Initial Polyvinyl Alcohol Concentration Research Articles

High-efficiency and energy-saving alternating pulse current electrocoagulation to remove polyvinyl alcohol in wastewater.

Conventional direct current electrocoagulation (DC-EC) has disadvantages such as easy passivation of electrodes, high energy consumption, and large sludge production, which limit its use in polyvinyl alcohol (PVA) wastewater. Therefore, alternating pulse current electrocoagulation (APC-EC) has been developed to overcome these problems. In this study, the influencing factors and energy consumption of PVA treatment by APC-EC and DC-EC were explored, and the best operating conditions of APC-EC were obtained via the response surface method (RSM). The best process conditions for APC-EC were determined to be the electrode type of Fe/Fe, current density of 1.0 mA cm−2, initial pH of 7, electrode distance of 2.0 cm, supporting electrolyte of 0.08 mol L−1 NaCl, initial PVA concentration of 150 mg L−1, duty cycle of 30%, and frequency of 500 Hz. In addition, the floc properties of APC-EC and DC-EC were compared to explore the basic mechanism for the removal of PVA. Adsorption and co-precipitation with hydroxide iron complexes are the main methods for removing PVA from wastewater in the APC-EC process. Compared with DC-EC, the application of APC-EC can reduce electrode passivation and production of sludge and operating costs, and improve electrode stability and PVA removal efficiency. This study provides a new strategy and method for the PVA removal from wastewater by APC-EC with low cost and high efficiency, showing broad prospect for the applications of the APC-EC in removing PVA.

The experimental study of polyvinyl alcohol (PVA) textile material degradation by ozone oxidation process

Polyvinyl alcohol (PVA), a water-soluble polymer, is widely used in the disposable textile industry and, in particular, in the manufacture of one-off work clothes that cannot be effectively treated by biological processes. The present study investigated the effect of the initial PVA concentration, reaction temperature, ozone penetration rate and initial pH value on the degradation rate of PVA. Additionally, the PVA degradation reaction mechanism was preliminarily explored. Initially, we identified the optional operative conditions: an initial PVA concentration of 20 g/L, an aqueous solution temperatureof 20 °C, an ozone penetration rate of 18 g/h and an initial pH value of 9. Subsequently we demonstrated that the PVA concentration of sample could decrease from 20 g/L to 0.286 mg/L with a degradation rate of PVA of almost 100%. Furthermore, in absence of ozone, almost no PVA polymer degradation was achieved. This study also proved that the feeding strategy of ozone could have a significant impact on the degradation of PVA molecules in the ozone oxidation process. We, therefore, provided new insights into the degradation process of PVA in aqueous solution.

Degradation and kinetic modeling of polyvinyl alcohol in aqueous solutions by a H2O2/Mn(II) system

This paper is about the degradation of polyvinyl alcohol (PVA) in aqueous solutions using a H2O2/Mn(II) system. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were applied to analyze the degradation products of PVA, and the results revealed that the backbone chain of PVA could be effectively broken and oxidized. Several unsaturated degradation products, including carboxylic acids, ketones, aldehydes, olefins, and alkynes were also detected and identified by gas chromatography-mass spectrometry (GC-MS), which indicated that higher treatment temperatures would considerably promote the generation of lower molecular weight degradation products. According to the work presented in this paper, the degradation efficiency of PVA increased from 55 % at 60 oC to 99 % at 90 oC after treatment when the initial PVA concentration was 5 %, at pH=3 with a H2O2 and Mn(II) dose of 100 ml/l and 0.6 mol/l, respectively. In addition, kinetic modeling indicated that the experimental results were best fitted by the Page-modified model with an activation energy of 48.78 kJ/mol.

