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1.
A novel Fe3O4/cellulose–polyvinyl alcohol (PVA) aerogel was successfully synthesized by an eco-friendly and facile method in this work. Cellulose/PVA matrix was prepared through an environmental friendly physical cross-linking process and further in-situ decorated with Fe3O4. Series of Fe3O4 decorated aerogels were prepared and the effects of Fe3O4 nanoparticles (NPs) on the aerogels were systematic investigated. As-prepared aerogels exhibited desirable properties including nanostructure, relatively high porosity, improved mechanical and superparamagnetism. The TEM results showed that Fe3O4 NPs were integrated in the three-dimensional matrix of cellulose/PVA with a diameter of 9–12 nm. Furthermore, the mechanical strength of the aerogels was significantly enhanced after the introduction of Fe3O4 NPs. Meanwhile, the obtained Fe3O4/cellulose/PVA aerogel exhibited excellent adsorption performance toward methyl blue dye, and can be reused through fenton-like catalysts oxidative degradation of organic dye in H2O2 solution. Therefore, they will have a great potential application as eco-friendly and economical adsorbents.  相似文献   

2.
In this research Fenton reagent (Fe2+/H2O2) was investigated as oxidants to degrade poly (vinyl alcohol) (PVA). The role of nano-TiO2 photocatalyst was discussed as an additive in Fenton reagent (Fe2+/H2O2). Pt/TiO2 composites were also synthesized by photo-reaction to be used as additive in Fenton reagent. The rapid degradation of PVA was obtained when Pt/TiO2 composites served as photocatalyst. The different photocatalytic efficiency of Pt/TiO2- Fenton reagent (Fe2+/H2O2) was studied compared with TiO2- Fenton reagent (Fe2+/H2O2) during the degradation of PVA.  相似文献   

3.
This study presents a photochemical kinetics model to describe the degradation of water-soluble PVA (Polyvinyl Alcohol) polymer in a UV/H2O2 batch reactor. Under the effect of UV light, the photolysis of hydrogen peroxide into hydroxyl radicals can generate a series of polymer scission reactions. For a better understanding and analysis of the UV/H2O2 process in the cracking of the PVA macromolecules, a chemical reaction mechanism of the degradation process and a relevant photochemical kinetics model are developed to describe the disintegration of the polymer chains. Taking into account the probabilistic fragmentation of the polymer, the statistical moment approach is used to model the molar population balance of live and dead polymer chains. The model predicts the PVA molecular weight reduction, the acidity of the solution, and hydrogen peroxide residual. In addition to previously published data collected in this laboratory, a new set of experiments were conducted using a 500 mg/L PVA aqueous for different hydrogen peroxide/PVA ratios for model validation. Measurements of average molecular weights of the polymer, hydrogen peroxide concentrations and pH of the PVA solution were determinant factors in constructing a reliable photochemical model of the UV/H2O2 process. Experimental data showed a decrease in the PVA molecular weight and a buildup of the solution acidity. The experimental data also served to determine the kinetics rate constants of the PVA photochemical degradation and validate the model whose predictions are in good agreement with data. The model can provide a comprehensive understanding of the impact of the design and operational variables.  相似文献   

4.
Polyvinyl alcohol (PVA), being a dominant contributor of total organic carbon (TOC) in textile wastewater, is not easily degradable by conventional methods of wastewater treatment. This study investigates the degradation of aqueous PVA in a continuous UV/H2O2 photoreactor since the feeding strategy of hydrogen peroxide proves to have considerable effects on the process performance. Response surface methodology involving the Box–Behnken method is adopted for the experimental design to study the effects of operating parameters on the process performance. Experimental analysis shows that the TOC removal varies from 16.11 to 42.70 % along with a reduction of the PVA molecular weights from 56.7 to 95.3 %. The TOC removal is significantly lower than the molecular weight reduction due to the generation of the intermediate products during oxidation. Operating the UV/H2O2 process in a continuous mode facilitates the degradation of highly concentrated polymeric solutions using a relatively small hydrogen peroxide concentration in the feed with a small residence time ranges from 6.13 to 18.4 min.  相似文献   

