Ultrasound-based treatment approaches for intrinsic viscosity reduction of polyvinyl pyrrolidone (PVP)

Abstract

The present work deals with achieving viscosity reduction in polymer solutions using ultrasound-based treatment approaches. Use of simple additives such as salts, or surfactants and introduction of air at varying flow rates as process intensifying parameters have been investigated for enhancing the degradation of polyvinyl pyrrolidone (PVP) using ultrasonic irradiation. Sonication is carried out using an ultrasonic horn at 36 kHz frequency at an optimized concentration (1%) of the polymer. The degradation behavior has been characterized in terms of the change in the viscosity of the aqueous solution of PVP. The intrinsic viscosity of the polymer has been shown to decrease to a limiting value, which is dependent on the operating conditions and use of different additives. Similar extent of viscosity reduction has been observed with 1% NaCl or 0.1% TiO2 at optimized depth of horn and 27°C, indicating the superiority of titanium dioxide as an additive. The combination of ultrasound and ultraviolet (UV) irradiation results in a significantly faster viscosity reduction as compared to the individual operations. A kinetic analysis for the degradation of PVP has also been carried out. The work provides a detailed understanding of the role of the operating parameters and additives in deciding the extent of reduction in the intrinsic viscosity of PVP solutions.

Intensification of degradation of guar gum: Comparison of approaches based on ozone, ultraviolet and ultrasonic irradiations

“…Kinetic analysis revealed that for the change in power dissipation from 8 W to 32 W, the rate constant was found to increase from 0.010 min À1 to 0.018 min À1 . Pawar et al [19] reported a similar trend for the ultraviolet induced degradation of aqueous solution of polyvinyl pyrrolidone (PVP) investigated over the power dissipation range of 5 W to 11 W and it was established that the kinetic rate constant increased from 3.1 Â10 À2 min À1 to 7.3 Â 10 À2 min À1 with an increase in the UV power dissipation from 5 W to 11 W.…”

“…In addition, after the completion of initial laboratory scale optimization studies, scale up studies have been performed to check the effectiveness of the degradation approaches at large scale operation. The extent of degradation has been quantified in terms of the change in the intrinsic viscosity of the polymer solution, which is an easy method for monitoring the rate of degradation [8,9,19,24]. Further, Fouriertransform infrared (FTIR) spectra for untreated and treated guar gum solution were also analyzed to check the possible changes in the chemical structure.…”

“…1. It has been observed that the extent of reduction in the intrinsic viscosity increases from 33.4% to 77.9% with an increase in the power dissipation of UV tube from 8 W to 32 W. Under the effect of UV irradiation, water-soluble polymer chain can rupture to yield smaller chains [19] due to the energy transfer from the incident UV irradiations resulting into formation of hydroxyl radicals which induce the brekage. It can be said that the extent of degradation is directly proportional to the quantum of hydroxyl radicals generated, which increases with an increase in the power.…”

“…The photo-degradation involves abstraction of hydrogen atom from the molecule by a radical produced from the water molecule. These radicals react with oxygen atom, forming other radicals which are responsible for chain scission in the polymers [18,19].…”

“…In the recent years, the combined methods have been applied for the degradation of water soluble polymers [8,15,16,[18][19][20] and it has been established that combined approach gives enhanced degradation. Yue and co-workers [15,16] investigated the effect of ozone in combination with ultrasonic and UV irradiations on the degradation of chitosan and reported enhanced degradation than that obtained for ozone alone.…”