Degradation of polyvinyl alcohol in textile waste water by Microbacterium barkeri KCCM 10507 and Paenibacillus amylolyticus KCCM 10508

Microbacterium barkeri KCCM 10507 and Paenibacillus amylolyticus KCCM 10508 were isolated and identified for the degradation of polyvinyl alcohol (PVA) contained in textile waste water. Kinetic parameters such as growth rate and substrate utilization rate were determined using a pure culture of two isolated strains. The degradation rate by a mixed culture of two isolated strains was higher than that by single strain only. Also, the effect of polymerization degree on biodegradation was negligible, but initial PVA concentration was very sensitive to biodegradation. Forty-two per cent of PVA and 55% of chemical oxygen demand in textile waste water were removed by a mixed culture of two isolated strains after 5 days.

Degradation of polyvinyl alcohol in aqueous solutions using UV/oxidant process

This study evaluates the effectiveness of the UV/S2O82− and UV/H2O2 processes in degrading polyvinyl alcohol (PVA) in aqueous solutions. The effects of pH, oxidant dosage, and initial PVA concentration on the efficiency of degradation of PVA were examined. Under acidic conditions, the efficiencies of degradation of PVA by the UV/S2O82− and UV/H2O2 processes exceeded those under alkaline conditions. The efficiencies of degradation of PVA by the UV/S2O82− and UV/H2O2 processes increased with oxidant dosage, but fell as the initial PVA concentration was increased. In the UV/S2O82− process, adding salts (Na2SO4, NaNO3, and NaCl) reduced the efficiency and rate of degradation of PVA. However, in the UV/H2O2 process, adding Na2SO4 and NaNO3 did not influence the degradation of PVA, whereas adding NaCl weakened the degradation of PVA to a greater extent than in the UV/S2O82− process. At pH 3 with an oxidant dosage of 0.25mM and an initial PVA concentration of 20mg/L, the degradation efficiencies of the UV/S2O82− and UV/H2O2 processes, as measured after 5min, were 100 and 58%, respectively. The corresponding observed degradation rate constants of the UV/S2O82− and UV/H2O2 processes were 1.5509 and 0.2052min−1, respectively. This result is attributable to the fact that SO4− was better able to degrade PVA than was OH. Therefore, the UV/S2O82− process was more effective than the UV/H2O2 process in degrading PVA.

Removal of polyvinyl alcohol from aqueous solutions using P-25 TiO2 and ZnO photocataysts: A comparative study

Abstract This investigation evaluates the effectiveness of P-25 TiO2 and ZnO in removing polyvinyl alcohol (PVA) from aqueous solutions. The effects of pH, photocatalyst dosage, initial PVA concentration, and UV wavelength on the removal efficiency of PVA were studied. Under acidic conditions, the removal efficiency of PVA using P-25 TiO2 exceeded that under alkaline conditions. However, the removal efficiency of PVA using ZnO under alkaline conditions exceeded that under acidic conditions. Additionally, the removal efficiency of PVA increased with photocatalyst dosage, but declined as the initial PVA concentration increased. The UV wavelength slightly affected the removal efficiency of PVA using P-25 TiO2, but dramatically affected that using ZnO. At UV-254 nm, pH 9, a photocatalyst dosage of 0.12 g/L, and an initial PVA concentration of 20 mg/L, the removal efficiencies of PVA using P-25 TiO2 and ZnO were 54% and 74%, respectively. Therefore, at UV-254 nm and pH 9, ZnO was more effective than P-25 TiO2.

Performance of UV/S2O82− process in degrading polyvinyl alcohol in aqueous solutions