5.
Linear low-density polyethylene (LLDPE) was blended with low-density polyethylene (LDPE) at a fixed ratio (80 wt LLDPE and 20 wt %LDPE) and filled with nanoparticles of SiO2 and TiO2 at a ratio up to wt 5%, so as to develop the polymeric composites suitable to preparing the agricultural micro-irrigation pipes having good environmental adaptability. These compounds were blended using calcium stearate, polyethylene wax, and titanate coupling agent as the auxiliary dispersants, and ethylene-vinyl acetate copolymer (EVA) as the toughness improver. The LLDPE/LDPE composites filled with the nanoparticles were extruded and injected to prepare the composites specimens for the performance evaluations and micro-irrigation pipe field test. The mechanical properties, thermostability, and processibility of the injected composites were investigated. The effect of heating in an oven and irradiating by ultraviolet on the mechanical properties of the composites was explored. The environmental adaptability of the micro-irrigation pipes made of the filled LLDPE/LDPE composites was evaluated making use of long-term outdoor field test in northwest China where the arid and harsh natural conditions are of great concerns. It was found that the LLDPE/LDPE blend with the LLDPE mass fraction fixed as 80% showed balanced mechanical and thermal properties and flexibility, and was suitable to be used as the basic resin matrix. The incorporation of nano-TiO2 contributed to effectively improving the resistance to heating and ultraviolet irradiation of the composites. The composite made from 91% basic resin matrix, 6% EVA, and 3% mixed nano-SiO2 and TiO2, showed balanced comprehensive properties. The micro-irrigation pipes made of this filled LLDPE/LDPE composite had good environmental adaptability and service behavior in a three-year field test and were suitable to be used in arid area.  相似文献   

6.
From the point of view of a sustainable and environment-friendly society based on the recycling of material resources, it is preferable to utilize waste gypsum as a substitute for lime, which is currently produced by the calcination of limestone. In the present work, the reductive decomposition of CaSO4 was investigated under an atmosphere of CO: 2 vol%, CO2: 30 vol%, with N2 as a carrier gas without and with the addition of SiO2, Al2O3, or Fe2O3. It was found that the decomposition temperature of CaSO4 was significantly reduced from 1673 K to 1223 K when only 5 wt% Fe2O3 was added to CaSO4. In the case of the addition of SiO2 or Al2O3 to CaSO4, the decomposition temperature was reduced from 1673 K to 1623 K. This was due to the formation of composite oxides (calcium ferrite, calcium silicate, or calcium aluminate) during the reaction of CaSO4 with the additives at a lower temperature. In addition, the formation of unfavorable product CaS was inhibited in the presence of 5 wt% Fe2O3, and this inhibition effect further increased as the addition of Fe2O3 was increased. In contrast, no significant effect on the inhibition of CaS formation was observed on the addition of SiO2 or Al2O3.  相似文献   

7.
This paper presents a study regarding the preparation of MgCr2O4 from waste tannery solution, and chromium leaching behavior is also investigated with varying amounts of sulfate, chloride and calcium. The phase transformation, crystallinity index and crystallite diameter were characterized using XRD, FT-IR and thermal analysis. A well-crystallized MgCr2O4 was successfully prepared at 1400 °C. The sintering temperature had a major impact on the formation of MgCr2O4 compared with sintering time. The MgCr2O4 phase was observed initially at 400 °C and its crystallite diameter increased with increasing temperature. The concentration of total chromium leached and Cr(VI) decreased gradually with increasing temperature. The considerable amount of Cr(VI) was found in the leachate at 300–500 °C caused by Cr(VI) intermediary products. Sulfate and chlorine could impact the transformation efficiency of chromium adversely, and chlorine has a more significant effect than sulfate. The presence of calcium disturbed the formation of MgCr2O4 and new chromium species (CaCrO4) appeared, which resulted in a sharp increase in the concentration of leached Cr(VI). Incorporating Cr(III) into the MgCr2O4 spinel for reusable products reduced its mobility significantly. This was demonstrated to be a promising strategy for the disposal of chromium containing waste resource.  相似文献   

