Degradation Of Polyvinyl Alcohol Research Articles

The self-designed reactor to achieve efficient degradation of polyvinyl alcohol under high-pressure and high-temperature conditions

ABSTRACT A huge amount of polyvinyl alcohol (PVA) fabric is abandoned from nuclear power plants every year, the traditional treatment process will occupy land resources and pollute the environment; therefore, a lot of research has been carried out on the chemical treatment of PVA fabric. Herein, the performance of degradation of polyvinyl alcohol under high-pressure and high-temperature conditions is investigated. The effects of the initial pH value, reaction temperature, molar ratio of H2O2/Fe2+, and H2O2 dosage on PVA degradation were evaluated. In the tested ranges in this work, the degradation of PVA fabric via high-pressure and high-temperature method was optimum at the initial pH value of 4, reaction temperature of 300℃, molar ratio of H2O2/Fe2+ as 10, and H2O2 dosage of 13 g/L. The PVA removal rate and TOC removal rate were 99.99% and 97.36%, respectively. Meanwhile, the high-pressure and high-temperature methods also had a great effect on the removal of Rhodamine-B and Reactive Red X-3B, the removal rates of Rhodamine-B and Reactive Red X-3B were 99.83% and 99.76%, respectively. The reaction mechanism of high-pressure and high-temperature methods was also discussed in this study.

Promotion effect of foam formation on the degradation of polyvinyl alcohol by ozone microbubble

Polyvinyl alcohol (PVA), extensively utilized in diverse industries, presents a challenge in terms of degradation. The combination of ozone (O3) with microbubbles enhances ozone's residence time and oxidation efficiency, offering a promising avenue for effective PVA degradation. This study investigated PVA degradation using ozone microbubble (MB/O3) and oxygen microbubble (MB/O2). Bubbles evolving into remarkably resistant foam was observed for the first time. PVA removal via MB/O3 and MB/O2 followed a first-order kinetic model, exhibiting removal rates of 98.58 % and 48.68 %, respectively, within the initial 20 min. The physicochemical reaction of PVA degradation by MB/O3 and the physical removal reaction by MB/O2 were demonstrated. The microscale changes of bubbles and foam were captured, uncovering the phenomenon of self-pressurized dissolution of MB/O3 and the creation of larger foam structures through intact microbubbles, ultimately leading to their rupture. A comprehensive four-stage theory was proposed to explain PVA degradation by MB/O3, where physical separation, foam film degradation, and bubble coalescence within the foam play crucial roles. This theory was validated under varying pH and salt concentration conditions. Moreover, when the pH was decreased from 8.69 to 3.3, there was a 33.2 % increase in the COD removal rate. Mechanism analysis further confirmed the theory and revealed that, during PVA degradation, MB/O3 underwent stochastic cleavage, yielding small molecule remnants comprising aldehyde, carboxyl, and ester moieties. Finally, by comparison with other PVA degradation processes, the trial of MB/O3 was proven to be a straightforward and effective treatment approach for PVA degradation.

A Comparative Study among the Technology Classic Fenton and Electro-Fenton for the Degradation of Polyvinyl Alcohol in Textile Industrial Wastewater

A Comparative Study among the Technology Classic Fenton and Electro-Fenton for the Degradation of Polyvinyl Alcohol in Textile Industrial Wastewater

Degradation of polyvinyl alcohol (PVA) in neutral conditions based on copper-manganese bimetallic catalyst.

There have been many studies on the degradation of polyvinyl alcohol (PVA) by the Fenton-like method, but the narrow acid-base (pH) range, poor degradation effect, and time-consuming of the Fenton-like method limit its development. Therefore, to improve the shortcomings of the Fenton-like method, the study aimed to synthesize copper-manganese bimetal oxide loaded catalysts (MnCuO@γ-Al2O3) through the impregnation calcination method, and its potential to activate hydrogen peroxide (H2O2) for the degradation of PVA was evaluated. The X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) characterizations revealed the chemical composition, structure and morphology of the prepared MnCuO@γ-Al2O3, furthermore the synergistic mechanism was proposed. Results indicated that copper and manganese could successfully attach to γ-Al2O3 and reduce the specific surface area of γ-Al2O3, promoting the transformation of multivalent metals and the generation of oxygen vacancies. In addition, comparative experiments demonstrated that the PVA removal efficiency was significantly improved at the catalyst calcination temperature of 500 °C, reaction temperature of 70 °C, H2O2 dosage of 125 [Formula: see text], and catalyst dosage of 625 [Formula: see text]and more than 96% of PVA was removed within 20 min in neutral conditions. Lastly, four catalyst cycle degradation experiments of PVA were carried out, and the degradation effect could reach more than 96% in a certain time.

