High Strength And Capacity Of Polyvinyl Alcohol Ion Exchange Fiber Preparation And Application

Ion-exchange fiber is a fiber-form ion-exchange material. It has bigger specific surface area and faster rate of exchange and elution than that of ion-exchange resin. It can be applied in many kinds of forms, such as: fiber, yarn, fabric, non-woven etc., and can be applied to various processes of exchange. Ion-exchange fiber can be applied to the preparations of electronic pure water, medical water and biological agent, the purification of industrial sewage, adsorption of poisonous and mephitic gases, the carrier of catalysts, the recovery of heavy metals and rare-earth elements and so on. It is a new type ion-exchange material with promising prospects. At the same time, existing ion-exchange fibers generally have some defects, i.e. low strength and small exchange capacity etc. In this paper, we used high strength and high modulus polyvinyl alcohol fiber as the stuff, and fabricated ion-exchange fiber with high cross-linkage through treatments of benzalation and semi-carbonization so as to it can be suitable for the needs of application. We sulphonated the fiber to gain cation-exchange fiber and mercaptoethylated the fiber to gain mercapto-polyvinyl alcohol chelating fiber respectively. We throughout studied the technology of making ion-exchange fiber and the application of adsorption of heavy metal ions in wastewater. We gained the chelating fiber of high strength and high exchange capacity, and overcome the shortcoming of the incompatibility of mechanistic property and exchange capability of the former fiber, and it has high practicability. The conclusions are showed as follows:1. The optimal reactive condition of benzalation is: [CH₃CH₂OH]=392g/L, [BD]=130g/L, [ZnCl₂]=60g/L and [H₂SO₄]=73.6g/L, the bath ratio=1:50, at 65℃ for 90min, here the maximal degree of acetalization is 12.2%; The temperature of benzalation will not exceed 70 ℃, otherwise the fiber will be dissolved in the solution; The change of the concentration of ZnCl₂ has no influence on degree of acetalization.2. The treatment of semi-carbonization has heavy influence on making polyvinyl alcohol ion-exchange fiber. The temperature of semi-carbonization should be controlled at 200℃ and the period is no more than 60min at the same time, otherwise the strength of the fiber will be not enough; the exchange capability of the cation-exchange fiber are related with the period of semi-carbonization and sulfonation, when the period of semi-carbonization andsulfonation is 60min and 8h, the fiber has the maximal exchange capability.3. The optimal technology of making the mercapto-polyvinyl alcohol fiber is: 2g of the fiber that had been benzaldehyde-acetalized and semi-carbonized entered the C2H4O2S 20mL, (CH3CO)2O 18 mL, CH3COOH(36%) lOmL, H2SO4 0.2 mL and H2O 5mL for 90min, placed them in the oven at 30"C for 96h.4. The polyvinyl alcohol cation-exchange fiber has good adsorption property for Na+ in aqueous solution. Its maximal exchange capacity can reach 2.55mmol/g. No residues were left in the exchange-column when the fibers were used for several times. It can effectively avoid the repeated pollution. It was proved that this fiber had good practicability at water treatment.5. The mercapto-polyvinyl alcohol chelating fiber has good adsorptions of heavy metal ions in aqueous solution, the maximal adsorption capacities for metal ions of Cu2+, Zn2+, Pb2+ are all about lmmol/g, and it can be used timeless. This fiber is suitable for leaching the deleterious ions. The strength of this fiber is 4.04CN/dtex, the strength is close to the strength of ordinary polyvinyl alcohol fiber, and has good practicability.