Magnetic porous Ag2O/Chitin nanostructure adsorbent for eco-friendly effective disposing azo dyes

Water treatment is as much important as it is to satisfying 11 worldwide sustainable development goals out of 17. The removal of Azo is much important as they are toxic and their existence in water, air and food can easily affect humans by triggering allergies, forming tumours etc. Azo contained Dyes Production was banned in many countries. This research aims to synthesize composite Nanorods and Nanospheres and characterize and test to remove Azo dyes from the wastewater. This research used a previously reported method to rapidly synthesize chitin magnetite nanocomposites (ChM) by co-precipitation while irradiating with ultrasound (US). Detailed structural characterization of ChM revealed a crystalline phase analogous to magnetite and spherical morphologies; extending the reaction time to 8 min yielded a "nanorod" type morphology. Both the morphologies displayed a nanoscale limit with particles averaging between 5 and 30 nm in size, resulting the superparamagnetic performance and saturation magnetization values between 45 and 58 emu/g. The nitrogen adsorption-desorption isotherms showed that the surface modification of ChMs resulted in a rise of specific surface area and pore size. Anionic azo dyes (methyl orange (MO) and reactive black 5 (RB5)) adsorption on the surface of nanocomposites was also demonstrated to be pH-dependent, with the reaction favoured for surface-modified samples at pH 4 and unmodified samples at pH 8. Adsorption capacity studies showed that molecule size effect and electrostatic attraction were two distinct adsorption processes for unmodified and modified ChMs. Chitin Magnetite nanoparticles appear to be a substitute for traditional anionic dye adsorbents. Additionally, the two key materials sources, chitin, and magnetite are inexpensive and easily accessible.

The interactions between Reactive Black 5 and human serum albumin: combined spectroscopic and molecular dynamics simulation approaches

Azo dyes are made in significant amounts annually and released into the environment after being employed in the industry. There are some reports about the toxic effects of these dyes on several organisms. Thus, the textile dye Reactive Black 5 (RB5) has been examined for its cytotoxic effects on the human serum albumin (HSA) structure. Molecular interaction between RB5 and HSA indicated the combination of docking methods, molecular dynamic simulation, and multi-spectroscopic approaches. HSA's intrinsic fluorescence was well quenched with enhancing RB5 level, confirming complex formation. Molecular dynamics (MD) simulation was done to study the cytotoxic effects of RB5 and HSA conformation. Molecular modeling revealed that the RB5-HSA complex was stabilized by hydrogen bonds and van der Waals interactions. The results of molecular docking revealed that the binding energy of RB5 to HSA was - 27.94 kJ/mol. The change in secondary structure causes the annihilation of hydrogen bonding networks and the reduction of biological activity. This research can indicate a suitable molecular modeling interaction of RB5 and HAS and broaden our knowledge for azo dye toxicity under natural conditions.

Optimization of complete RB-5 azo dye decolorization using novel cold-adapted and mesophilic bacterial consortia

Azo dyes are an important group of recalcitrant xenobiotics, which are difficult to degrade and deteriorate in cold environments. In this study, two microbial consortia consisting of cold-adapted and mesophilic bacteria were developed for effective decolorization of Reactive Black-5 azo dye. These bacteria were isolated from textile wastewater and soil of a cold region. Identification of bacterial isolates using 16s rRNA gene analysis revealed that they belong to genus Pseudoarthrobacter, Gordonia, Stenotrophomonas, and Sphingomonas. Decolorization assay was performed for every strain at dye concentrations of 25, 50 and 100 mg/L and the consortia PsGo consisting of mesophilic bacteria and StSp consisting of cold-adapted bacteria were constructed accordingly. Results showed that the consortia PsGo and StSp were able to decolorize 54 and 34 percent of RB-5 (50 mg/L) during 7 days. To improve the dye removal efficiency of the consortia, several parameters including temperature, pH, carbon and nitrogen sources were optimized. Over longer periods, StSp consortium managed to completely decolorize RB-5 (50 mg/L) at optimized conditions of 25-30 °C, pH 9, and using glucose and NH₄H₂PO₄ as carbon and nitrogen source respectively, whereas PsGo consortium decolorized RB-5 (50 mg/mL) completely at 37 °C, pH 11, and with lactose and NH₄H₂PO₄ used as carbon and nitrogen sources. Kinetic of reactions for StSp and PsGo consortia were found to be 0.05 and 0.13 day^-1 respectively, but became 0.71 and 0.9 day^-1 after optimization. In general, cold ecosystems are good sources for the isolation of novel bacterial strains with a potential application, especially when used as consortia, in environmental biotechnology such as decolorization of RB-5.