Radiation crosslinked polyvinyl alcohol/polyvinyl pyrrolidone/acrylic acid hydrogels: swelling,crosslinking and dye adsorption study

Iranian Polymer Journal - Hydrogels were produced from mixtures of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), and acrylic acid (AAc) using γ-radiation at doses of 3, 7, and...     

受控水解法制备纳米TiO2光解染料废水的研究

以强酸性控制水解法制备了纳米TiO2,结合XRD表征,研究了其悬浊液对含阳离子艳红5GN的模拟染料废水进行光催化降解的活性和规律.结果表明:在强酸性控制水解法中,500 ℃焙烧纳米TiO2催化剂具有最高催化活性,对比沉淀法和sol-gel法制备的纳米TiO2,其对阳离子艳红的降解速率提高了1.34倍和2.81倍;实验确定的优化降解条件为:6 W紫外光照、阳离子艳红5GN初始质量浓度为20 mg/L、催化剂投加量为1.5～2.0 g/L和空气曝气器功率2.50 W,此时阳离子艳红5GN在1 h内的降解率＞90%;在阳离子艳红5GN初始质量浓度为10～40mg/L时,其降解过程遵循一级反应规律.     

Photocatalytic degradation of Direct Yellow 12 dye using UV/TiO2 in a shallow pond slurry reactor

The adsorption and photocatalytic degradation of diazo Direct Yellow 12 (Chrysophenine G), commonly used as a cotton, paper and leather dye has been investigated in aqueous suspension of semiconductor oxide TiO₂ as photocatalyst in a non-concentrating shallow pond slurry type reactor under UV light. The adsorption of dye on the semiconductor shows a strong dependence on the pH and follows a Langmuir adsorption model. The studies include dark adsorption experiments at different pH conditions and their effect on initial rate of photodegradation. The effect of initial concentration of dye, catalyst loading, pH, addition of oxidant on the reaction rate was ascertained and optimum conditions for maximum degradation was determined. The disappearance of the organic molecule follows approximately a pseudo-first kinetic order according to the Langmuir–Hinshelwood model. COD analysis of the dye under optimum conditions showed 94% reduction in COD after 2.5 h and complete decolourisation as determined by UV–vis analysis was achieved in 1.5 h.     

Development and evaluation of pH-dependent interpenetrating network of acrylic acid/polyvinyl alcohol

The objective of the present work was to synthesize interpenetrating networks (IPNs) of acrylic acid/polyvinyl alcohol (AA/PVA) by free radical polymerization using N,N-methylenebisacrylamide (MBAAm) and glutaraldehyde as cross-linkers. The IPNs were evaluated for swelling, diffusion coefficient and network parameters by using Flory–Huggins theory, i.e., the average molecular weight between cross-links (M _c), polymer volume fraction in swollen state (V _2,s), number of repeating units between cross-links (M _r) and cross-linking density (N). It was found that the degree of swelling of AA/PVA interpenetrating network increases greatly within the pH range 5–7 depending on composition. The gel fraction and porosity increased by increasing the concentration of AA or PVA, while by increasing the degree of cross-linking, porosity decreased and gel fraction increased. Selected samples were loaded with chlorpheniramine maleate as a model drug. Drug release was studied in USP, hydrochloric acid buffer solution of pH 1.2 and phosphate buffer solutions of pH 5.5 and 7.5. Drug release data were fitted into various kinetics models, e.g., zero-order, first-order, Higuchi and Peppas models. The results of the kinetics investigation showed that the drug release from IPNs followed non-Fickian diffusion. Fourier transform infrared spectra confirmed the formation of cross-linked IPNs as there was a shifting to lower frequency of 1,713–1,718 cm^?1 with reduced intensity, while scanning electron microscopy revealed uniform distribution of drug in IPNs.     

