Honors College Thesis


Comparison of Aqueous Cu⁺², Pb⁺², and Zn⁺² Adsorption with Pyrolyzed Hazelnut Shells and a Commercially Produced High-Carbon Fly Ash Public Deposited

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  • Contamination of stormwater with Cu⁺², Pb⁺², and Zn⁺² has become an important issue with recognition of the neurotoxic effects of these metal ions on aquatic life. Low levels of aqueous Cu⁺² disrupt olfactory functioning in endangered Pacific Northwest salmon, decreasing their ability to avoid predation. One common solution is stormwater filtration with an adsorbent material, often activated carbon. Locally sourced biochar generated as a byproduct of energy production has the potential to be a more sustainable and cost effective alternative. This study compares two lab-produced pyrolytic chars from hazelnut shells and Douglas fir chips with a commercially available high-carbon fly ash. Proximate carbon analysis, FTIR spectroscopy, biochar pH, and EPM found few significant differences between adsorbents. All three were characterized by high fixed carbon (85 - 90%), no identifiable surface functional groups, high pH (8.3 - 9.0), and a negative surface charge at stormwater-relevant pH values. The commercial char exhibited superior adsorption of Cu⁺² and Pb⁺² during batch testing, resulting in maximum adsorption capacities of 2.0 mg/g and 4.8 mg/g respectively. Bench scale column tests with equal-volume char samples indicated superior Pb⁺² adsorption by the hazelnut shell char (breakthrough at 20.2 hours compared to 14.8 hours for the commercial char). Breakthrough for Cu⁺² occurred at ~10.5 hours for both chars. Competition between metals resulted in poor Zn⁺² adsorption and decreased Cu⁺² adsorption from levels seen without competition.
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