Polysaccharide/Fe(III)-porphyrin hybrid film as catalyst for oxidative decolorization of toxic azo dyes: An approach for wastewater treatment

A hybrid film of chitosan/poly(vinyl alcohol)/cationic Fe(III)-porphyrin (Cht/PVA-FeTMPyP) was synthesized to act as a Fenton-like catalyst to decolorize methyl orange and methyl red azo dyes. The Cht/PVA-FeTMPyP film was characterized by different analytical and microscopy techniques, which indicated that the metalloporphyrin affects different properties of the hybrid film. Batch experiments revealed that the hybrid film exhibits enhanced catalytic activity towards dyes decolorization in the presence of H₂O₂ as compared to the “free” FeTMPyP. Fast decolorization rates as high as 90 min were observed for both azo dyes under mild conditions (pH 7 and room temperature), even at low concentrations of the catalyst in H₂O₂. After the decolorization, FTIR analysis showed that simple molecules are released as by-products. Moreover, the hybrid film performed well in cyclic runs without leaching out iron ions or losing its catalytic activity. All these features associated with its ease handling ranks the Cht/PVA-FeTMPyP hybrid film as a promising heterogeneous Fenton-like catalyst for the decomposition of azo dyes in water.     

Heterogeneous Suzuki and copper-free Sonogashira cross-coupling reactions catalyzed by a reusable palladium(II) complex in water medium

A new polystyrene anchored Pd(II) azo complex has been synthesized and characterized. The present Pd(II) azo complex behaves as a very efficient heterogeneous catalyst in the Suzuki coupling and Sonogashira coupling reaction in water medium. Aryl halides, coupled with phenylboronic acids (Suzuki-Miyaura reaction) or terminal alkyne (Sonogashira reaction), smoothly afford the corresponding cross-coupling products in excellent yields (83-100% yield for Suzuki reaction and 68-96% yield for Sonogashira reaction of aryl halides) under phosphine-free reaction conditions in the presence of polystyrene anchored Pd(II) azo complex catalyst in water medium. Furthermore, the catalyst has shown good thermal stability and recyclability. This polymer-supported Pd(II) catalyst could be easily recovered by simple filtration of the reaction mixture and reused for more than six consecutive trials without a significant loss of its catalytic activity.     

Functionalized cellulose-preyssler heteropolyacid bio-composite: An engineered and green matrix for selective,fast and in–situ preparation of Pd nanostructures: synthesis,characterization and application

A new and green engineered biocomposite was synthesized by sol–gel method, using different loadings of the Preyssler heterpolyacid (8, 15, 25, 40 and 50 wt%) on the functionalized microcrystaline cellulose surface. For the first time, this two-component polymeric biocomposite used for in-situ catalytic synthesis of Pd nanoparticles with the aim of producing tricomponent nanobiocomposites. Preyssler loading on the functionalized surface, controled the size and shape of Pd nanoparticles, time, and pH of their formation. All biocomposites and nanobiocomposites were characterised by FTIR, XRD, BET, TGA, SEM, EDS and TEM. The SEM analysis for two component polymeric biocomposites confirmed the presence of the Preyssler on the surface of functionalized cellulose. The formation of Pd nanoparticles on the surface, was observed by color changing (yellow to deep brown) and confirmed by UV–visible spectroscopy. The Pd nanoparticles formation was fast (2–4 min) for 8 wt% in pH = 2–3 at 80 °C. TEM analysis illustrated the spherical Pd nanoparticles with a size of 5–20 nm, at the lowest loading of Preyssler, and rod shapes with a size of 30–40 nm at the highest loading. The obtained nanobiocomposite exhibited high catalytic activity for the decolourisation of tartrazine, as a model of dyes pollutant in the industry with high degradation efficiency. The catalytic reactions were extended with other azo dyes including methyl orange and rodamine B.     

