Gram-scale Synthesis Of Monodisperse Sulfonated Polystyrene Spheres For Rapid And Efficient Sequestration Of Heavy Metal Ions

Being one of low-cost and abundant polymers,polystyrene?PS?has been extensively used in medicine,biology,food,environmental protection,water treatment,aerospace and other fields because of unique properties.In this thesis,styrene was used as a raw material to prepare PS microspheres and PS nanospheres via emulsion polymerization.SPS microspheres and SPS nanospheres were prepared via a simple sulfonation process.Adsorption isotherms and kinetics of heavy metal adsorption over SPS microspheres were investigated.The desorption,regeneration and cyclic adsorption performance of SPS sorbents were also studied.The as-prepared SPS nanospheres were practically applied for rapid sequestration of heavy metals in water and polypeptide solutions.The main content of this thesis is listed as follows:?1?Synthesis of SPS microspheres.Styrene,polyvinylpyrrolidone,ethanol and azobisisobutyronitrile were used as the monomer,dispersant,dispersion medium and initiator,respectively.PS microspheres were prepared by emulsion polymerization.The average particle size of PS microspheres was 1.21?m.PS microspheres were modified by sulfonation at 40^oC for 48 h.The average particle size of PS microspheres was ca.1.37?m.The degree of sulfonation was 0.53±0.01 mmol/g and the specific surface area was 1.60 m²/g.?2?Synthesis of SPS microspheres.Styrene,potassium persulfate,sodium lauryl sulfate,and sodium carbonate were used as the monomer,initiator,emulsifier,buffer,and dispersion medium,respectively.PS nanospheres were prepared by emulsion polymerization.The average particle size of the resulting PS microspheres was ca.125 nm.The sulfonation,process were conducted at room temperature for 3 h.The obtained SPS nanospheres had an average particle size of 132 nm.The degree of sulfonation was 1.16±0.02 mmol/g and the specific surface area was 14.2 m²/g.Because of a large number of sulfonic acid groups,polystyrene microspheres are highly hydrophilic?3?Adsorption Kinetics of heavy metals on SPS microspheres.The as-prepared SPS microspheres were used to sequestrate heavy metals Pb²⁺,Zn²⁺and Cu²⁺from solutions.Adsorption kinetics was well discribed by the pseudo-secondary equation while the adsorption isotherms can be fitted by the Langmuir model.The maximum adsorption capacities of Pb²⁺,Zn²⁺,and Cu²⁺over SPS microspheres were 7.5,15.2,and 13.7 mg/g,respectively.The maximum adsorption capacities of Pb²⁺,Zn²⁺,and Cu²⁺over SPS microspheres were 83.6,24.9,19.3 mg/g,respectively.?4?Study on adsorption properties of heavy metals on SPS microspheres.The adsorption performance of the as-prepared SPS microspheres was compared to thoseof activated carbon graphene,?-Fe₂O₃,?-Fe₂O₃ and macroporous ion exchange resins.The results showed that SPS microspheres possessed the best performance in term of adsorption efficiency and adsorption rate.In particular,SPS nanospheres outperformed SPS microspheres.With an intial concentration of 10 mg/L,nano-SPS microspheres could reduce Pb²⁺concentration to 6 ppb in1 min,leading to an adsorption rate of 99.83%.The Pb²⁺concentration in treated solutions is below the regular standards of drinking water in China,the United States,the European Union,and the World Health Organization.The spent SPS microspheres could be readily regenerated by acid wash and exhibited excellent cyclic performance.As a proof of concenpt,SPS nanospheres were practically employed to extract heavy metals from peptide solutions.After a single treatment,the concentrations of heavy metal ions were significantly reduced whilst that of peptides remained unchanged.