Ag-N共掺杂TiO_2/膨润土光催化降解染料废水

采用溶胶-凝胶法制备了银氮共掺杂光催化剂Ag-N-Ti O2/膨润土,通过XRD和FTIR对其结构进行了表征,优化了该催化剂降解耐酸枣红染料废水的反应条件。结果表明,催化剂中有锐钛矿型Ti O2生成,部分Ti O2进入了膨润土层间,增大了其晶面层间距,并通过Ti—O—Si键实现了膨润土对Ti O2的固载;掺杂的Ag、N可能进入了Ti O2晶格,拓宽了其光谱响应范围,并提高了其光催化活性。当催化剂用量为2 g/L,溶液p H为3,光照时间为120 min,紫外光或可见光照射下,该催化剂对50 mg/L的耐酸枣红的降解率分别达到93.0%和89.3%,并在可见光下对其它3种50 mg/L的染料废水的降解率也达到了90%以上。     

Yb/TiO2光催化降解染料废水的研究

采用胶-溶凝胶法制备纳米掺镱TiO2光催化剂Yb/TiO2.在紫外灯下照射,对罗丹明B模拟染料废水进行光催化降解研究,优化了光催化的反应条件.结果表明:当掺镱量n(Yb)/n(TiO2)为1.0％,催化剂用量为2g·L-1,溶液pH值为4,光照时间为3h,染料废水的起始浓度为10mg·L-1时,染料废水的降解率可达95.32％.     

氮掺杂TiO2/壳聚糖复合膜吸附和光降解染料

氮掺杂二氧化钛/壳聚糖(CS)复合膜是一种有前途的有机染料废水处理材料,相对于传统的废水处理材料更具优势。在模拟太阳光照射下,用氮掺杂二氧化钛/壳聚糖(CS)复合膜对有机染料甲基橙溶液进行降解,通过吸附和光催化的双重作用,甲基橙的降解率可达99%。采用X射线衍射(XRD)、扫描电子显微镜(SEM)等对复合膜进行了表征,并通过傅里叶红外光谱(FT-IR)分析表明其壳聚糖中活性官能团 NH₂, OH在氮掺杂TiO₂ 复合膜中同时存在。研究表明,氮掺杂二氧化钛/壳聚糖(CS)复合膜是一种高效节能的污水处理材料。     

Photocatalytic degradation of azo dye using TiO2 supported on spherical activated carbon

TiO₂ supported on spherical activated carbon (TiO₂/SAC) was prepared through an ion-exchange method followed by a heat-treatment process. The adsorption characteristic of TiO₂/SAC was evaluated using azo dye methyl orange (MO) as a target substance, and the photocatalytic degradation of MO under UV irradiation was also discussed. A synergistic effect of both the adsorption capacity of activated carbon and the photoactivity of TiO₂ on the removal of MO from aqueous solution was observed. Experimental results revealed that the photocatalytic degradation of MO improved with increasing photocatalyst dosage and followed a pseudo-first order kinetic. After five-cycle runs, TiO₂/SAC still exhibited relatively high photocatalytic characteristic for the degradation of MO. Besides, the prepared TiO₂/SAC can be helpful in the easy separation of photocatalyst from solution after photocatalysis of MO. Furthermore, the use of liquid chromatography/mass spectrometry (LC/MS) technique, identified three intermediates as degradation products during the photocatalytic reaction of MO with TiO₂/SAC.     

Controlled release of testosterone propionate based on poly N-vinyl pyrrolidone/2-acrylamido-2-methyl-1-propanesulfonic acid hydrogels prepared by ionizing radiation

The mechanical properties of SAN/PB-g-SAN blends of different compositions under uniaxial tensile tests were studied. Matrix ligament thickness (MLT) concept was employed to correlate microscopic deformations with macroscopic mechanical response. It was found that, the experimental values of the blends moduli are in a good agreement with the theoretical values obtained from Takayanagi and mixture rules in parallel models. The MLTs in which transition from brittle-to-ductile and from ductile-to-rubbery occur were determined according to interparticle distance model. Fractography studies of the samples with MLT values greater than brittle to ductile transition showed that rubber particles act as craze initiators rather than craze terminators. Due to poor overlapping of stress fields around the particles, no extensive shear yielding took place during the fracture process, leading to unstable macroscopic behavior. For the samples with MLTs smaller than brittle-ductile transition, a necked region developed. The stability of necked region increased with PB-g-SAN content, which resulted in improved post yield deformation stability. This process was accompanied by the participation of larger volume of material in the deformation process and strong overlapping of the stress field around the particles, which facilitated matrix shear yielding. Based on macroscopic response, this delocalized deformation manifested itself by a gradual decrease in load drop after yielding point. For the samples with PB-g-SAN content higher than 75 wt%, the great reduction in MLT and direct interconnection between the neighbor rubber particles caused the appearance of rubbery behavior. These results were also confirmed by analyzing of the fractured surfaces.     

