Purification of aqueous fluids from basic fuchsine employing a new polymer of CMC-CMS hydrogel mixture: sustainability perspective.

Medical laboratory waste, generated during diagnostic and research activities, contains pathogenic microbes and carcinogenic chemicals that pose significant risks to environmental and human health. To address this issue, physicochemical treatment methods such as hydrogel-based adsorption have been explored. This study investigates the water layer adsorptive extraction of basic fuchsine and malachite green dyes from aqueous solutions using hydrogels prepared from carboxymethyl cellulose (CMC) and carboxymethyl starch (CMS) via a freeze-thawing physical cross-linking method. The hydrogels were characterized by mechanical properties including gel fraction, swelling ratio, and water content at varied CMC-CMS ratios. Adsorption experiments were conducted at an ambient temperature of 23 ± 2 °C, initial dye concentration of 1% (0.02 M), and controlled solution pH, with contact times ranging from 24 to 144 h. The effect of ionic strength was also assessed through variation in the polymer ratio and salt conditions, influencing adsorption efficiency, while the process was analyzed using Langmuir, Elovich, and Flory-Huggins isotherm models, with the best fit determined by linear regression coefficient (R²). Kinetic studies revealed that the adsorption followed a pseudo-second order. Optimization studies identified an ideal hydrogel formulation, with varying ratios influencing adsorption performance. The CMC-CMS hydrogel demonstrated high removal efficiency (> 90%) for both dyes, while the 100% CMC hydrogel exhibited the highest malachite green adsorption, with removal increasing linearly. These findings confirm the efficient application of CMC and CMS hydrogels for dye adsorption, offering a promising approach for treating hazardous laboratory waste.