Sharif Digital Repository

Biological treatment, especially enzymatic methods, can be employed for effective and environmental- friendly treatment of dye effluents. Laccase, belonging to the blue multi-copper oxidases category, can oxidize a wide variety of substrates, especially synthetic dyes. In this study, laccase was used to biodegrade two azo dyes, i.e., Direct Red 23 and Acid Blue 92. Before conducting the experiments, the laccase used in this study was enzymatically characterized. Face-centered central composite design (FCCCD) was used to optimize the main parameters of the decolorization process. The optimum conditions to maximize the bio-decolorization process of AB92 were X1=11.85 mg L-1, X2=5.10, and... 

Laboratory scale experiments were conducted in order to investigate the photolysis of Reactive Blue 19 (RB 19) dye using UV as the irradiation source in alkaline solution. The effects of operating parameters such as, pH, initial dye concentration, UV dosage, hydrogen peroxide and oxygen have been evaluated. The results indicate that the UV photolysis process in alkaline solution is ideal for decolorizing of RB 19 and it can be taken as a starting step to establish the economical feasibility of the method for the decolorization of wastewater from textile industries  

In this study, decolorization of the diazo dye, Reactive Black 5 (RB5) in a Coprinus cinereus peroxidase-catalyzed reaction has been investigated. A bisubstate kinetic model for the reaction rate based on the Ping-Pong mechanism was assumed for the enzymatic decolorization. Experiments were conducted at different RB5 and hydrogen peroxide concentrations in a batch manner to estimate the intrinsic kinetic parameters. These parameters were used for the modeling of decolorization in a continuous reactor that was compared with experimental results. An acceptable agreement was observed between the model and experimental data  

An efficient dye decolorization platform was developed through one-step hydrothermally route based on magnetic polymeric resin and employed in aqueous crystal violet (CV) adsorption. The polymer nanohybrid composed of ZnFe2O4 and hydroxybenzoic acid–resorcinol resin as metal and organic fragment, respectively. Several techniques such as X-ray diffraction, N2 – adsorption desorption, vibration sample magnetometer, field emission scanning electron microscopy and Fourier transform infrared spectroscopy were employed for characterization of as-prepared nanohybrid. CV adsorption showed low equilibrium time within 10 min with the adsorption capacity of 83.3 mg g–1. Regeneration of the sorbent... 

In this study, we have used a low temperature plasma, produced by a DC magnetron sputtering device, for decolorizing of denim fabrics, and the effect of using different gases such as Argon and Oxygen as the discharge medium have been investigated. The results obtained under equal periods of time have been compared and the effect of washing on the treated denims has been reported. © 2006 Elsevier B.V. All rights reserved  

Photo-oxidation of dyes is a new concern among researchers since it offers an attractive method for decoloration of dyes and breaks them into simple mineral forms. An advanced oxidation process, UV/H2O2, was investigated in a laboratory scale photoreactor for decolorization of the Reactive blue 19 (RB19 dye from synthetic textile wastewater. The effects of operating parameters such as hydrogen peroxide dosage, pH, initial dye concentration and UV dosage, on decolorization have been evaluated. The RB19 solution was completely decolorized under optimal hydrogen peroxide dosage of 2.5 mmol L-1 and low-pressure mercury UV-C lamps (55 w) in less than 30 min. The decolorization rate followed... 

The aim of this research work was to decolorize anaerobically digested (UASB) and aerobically treated distillery wastewater of a process for ethanol production. An Aspergillus species isolated from the soil was used for decolorization. A sequential Plackett-Burman design in three stages was used for optimization of decolorization conditions. Both maximum decolorization and COD reduction under optimized conditions were obtained as 84%. By implementing the optimum values in a pilot scale of an activated sludge system a continuous process for decolorization was conducted. The decolorization efficiency of this system with 48 h retention time was about 75% in a limited period of 4 days. For... 

Enzymatic decolorization of reactive blue 221 (RB221) using laccase was investigated in a dual-chamber microbial fuel cell (MFC). Suspended laccase was used in the cathode chamber in the absence of any mediators in order to decolorize RB221 and also improve oxygen reduction reaction in the cathode. Molasses was utilized as low cost and high strength energy source in the anode chamber. The capability of MFC for simultaneous molasses and dye removal was investigated. A decolorization efficiency of 87% was achieved in the cathode chamber and 84% COD removal for molasses was observed in the anode chamber. Laccase could catalyze the removal of RB221 and had positive effect on MFC performance as... 

Denim jeans have consistently been fashionable around the world. This fabric inspired strong opinions from historians, teenagers, and movie stars, and has acquired different styles throughout the years. Most jeans today are stonewashed; this technique first become popular in 1970. Now, in addition to pumice stones, enzymes are used on the cotton fabrics to create the stonewashed look. Nowadays, plasma treatment is a cost-effective and environment-friendly process which is able to modify the properties of the fabric surface in order to achieve this effect. Plasma surface treatment changes the properties of the fabric up to a limited depth (several molecular layers), leaving the bulk... 

