Azo Dyes In Presence Research Articles

Brown algae-based preparation, characterization and application of Pd nanocatalyst for enhanced reductive azo dye degradation

This study describes a simple green one-pot synthesis of the Palladium Nanocatalyst (PdNC) using the crude extract of a seaweed Saragassum cervicorne ( S. cervicorne ). The formation of PdNC was monitored by Ultraviolet-visible (UV-Vis) spectroscopy. The characteristic functional groups of phytochemicals in extract and capped PdNC surfaces were identified by FTIR analysis. The Scanning electron microscopy (SEM) analysis of the extract revealed the smooth surface area while that of the catalyst was found to be rough and irregular whereas Energy-dispersive X-ray spectroscopy (EDS) confirms the existence of Pd in the catalyst. The powder X-ray diffraction (XRD) analysis confirmed the crystalline nature of PdNC with a cubic face-centred structure. The transmission electron microscopy (TEM) was used to record the images of PdNC with a particle size of 3.131 to 16.45 nm. TGA reports reveal the degradation of the PdNC occurred at 197.8 ° C. The catalytic activity PdNC was tested against the reduction of hazardous azo-dyes such as Congo red (CR), Methyl orange (MO) and Methyl red (MR) with NaBH 4 as electron donor. The PdNC catalysed azo-dyes in presence of aqueous NaBH 4 and was examined by UV–visible spectroscopy where PdNC mediated the electron transfer from NaBH 4 to azo-dyes as a carrier. The maximum degradation was observed for Methyl Orange (0.08 mM) of about 99.66% with 60 μg/μL PdNC. Congo red (0.1 mM) showed the highest degradation of 99.25% with a catalyst loading of 40 μg/μl while that of Methyl red (0.1 mM) with 80 μg/ μL catalyst was 95.45%. The preparation of catalyst using water and exploiting water-soluble components of S. cervicorne as reducing agents makes this one-pot preparation of catalyst a novel approach for the preparation of Pd nanocatalyst. The replacement of non-toxic solvents, as well as the use of unexplored brown seaweed, is of primary importance from an economic as well as environmental perspective. Therefore, the newly prepared PdNC is a promising catalytic material obtained by the green facile synthetic method and exhibit enhanced catalytic activity in stimulation on the reduction of harmful azo dyes.

Homogeneous and heterogeneous catalytic oxidation of some azo dyes using copper(II) ions.

The kinetics of the homogeneous and heterogeneous catalytic oxidation processes of three azo dyes in presence of copper (II) - ions, copper (II) - ions - supported on alumina and on zinc oxide as well as copper ammonia complex supported on alumina were investigated in aqueous solutions. The dyes are Chromotrope 2B (C2B), Chromotrope 2R (C2R) and Chrysophenen (CRY). The reaction progress was followed by monitoring the decrease in absorbance at ℷmax 512, 511 and 401 nm, respectively. The rate of reaction increased with increasing either the concentration of the dye or the catalyst, giving a plateau at high concentrations of the catalyst. On the other hand, the rate of reaction increased gradually with increasing hydrogen peroxide concentration attaining a maximum then decreased thereafter. The reaction rate was also increased with increasing pH and temperature and was found to be entropy controlled. This work could be applied for dye baths water reuse to reduce costs in textile and dyeing factories as will as for environmental purposes.

Green synthesis of Ag-Au bimetallic nanocomposites using a biodegradable synthetic graft copolymer; hydroxyethyl starch-g-poly (acrylamide-co-acrylic acid) and evaluation of their catalytic activities

An eco-friendly method for the synthesis of Ag-Au bimetallic nanocomposites from aqueous solution using a novel biodegradable graft copolymer hydroxyethyl starch-g-poly (acrylamide-co-acrylic acid) acting as a reducing and stabilising agent was reported. The graft copolymer was prepared using a solution polymerization technique using potassium perdisulfate as the initiator at 70°C and was characterized by measuring its molecular weight and molecular weight distribution using size exclusion chromatography, FTIR spectroscopy, XRD and SEM studies. Biodegradation study was carried out by enzyme hydrolysis. Ag-Au nanocomposites prepared by using the synthesised graft copolymer was characterized by using UV–VIS and FTIR spectroscopy, HR-TEM with SAED analysis, FESEM and EDAX analysis. Catalytic activities of the bimetallic nanocomposites were evaluated for the reduction of 4-nitrophenol to 4-aminophenol, degradation of ‘NN’ (azo bond) bond in some azo dyes in presence of sodium borohydride. Three commercial azo dyes namely congo red, sudan-1 and methyl orange were used for azo bond degradation. The kinetics of catalytic activities were studied using UV–VIS spectroscopy.

Simultaneous decolorization of reactive Orange M2R dye and reduction of chromate by Lysinibacillus sp. KMK-A

Azo dyes constitute the largest and diverse group of dyes, widely used in number of industries that are contributing toward organic and inorganic load of effluent treatment. In the present study, Lysinibacillus sp. KMK-A was able to effectively decolorize Orange M2R dye up to 2000mgl−1 (Vmax of 19.6mgl−1h−1 and Km of 439mgl−1) and reduce Cr(VI) up to 250mgl−1 (Vmax of 3.6mgl−1h−1 and Km 28.3mgl−1). It also has an ability of simultaneous decolorization of Orange M2R dye (200–1000mgl−1) with reduction of Cr(VI) (50–200mgl−1). Significant reduction in total organic carbon content, chemical and biological oxygen demand along with spectroscopic and chromatographic analysis confirmed the biotransformation of Orange M2R. Involvement of enzymes namely azoreductase and chromate reductase was observed during biotransformation. The phyto and geno toxicity studies demonstrated that metabolites of dye degradation were non-toxic. Higher tolerance with simultaneous decolorization and detoxification of azo dyes in presence of Cr(VI) makes Lysinibacillus sp. KMK-A, a potential candidate for eco-friendly remediation of metal contaminated dye effluents.