Rapid and deep photocatalytic degradation of polyvinyl alcohol by black phosphorus quantum dot sensitized g-C3N4

To address the pollution caused by polyvinyl alcohol (PVA) waste, a composite photocatalyst is developed by sensitizing g-C3N4 with black phosphorus quantum dots (BPQDs) using a simple mechanical stirring method. Both g-C3N4 and BPQDs are inorganic nonmetallic semiconductors with well-matched band positions, facilitating efficient photoinduced charge transfer. The periodic table’s adjacent relationship between C, N and P elements allows easy formation of P-N or P-C bonds by replacing C or N atoms with P atoms. The resulting composite shows uniform decoration of two-dimensional layered g-C3N4 with BPQDs with an average size of 2.2 nm. Under solar light simulator irradiation for 20 min, the composite photocatalyst exhibits significantly enhanced photocatalytic activity, with PVA degradation efficiency increasing from 27.1% (pure g-C3N4) to 85.9%. Experimental results and density functional theoretical calculations suggest the formation of a Z-scheme route at the g-C3N4/BPQDs interface. This facilitates photoinduced electron transfer from g-C3N4 to BPQDs, leading to improved carrier production and separation, reduced charge-transfer resistance, and accelerated PVA degradation. The proposed composite photocatalyst holds promise for addressing PVA pollution and improving environmental sustainability.

Thermal Behavior and Kinetic of Degradation of PVA and PVA/CS/AL Blend

Studying thermal behavior, especially regarding the kinetics of the degradation of materials has attracted attention in this recent years because it can provide information about the stability of materials in various conditions and how the mechanism of material degradation. In this research, the thermal behavior and kinetics of thermal degradation of polyvinyl alcohol (PVA) and polyvinyl alcohol (PVA)/cassava starch (CS)/alkaline lignin (AL) with glycerol as a plasticizer were investigated and compared by the thermogravimetric analyzer. The test was carried out for samples under non-isothermal conditions in nitrogen at a single heating rate of 10 °C/min. The activation energies were calculated using Coats-Redfern, Broido, and Horowitz-Metzger methods. The results showed that PVA/0 and PVA/CS/AL had four decomposition steps with the main degradation of PVA/0 and PVA/CS/AL in the second and third decomposition steps. The first degradation of PVA/0 and PVA/CS/AL occurred at 125 °C - 270 °C with a decomposed mass of 35.94%, and 135 °C – 250 °C with a decomposed mass of 31.84%, respectively. The second degradation of PVA/0 and PVA/CS/AL was at 270 °C - 385 °C with a decomposed mass of 40.33% and 250 °C – 395 °C with a decomposed mass of 38.62%. The values of activation energies using Coats-Redfern, Broido, and Horowitz Metger methods of PVA/0 were 57.08 KJ/mol, 64.82 KJ/mol, and 70.57 KJ/mol, respectively. The values of activation energies using Coats-Redfern, Broido, and Horowitz Metger methods of PVA/CS/AL were 74.49 KJ/mol, 82.17 KJ/mol, and 95.65 KJ/mol, respectively. The lower activation energy indicates that degradation reactions occur more easily. PVA/CS/AL has slightly better thermal stability than PVA/0.

Performance of alkali and Cu-modified ZSM-5 during catalytic ozonation of polyvinyl alcohol in aqueous solution.

