Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

Major

Civil Engineering

First Advisor

Say Kee . Ong

Second Advisor

Kejin . Wang

Abstract

Fly ash-based geopolymer were synthesized from Class-F fly ash and slag with an alkaline activating solution and characterized for their physical-chemical properties. The geopolymer samples were tested to investigate their environmental impacts when used for environmental applications. Batch adsorption studies were conducted using fly ash-based geopolymer as a reactive material or an adsorbent for heavy metals (Cu2+, Cd2+ and Pb2+). The removal capacities for Cu2+, Cd2+ and Pb2+ ranged from 20.66 – 35.21, 28.74 – 42.02, and 116.28 – 121.95 mg/g for initial pHs ranged from 2.5 to 4.0, respectively, at room temperatures of 21 – 23 oC. Fixed bed column studies were carried out using fly ash-based geopolymer as a filtration medium for removal of metal (Cu2+, Cd2+, and Pb2+) in low pH solutions. Breakthrough curves showed that the adsorption affinity of the geopolymer for metals was in the order of Pb2+ > Cd2+ > Cu2+ for a single metal solution and in the order of Pb2+ > Cu2+ > Cd2+ for a multi-metal solution which shows that there was a competition for adsorption sites on the geopolymer. The geopolymer can be used to neutralize the pH of acidic waste streams and at the same time adsorb or precipitate metal pollutants. In addition, magnetic geopolymers were synthesized by incorporating magnetic Fe3O4 particles to modify the fly ash-based geopolymer. Magnetic fly ash geopolymer showed similar adsorption properties as fly ash-based geopolymer with a maximum adsorption capacity of 111.1 mg/g. The magnetic fly ash geopolymer has a saturation magnetization of 18 emu/g and was found to separate out from an aqueous solution within 2 minutes by using a magnetic field of 0.48 Tesla. Applications of the magnetic fly ash geopolymer include using it as a powdered adsorbent to maximize heavy metals removal and recovery in wastewater treatment.

Copyright Owner

Guyu Shi

Language

en

File Format

application/pdf

File Size

209 pages

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