Degree

Doctor of Philosophy (PhD)

Department

School of Plant, Environmental and Soil Sciences

Document Type

Dissertation

Abstract

Biochar is a porous carbonated substance that is manufactured through pyrolysis of biomass feedstocks in an oxygen-deficiency environment. The production of biochar from agricultural waste materials provides a potential solution for eliminating pollution while improving carbon sequestration. While biochar is shown to provide multiple benefits to soil health and fertility, its use in environmental remediation has been hampered by its low affinity for hazardous anionic species and the difficulty in isolating from water phase. To overcome these obstacles, various efforts have been made to modify biochar surface chemistry and morphology.

Fe/Mg co-doped biochar composites from sugarcane harvest residue were prepared at different pyrolysis temperatures with varying impregnation ratios to investigate the changes on structure, magnetic property and phosphate affinity. Results revealed that Fe-biochar prepared at 450 ̊C demonstrated good magnetic feature but poor phosphate adsorption, and the incorporation of Mg substantially improved the phosphate removal efficiency from solution. Biochar pyrolyzed at 650 ̊C with both Fe and Mg modification, especially 650-15Fe30Mg, showed superior magnetic property, excellent phosphate adsorption capacity (117 mg P/g) and satisfactory stability with low leaching losses of metals. To minimize the issues with powder biochar application, chitosan-modified MgO/Mg(OH)2-biochar composite beads were also synthesized and investigated for phosphate removal. Adsorption study showed that prepared chitosan: MgO/Mg(OH)2-biochar ratio of 1:2 (1CH2MBC) exhibited the best performance. The beads displayed greater stability than unmodified MgO/Mg(OH)2 biochar as evaluated by leaching study under mild and extreme conditions. Furthermore, additional effort was made to develop a biochar-bioreactor system for simultaneous removal of phosphate and nitrate by an innovatively mixed media composed of magnesium-doped biochar and low-temperature biochar. Finally, Fe/Mn-biochar composites catalyst were developed and optimized to activate peroxymonosulfate (PMS) for degradation removal of organic pollutants in potential application of advanced oxidation process (AOP). The model pollutant Orange G was successfully eliminated from aquatic solution in less than 30 minutes with over 99 % removal rate through both radical and non-radical pathways. Overall, this work provided promising solutions for synthesizing biochar adsorbents for treating phosphate- and nitrate-rich wastewater, and novel FeMn-biochar composite catalysts for the degradation of organic pollutants by PMS.

Date

11-3-2022

Committee Chair

Wang, Jim J.

Available for download on Sunday, November 02, 2025

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