Immobilized Pd nanoparticles on Tris-modified SiO2：Synthesis,characterization, and catalytic activity in Heck cross-coupling reactions

The preparation of supported Pd nanoparticles on Tris (tris(hydroxymethyl)aminomethane)- modified SiO₂ gel and their catalytic application in Heck coupling are investigated. The catalyst was characterized using a combination of X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. The supported Pd nanoparticles were found to be a highly active and reusable catalyst for the Heck reaction at a low Pd loading (0.02 mol%) because of stabilization by the Tris moieties. Several reaction parameters, including the type and amount of solvent, base, and temperature, were evaluated. The heterogeneity of the catalytic system was investigated using different approaches, and showed that slight Pd leaching into the reaction solution occurred under the reaction conditions. Despite this metal leaching, the catalyst can be reused seven times without significant loss of its activity.     

Decolorization of Some Azo Dyes by Immobilized <Emphasis Type="Italic">Geotrichum</Emphasis> sp. Biomass in Fluidized Bed Bioreactor

Geotrichum sp. strain, which is able to decolorize azo dyes enzymatically, was used in this study for decolorization of synthetics solutions contaminated by toxic azo dyes orange G, trypan blue, azorubine, and methyl red. The biomass of Geotrichum sp. was immobilized in calcium alginate and polyacrylamide gels and used for the decolorization of tested azo dyes in fluidized bed bioreactor. The highest specific decolorization rate was obtained when the fungal biomass was entrapped in calcium alginate beads. Immobilized biomass in calcium alginate continuously decolorized azo dyes after eight repeated batch decolorization experiments without significant loss of activity whereas polyacrylamide immobilized biomass retained only 10% of its activity after 4 days of incubation. The effects of some physicochemical parameters such as temperature, pH, and dyes concentration on decolorization performance of isolated fungal strain were also investigated.     

高活性Pd/MgO催化剂的制备及其CO氧化偶联制草酸二甲酯催化反应

利用溶液法结合高温煅烧处理合成MgO载体,通过浸渍法制备Pd/MgO催化剂并对其进行CO氧化偶联制草酸二甲酯催化性能研究。通过X射线粉末衍射、CO2程序升温脱附、比表面仪、热重分析、扫描电镜、透射电镜和微型催化评价装置对合成的样品进行结构和性能表征。结果表明,合成的MgO载体是一种Lewis碱性很强的纳米片结构,Pd纳米颗粒高度分散在MgO载体上,粒径小且分布均一。此MgO纳米片作为载体制备的Pd/MgO催化剂在较低的Pd负载量(0.5%)下表现出优异的CO氧化偶联催化性能,在反应温度130℃时CO单程转化率高达65%,草酸二甲酯选择性96%,稳定性超过100 h,明显越于工业催化剂(Pd/α-Al2O3),具有潜在的工业应用前景。     

Synthesis,Characterization, and Catalytic Activity of New Cu(II) Complexes of Schiff Base: Effective Catalysts for Decolorization of Acid Red 37 Dye Solution

In this paper, three new Cu(II) Schiff base complexes with three different anions (acetate, chloride, and nitrate) were successfully synthesized and characterized by elemental analysis, mass spectra, molar conductance, FT‐IR, NMR,UV–vis spectroscopy, magnetic moment, ESR, and thermal analysis. The catalytic performances of these complexes in decolorization of azo dye, Acid Red 37, were evaluated. Copper(II) complexes were found to be an efficient catalyst for decolorization of Acid Red 37 in the presence of hydrogen peroxide. The catalytic investigation revealed that the Cu(II) complex with acetate anion (complex 1 ) performed the highest catalytic activity. The kinetics of the decolorization of AR37 with this catalyst was studied, and the observed rate constant was determined. The effects of different reaction parameters such as catalyst dosage, solution pH, initial concentration of H₂O₂, dye solution, and reaction temperature on the reaction rate constant were studied. The best reacting conditions should be catalyst dosage = 0.004 g, initial pH 4.0, [H₂O₂]₀ = 0.8 M, and [AR37]₀ = 1.16 M at temperature 25°C. Under these conditions, about 99% of AR37 was decolorized within 60 min. The results indicated that the Cu(II) complex with the acetate anion is a promising catalyst for wastewater treatment.     