Properties of PVA-PSA hybrid materials prepared through the incorporation of polysilicic acid (PSA) into polyvinyl alcohol

A quick method of preparing transparent organic-inorganic hybrid material was studied. The hybrid, PVA/PSA, was prepared through incorporating the nanoscaled polysilicic acid (PSA) obtained through hydrolysis and condensation of metasilicate salt directly into a polyvinyl alcohol (PVA). The interfacial force, microstructure, and dynamic mechanical property of the hybrid were studied by means of spectroscopy (FTIR, X-ray diffraction and solid-state ²⁹Si NMR) and dynamic mechanical analysis, and the results were compared with that of the hybrids, PVA/TEOS, prepared through the traditional sol-gel process. It was found that the microstructure of PVA/PSA was different from that of PVA/TEOS because of the different preparation methods. The structures of the crystals in both hybrids were similar to that of the pure PVA. Other physical properties, such as T_g, storage modulus, tensile strength and solvent resistance of the PVA/PSA hybrid, were improved significantly with the addition of the silica content. The extent of improvement was a little lower than that for the PVA/TEOS.     

磁性氧化石墨烯/TiO_2复合材料的制备及光催化降解染料废水的研究

为了提高TiO2的光催化性能,采用Hummers法自制氧化石墨、纳米TiO2、FeCl3等为原料制备了磁性氧化石墨烯/TiO2(磁性GO/TiO2)复合光催化材料。以活性艳红X-3B为模拟废水,对该催化剂在紫外光下的催化活性进行了评价。结果表明,TiO2/GO材料中GO含量为3%时光催化活性最好,磁性GO/TiO2复合材料GO含量为8%时在1.4 h时可以达到93%的降解率。     

磁性氧化石墨烯/TiO_2复合材料的制备及光催化性能的研究

利用水热法以氧化石墨烯为载体制备磁性氧化石墨烯/TiO2光催化复合材料,对不同Fe3O4掺杂比例的复合光催化剂采用SEM、XRD、UV-Vis等测试方法对其进行表征,并在紫外灯照射下研究了对活性艳红溶液光催化性能。结果显示,Fe3O4及氧化石墨烯的引入会提高TiO2的光催化性,这主要是因为提高了TiO2的导电性和吸附性。由此可见Fe3O4、氧化石墨烯与TiO2复合,能够有效提高TiO2的催化性能。     

纳米TiO2/AC光催化降解罗丹明B废水的研究

采用负载型纳米TiO2/AC在流化床反应器中降解罗丹明B染料废水。试验结果表明,罗丹明B的光催化降解率受反应条件的影响较大,其最佳工艺条件：进水罗丹明B质量浓度80mg／L、催化剂为10g／L、pH2．5、H2O2投加量3．5mL／L、反应时间30min,此条件下罗丹明B的光降解率可高达96．1％。     

TiO2纳米管/UV/O3对腐殖酸的降解动力学

用自制的TiO₂纳米管（TNTs）作为催化剂,对腐殖酸进行TNTs/UV/O₃工艺降解研究.从动力学角度分析了光催化、臭氧化的协同作用及催化剂煅烧温度的影响,考察了反应温度、初始pH值、催化剂投加量和臭氧投加量对降解速率的影响,建立了新型动力学模型.结果表明,光催化和臭氧化有很强的协同作用,催化剂最佳煅烧温度为400℃,腐殖酸的TOC降解过程符合零级反应,模型显示当原水pH值为7.35,TNTs投加量0.806g·L^-1,O₃投加量0.49g·h^-1时TNTs/UV/O₃对腐殖酸TOC的降解取得最佳反应速率,当反应温度T为25℃时,最佳k为0.8095mg·L^-1·min^-1,当反应温度T为30℃时,最佳k为0.8231mg·L^-1·min^-1.试验结果和模型结果对比得出试验值基本符合动力学模型.     

