Preparation Of Porous Polyurea Materials And Its Application

Porous polyurea material with rich amine group was prepared through precipitation polymerization of toluene diisocyanate?TDI? and ethylenediamine?EDA?. The optimal polymerization time was determined; the effect of species of solvent and the mass ratio of acetone/ acetonitrile on the properties of the porous polyurea was studied. The pore structure of the polyurea was characterized by mercury intrusion and nitrogen adsorption desorption, the morphology was observed by scanning electron microscopy?SEM?, the degree of polymerization was characterized by nuclear magnetic resonance, the hydrogen bonding degree in the molecular chains was characterized by fourier transform infrared spectroscopy, the crystallinity was characterized by X-ray diffraction and the thermal stability was characterized by thermogravimetric analyzer. Results showed that 48 h of polymerization was needed for the polymerization to get full completed. The porous polyurea material prepared in acetonitrile had higher specific surface area, higher pore volume, broader pore size distribution and polymerization degree than that prepared in acetone, and the amount of primary amine groups at end of the polyurea molecules lower than that prepared in acetone. The surface area and pore volume of the porous polyurea material decreased correspondingly, and the distribution of pore size narrowed with the increase of acetone amount in the binary mixture of the two solvents. The porous polyurea prepared in acetonitrile had pores with size varying from 2 nm to 4 ?m, and the particle size was between 10 ?m and 100 ?m. Partial ordered structure was present in the porous materials, owing to the heavy presence of hydrogen bonding, formed between the urea carbonyl and the adjacent amide?-NH-?. And the porous polyurea have high thermal stability.Porous polyureas with different specific surface area and pore volume were prepared by TDI and different polyamine. In the polymerization of TDI and aliphatic diamine, specific surface area and primary amine group content of the porous material reduced with the increase of the number of carbon atoms. Owing to the presence of hydrogen bonding, partial ordered structure was present in the porous polyurea materials with prepared by TDI and aliphatic diamine or aromatic diamine. Partial ordered structure was not existent in crosslinked polyureas prepared by TDI and diethylenetriamine or triethylenetetramine?TETA?.Porous polyurea materials prepared using TDI and EDA or TETA as monomers in acetonitrile were used as adsorbent. The porous polyurea material prepared with TETA have lower specific surface area, higher pore volume, narrower pore size distribution and lower amine group content than that prepared with EDA. Polyurea resin containing carboxylic acid was obtained through aminocarboxylic acid modifying of two polyurea, and was used to adsorb heavy metal ions. The morphology of the porous adsorption materials was observed by SEM; the pore structure was characterized by N2 adsorption method and mercury intrusion porosimetry. The optimal adsorption conditions were determined by investigating the effects of pH of adsorption systems, contact time and initial metal ionic concentration on the adsorption property of porous adsorbents. The adsorption selectivity for metal ions, desorption and reusing of porous adsorbents under the optimal adsorption conditions were further studied. Results showed that the specific surface area and pore volume were decreased through carboxyl modification of amine of polyurea. Porous polyurea material and aminocarboxylic acid resin both have adsorption selectivity, and the adsorption property of Cu²⁺, Ni²⁺, Pb²⁺, Cd²⁺ and Cr³⁺ was decreased gradually. The rate of adsorption and desorption, repeated use of the aminocarboxylic acid resin for each ion are higher than porous polyurea material. The adsorption capacity of polyurea porous adsorbent TDI-EDA to Cu²⁺ and Pb²⁺ is higher than polyurea porous adsorbent TDI-TETA, which was opposite to Ni²⁺ and Cd²⁺. The adsorption capacity of the aminocarboxylic acid chelating resin TDI-EDA to metal ions possessing small ion radius such as Cu²⁺ and Ni²⁺ is higher than porous adsorbent TDI-TETA, which was just the opposite of metal ions with large ion radius such as Pb²⁺ and Cd²⁺.