Improved Biodegradation of Synthetic Azo Dye by Anionic Cross-Linking of Chloroperoxidase on ZnO/SiO<Subscript>2</Subscript> Nanocomposite Support

A novel ZnO nanowire/macroporous SiO₂ composite was used as a support to immobilize chloroperoxidase (CPO) by in situ cross-linking method. An anionic bi-epoxy compound was synthesized and used as a long-chained anionic cross-linker, and it was adsorbed on the surface of ZnO nanowires through static interaction before reaction with CPO, creating a new approach to change the structure, property, and catalytic performance of the produced cross-linking enzyme aggregates (CLEAs) of CPO. The immobilized CPO showed high activity in the decolorization of three azo dyes. The effect of various conditions such as the loading amount of CPO, solution pH, temperature, and dye concentration was optimized on the decolorization. Under optimized conditions, the decolorization percentage of Acid Blue 113, Direct Black 38, and Acid Black 10 BX reached as high as 95.4, 92.3, and 89.1%, respectively. The immobilized CPO exhibited much better thermostability and resistance to pH inactivation than free CPO. The storage stability and reusability were greatly improved through the immobilization. It was found from the decolorization of Acid Blue 113 that 83.6% of initial activity retained after incubation at 4 °C for 60 days and that 80.9% of decolorization efficiency retained after 12 cycles of reuses.     

Diethylenetriamine-functionalized single-walled carbon nanotubes (SWCNTs) to immobilization palladium as a novel recyclable heterogeneous nanocatalyst for the Suzuki–Miyaura coupling reaction in aqueous media

Pd supported on diethylenetriamine (DETA) modified single-walled carbon nanotubes (SWCNT-DETA/Pd) hybrid materials were fabricated for the first time. The prepared heterogeneous catalyst was characterized by XRD, FTIR, SEM, TGA, and TEM. The catalytic activity of the prepared catalyst was investigated by employing the Suzuki–Miyaura coupling reaction as a model reaction. A series of biphenyl compounds were synthesized through the Suzuki–Miyaura reaction using SWCNT-DETA/Pd²⁺ as a catalyst. The yields of the products were in the range from 80% to 98%. The catalyst can be readily recovered and reused at least for seven consecutive cycles without significant loss of its catalytic activity.     

Fullerene‐Catalyzed Reduction of Azo Derivatives in Water under UV Irradiation

Metal‐free fullerene (C₆₀) was found to be an effective catalyst for the reduction of azo groups in basic aqueous solution under UV irradiation in the presence of NaBH₄. Use of NaBH₄ by itself is not sufficient to reduce the azo dyes without the assistance of a metal catalyst such as Pd and Ag. Experimental and theoretical results suggest that C₆₀ catalyzes this reaction by using its vacant orbital to accept the electron in the bonding orbital of azo dyes, which leads to the activation of the N?N bond. UV irradiation increases the ability of C₆₀ to interact with electron‐donor moieties in azo dyes.     

Use of titanium dioxide photocatalysis on the remediation of model textile wastewaters containing azo dyes

The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO(2) P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO(2) used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO(2) reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes.     

Keggin和Dawson结构多金属氧酸盐光催化脱色偶氮染料

The investigation photocatalytic degradation of three azo dyes solution(Acid Mordant Navy Blue RRN,Acid Mordant Black PV,Acid Mordant Brown RH) under UV light irradiation using the polyoxometalates as catalyst was reported in this article.The research results showed that the photocatalytic activity of Keggin catalyst is higher than that of Dawson,and the catalyst α-H4SiW12O40 had the best efficiency to the photocatalytic decoloration of RRN.In 350 mg·L-1(30 mL) RRN solution,the optimum reaction condition wa...     

