Date of Award

Winter 2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

Committee Director

James W. Lee

Committee Member

John B. Cooper

Committee Member

Patrick G. Hatcher

Committee Member

Sandeep Kumar

Abstract

Biochar is the carbon rich solid by-product of biomass pyrolysis. Interest in biochar can be broken down to several main categories: use as a carbon sequestration agent, use as a medium for the removal via adsorption of unwanted materials in wastewater, and as a soil amendment for the increase of cation exchange capacity (CEC). In order to generate a biochar which is stable enough for carbon sequestration, higher temperature pyrolysis must be used in order to ensure a lower O:C ratio in order to increase the half-life of biochar in soil. This dissertation addresses the evaluation of biochars made from pinewood, peanut, and bamboo biomass by pyrolysis over different temperatures (300, 400, and 500 °C), and by hydrothermal conversion (HTC) at 300 °C. Furthermore, this dissertation investigates different methods of partial oxygenation procedures to re-incorporate oxygen functional groups during post-production treatment of biochar samples through the use of either H2O2 or O3 treatments.

Biochars produced from pinewood, peanut and bamboo via pyrolysis were found to have lower CEC, higher pH, and lower O:C ratios when compared to biochars produced by HTC. Upon analysis it was found that a very strong correlation between O:C ratio and CEC exists, as illustrated by both elemental analysis and FTIR-ATR spectra. It was concluded, however, that while HTC produces a very high quality biochar in terms of CEC, there are predominant problems in using large scale HTC for producing biochars due to high cost of equipment and high pressures involved.

Biochar produced from pinewood biomass at 400 °C via pyrolysis was subjected to varying concentrations of H2O2 (1, 3, 10, 20, 30% w/w) or varying durations of O3 gas flow (30, 60, 90 mins). In both partial oxygenation treatments, the treated biochar exhibited a lowering of pH and increase in CEC, with slight changes in both FTIR-ATR spectra as well as elemental analysis. These results reveal that the aforementioned partial oxygenation procedures were effective in increasing CEC while keeping the inherent stability of the biochar stable by leaving the bulk of the biochar composition unchanged in terms of O:C ratio.

DOI

10.25777/kdyj-qe21

ISBN

9780438970427

ORCID

0000-0003-2404-510X

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