Abstract This study evaluates the performance of UV/S 2 O 8 2− process in degrading polyvinyl alcohol (PVA) in aqueous solutions. The effects of pH, Na 2 S 2 O 8 dose, initial PVA concentration, and addition of inorganic anions on the degradation efficiency of PVA were determined. The degradation efficiency of PVA followed the order pH 3 > pH 7 > pH 11. Additionally, higher Na 2 S 2 O 8 dose and lower initial PVA concentration were associated with high degradation efficiency of PVA. Moreover, adding Cl − and NO 3 − reduced the degradation efficiency of PVA. Radical scavenging tests adopted to identify predominant radicals reveal that SO 4 − was the predominant radical at pH 3, but OH was the predominant radical at pH 11. At pH 3, an Na 2 S 2 O 8 dose of 1.00 mM, an initial PVA concentration of 20 mg/L, and a temperature of 25 °C, the degradation efficiency of PVA in the absence of inorganic anions was 97% with the observed degradation rate coefficient of 0.3785 min −1 , as measured after 10 min. Comparison with heat/S 2 O 8 2− process reveals that UV/S 2 O 8 2− process can enhance the degradation of PVA at ambient temperature, suggesting that UV/S 2 O 8 2− process would be alternative to degrade PVA in aqueous solutions.

Improvement of biodegradability of PVA-containing wastewater by ionizing radiation pretreatment

Polyvinyl alcohol (PVA) has been widely used as sizing agents in textile and manufacturing industry, and it is a refractory compound with low biodegradability. The objective of this paper was to treat the PVA-containing wastewater using gamma irradiation as a pretreatment strategy to improve its biodegradability and to determine the roles of different kinds of radical species played during pretreatment. Gamma radiation was carried out in a (60)Cobalt source station, PVA concentration was analyzed by using a visible spectrophotometer and specific oxygen uptake rate (SOUR, milligram of O(2) per gram of mixed liquor volatile suspended solids (MLVSS) per hour) was measured by a microrespirometer. The results showed that the biodegradability of PVA-containing wastewater with low initial concentration (e.g., 327.8 mg/l) could be improved greatly with increasing irradiation dose. However, PVA gel formation was observed at higher initial PVA concentration (e.g., 3,341.6 mg/l) and higher irradiation dose, which inhibited PVA degradation by aerobic microorganisms. However, the formed gel could be separated by microfiltration, which led to more than 90% total organic carbon (TOC) removal. Ionizing radiation could be used as a pretreatment technology for PVA-containing wastewater, and its combination with biological process is feasible.

Adsorption and photocatalytic degradation of polyvinyl alcohol in aqueous solutions using P-25 TiO 2

This investigation evaluates the effectiveness of P-25 TiO 2 in removing polyvinyl alcohol (PVA) from aqueous solutions. The effects of pH, P-25 TiO 2 dosage, initial PVA concentration, and addition of oxygen and inorganic anions on the removal efficiency of PVA were studied experimentally. The results importantly indicate that lower pH, higher P-25 TiO 2 dosage, and lower initial PVA concentration were associated with high removal efficiency of PVA during 150 min of operation. The observed behavior reveals that the removal of PVA using P-25 TiO 2 was attributable to adsorption and photocatalytic degradation, and the mechanism differed greatly from that with larger TiO 2 particles. Adding oxygen increased the removal efficiency of PVA, as measured after 150 min. However, Cl − and SO 4 2− ions reduced the removal efficiency of PVA after 150 min. NO 3 − ions did not affect the removal efficiency of PVA over such a period. In the absence of inorganic anions, around 100% of PVA was removed at pH 5, with a P-25 TiO 2 dosage of 0.12 g L −1, an initial PVA concentration of 20 mg L −1, and an air flow rate of 400 mL min −1, as measured after 150 min.

Adsorption Characteristics of Polyvinyl Alcohols in Solution on Expanded Graphite

Expanded graphite (EG) adsorbent was prepared with 50 mesh graphite as raw materials, potassium permanganate as oxidant, and vitriol as intercalation compound. Three kinds of polyvinyl alcohol (PVA) with different degree of polymerization (DP) in aqueous solution were used as adsorbates. We have studied the influence of initial PVA concentration, temperature and ionic strength on adsorption capacity. Langmuir constants and Gibbs free energy change (⊿G°) were calculated according to experimental data respectively. Thermodynamic analysis indicates the equilibrium adsorbance of PVA on EG increase with the rise of SO42– concentration. Adsorption isotherms of PVA with different degree of polymerization are all types and we deduce PVA molecules lie flat on EG surface. Adsorption processes are all spontaneous. Kinetic studies show that the kinetic data can be described by pseudo second‐order kinetic model. Second‐order rate constants and the initial adsorption rate rise with the increasing of temperature and half‐adsorption time decreases with the increasing of temperature. The adsorption activation energy of each PVA is less than 20 kJ•mol−1, physical adsorption is the major mode of the overall adsorption process.

