Linearized form effect on estimation adsorption parameters of three industrial dyes by lignocellulosic sorbent

Zeolites as Adsorbents and Photocatalysts for Removal of Dyes from the Aqueous Environment

This study investigated the potential of zeolites (NH₄BETA, NH₄ZSM-5, and NaY) to remove two frequently used dyes, methylene blue (MB) and rhodamine B (RB), from an aqueous environment. The removal of dyes with zeolites was performed via two mechanisms: adsorption and photocatalysis. Removal of dyes through adsorption was achieved by studying the Freundlich adsorption isotherms, while photocatalytic removal of dyes was performed under UV irradiation. In both cases, the removal experiments were conducted for 180 min at two temperatures (283 K and 293 K), and dye concentrations were determined spectrophotometrically. Additionally, after photodegradation, mineralization was analyzed as chemical oxygen demand. A computational analysis of the structures of MB and RB was performed to gain a deeper understanding of the obtained results. The computational analysis encompassed density functional theory (DFT) calculations and analysis of two quantum-molecular descriptors addressing the local reactivity of molecules. Experimental results have indicated that the considered zeolites effectively remove both dyes through both mechanisms, especially NH₄BETA and NH₄ZSM-5, due to the presence of active acidic centers on the outer and inner surfaces of the zeolite. The lowest efficiency of dye removal was achieved in the presence of NaY zeolite, which has a lower SiO₂/Al₂O₃ ratio. A more efficient reduction was completed for RB dye, which agrees with the computationally obtained information about reactivity.

Sustainable application of Cassia obovata-based chrysophanic acid as potential source of yellow natural colorant for textile dyeing

In the current pandemic scenario, sustainable green products particularly antiviral, antioxidant, and antibacterial in nature are gaining worldwide fame in almost every walk of life. Cassia obovata (C. obovata) has been valorized as a source of yellow natural dye for nylon dyeing. For the isolation of dye extracts and for surface tuning, nylon fabrics were treated with microwave rays up to 10 min. For getting new shades with good to excellent fastness characteristics, sustainable bio-mordants in comparison with chemical mordants have been used at 60 °C, 70 °C, and 80°C. It has been found that for getting effective colorant yield, acidic extract should be exposed to MW ray treatment up to 6 min, and for getting improved fastness rating, bio-mordants have given excellent color characteristics. Statistical optimization of dyeing variable shows that application of 40 mL of C. obovata acidic extract of RE of 6 pH containing 3 g/100 mL of salt when employed at 55 °C for 45 min has given excellent results onto irradiated nylon fabric (RNF). It is inferred that Cassia obovata has an excellent potential for coloration of surface-modified fabrics, where the application of low amount of bio-mordants under statistical optimized conditions has made process more ecological, economical, and sustainable.