In this paper, three metal-organic frameworks (Materials of Institut Lavoisier: MILs-100 (Fe)) as porous nanomaterials were synthesized using FeCl3, Fe(NO3)3 and Fe2(SO4)3 and denoted as MIL-100-1, MIL-100-2 and MIL-100-3, respectively. The synthesized MILs-100 (Fe) were characterized by FTIR, SEM, TEM, XRD, UV–vis DRS and zeta potential. Basic Blue 41 (BB41) was used as a model dye to study the photocatalytic dye degradation ability of the synthesized metal organic frameworks. The results showed that the synthesized nanomaterials decolorized BB41. The decolorization kinetics followed first-order kinetic model. The rate constant was 0.0034, 0.0041, 0.0091 and 0.0289 (1/min) for 0.01, 0.02,... 

The photocatalytic decolorization of aqueous solutions of Direct Red 27 in the presence of various amounts of semiconductor powder suspensions has been investigated in a batch reactor with the use of artificial light sources. ZnO and TiO2 have been found the most active photocatalysts; the effect of catalyst loading and type on the reaction rate was optimized for maximum degradation. The results imply that 1:1 ratio is proper for the photocatalytic removal of Direct Red 27. In addition, the effects of particle size and surface area were examined in this photocatalytic process. The results showed that the decolorization efficiency increases with increase in surface area, and decrease in... 

Manganese Peroxidase (MnP), is one of the most promising lignin depolymerization enzymes, which has been widely used for degradation purposes. Nevertheless, MnP tends to lose activity rapidly during its maintenance phase and degradation process, especially in the inevitable presence of hydrogen peroxide. This study aimed to improve MnP efficiency produced by Phanerochaete chrysosporium, via enhancing its sustainability. In this context, the effects of MnO2, Fe3O4, PEG, Veratryl Alcohol (VA), and DMSO as stabilizing agents on MnP activity were explored both in vivo and in vitro. During in vivo experiments, heterogeneous Fe3O4 was found to be the desirable choice to enhance MnP production,... 

Effect of cathodic enzymatic decolorization of reactive blue 221 (RB221) on the performance of a dual-chamber microbial fuel cell (MFC) was investigated. Immobilized laccase on the surface of a modified graphite electrode was used in the cathode compartment in order to decolorize the azo dye and enhance the oxygen reduction reaction. First, methylene blue which is an electroactive polymer was electropolymerized on the surface of a graphite bar to prepare the modified electrode. Utilization of the modified electrode with no enzyme in the MFC increased the power density up to 57% due to the reduction of internal resistance from 1000 to 750 Ω. Using the electropolymerized-enzymatic cathode... 

In the present study, capability of nanodiamond (ND) for the adsorption of anionic (methyl orange, MO) and cationic (methylene blue, MB) dyes from aqueous solution was investigated. Employing fourier transform infrared (FTIR) spectroscopy, Boehm titration method and zeta potential, it was found that the simple thermal oxidation of ND at 425 °C, increased the content of carboxylic acid of ND and accordingly the zeta potential of ND decreased considerably. Therefore, a series of oxidized NDs (OND) at various oxidation times and as-received untreated ND (UND) was used as adsorbents of MO and MB. The adsorption experiments exhibited that UND had large adsorption capacity, very fast adsorption... 

The supernatant obtained from the extracellular laccase produced by Phanerochaete chrysosporium was used as the enzyme source to conduct a partial purification, characterization and dye decolorization study. The partially purified enzyme was stable in the pH range of 3–5 and showed an optimum activity at pH 4.0, using guaiacol as a substrate. Laccase stability of pH was determined and discovered to retain 100% of its activity at a pH of 4.0 after 2 h. The maximum enzyme activity was obtained between 30 and 50 °C. The maximum velocity and Michaelis constant were calculated as 3.171 µM−1·min and 1628.23 µM, respectively. The enzyme was activated by Fe2+, Zn2+, Ca2+ and Cu2+, while Hg2+, Mn2+,... 

Zirconium based metal-organic frameworks (Zr-MOFs) are promising candidates for photocatalytic wastewater treatment due to their excellent properties such as high chemical and thermal stability and high photodegradation ability. Herein, we report a novel porous TiO2/ZrO2 photocatalyst derived from UiO-66 and Titania hybrids. UiO-66 nanoparticles was synthesized through solvothermal method and utilized as catalyst support to grow TiO2 particles on its surface. The prepared Titania/MOF nanocomposite was calcined to obtain porous TiO2/ZrO2 photocatalyst for degradation of organic pollutants from colored wastewater under LED visible light. The prepared materials were fully characterized with... 

Enzymatic decolorization of the monoazo dye, acid orange 7 (AO7) by the fungal peroxidase from Coprinus cinereus NBRC 30628 is a complex system, which is greatly affected by temperature, pH, enzyme activity and the concentrations of H2O2 and dye concentration. The study of these factors and investigating the combined interactions between them by applying one-factor-at-a-time (OFAT) method and two other statistical methods including 2-factorial method and response surface methodology (RSM) were aimed in this work. Through OFAT analysis the optimized conditions were a temperature of 25 °C, pH 9.0 with H2O2 concentration of about 3.9 mM and AO7 concentration of 40 mg/l. A complete...