8.
The aim of this study is to evaluate the impact of nano-SiO2 and bark flour (BF) on the natural fiber–plastic composites engineering properties made from high density polyethylene (HDPE) and beech wood flour (WF). For this purpose, WF and BF in 60 mesh size and weight ratio of (50, 0 %), (30, 20 %), (10, 40 %) and (0, 50 %) respectively were mixed with HDPE. In order to increase the interfacial adhesion between the filler and the matrix, the maleic anhydride grafted polyethylene was constantly used at 3 wt% for all formulations as a coupling agent. The nano-SiO2 particles with weight ratio of 0, 1, 2, and 4 % were also utilized to enhance the composites properties. The materials were mixed in an internal mixer (HAAKE) and then the bark and/or wood–plastic composite samples were made utilizing an injection molding machine. The physical tests including water absorption and thickness swelling, and mechanical tests including bending characteristics and un-notched impact strength were carried out on the samples based on ASTM standard. The results indicated that as the BF content increased in the composite, mechanical and physical properties were reduced, but the given properties were increased with the addition of nano-SiO2. The addition of nano-SiO2 had a negative impact on the physical properties, but when it was up to 2 %, it increased the impact strength.  相似文献   

9.
Carbon nanotubes have exceptional mechanical properties which make them very attractive for the development of composite membranes. In this research, NH3/N2 gas permeation behavior of flat sheet composite membranes was examined. The cellulose acetate-multiwalled carbon nanotubes composite membranes were synthesized using solution casting method. The morphology and dispersion of carbon nanotubes were observed through SEM. However, the composite membranes were also characterized using several analytical techniques such as X-ray diffraction analysis, tensile testing analysis, and thermal gravimetric analysis. Characterization of these membranes depicted that carboxylic group functionalized MWCNTs are extremely compatible with CA. The permeation experiments were performed with NH3 and N2 to explore the host–guest interaction of MWCNTs with chosen gases. The permeability of NH3 was found pronounced compared to N2. The NH3/N2 selectivity up to 90 was documented.  相似文献   

10.
The present study includes synthesis of two γ-Al2O3 samples from waste aluminum cans using a simple precipitation method. Precipitation was carried out using two different precipitating agents (i.e. NaOH and NH4OH). The two prepared alumina samples were characterized by means of X-ray diffraction (XRD) and N2 adsorption–desorption techniques. Surface acidity of γ-Al2O3 samples was measured by adsorption of two different probe molecules (i.e. pyridine and dimethyl pyridine) followed by desorption measurements using thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Catalytic activity of the two prepared alumina samples towards the dehydration of methanol (to dimethyl ether) was studied in a fixed bed reactor at 300 °C. For comparison reasons, commercial γ-Al2O3 sample was, also, tested for the same catalytic reaction under the same conditions. Results showed that the alumina sample prepared using NaOH as a precipitating agent exhibited a better catalytic activity and stability compared with that prepared using NH4OH and showed a similar activity as the commercial γ-Al2O3 sample.  相似文献   

11.
Styrene (St) was graft-polymerized onto the surfaces of micro-sized silica gel particles, and the surface-grafted composite particles PSt/SiO2 were obtained. With the surface-grafted composite particles PSt/SiO2 as a starting material, water-insoluble antibacterial materials with quaternary ‘onium’ salt-type were synthesized via two polymer reaction steps. The grafted polystyrene was first chloromethylated, resulting in grafted particles CMPS/SiO2, and then quaterisation (QN) and quaternary phosphonium reaction (QP) were conducted with triethylamine, tri-n-butylamine and triphenyl phosphine as reagents, respectively. Two kinds of water-insoluble antibacterial materials, QN-PSt/SiO2 and QP-PSt/SiO2 were prepared. Their antibacterial property was mainly investigated by using Escherichia coli (E. coli) as a model bacterium and by adopting colony count method. The relationship between the chemical structure of the antibacterial group and antimicrobial activity for the water-insoluble antibacterial materials was studied in detail, and their antibacterial mechanism was investigated by TTC-dehydrogenase activity determination and extracellular DNA and RNA measurement methods. The experimental results show that QN-PSt/SiO2 and QP-PSt/SiO2 possess strong antibacterial activity. The main factors affecting the antibacterial ability of the water-insoluble materials are the chemical structure of the antibacterial groups, the bound density of the antibacterial groups on the surface of the water-insoluble antibacterial materials as well as the pH value of the medium. QP-PSt/SiO2 has stronger antibacterial activity than QN-PSt/SiO2; the QN-PSt/SiO2 prepared with tri-n-butylamine has stronger antibacterial activity than that prepared with triethylamine; the water-insoluble material with higher bound density of the antibacterial groups has stronger antibacterial ability; as the pH value of the medium is over the isoelectric point of E. coli, the antibacterial ability is strengthened with the increase of pH value.  相似文献   