A novel hierarchical Cu/ZSM-5 was prepared over alkaline treatment and incipient wet impregnation method for the catalytic ozonation of polyvinyl alcohol (PVA). Under the optimum preparation conditions, hierarchical Cu/ZSM-5 exhibited an excellent mineralization performance during the PVA degradation process, and the removal rate of TOC after 60min of reaction was 47.86%, much higher than that of ozonation alone (5.40%). Its high catalytic activity could attribute to the large pore volume (0.27 cm3/g) and pore size (6.51nm) which are beneficial for the distribution of loaded copper and adsorption performance for PVA. Compared to ·OH, 1O2 (2.66 times in 10min) contributed more to the removal of PVA. The degradation of PVA was a combined process of direct ozone oxidation, catalytic ozonation and adsorption. With its high catalytic performance and stability, hierarchical Cu/ZSM-5 has a very broad application prospect in the process of catalytic ozonation of refractory pollutants.

Visible-light photocatalytic degradation of water-soluble polyvinyl alcohol in aqueous solution by Cu2O@TiO2: Optimization of conditions, mechanisms and toxicity analysis

Polyvinyl alcohol (PVA), a water-soluble synthetic polymer, is one of the most prevalent non-native polyvinyl alcohols found in the environment. Due to its inherent invisibility, its potential for causing severe environmental pollution is often underestimated. To achieve efficient degradation of PVA in wastewater, a Cu2O@TiO2 composite was synthesized through the modification of titanium dioxide with cuprous oxide, and its photocatalytic degradation of PVA was investigated. The Cu2O@TiO2 composite, supported by titanium dioxide, facilitated photocarrier separation and demonstrated high photocatalytic efficiency. Under alkaline conditions, the composite exhibited a 98% degradation efficiency for PVA solutions and a 58.7% PVA mineralization efficiency. Radical capture experiments and electron paramagnetic resonance (EPR) analyses revealed that superoxide radicals primarily drive the degradation process within the reaction system. Throughout the degradation process, PVA macromolecules are broken down into smaller molecules, including ethanol, and compounds containing aldehyde, ketone, and carboxylic acid functional groups. Although the intermediate products exhibit reduced toxicity compared to PVA, they still pose certain toxic hazards. Consequently, further research is necessary to minimize the environmental impact of these degradation products.

Comparison of Medium-Pressure UV/Peracetic Acid to Remove Three Typical Refractory Contaminants of Textile Wastewater

In this work, the performance of medium-pressure UV/peracetic acid (MPUV/PAA/H2O2) was explored on removing reactive black 5 (RB5), aniline (ANL), and polyvinyl alcohol (PVA), three typical refractory contaminants in printing and dyeing wastewater, compared with MPUV/H2O2. MPUV/PAA/H2O2 showed 75.0, 44.9, and 57.7% removals of RB5, ANL, and PVA, respectively, within 5 min. The removal of RB5 increased from 68.98 to 91.2%, with pH increasing from 6 to 9, while the removals of ANL and PVA were much less pH-dependent. Quenching experiment results indicated that UV photolysis and radical (i.e., •OH and R-C•) oxidation contributed to RB5 removal, while PAA showed high activity in the oxidation of ANL. For PVA, •OH oxidation and UV photolysis were likely the main mechanisms. The coexisting natural organic matter had a negative effect on the degradation of RB5 and PVA. In addition, MPUV/PAA/H2O2 could effectively degrade those pollutants without increasing the toxicity. This work provides a theoretical reference for the utilization of MPUV/PAA/H2O2 in removing structurally diverse refractory contaminants from printing and dyeing wastewater.

Effect of additives on degradation of poly vinyl alcohol (PVA) using ultrasound and microwave irradiation

Abstract The degradation of polyvinyl alcohol (PVA) has been investigated using ultrasonic (US) as well as microwave (MW) irradiation techniques with the approach of process intensification based on different additives, such as Titanium Dioxide (TiO2), Sodium Lauryl Sulphate (SLS), Zinc Oxide (ZnO) and air. The effects of sonication time, initial polymer concentration, and temperature on the extent of reduction in viscosity have been thoroughly investigated using US as well as MW irradiation approaches. Basically, the degradation process has been optimized by utilizing two different ultrasonic reactors in a combined approach of ultrasonic horn and bath. The maximum extent of degradation of PVA was found to be 69.33% using MW irradiation with a required energy of 0.321 g/JL, and 62.47% using US horn with a required energy of 0.054 g/JL when operated at 0.1 g/L of TiO2 catalyst. The combination of US horn and US bath results in same degradation as 0.1 g/L of TiO2 catalyst with US horn. It has also been observed that the maximum degradation of PVA was obtained with a minimum treatment time of 3 min using MW irradiation, whereas the US horn required 40 min. Moreover, a lower extent of PVA degradation was obtained when additives were used, such as surfactants (SLS) and air. As a result, it can be inferred that the MW-assisted approach in the presence of process-intensifying additives/catalysts is the best approach for the degradation of PVA with a minimum energy consumption.

