Degradation Of Polyvinyl Alcohol Research Articles

Oxidative degradation of poly vinyl alcohol by the photochemically enhanced Fenton reaction

The effective degradation of polyvinyl alcohol (PVA) was achieved by the application of the photochemically enhanced Fenton reaction. This ‘Advanced Oxidation Process’ was studied in a batch reactor ( V = 0.75 1) using a mercury medium pressure light source. The accuracy of the DOC measurements in function of irradiation and reaction time was remarkably enhanced by the addition of a reduction and precipitation agent, consisting of an aqueous solution of Na 3PO 4, Na 2SO 3 and Kl. Effective oxidation was observed when employing low iron(II) concentrations of approximately 1 equivalent of iron(II) per 20 PVA-units (C 2H 4O) and a stoichiometric amount of H 2O 2 with respect to the PVA-units to be oxidized.

Enzymatic Desizing of Polyvinyl Alcohol from Cotton Fabrics

Enzymatic degradation of polyvinyl alcohol (PVA) was used for the desizing of cotton fabrics. A mixture of two different PVA-degrading enzyme activities, including PVA oxidizing, was partially purified from the culture filtrate of a PVA-degrading mixed culture by ionic exchange chromatography. Optimum conditions for PVA-degradation by using this enzyme mixture were pH 8·0 and temperatures ranging from 30°C to 55°C. Cotton fabrics sized with a PVA solution (25 g dm−3) were desized with the enzyme mixture after a 1 h treatment at 30°C and pH 8·0. In this case, similar amounts of residual PVA in fabrics were detected in comparison with the conventional desizing process which uses hot water (80°C, 30 min). Minimum amounts of residual PVA were found when the enzymatic desizing time was extended to 6 h. Also, the PVA content in the liquid waste from the enzymatic desizing carried out during 4 h was negligible with a 7·4-fold increase in the biochemical oxygen demand as compared with the initial value. © 1997 SCI.

Degradation of Polyvinyl Alcohol in Sequencing Batch Reactors

This paper presents the experimental results of degradation of polyvinyl alcohol (PVA) in sequencing batch reactors (SBR) under different operating conditions. The set up of an anaerobic mixing period in an SBR's cycle did not benefit for PVA degradation, while the introduction of nitrate (NO3-N) could slightly increase PVA removal efficiency. But the induced denitrification might lead to the formation of some intermediates which were degraded with a great difficulty during the subsequent aeration period, resulting in relatively a poorer chemical oxygen demand (COD) reduction. An anaerobic SBR seeded with anaerobic sludge could partly hydrolyze and acidify PVA into readily-degradable intermediates, which were subsequently treated through a 14-h aeration in a conventional SBR, a total PVA reduction of 91.8% could be achieved. The fill mode had no significant influence on the performance of SBRs treating PVA-containing wastewater. For making full use of the purification capability of the SBR during the fill...

The Influence of Dyes on Thermal and Thermo-Oxidative Degradation of Dyed Polymeric Fibers

Abstract The influence of reactive dyes and their deactivated forms on the thermal degradation of polyvinylalcohol (PVA) and polycaproamide (PCA) fibers was investigated. Complex thermographic analysis in air and inert atmosphere showed that fibers dyed by reactive dyes are more resistant to thermo-oxidative degradation than untreated PVA and PCA fibers. A possible mechanism of the stabilizing influence of the dyes on the thermooxidative degradation of the investigated polymers was proposed.

Photo-oxidative degradation of polyvinyl alcohol and measurement of thermally stimulated current

An investigation was made of the correlation between changes in the chemical structure of polyvinyl alcohol during photo-oxidation and a thermally stimulated current. Photo-oxidation was initiated by dehydration and greatly accelerated as a result of chain scission, which resulted from the formation of carbonyl groups of ester, aldehyde, ketone and carboxylic acid types. Two main peaks of thermally stimulated current were observed at 220 and 250 K in photo-oxidized polyvinyl alcohol. It became clear that these two peaks, resulting from depolarization of dipoles, correspond to an increase in the content of carbonyl groups and a decrease in the content of hydroxyl group, respectively.

Degradation of polyvinyl alcohol by microorganisms. III. Oxidation of secondary alcohols by polyvinyl alcohol-degrading enzyme produced by Pseudomonas O-3.

Some characteristics of polyvinyl alcohol (PVA) degrading enzyme produced by Pseudomonas O–3 which utilizes PVA as the sole carbon source were examined. The enzyme contains 1 atom iron per molecule and its solution has absorption maxima at 280, 365 and 470 nm. It produced hydrogen peroxide with the degradation of PVA. Equivalence was established between the amounts of oxygen consumed and hydrogen peroxide produced, indicating that this enzyme belongs to an oxidase but not to an oxygenase. In its substrate specificity, it oxidizes secondary alcohols such as 2-pentanol, 2-hexanol, 3-hexanol, 2-heptanol, 3-heptanol and 4-heptanol. Among PVA analogues, it does not oxidize low molecular weight analogues such as dimer and trimer but oxidizes analogues with molecular weight larger than 300.

Degradation of polyvinyl alcohol by microorganisms. II. Purification and some properties of polyvinyl alcohol-degrading enzyme produced by Pseudomonas O-3.

Purification was conducted on polyvinyl alcohol (PVA) degrading enzyme produced and secreted into the culture medium by Pseudomonas O–3 strain. The enzyme was found to separate into several fractions by ion-exchange chromatography and gel filtration. Among these fractions, a fraction adsorbed to SP-Sephadex C–50 at pH 6.0 was purified to homogeneity by polyacrylamide gel electrophoresis. Some properties of this purified enzyme were examined. Optimum pH and temperature were 9.0 and 40°C, respectively. The enzyme was stable up to 50°C and in a pH range between 5 and 11 at 5°C. The enzyme activity was inhibited by Co2+, Ni2+, EDTA, hydroxylamine and salicylaldoxime. In substrate specificity, this enzyme oxidized several kinds of modified PVA, as well as normal PVA, but did not oxidize other synthetic polymers, such as vinylon, polyacrylamide and polyvinyl acetate. The effect of oxygen on this enzyme was examined, and without oxygen, PVA was not broken down by this enzyme. The molecular weight of this enzyme ...

A spectroscopic study of the kinetics of thermal-oxidative degradation of polyvinyl butyrals (PVB)

Infrared (IR) and ultraviolet (UV) spectroscopy was used to study the kinetics of thermal-oxidative degradation of polyvinyl alcohol (PVALC) and PVB having different degrees of substitution. An increase in the butyral units in PVALC was found to reduce the length of the polyene systems formed during heat treatment. The rate of formation of the polyene systems and of carbonyls in the PVB greatly depended on the content of butyral groups and the reaction temperature. The formation of these systems can be divided into two stages characterized by different rates.

過酸化水素によるポリビニルアルコールの酸化および分裂反応

ポリビニルアルコールと過酸化水素とを, 中性水溶液中, 60℃ で反応させると, ポリビニルアルコールの分裂がおこり, 粘度が低下するとともに, カルボニル基量が増加する.ポリビニルアルコールの分裂量, 総カルボニル基量および主鎖中のカルボニル基量を測定した結果, 分裂によって生成する以外に主鎖中に相当量のカルボニル基の生成することを認めた。また主鎖中のカルボニル基の一部はβ-ジケトン構造をとって存在していることも認められた。これら主鎖中のカルボニル基は, 過酸化水素との反応に際して分裂を促進する.一方カルボキシル基も生成するが, 中性ではカルボニル基の生成に比べて少ないことを認めた。