12.
A poly(lactic acid) (PLA)/polyamide 11 (PA11)/SiO2 composite was mixed from PLA, PA11, and nanosilica particles through twin-screw extrusion. The PLA/PA11/SiO2 composite was evaluated with tensile and Izod impact tests, light transmission and haze measurement, and isothermal and nonisothermal crystallization behavior determinations. The PLA/PA11/SiO2 (97.0/3.0) composite had approximately 10.8% less ultimate tensile strength than neat PLA, but it had greater ductility and approximately ninefold greater elongation at break. A dimple morphology was observed on the fractural surface of the PLA/PA11/SiO2 composite, indicating that the incorporation of PA11 and nanosilica particles increased the ductility of the PLA matrix. PLA with less than 3 wt% of PA11 and 0.5 phr of nanosilica particles had an Izod impact strength of 8.72 kJ/m2. PA11 and nanosilica particles effectively toughened this PLA polymer; they accelerated both isothermal and nonisothermal crystallization rates and increased the crystallinities of the resulting composites under isothermal and nonisothermal crystallization processes.  相似文献   

13.
Activated carbons were prepared from cattle manure compost (CMC) by ZnCl2 activation with various ZnCl2/CMC mass ratios. Based on the N2 adsorption-desorption isotherms, mathematical models including the Dubinin-Radushkevich (DR) equation, the αs plot, and the Horvath-Kawazoe method were used to analyze the pore structural characteristics of the prepared activated carbons. It was found that for carbons possessing both micro-and mesopores, the DR method provided a more accurate estimation than the αs method for the extent of microporosity. The effect of the ZnCl2 impregnation ratio on the pore structure was discussed using the DR method. The results revealed that pore evolution involved three distinct regions with increases in the amount of impregnated ZnCl2: raising the ZnCl2/CMC mass ratio from 0.00 to 0.50 resulted in a 19-fold increase in micropore volume (Vme D) but caused no change in the mesopore volume (Vme D); increasing the ZnCl2/CMC mass ratio from 0.50 to 1.00 led to an increment in Vmi D of about 50% and in Vme D of 170%; while raising the ratio from 1.50 to 2.50 caused a slight decrease in Vmi D but a 200% increment in the value of Vme D.  相似文献   

