the Cr binding environment and speciation on the biochar was conducted. Wheat Straw biochar (WSBC), produced by the Alberta Biochar Initiative, was used to sorptively remove and subsequently reduce hexavalent chromium (Cr(VI)) from solution over the course of days at a range of acidic pH (between 2 – 3). Sorption and reduction kinetics were monitored and concentration-independent intrinsic rate constants for both phenomena were calculated. To understand the Cr binding environment on the surface of WSBC following metal reduction, synchrotron X-ray adsorption spectroscopy, synchrotron-based X-ray fluorescence mapping, Fourier transform infrared spectroscopy, Raman microscopy and scanning electron microscopy were performed. The results show that (1) the reduction and sorption of Cr(VI) with WSBC is possible, especially in acidic media, (2) that the distribution of Cr on the WSBC surface is heterogeneous, and (3) the Cr(III) binding to WSBC surfaces are dominated by O-containing functional groups, with hydroxyl groups comprising the majority of the Cr binding sites, followed by binding to carboxyl and carbonyl groups.

• Subjects / Keywords

  • Chromium
  • Reduction
  • Wheat straw
  • Biochar
  • Hexavalent

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3959CN58

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.