Synergistic adsorption and oxidative degradation of polyvinyl alcohol by acidified OMS-2: Catalytic mechanism, degradation pathway and toxicity evaluation

The present work introduced the use of acidified rod-like manganese dioxide (H-OMS-2) as effective peroxymonosulfate (PMS) activator and adsorbent for the removal of polyvinyl alcohol (PVA). The adsorption efficiency for PVA solution (80 mg/L) was 78 % after 60 min when H-OMS-2 (0.6 g/L) was used as adsorbent and the maximum adsorption capacity was 25.5 mg/g. After the addition of PMS (7 mM), PVA was entirely degraded within 40 min after adsorption/desorption equilibrium, and 64 % mineralization rate was reached after 5 h via the synergistic adsorption and oxidation process. The apparent activation energy (Ea) of H-OMS-2/PMS system was 11.14 kJ/mol that was lower than the value in OMS-2/PMS system (24.87 kJ/mol). And, H-OMS-2 could be recycled for 4 times with 90 % of degradation rate at 40 min and 56 % of mineralization rate after 24 h. Quenching test and electron paramagnetic resonance (EPR) results demonstrated that 1O2 was the primary reactive oxygen species rather than ·OH, SO4̇- and O2̇-. In addition, non-radical pathway via the direct electron transfer existed. The complex between Mn3+ and PMS (electron acceptor) acted as main active species to oxidize adsorbed PVA (electron donor). The characterization and degradation performance of catalyst indicated that abundant Lewis- and Brønsted-acid sites on H-OMS-2 are beneficial to CC cleavage of PVA, along with the void-confinement effects of H-OMS-2 due to its highly structured mesoporous pore size, which can result in the promotion of the degradation. Finally, study on the degradation pathway of PVA along with the aquatic toxicity experiment via zebrafish model system indicated that intermediates containing carbonyl groups are harmful for the survival and development of zebrafish.

Activation of peroxydisulfate by Ce-doped Cu-Fe@γ-Al2O3 microspheres for polyvinyl alcohol, Reactive Red X-3B, and Rhodamine-B degradation

Advanced oxidation processes based on copper-iron bimetallic activated peroxydisulfate (PDS) can degrade pollutants, but the catalytic activation of PDS by copper-iron bimetallic catalysts can be further improved. In this work, Ce-doped Cu-Fe@γ-Al2O3 microspheres were fabricated and used to degrade polyvinyl alcohol (PVA). Contrast experiments showed that the Ce-doped Cu-Fe@γ-Al2O3/PDS system degraded 100 % of PVA after 180 s treatment at pH 7, a Ce(NO3)4·6H2O dosage of 15 %, a catalyst dosage of 1.25 g/L, a reaction temperature of 60 °C, and a PDS dosage of 2 g/L. Experiments showed that adding Ce atoms enhanced the stability and reusability of the catalyst containing copper and iron. In addition, the Cu-Fe@γ-Al2O3/PDS system showed degraded 99.98 % of Rhodamine-B and 99.96 % of Reactive Red X-3B dyes. EPR results showed that SO4·-, ·OH, O2·-, and 1O2 radicals were responsible for the degradation of PVA, Reactive Red X-3B, and Rhodamine-B. This study clarified the interaction mechanism between Ce, Cu, and Fe in the Cu-Fe@γ-Al2O3/PDS system. Our study provides guidance for improving the activation efficiency of PDS by Cu-Fe catalysts.