14.
The common biodegradable properties of polymer make them an excellent pair for blending, and the water solubility of polyvinyl alcohol (PVA) makes it easy to mix evenly with the starch. In this study, PVAs with different molecular weights were blended with various compositions of cross-linked starch (CLS) to explore the effects of molecular weight of PVA on the biodegradable characteristics of the PVA/starch blends. Comparing the biodegradability of all the various PVA/starch blends, a PVA was singled out from the PVA/starch blends of higher biodegradability. Further, the chosen PVA was then blended with the acid-modified starch (AMS) to systematically investigate the effects of the modified processing of starch on the biodegradable characteristics of the PVA/starch blends. Differential scanning calorimetry (DSC) analysis of PVA and PVA/starch specimens reveal that the Tm values of PVA/starch specimens reduce gradually as their CLS or AMS contents increase. After the CLS is blended in PVAs of different molecular weights, the tensile strength (??f) and elongation at break (??f) values of (P100S0)G20M1 specimen increase and simultaneously reduce, respectively, as their molecular weights of PVA increase from about 80,000 (PVABF-17) to 120,000 (PVABF-26). The ??f and ??f values of the PVA/modified-starch blends decrease with an increase in the modified starch contents. The ??f values of the PVA/AMS specimens decrease with an increase in the concentrations of hydrochloric acid. Comparing the ??f values of the PVA/CLS specimens with those of the PVA/AMS specimens, the ??f values of the PVA/CLS specimens are better than those of the PVA/AMS specimens. On the contrary, the ??f values of the PVA/AMS specimens are better than those of the PVA/CLS specimens. According to the biodegradability of all the PVA/starch blends, PVA with higher molecular weights displays higher biodegradability. The biodegradability of the PVA/modified-starch blends increase as the modified starch contents of the PVA/modified-starch blends increase. As evidenced by the results of the biodegradability test, the biodegradability of the PVA/modified-starch blends, therein PVA is blended with 1N AMS, shows better biodegradability. The result of bio-reaction kinetics experiment can evaluate the decomposition tendency of the PVA/starch blends up to any biodegradable rate under ambient environment. Using the kinetic model of the first order reaction, it is estimated that 16.20?years and 12.47?years will be needed for the PVABF-17/starch blends, containing 20 and 40% of CLS respectively, to be degraded up to 70% under ambient environment. In addition, it is 1.68?years for the PVABF-26 blends with the 40% 2N AMS under decomposition environment while it is 1.94?years for the 40% 1N AMS. Overall, the decomposition potential of PVA/AMS specimens is better than PVA/CLS specimens. Furthermore, the 1N(26P60AS40)100G20M1 specimen is coincidence the biodegradable material criteria of Environmental Protection Administration (EPA) of Taiwan.  相似文献   

15.
The aim of this paper is to study the influence of the K2S2O8 content on the properties of poly (vinyl alcohol, (PVA). Firstly, PVA was dissolved in distilled water by heating by heating at 70 °C and then K2S2O8 was added in PVA solution under stirrer. The viscosity of PVA solution in the presence of K2S2O8 was analyzed by Brookfield Viscometers. The effects of K2S2O8 contents, PVA solution, temperature and reaction time on the viscosity of PVA solution were investigated. This was confirmed by Brookfield Viscometers. It is clear that the viscosity of PVA solution in the presence of K2S2O8 increased as function of reaction time and PVA content in solution. Rate of modified PVA was proportional to K2S2O8 contents and temperature and its activation energy was 16 kJ/mol. The structure of PVA in the presence of K2S2O8 changed from original PVA confirmed by ATR-FTIR and solid state NMR. In addition, the thermal properties of PVA containing K2S2O8 were also studied by TGA.  相似文献   

16.
To control the emission of halides into the environment, an experiment on the nonthermal plasma decomposition of the halides CF4, CHF3, C2HCl3, and CHClF2 was conducted in a wire-in-tube corona reactor. It was found that the decomposition of C2HCl3 and CHClF2 was easy compared with the decomposition of CF4 and CHF3. With the addition of H2 in N2 gas, the decomposition ratio of CF4, C2HCl3, and CHClF2 increased. In contrast, the decomposition ratio of CHF3 in a hydrogen-rich atmosphere was lower than that in an N2 atmosphere. It was demonstrated that the yields of HF and/or HCl formed during halide decomposition clearly increased in the presence of H2 in N2 gas. Furthermore, in order to prevent the production of unwanted products from halide decomposition, a combination of plasma decomposition and in situ alkaline absorption was devised by coating a layer of Ca(OH)2 onto the surface of the grounding electrode. It was demonstrated that the Ca(OH)2 sorbent played an effective role as a scavenger, participating in halide decomposition by capturing reaction products such as HCl and HF, therefore resulting in increased halide decomposition.  相似文献   

17.
In this work, high-alcoholysis polyvinyl alcohol (PVA) films were fabricated by melt processing and the plasticizing effect of compound polyol plasticizers on PVA were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), rheological measurements, mechanical tests etc. Hydrogen bonding interactions occurred between PVA and plasticizer. With the increase of plasticizer, the flowability of PVA was improved and reached the maximum value at the plasticizer of 20%. Glass transition temperature (T g) and melting point (T m) decreased with the increase of plasticizer content. For the heterogeneous nucleation effect of plasticizer, new polymorph of PVA formed. The viscosity was sensitive to the shear rates. The incorporation of plasticizers into PVA resulted in the increase of elongation at break and impact strength, as well as the decrease of tensile strength.  相似文献   