Decolorization of Synthetic Dyes by Crude and Purified Laccases from Coprinus comatus Grown Under Different Cultures: The Role of Major Isoenzyme in Dyes Decolorization

Coprinus comatus laccase isoenzyme induction and its effect on decolorization were investigated. The C/N ratio, together with aromatic compounds and copper, significantly influenced laccase isoenzyme profile and enzyme activity. This fungus produced six laccase isoenzymes in high-nitrogen low-carbon cultures but much less in low-nitrogen high-carbon (LNHC) cultures. The highest laccase level (3.25 IU/ml), equivalent to a 12.6-fold increase compared with unsupplemented controls (0.257 IU/ml), was recorded after 13 days in LNHC cultures supplemented with 2.0 mM 2-toluidine. Decolorization of twelve synthetic dyes belonging to anthraquinone, azo, and triphenylmethane dyes, by crude laccases with different proportion of isoenzymes produced under selected culture conditions, illustrated that the LacA is the key isoenzyme contributed to dyes decolorization especially in the presence of 1-hydroxybenzotriazol, which was further confirmed by dyes decolorization with purified LacA in the same condition. The crude laccase only was able to decolorize over 90 % of Reactive Brilliant Blue K-3R, Reactive Dark Blue KR, and Malachite Green, and higher decolorization for broader spectrum of synthetic dyes was obtained in presence of redox mediator, suggesting that C. comatus had high potential to decolorize various synthetic dyes as well as the recalcitrant azo dyes.     

炭负载Pd/Ce双金属催化剂对Heck反应的催化性能

通过简便的方法制备了炭负载Pd/Ce双金属催化剂,利用Pd/Ce双金属催化剂的协同效应提高催化剂对Heck反应的催化效率。 以碘苯与丙烯酸的Heck芳基化反应为模型反应,研究了反应条件对催化剂催化性能的影响。 结果显示,在反应温度为130 ℃,反应时间为5 h,N,N-二甲基甲酰胺(DMF)作为溶剂和三丁胺(Bu₃N)作为碱的条件下,炭负载Pd/Ce双金属催化剂对丙烯酸和碘苯的Heck芳基化反应具有良好的催化性能,产率达到70%以上。 另外,该催化剂属于非均相催化剂,催化剂易与反应溶液分离;也可以重复利用,使用3次反应产率仍达到66.9%,显示了炭负载Pd/Ce双金属催化剂良好的催化活性。     

负载型Pd/TiO2和Pd-Ag/TiO2催化剂的乙炔选择性加氢催化性能

利用程序升温还原(TPR)、X-射线衍射(XRD)、CO吸附-红外光谱(CO-IR)、电子顺磁共振(EPR)和微型催化反应评价等手段, 研究了负载Pd/γ-Al2O3, Pd/TiO2和Pd-Ag/TiO2催化剂的结构和乙炔选择性加氢催化性能. 结果表明, Pd/TiO2催化剂具有较Pd/γ-Al2O3催化剂更优良的乙炔选择性加氢催化性能, 这与Pd-TiO2之间的强相互作用密切相关. Pd-TiO2之间的强相互作用不仅使负载型钯金属催化剂具有较高的乙炔加氢催化选择性, 而且具有较高的乙炔加氢催化活性. Pd/TiO2催化剂中添加Ag 组分后, Pd金属可促进Ag+的还原并可能形成Pd-Ag合金, 催化剂的乙烯选择性虽有所增加, 但乙炔转化率和乙烯收率下降.     

Pd/MIL-101的制备及非均相催化吲哚C-H活化

水热合成MIL-101,过量浸渍法吸附Pd(OAc)_2,原位还原Pd~(2+)制得Pd/MIL-101催化剂.采用XRD、XPS、SEM、ICP、HRTEM和N_2吸/脱附实验对其结构进行表征,催化剂Pd纳米粒子尺寸在1.5~2.5 nm之间,含量为1.5%.催化实验表明,Pd/MIL-101能高效催化吲哚C_2位芳基化,对于活性较差的溴代芳烃,也能得到中等以上的收率,催化剂循环5次后仍能保持较高的反应活性,发展了吲哚C_2位衍生物的简单、高效的合成方法.     