Efficient polyvinyl alcohol degradation via peroxymonosulfate activated by natural illite supported CoNi3O4 nanosheets

In this study, natural illite supported CoNi3O4 nanosheets (CN@I) were fabricated using a simple one-step coprecipitation process and tested for their ability to activate peroxymonosulfate (PMS) for polyvinyl alcohol (PVA) degradation. The probable activation mechanism of PMS by CN@I might be ascribed to the natural mineral carrier effect, numerous surface-bonded and structural hydroxyl groups, and efficient bonding with Co or Ni ions, according to density function theory (DFT) calculations. It is deduced from the results of electron paramagnetic resonance (EPR) and radical quenching tests that both the radical (•OH and SO4•-) and non-radical (1O2) pathways were engaged in the CN@I/PMS degradation of PVA. In addition, the possible degradation pathways of PVA were proposed based on the DFT calculation. The optimum operational conditions, impacts of ions and the reusability of catalyst during CN@I/PMS degradation of PVA degradation were further investigated. This work provides an interesting direction for the use of natural mineral-based catalysts to activate PMS for the treatment of PVA wastewater.

Peroxymonosulfate activated by FeOx/MnOy modified kaolinite for the degradation of polyvinyl alcohol: Catalytic performance, mechanism and DFT study

In this work, FeOx/MnOy modified kaolinite catalyst (FeMn@K) was prepared by impregnation and pyrolysis processes, and its potential to activate peroxymonosulfate (PMS) for the degradation of polyvinyl alcohol (PVA) was evaluated. The properties of the prepared catalysts were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Overall, FeMn@K has a higher specific surface area, a larger pore volume and more hydroxyl groups than the bare MnFe2O4, which led to a higher catalytic activity for PMS and a better PVA degradation efficiency. MnFe2O4 was uniformly fixed on the kaolinite surface because of Fe-O-Al bonds, which avoided the leaching of metal ions for the good reusability of FeMn@K. The presence of Mn and Fe active sites and hydroxyl groups on FeMn@K surface could efficiently promote the electron transfer, thus accelerating the redox cycles of Mnn+1/Mnn and Fe3+/Fe2+. In FeMn@K/PMS system, •OH and SO4•- played the dominant role for PVA degradation. The mechanism was elaborately elucidated through density functional theory (DFT) calculations, which may be due to natural mineral carrier effects. The degradation intermediates of PVA were identified, and two possible degradation pathways were proposed based on DFT calculations.

Ceria-promoted heterogeneous Fenton-like oxidation of polyvinyl alcohol, Rhodamine-B, and Reactive Red X-3B over Fe/Cu@γ-Al2O3 microspheres under neutral conditions

To improve the catalytic activity and stability of a copper-iron-based Fenton-like system, the element cerium was added to the Cu-Fe-based catalyst via spray drying-calcination method. Polyvinyl alcohol (PVA) was chosen as the target pollutant to evaluate the properties of the ceria-promoted Fe/Cu@γ-Al2O3 (Ce-Fe/Cu@γ-Al2O3) microspheres. The experimental results showed that the PVA removal rate reached 99.74% in the Ce-Fe/Cu@γ-Al2O3/H2O2 system. After 10 consecutive catalytic reactions, the PVA removal rate was still maintained above 96%. Comparative experimental results showed that the addition of Ce significantly improved the catalytic activity and stability of the Cu-Fe-based catalyst. In addition, this catalytic system also showed good degradation efficiency for Rhodamine-B and Reactive Red X-3B dyes, with removal rates reaching 99.97% and 99.94%, respectively. The mechanism of the synergistic effect of Cu, Fe, and Ce was established, and electron paramagnetic resonance (EPR) experiments revealed that hydroxyl (·OH), superoxide (O2·-), and singlet oxygen (1O2) radicals were involved in the catalytic degradation of PVA. This study demonstrates a novel spray drying-calcination method for the preparation of Ce-Fe/Cu@γ-Al2O3 microspheres with outstanding catalytic activity and stability in Fenton-like systems. The Ce-Fe/Cu@γ-Al2O3 catalyst prepared in this research provides a potential alternative for the efficient removal of organic pollutants in wastewater.

