Preparation of nano disperse dyes using sulfomethylated lignin: Effects of sulfonic group contents

Multi-site sulfonation of lignin for the synthesis of a high-performance dye dispersant

Sulfonated lignin-based dye dispersants have intensively attracted attention due to their low cost, renewability and abundant sources. However, their utilization is limited by the low content of sulfonic groups and high content of hydroxyl groups in their complex lignin structure, which results in various problems such as high reducing rate of dye, severe staining of the fibers and uneven dyeing. Here, the multi-site sulfonated lignin-based dispersants were prepared with high sulfonic group content (2.20 mmol/g) and low hydroxyl content (2.43 mmol/g). When using it as the dispersant, the dye uptake rate was improved from 69.23 % to 98.55 %, the reducing rate was decreased from 20.82 % to 2.03 %, the K/S value was reduced from 0.69 to 0.02, and the particle sizes in dye system before and after high temperature treatment were stabilized below 0.5 μm. Besides, the dispersion effect was significantly improved because no obvious separation between dye and water was observed even if without the assistance of grinding process. In short, the multi-site sulfonation method proposed in this work could remarkably improve the performances of the lignin-based dye dispersants, which would facilitate the development of the dye dispersion and the high value utilization of lignin.

Adsorption and antibacterial studies of a novel hydrogel adsorbent based on ternary eco-polymers doped with sulfonated graphene oxide developed from upcycled plastic waste

A novel ternary blended polymer composed of cost-effective and readily available polymers was synthesized using poly (vinyl alcohol) (PVA), iota carrageenan (IC), and poly (vinyl pyrrolidone) (PVP). Sulfonated graphene oxide (SGO), prepared from recycled drinking water bottles, was utilized as a doping agent. Varying amounts (1-3 wt%) were combined into the polymer matrix. The produced hydrogel film was examined as a potential adsorbent hydrogel film for the removal of methylene blue (MB) and Gentamicin sulfate (GMS) antibiotic from an aqueous solution. The experimental results demonstrate that the presence of SGO significantly increased the adsorption efficiency of PVA/IC/PVP hydrogel film. The antimicrobial tests revealed that the PVA/IC/PVP-3% SGO hydrogel film exhibited the most potent activity against all the tested pathogenic bacteria. However, the adsorption results for MB and GMS showed that the addition of 3 wt% SGO resulted in a removal percentage that was a two fold increase in the removal percentage compared with the undoped PVA/IC/PVP hydrogel film. Furthermore, the response surface methodology (RSM) model was utilized to examine and optimize several operating parameters, including time, pH of the solution, and initial pollutant concentration. The adsorption kinetics were better characterized by the pseudo-second-order kinetics model. The composite film containing 3 wt% SGO had a maximum adsorption capacity of 606 mg g-1 for MB and 654 mg g-1 for GMS, respectively. The generated nanocomposite hydrogel film demonstrated promising potential for application in water purification systems.

Exploring chemical reactions to enhance thermal and dispersion stability of kraft and organosolv lignin

Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, 31P NMR, 13C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T50% values, suggesting a better stability towards degradation.

Novel Monosulfonated Azo Dyes: Design, Synthesis, and Application as Disperse Dyes on Polyester Fabrics

This study synthesizes and characterizes a series of disperse dyes based on azo Schiff bases, compounds 8-10. Their structures were identified using various analytical techniques, such as FT-IR, 1H/13C NMR, and mass spectrometry. The study's primary objective was to investigate the behavior of disperse dyes 8-10 when used for dyeing polyester fabrics under different conditions, including variations in time, temperature, shade, and pH. The polyester fabric was chosen for this research due to its wide usage and popularity in the textile industry. By examining the effect of temperature and time on the dyeing process, it was observed that increasing the dyeing temperature from low to high (ranging from 90 to 120 °C) and extending the dyeing time from 10 to 30 min resulted in higher K/S values for the polyester samples dyed with disperse dyes. Additionally, dyes 9 and 10 exhibited the most excellent K/S values among the tested dyes. Furthermore, the study found that dye 8 showed the best dyeing performance as the pH of the dye bath increased to 6.

Relationship between reactive group chemistry and printing properties of heterofunctional reactive dyes via screen printing

Screen printing of cotton fabric using newly synthesized azo reactive dyes was carried out in the present study. Functional group chemistry and its effect on the printing properties of cotton fabric by varying the nature, number and position of reactive groups of synthesized azo reactive dyes (D1-D6) was studied. Different printing parameters (Temperature, alkali and urea) and their effect was explored on the physicochemical printing properties e.g., fixation, color yield, and penetration of the dyed cotton fabric. Data revealed that dyes with more reactive groups and having linear and planar structures (D-6) showed enhanced printing properties. Spectraflash spectrophotometer was used to evaluate the colorimetric properties of screen-printed cotton fabric and results showed superb color buildup. Printed cotton samples displayed excellent to very good ultraviolet protection factor (UPF). Presence of sulphonate groups and excellent fastness properties may entitle these reactive dyes as commercially viable for urea free printing of cotton fabric.