Synthesis of Azo Dyes Derived from 4-Nitroaniline for Textile Coloration and Their Removal from Effluents Using Chemically Modified Sugarcane Bagasse Adsorbent

This inspection explores the potential of 4-nitroaniline’s potential as a novel diazo component in synthesizing azo dyes, highlighting the research’s novelty. Two new azo dyes, designated 4-(4-nitrophenylazo) salicylic acid (SS) and 4-(4-nitrophenylazo) catechol (OH), were prepared by diazotization of 4-nitroaniline followed by coupling with salicylic acid and catechol, respectively. Fourier transform infrared spectroscopy and other analytical techniques confirmed the structural integrity of the dyes before and after application to cotton, wool, acrylic, and polyester fabrics. The dyes exhibited the best color strength (K/S) and fastness properties on cotton. The exhaustion and fixation of the dyes onto cotton fibers improved with increasing temperature, reaching optimal efficiencies (83.92 and 80.34% for SS and 89 and 84.36% for OH) at 95 °C. Furthermore, the study investigates a sustainable method for removing the dyes from textile wastewater. Sugarcane bagasse, a cost-effectiveness and environmentally friendly sorbent, achieved effectual dye elimination from wastewater after sulfuric acid pre-treatment (superior to formaldehyde). This treatment achieved a remarkable 99.34% removal efficiency under optimal conditions (2.5 g, 50 ppm, pH 9, 200 rpm, 120 min). Adsorption exhibited characteristics of both Langmuir isotherm and pseudo-second order kinetics. Diffusion studies revealed intraparticle diffusion as the rate-controlling step, with film diffusion likely governing the adsorption. Regression modeling yielded an R² of 93.89% between process factors and dye removal. The effectiveness was further validated by treating real-world, highly polluted textile wastewater obtained from an Egyptian factory. The sugarcane bagasse treatment effectively removed dyes (almost 98.8%) under optimal conditions, demonstrating its reusability after multiple dye-removal cycles.