Efficiently Enhanced Fenton-Like Reaction via CuO@γ-Al2O3 Particles for the Catalytic Hydrogen Peroxide Degradation of Polyvinyl Alcohol, Rhodamine-B, and Reactive red X-3B over a Wide pH Range

Efficiently Enhanced Fenton-Like Reaction via CuO@γ-Al2O3 Particles for the Catalytic Hydrogen Peroxide Degradation of Polyvinyl Alcohol, Rhodamine-B, and Reactive red X-3B over a Wide pH Range

Enhanced degradation of polyvinyl alcohol over a Cu0-carbon@γ-Al2O3 composite through heterogeneous Fenton-like reactions: Preparation, mechanism, and applications

In this study, we used cotton as the source of the carbon layer and prepared Cu0-carbon@γ-Al2O3 composites by spray drying and calcination method. Cu0-carbon@γ-Al2O3 composites were prepared to degrade polyvinyl alcohol (PVA), Reactive Red X-3B, and rhodamine B. The SEM and TEM analysis reveal the Cu0 particles loaded on the carbon layers and γ-Al2O3 were the active sites for the catalytic reaction. The electron paramagnetic resonance (EPR) analysis and quenching experiments indicated the generation of·OH, 1O2, and HO2·during the catalytic reaction. The catalytic reactions maintained a high catalytic efficiency of more than 82% when the Cu0-carbon@γ-Al2O3 composites were reused 10 times. This study will promote wide applications of Cu0 as a functional material and provide new ideas for broadening the application field of cotton. Meanwhile, this study also demonstrated that Cu0-carbon@γ-Al2O3 is a promising composite material for advanced oxidation technology.

Novel hollow α-Fe2O3 nanofibers with robust performance enabled multi-functional applications

The synthetic strategies of achieving low-cost and high-performance nanofibers are of great significance in the field of catalysis and detection. In this work, a series of electrospun α-Fe2O3 nanofibers with hollow structure were prepared via combination technology of electrospinning, hydrothermal synthesis, and controlled calcination process. Especially, the influences of the crystal structure and morphology on the comprehensive properties of nanofibers have been explored in detail. The results indicated that α-Fe2O3 nanofibers could be obtained via the calcination at 600–800 °C. Rice-like α-Fe2O3 particles were observed to assemble a stable exoskeleton, supporting a robust tubular cavity. And this tubular structure turned gradually into groove-like structure as the calcination temperature increased, accompanied by tunable crystallization, specific surface area and magnetic property. Finally, combined with series of validation tests, including dye decolorization, electrochemical detection of trace cadmium ions and Fenton degradation of polyvinyl alcohol, the resultant α-Fe2O3 nanofibers have been demonstrated to show the potential application prospects.

Simple and green method for preparing copper nanoparticles supported on carbonized cotton as a heterogeneous Fenton-like catalyst

In this study, copper nanoparticles supported on carbonized cotton as a heterogeneous Fenton-like three-dimensional (3D) structure catalyst were constructed for catalytic degradation of polyvinyl alcohol (PVA), Rhodamine-B, and Reactive Red X-3B. Herein, cotton in natural fibers was used as a carbon source, which provides a new method for the preparation of catalysts supported by carbon materials. In copper@carbonized cotton nanoparticles (CCCNs), the carbon layer is produced during the calcination process, which not only enhances the conversion of Cu0 to Cu+/Cu2+, but also accelerates the electron transfer and promotes the catalytic decomposition of hydrogen peroxide (H2O2) to generate·OH radicals. In a wide pH range (3−7), the CCCNs/H2O2 system could effectively degrade PVA, and the removal rates of PVA and TOC were found to be 99.5% and 98.68%, respectively. The optimized experimental conditions are as follows: pH, 7; mass ratio of Cu(OH)2CO3 to cotton, 10:4; catalyst dosage, 2.6 g L−1; reaction temperature, 65 °C; H2O2 dosage, 0.16 g mL−1, and without adjusting pH. In addition to the high catalytic activity, CCCNs exhibited good stability and reusability due to the strong 3D carbon layer. The CCCN composite material has been proven to be ideal catalyst to enhance the removal rate of the heterogeneous Fenton-like reaction system in removing organic pollutants present in wastewater.

Enhanced Degradation of Polyvinyl Alcohol Over a Cu0-Carbon@Γ-Al2o3composite Through Heterogeneous Fenton-Like Reactions: Preparation, Mechanism, and Applications

Enhanced Degradation of Polyvinyl Alcohol Over a Cu0-Carbon@Γ-Al2o3composite Through Heterogeneous Fenton-Like Reactions: Preparation, Mechanism, and Applications