A hybrid photocatalytic and enzymatic process using glucose oxidase immobilized on TiO2/polyurethane for removal of a dye

A rectangular recycling photo-bioreactor using glucose oxidase (GOx) immobilized on TiO₂/polyurethane (PU) was developed as a novel coupling of photodegradation and enzymatic process. This method was tested for removal of Acid Orange 7 (AO7), as a model pollutant. High efficiency of decolorization (>99%) was achieved after 22 min using the GOx/TiO₂/PU photo-biocatalyst. Roles of various processes including photodegradation (TiO₂/PU), enzymatic process (GOx/PU) and a coupling of photocatalytic–enzymatic (GOx/TiO₂/PU) process were investigated in the presence and absence of UV light. All the experiments were performed in a circulation photoreactor equipped with a 6 W UV lamp with rate of 5 mL/min.     

Photocatalytic degradation of C.I. Acid Orange 7 by TiO2 nanoparticles immobilized onto/into chitosan‐based hydrogel

Photocatalytic degradation of dye C.I. Acid Orange 7 in aqueous solution using TiO₂/hydrogel nanocomposite under solar light simulating source was studied. Hydrogel based on chitosan, itaconic and methacrylic acid was modified with colloidal TiO₂ nanoparticles synthetized by acidic hydrolysis of TiCl₄ and commercial Degussa P25 TiO₂ nanoparticles. SEM/EDX analysis confirmed the presence of TiO₂ nanoparticles onto/into hydrogel. It was found that both types of photocatalysts efficiently removed the dye from solution, but sorption rates and photodegradation efficiency were higher in the case of colloidal TiO₂ nanoparticles. They ensured complete discoloration of dye solution. The efficiency of the reused TiO₂/hydrogel nanocomposite showed that photodegradation activity was maintained at satisfactory level after three repeated cycles of illumination. POLYM. COMPOS., 35:806–815, 2014. © 2013 Society of Plastics Engineers     

Combination of photocatalytic and photoelectro-Fenton/citrate processes for dye degradation using immobilized N-doped TiO2 nanoparticles and a cathode with carbon nanotubes: Central composite design optimization

In this report, commercial TiO₂ nanoparticles were doped with nitrogen by a manual grinding method using urea. The prepared catalyst was characterized by X-ray diffraction (XRD), diffuse reflectance spectra (DRS), and transmission electron microscopy (TEM). N-doped TiO₂ was immobilized on ceramic plates by methyl tri-methoxy silane. Next, multi-walled carbon nanotubes (CNTs) were stabilized on carbon paper to fabricate the cathode. Scanning electron microscopy (SEM) was employed to confirm stabilization of the CNTs. The prepared cathode and immobilized catalyst were utilized for the degradation of C.I. Direct Red 23 (DR23) by the photoelectro-Fenton (PEF) process in the presence of citrate (Cit) combined with a photocatalytic process. The coupled PEF/Cit/N-TiO₂ process could be performed under visible light, not only due to the formation of iron–citrate complexes, but also because of the incorporation of nitrogen to the crystalline structure of TiO₂ and the generation of TiO₂ complexes with electrogenerated H₂O₂. Results demonstrated that the degradation efficiency of DR23 (20 mg/L) using the identical operational conditions, followed a decreasing order of: PEF/Cit/N-TiO₂ > PEF/Cit > PEF > EF > N-TiO₂. Eventually, a model was developed by the central composite design (CCD) method, describing the degradation efficiency as a function of the operational parameters.     

Photocatalytic degradation of azo dyes by organic-capped anatase TiO2 nanocrystals immobilized onto substrates

The UV-induced photocatalytic degradation of two azo dyes, Methyl Red and Methyl Orange, has been carried out in aqueous media in the presence of oleic acid (OLEA)- and tri-n-octylphosphine oxide (TOPO)-capped anatase TiO₂ nanocrystal powders (mean particle size: 6 nm) deposited onto a quartz substrate. The progress of photodegradation was followed by combining UV–vis absorption measurements with HPLC–MS analysis. The abatement efficiency for the two organic compounds was compared with that obtained with commercial TiO₂ P25 Degussa by evaluating a few significant variables, such as the dye chemical structure, pH of the solution, and catalyst surface status. Identification of several by-products by HPLC–MS analysis has allowed to propose a reasonable degradation pathway for both target molecules. Significantly, although all titania catalysts were effective in removing both parent dyes and their related derivatives, the degradation rate by the OLEA-capped TiO₂ nanocrystals was double as that obtained with both its TOPO-capped analogous and TiO₂ P25 Degussa. It is suggested that efficient catalysis strictly depends on microscopic mechanisms that occur at the catalyst surface, basically involving specific dye adsorption and local density of terminal OH moieties.