18.
Despite many studies of the N2O emission, there is a lack of knowledge on the role of subsoil for N2O emission, particularly in sandy soils. To obtain insight into the entrapment, diffusion, convection and ebullition of N2O in the soil, the N2O concentration in the soil atmosphere was measured over a period of 1 year in 4 lysimeters (agricultural soil monoliths of 1 m2 × 2 m) at 30, 50, 80, 155, and 190 cm depth with altogether 86 gas probes. Additionally the N2O emission into the atmosphere was measured in 20 closed chambers at the soil surface. Concurrently the soil temperature and soil water content were recorded in order to quantify their effects on the fate of N2O in the soil. Results of the continuous measurements between January and December 2006 were: N2O concentrations were highest in the deeper soil; maximum concentration was found at a depth of 80 cm, where the water content was high and the gas transport reduced. The highest N2O concentration was recorded after ‘special events’ like snowmelt, heavy rain, fertilization, and grubbing. The combination of fertilization and heavy rain led to an increase of up to 2,700 ppb in the subsoil.  相似文献   

19.
Present study envisaged the sequential experimental design approach for the development of biodegradable Gelatin-Tapoica/polyacrylamide superabsorbent. Percentage water uptake efficacy of candidate sample was optimized using Response Surface Methodology (RSM) design under microwave irradiation. Different process variables such as potassium persulphate and ammonium persulphate (KPS:APS) ratio, pH, reaction time concentration of acrylamide and N,N-methylene-bis-acrylamide (MBA) were investigated as a function of percentage swelling using sequential experimental design. Maximum liquid efficacy of 1550% was obtained at KPS:APS?=?1.0:0.5; acrylamide?=?7.67?×?10?1 mol L?1; MBA?=?1.76?×?10?2 mol L?1; pH 10 and time?=?110 s. The 3D crosslinked network formed was characterized using Fourier Transformation Infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopic (SEM) techniques and thermal stability was ensured by Thermal gravimetric Analysis/Differential Thermal Analysis/Differential Thermal Gravimetric (TGA/DTA/DTG) studies. Superabsorbent synthesized could increase the moisture content in different type of soils and was found to enhance the water-holding capability of the soil upto 60 days in clayey, 40 days in sandy and 51 days in mixture of two soils under controlled conditions. Further, candidate polymer was investigated for the in-vitro controlled release of the KNO3 with diffusion exponent ‘n’ was found to be 0.4326 indicating Fickian type diffusion. Also, initial diffusion coefficient (DI?=?3.49?×?10?5 m2 h?1) was found to be greater than the lateral diffusion coefficient (DL?=?3.76?×?10?6 m2 h?1) indicated rapid release of KNO3 during initial hours with slow release afterwards. The ecofriendly nature of the synthesized polymer was also tested by conducting biodegradation studies and it was found to degrade upto 94% and 88.1% within 70 days with degradation rate of 1.34 and 1.26% per day using composting method and vermicomposting method respectively. So, the synthesized candidate polymer was found to be boon for agriculture-horticulture sector with wide applicability.  相似文献   

20.
Activated carbons were produced from waste pine wood sawdust using fast activation with H3PO4 in a spouted bed. In this study, activation temperature was set as 800 °C, and activation time ranged from 1 to 15 min. Experimental results show that sawdust impregnated with higher mass ratio of H3PO4 would be agglomerated in spouted bed, and difficult to fluidize. Therefore, an amount of quartz sand was added to assist for good fluidization. Fluidization of particle can improve the BET surface area or micropore volume of activated carbons. High BET surface area activated carbons can be obtained with activation time of only 1–5 min by combining the fluidization and H3PO4 fast activation. The obtained activated carbons contained developed pore structure and abundant surface functional groups (carboxyl, carbonyl and P-containing groups) by SEM–EDS, FTIR and XPS techniques. The particles of impregnation ratio of 1:1 can achieve fluidization without adding the quartz sand, which was convenient for experimental operation and even industrial production, and the BET surface area can reach more than 1000 m2/g in activation time of only 5 min.  相似文献   

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