Cost-effective ecofriendly nanoparticles for rapid and efficient indigo carmine dye removal from wastewater: Adsorption equilibrium, kinetics and mechanism

In this study, a novel, ecofriendly and inexpensive nanoscale adsorbent, derived from the byproducts of water industry (nWTRs), was prepared and characterized for efficient removal of Indigo Carmine (IC) dye from contaminated water. The adsorption study analyzed the influence of pH, adsorbent/IC solution ratio, exposure time, IC concentration, and temperature to maximize IC dye removal from contaminated wastewater. The adsorption equilibrium data fitted to Langmuir model whereas power function and first order models fitted the adsorption kinetic data. The maximum adsorption capacity (qmax) of IC was found to be 30.86 mg⋅ g−1 for bulk WTR and 172.4 mg⋅ g−1 for nWTR. The nanosized adsorbent was 5.6 times more effective than the bulk WTR and the adsorption equilibrium can be reached within 30 min. The thermodynamic study in the interval 25–45 °C proved that IC adsorption in nWTR was spontaneous and endothermic. Hydrogen bonding, Al and Fe complexes formation and electrostatic interlinkage are the dominant processes of IC adsorption in nWTR. Repeated cycles of adsorption/desorption of IC in nWTR confirmed the stability of the adsorbent. The excellent IC dye removal efficiency of nWTRs from textile industry effluent suggests its promising potential in remediating IC contaminated wastewater.