PdNiO/C在碱性介质中对甲醇的电氧化

应用循环伏安,计时电流,计时电位和XRD等方法研究了碱性介质中甲醇在自制PdNiO/C和Pd/C催化剂上的电化学氧化以及高温热处理对催化剂结构和性能的影响.结果表明,还原温度为70℃,Pd、Ni原子比为8∶2时,PdNiO/C催化剂对甲醇电化学氧化具有较好的催化活性.热处理可增大催化剂粒径,升高结晶度,降低分散度和催化活性,并且可使NiO从Pd的晶格中脱离出来.与Pd/C催化剂相比,优选的PdNiO/C催化剂有更高的催化活性和更好的抗毒化能力.     

Investigation of photocatalytic effect of SnO2 nanoparticles synthesized by hydrothermal method on the decolorization of two organic dyes

Tin oxide nanoparticles about 4 nm in size were successfully synthesized using hydrothermal method. The photocatalytic activity of the particles was determined by the decolorization of malachite green (MG) and titanium yellow (TY) under UV light. 12 ppm of MG and TY were used for the solution with an initial volume of 100 mL. The amounts of catalysts were 10, 30 and 50 mg. The effect of the catalyst loading on the reaction kinetic parameters and the decolorization rate constants (k) were determined. In order to reveal the photocatalytic efficiency of the nano particles, further experiments were conducted with bulk SnO(2). The oxygen species registered no observable effect on the reaction mechanism as nitrogen bubbling leads to no change in decolorization rates. Results showed that the synthesized nano tin oxide particles represent excellent photocatalytic activity for the decolorization of 12 ppm MG under UV light with 150 min of irradiation time. The energies of the highest occupied molecular orbital (HOMO) E(HOMO) of the dyes were also calculated by using the quantum chemical software in order to discuss the differences for the decolorization of two dyes. Electrical energy efficiency values for the decolorization of two dyes were also calculated.     

Decolorization and partial degradation of selected azo dyes by methanogenic sludge

The toxicity potential and decolorization of three acid azo dyes (Acid Orange 6, Acid Orange 7, and Acid Orange 52) by methanogenic granular sludge from an anaerobic expanded granular sludge bed reactor was assayed. Complete bioreduction was found for all three azo dyes. Sulfanilic acid and 4-aminoresorcinol were detected from the decolorization of Acid Orange 6, sulfanilic acid and 1-amino-2-naphtol were detected from the reduction of Acid Orange 7, and sulfanilic acid and N,N-dimethyl-1,4-phenylenediamine (DMP) were found to be intermediates of Acid Orange 52 degradation. Sulfanilic acid and 1-amino-2-naphtol were persistent in the anaerobic conditions, whereas 4-aminoresorcinol was completely mineralized by anaerobic sludge and DMP was transformed into 1,4-phenylenediamine. Enrichment cultures obtained via consecutive passages on basal medium with only azo dye as a carbon and an energy source seemed to be morphologically heterogeneous. Baculiform and coccus cells were found when viewed under a light microscope. Cocci were joined in chains. Because anaerobic sludge contains sulfate-reducing bacteria and therefore may generate sulfide, azo dyes were tested for chemical decolorization by sulfide to compare rates of chemical and biologic reduction.     

磁性纳米Pd/Fe3O4催化剂的制备及其在Heck反应中的应用

通过使用聚乙烯吡咯烷酮作为稳定剂,合成了磁性Pd/Fe₃O₄纳米颗粒催化剂。对该催化剂进行粉末X射线衍射、透射电子显微镜、感应耦合等离子体和磁性表征。将Pd/Fe₃O₄催化剂用于Heck反应,检测其催化性能。测试结果表明Pd纳米颗粒负载在Fe₃O₄纳米颗粒上,而且催化剂的尺寸<20 nm,并在Heck反应中表现了极好的催化性能。此外,催化剂可以通过磁场回收利用, 且催化活性没有显著的降低。