THESIS
2019
xx, 179, that is, xxiv, 179 pages : illustrations (some color) ; 30 cm
Abstract
Eutrophication of water bodies is a serious and widespread environmental problem. Achieving
low levels of phosphate concentration to prevent eutrophication is one of the important goals of
the wastewater engineering and surface water management. Meeting the increasingly stringent
standards is feasible in using a phosphate-selective sorption system. In this study, zirconium-,
lanthanum-, and cerium-based sorbents were developed for selective phosphate removal from
water and wastewater.
Two zirconium oxide-based sorbents (i.e. ZrO
2@SiO
2@Fe
3O
4 and ZrO
2@Fe
3O
4) were
developed and compared for phosphate removal. The direct coating of ZrO
2 on Fe
3O
4 to form
the core/shell ZrO
2@Fe
3O
4 leaded to a significantly ehanced phosphate sorption kinetics and
sorption capacity in comparison to ZrO...[
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Eutrophication of water bodies is a serious and widespread environmental problem. Achieving
low levels of phosphate concentration to prevent eutrophication is one of the important goals of
the wastewater engineering and surface water management. Meeting the increasingly stringent
standards is feasible in using a phosphate-selective sorption system. In this study, zirconium-,
lanthanum-, and cerium-based sorbents were developed for selective phosphate removal from
water and wastewater.
Two zirconium oxide-based sorbents (i.e. ZrO
2@SiO
2@Fe
3O
4 and ZrO
2@Fe
3O
4) were
developed and compared for phosphate removal. The direct coating of ZrO
2 on Fe
3O
4 to form
the core/shell ZrO
2@Fe
3O
4 leaded to a significantly ehanced phosphate sorption kinetics and
sorption capacity in comparison to ZrO
2@SiO
2@Fe
3O
4. The developed ZrO
2@Fe
3O
4 sorbent showed a high selectivity towards phosphate in the presence of competitive anions, and a high
phosphate recovery rate.
To further design phosphate-selective sorbents with higher sorption capacity, La(OH)
3/Fe
3O
4
nanocomposites with varied La-to-Fe mass ratios were synthesized through a precipitation and
hydrothermal method. The optimized La(OH)
3/Fe
3O
4 (4:1) nanocomposite had fast sorption
kinetics, high sorption capacity, and strong selectivity for phosphate in presence of competing
ions. Sorption-desorption cyclic experiments demonstrated the good reusability of the
La(OH)
3/Fe
3O
4 (4:1) nanocomposite.
Mechanism studies indicated that both the ZrO
2@Fe
3O
4 and La(OH)
3/Fe
3O
4 (4:1) removed
phosphate by forming the inner-sphere complexation through the ligand exchange process, i.e.,
hydroxyl groups on the surface of the Zr- and La-based sorbents were replaced by the
phosphate. Therefore, increasing the amount of the surface hydroxyl groups of metal-based
sorbents can greatly enhance the phosphate sorption performance. Consequently, a
straightforward, effective method was proposed for increasing the amount of the surface
hydroxyl groups of CeO
2 particles. By simply reducing the volume of water used during the
ethylene glycol-mediated solvothermal synthesis of CeO
2 particles, the amount of surface
hydroxyl groups was increased, and the phosphate sorption performance was greatly improved.
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