Purification Of Polyvinylpyrrolidone(PVP)by Adsorption

Polyvinylpyrrolidone(PVP),a highly water-soluble polymer obtained by polymerization of Nvinylpyrrolidone, was purified by adsorption onto activated carbon and strong acidic ionexchange resin.Various parameters that can affect the process were studied such as effect of contact time,effect of adsorbent dosage,effect of temperature,effect of PVP concentration, effect of NVP initial concentration.Adsorbent capacities were determined by mathematical fitting of equilibrium data using the most common isotherms:Freundlich isotherm and Langmuir isotherm.Several kinetic models were applied to the process.Thermodynamic parameters:△S~0,△H~0,△G~0 and Ea were determined.The results show that the removal of monomer from the solution depends heavily on contact time that is the longer the contact time,the more NVP is removed.But this dependence is limited by equilibrium where the increase in contact time has no effect on the NVP concentration neither on the solid surface nor in the solution.The same situation has been observed when studying the effect of adsorbent dosage:at the beginning an increase in adsorbent amount leads to a considerable increase in the removal of the monomer.However,as a very large amount of adsorbent is applied,the increase in removal slows down progressively and it almost disappears at with increase of adsorbent.As temperature effect was assessed,the results of this work showed that NVP removal increases with increasing temperature,in the temperature range under investigation that is from 30 to 50℃.The effect of PVP concentration was also studied:at a constant initial concentration of NVP,the equilibrium NVP concentration increases with increase of PVP concentration up to a plateau.Initial NVP concentration has a great impact on NVP equilibrium concentration: equilibrium concentration increases with initial concentration;at low initial NVP concentration this increase is not significant and becomes greater as the initial concentration improves.Furthermore kinetic modeling revealed that the process follows pseudo-second-order kinetic model,it was found to be spontaneous and endothermic.It is also important to mention here the lowest NVP values achieved by both adsorbents:in suspension,from an initial NVP concentration of 1000ppm,activated carbon achieved 2ppm while resin achieved lppm.In column from an initial NVP concentration of 31ppm,both adsorbents achieved a concentration less than 1ppm.Results of this work are important and have a great prospect for producing pharmaceutical grade Polyvinylpyrrolidone.