Selective Removal Of Phenol And Heavy Metal Ions By Spherical Cyclodextrin Polymer Particles And Spherical Polyelectrolyte Brushes

Water pollution is one of the most serious environmental pollution problems. Cyclodextrin multifunctional materials have been widely used in the phenols adsorption and for the adsorption of heavy metal ions. Nano-sized spherical polyelectrolyte brushes containing mercapto group have opened a new path to selectively remove heavy metal ions,a-, β-and y-Cyclodextrin (CD) spherical polymer particles were prepared by suspension polymerization. The selective adsorption and recovery of phenol and aromatic compounds by these CD spherical polymer particles were studied. The kinetics and isothermal equilibrium models were used to fit the experimental data of phenol removal. Due to the large specific surface area and ease to be separated of the CD polymer particles by filtration, they were conducive to the industrial production and application. To improve the adsorption capacity of phenol, the nano-sized spherical cyclodextrin brushes were synthesized by photo-emulsion polymerization. The selective adsorption and recovery of phenol by nano-sized spherical cyclodextrin brushes were studied. For selective removal of heavy metal ions, the nano-sized spherical thiol polyelectrolyte brushes were prepared by photo-emulsion polymerization. The selective adsorption and recovery of heavy metal ions by the nano-sized spherical thiol polyelectrolyte brushes were studied. Details for this thesis are listed as follows:(1) Spherical particles of a-,β-and γ-CD polymers were prepared by suspension polymerization in liquid paraffin using epichlorohydrin as crosslinker. The shape and size of the polymerized CD particles were controlled by the amounts of water and crosslinker.(2) Due to the selective inclusion associations between CDs and phenol, these CD polymer particles are suitable for phenol removal. The adsorption amount of phenol by CD polymers was determined by the UV spectrum. The phenol adsorption capacity of CD polymers was found to depend on host-guest interactions and the size match of the inner cavity of CD molecular. The β-CD polymer particles showed the best result to adsorb phenol, attributed to the best size matching. The kinetics and isothermal equilibrium models were used to fit the experimental data of phenol removal from aqueous solution using these CD polymer particles. It was found that kinetics followed the Ho and Mckay equation, suggesting that the adsorption process of phenol controlled by diffusion and the host-guest interaction between CD and phenol. Equilibrium isothermal data can be well fitted by Freundlich equation. The negative free energy change indicated the spontaneous nature of adsorption of phenol by a-, β-and y-CD spherical polymer particles, while the lowest one for β-CD polymer reflected its best adsorption ability, compared to a-and γ-CD polymer particles. The adsorption results of phenol, naphthalene, hydroxy benzoic acid and benzidine by a-,(3-and y-CD spherical polymer particles are quite different. The better size match between the structure of aromatic compounds and the cavity of the cyclodextrin match better, the higher adsorption results. The CD polymer particles can be easily recovered by extraction with ethanol at room temperature. The adsorption abilities keep almost unchanged after several cycles of regeneration.(3) The6A-(methacryloyl)-6A-1,6-ethylenediamine-6A-deoxy-β-cylcodextrin was prepared and the nano-sized spherical β-cyclodextrin (β-CD) brushes were synthesized by photo-emulsion polymerization. The nano-sized spherical P-CD brushes were with narrow size distribution were prepared and confirmed by monitoring the size increase of polymer particles using dynamic light scattering (DLS). Since β-CD can selectively form host-guest association with phenol, the obtained nano-sized spherical brushes contain β-CD should be ideal candidate for removal or recovery of phenols from wastewater.(4) Nano-sized spherical polyelectrolyte brush has a well-defined core-shell structure. It can absorb and concentrate heavy metals from aqueous solutions due to the enhanced Donnan effect, which is thus suitable for removing heavy metal ions in wastewater. In order to improve the selectivity of absorption of heavy metal ions by the nano-sized spherical polyelectrolyte brushes, the mercapto groups were introduced in the nano-sized spherical polyelectrolyte brushes. The nano-sized spherical thiol polyelectrolymte brushes consisting of a polystyrene core and a poly(N-acrylcysteamine-co-acrylic acid) brush shell were prepared by photo-emulsion polymerization. They have well defined core-shell structure as determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The amount of heavy metal ions absorbed by these thiol brushes were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Nano-sized spherical polyelectrolyte thiol brushes showed the higher adsorption capacity to gold and mercury ions, compared to copper and nickel ions. Due to the selective coordination of mercapto group with heavy metal ions and electrostatic interactions, they were used to adsorb and concentrate heavy metal ions from aqueous solutions. They can be easily regenerated and the adsorption abilities keep almost unchanged after several cycles of regeneration. The adsorbed heavy metal ions can be recovered. Therefore, the nano-sized spherical polyelectrolyte thiol brushes are ideal candidates for selective remove heavy metal ions from wastewater.