جستجوی مقالات مرتبط با کلیدواژه « azo dye » در نشریات گروه « پزشکی »

Azo dyes are present in the wastewater of most textile factories, and if they enter water resources, they pose risks to the health of humans and the living environment due to the effects of toxicity, biological accumulation, and mutagenicity. This study aimed to determine the removal of azo dye by a biological method using wastewater treatment plant sludge in aerobic and anaerobic conditions and isolation and identification of bacteria.

This experimental study, was conducted in the faculty of health, at Mazandaran University of Medical Sciences. In this study, the removal of reactive red azo dye 195 in the wastewater of textile factories was investigated using the activated sludge of the wastewater treatment plant. Experiments were carried out in batch mode in both aerobic and anaerobic conditions with 192 samples. The concentrations of azo dye in the range available in the wastewater of textile factories were 50, 65, and 80 mg/liter. The culture medium used in this study was a mineral medium containing glucose. Bottles containing culture medium, sludge, and azo dye were kept at 30°C in an incubator in aerobic and anaerobic conditions for 8 days. The effect of factors including contact time, amount of sludge, and concentration of color was investigated. Sampling was done at the contact times of 1, 2, 4, and 8 days and after centrifuge, the color concentration was measured by spectrophotometric method at a wavelength of 545 nm. The total organic carbon (TOC) concentration of the samples was measured by a TOC analyzer. After removing the color, the bacteria in the bottles were identified by the differential diagnosis method and using special culture media, gram staining techniques, and biochemical tests.

In anaerobic conditions and contact time of 8 days, the removal of azo dye in concentrations of 50 and 80 mg/liter by using 5 ml of biomass was obtained by 93 and 82%, respectively. In the aerobic condition, the removal of the dye was achieved to more than 90% within two days, and after that, the removal efficiency reached 100% with a gently increasing slope up to 8 days. By increasing the concentration of dye from 50 to 80 mg/liter, the removal efficiency decreased by about 10%. Increasing the volume of sludge from 5 to 10 ml in both cases did not have a significant effect on increasing the amount of dye removal. The amount of azo dye removal was higher in aerobic than in anaerobic conditions. In aerobic conditions, for all dye concentrations, the TOC removal rate was about 85-90%. There was no significant difference in the amount of TOC removal for 5 and 10 ml of sludge. The average TOC removal in aerobic was about 10% higher than in anaerobic conditions. In the aerobic condition, the identified bacteria included Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Pseudomonas aerogenosa, and in the anaerobic condition, the identified bacterial species were Lactobacillus, Enterococcus faecalis, and Bacillus cereus.

Complete removal of azo dye from textile wastewater by sludge biomass under microaerophilic culture conditions is possible with a contact time of 8 days or more. The dye removal efficiency was higher in partial aerobic than in absolute anaerobic conditions. The identified azo dye-removing bacteria were mainly facultative anaerobic and microaerophilic.

Large quantities of dyes, including refractory azo dyes, are discharged directly into wastewater from the textile and petroleum industries and can be removed by bioremediation. In this study, bioinformatics tools were used to modify the structure of the enzyme azuridactase to improve its performance in degrading these dyes, including methyl red.

The amino acid sequence of the azoridactase enzyme was obtained from the UniProt database. The three-dimensional structure of the enzyme was predicted using modeling tools, and the best model was determined using Qmean web software. Due to the close proximity of the active site of this enzyme to that of Bacillus Smithii, the substrate (methyl red) was docked to a three-dimensional model of the active site using the PyRx program. Potential mutations at the active site were identified through sequence alignment. The exerted mutations were examined regarding the changes in binding energy and the interaction network.

The structure generated by Robetta was chosen as the best model for the Q9X4K2 sequence. The mutagenesis results, in terms of binding energy and interaction plot, indicated that the optimal mutation involves changing proline 132 to serine. This mutation reduces the binding energy between methyl red and azoridactase from -6.9 kcal/mol to -7.4 kcal/mol. Furthermore, an examination of the interaction network in the mutant protein revealed the formation of a new hydrogen bond.

The reduced binding energy between the enzyme and methyl red suggests that the enzyme is more favorably positioned towards the substrate, thereby enhancing the enzyme's efficacy in degrading azo dyes.

The most used dyes in textile industries are Azo Group dyes. Azo dyes have complex aromatic compounds, low chemical and biodegradable stability. Due to these properties, treatment of this type of wastewater by conventional methods will not meet environmental standards. The advanced oxidation process has been widely used to treat organic matter from wastewater. In this study, dye purification of azo dye Reactive Red 195 by UV/H2O2 process was investigated. Moreover, the parameters affecting this process have also been determined.

In this study, dye treatment was conducted in the presence of different concentrations of hydrogen peroxide, and at different retention time, temperature and pH values in a continuous photoreactor equipped with UV lamps. Using central composite design and response surface methodology (RSM), effects of various concentrations of hydrogen peroxide, retention time, temperature, and pH on the color and COD removal were studied in the range of 0–2%, 60-240 min, 25-80 oC, and 3-10, respectively.

The results showed that the concentration of hydrogen peroxide and retention time were the most influential parameters on color and COD removal. Color removal significantly enhanced by increasing retention time and H2O2 concentration to 200 min and 1.2%, respectively. pH increase had positive effect on color removal. There were increases in the rate of color and COD removal as the temperature went up to 50 oC. However, temperature of 80 oC negatively impacted AOP process. According to RSM, the optimum factor levels were achieved at 1.28%, 240 min, 49 oC and 10 for concentrations of hydrogen peroxide, reaction time, temperature, and pH, respectively.

According to the result, UV/H2O2 proved to be capable of degrading Reactive Red 195. Almost all the azo dye color destroyed after 209 min while 87.52 % of the COD was removed after 240 min of irradiation.