Degradation of polyvinyl-alcohol wastewater by Fenton’s reagent: Condition optimization and enhanced biodegradability

The pretreatment of refractory polyvinyl-alcohol (PVA) wastewater with low value of CODCr by Fenton’s reagent was investigated to enhance the biodegradability. The effects of operating conditions such as pH of the solution, Fe2+ dosage, H2O2 dosage, reaction time and initial PVA concentration on the removal efficiency of CODCr were discussed. It is demonstrated that the optimum value of pH for removal of CODCr is 5 and the most suitable dosages of H2O2 (2%) and FeSO4 (10 mg/L) are 5% and 8.0%, respectively. When the initial CODCr value of the PVA water is 760 mg/L, the favorable reaction time is 110 min. Under these optimum conditions, the removal ratio of CODCr is 58.6%–61.4%, and the value of biodegradability (CODB/CODCr) increases markedly from 8.9%–9.7% to 62.6%–68.3%.

Adsorption equilibrium and kinetics of polyvinyl alcohol from aqueous solution on powdered activated carbon

In this study, powdered activated carbon (PAC) was used to remove polyvinyl alcohol (PVA) from the aqueous PVA solution. The adsorption kinetics has been studied pertaining to various initial PVA concentration and PAC dosage. The rates of adsorption were found to conform to the second-order kinetics with good correlation. Boyd plot confirmed that external mass transfer was the rate-limiting step in the sorption process. The adsorption isotherm obtained resembled with H-type of isotherm, which indicated a high affinity of the solute for the sorption sites. The Freundlich model appeared to fit the isotherm data better than the Langmuir model. The thermodynamic parameters such as Δ H°, Δ S° and Δ G° were evaluated from the slope and intercept of linear plot of log K c against (1/ T) × 1000. The change in entropy (Δ S°) and heat of adsorption (Δ H°) of PAC was estimated as 1.45 kJ mol −1 K −1 and 365 kJ mol −1, respectively. The free energy of the adsorption at all temperatures was negative indicating a spontaneous process. The maximum PVA removal of 92% was obtained at a pH of 6.3 and contact time of 30 min for an adsorbent dose of 5 g/L.

Radiation-induced degradation of polyvinyl alcohol in aqueous solutions

The degradation of polyvinyl alcohol (PVA) by γ-ray irradiation was investigated. Degradation efficiency of PVA was influenced by several factors, such as initial PVA concentration, dose rate, pH, and the addition of H 2O 2. The degradation kinetics depended on initial PVA concentration and dose rate. At a relatively lower PVA concentration, e.g., 180 mg/L, and a higher dose rate, e.g., 55.7 Gy/min, the degradation followed pseudo-first-order kinetics. On the contrary, at a higher PVA concentration, e.g., 500 mg/L, but a lower dose rate, e.g., 12.1 Gy/min, a pseudo-zero-order reaction occurred. The removal of PVA was more effective under acidic or alkaline conditions than that under neutral conditions. At a certain dose rate there was an optimal dosage of H 2O 2 to facilitate the degradation of PVA. For instance, at a dose rate of 17.2 Gy/min, the optimal H 2O 2 dosage was found to be about 2.5 mmol/L. Radical scavenging experiments, total organic carbon determination, and FTIR analysis on the degradation products demonstrated that PVA radiolysis was initiated by OH and H , leading to chain scission and formation of ketones/enols. Ultimately, complete mineralization of PVA was achieved.