Removal of direct dyes from wastewater using chitosan and polyacrylamide blends

Abstract

This study investigated the feasibility of employing neat chitosan powder, polyacrylamide, and chitosan micro-beads as adsorbents for the rapid and efficient removal of Direct Blue 78 dye from textile industrial wastewater. A series of batch experiments were conducted to examine the impact of adsorbent dose, contact time, and pH on the adsorption process. The physicochemical analysis, including FTIR, zeta potential analysis, and SEM were performed to identify the adsorption mechanism of chitosan powder and micro-beads. It was found that increasing the powder chitosan dose to 4.5 g/L and contact time up to 40 min resulted in achieving a significant increase in dye removal efficiency up to 94%. The highest removal efficiency of 94.2% was achieved at an initial dye concentration of 50 mg/L, a chitosan dosage of 4.5 g/L, and an optimized contact time of 60 min. Utilizing a polyacrylamide gel dose of 45 mL/L reduced the sedimentation time of chitosan from 8 h to 5 min. Equilibrium studies showed an initial L-shaped equilibrium curve, indicating that the adsorption process primarily arises from electrostatic interactions between dye molecules and adsorbent particles (physical forces). The Langmuir isothermal model demonstrated the best fit to the equilibrium data. Combining chitosan powder with polyacrylamide gel emerges as an economically viable choice for dye removal in industrial wastewater effluents, offering a cost-effective alternative to pricey commercial adsorbents. The results of the study revealed that the presence of polyacrylamide dye enhanced the removal efficiency and settling time of DB78 dye using chitosan.