Synthesis of CuS nanoparticles loaded on activated carbon composite for ultrasound-assisted adsorption removal of dye pollutants: Process optimization using CCD-RSM, equilibrium and kinetic studies

In this study, the CuS nanoparticles loaded on activated carbon (CuS-NPs-AC) composite was synthesized and then, characterized by XRD and FE-SEM analyses. The prepared composite was used as a potential adsorbent for the simultaneous ultrasound-assisted removal of Indigo Carmine (1C) and Safranin-O (SO). The CuS-NPs-AC dose (0.01-0.03 g), sonication time (1-5 min), initial SO concentration (5-15 mg L-1) and initial IC concentration (5-15 mg L-1) as expectable effective parameters were studied by central composite design (CCD) under response surface methodology (RSM) to obtain an useful knowledge about the effect of simultaneous interaction between IC and SO on their removal percentage. The optimum SO and IC removal percentages were determined to be 98.24 and 97.15% at pH = 6, 0.03 g of the CuS-NPs-AC, 3 min sonication time, 12 and 10 mg L-1 of IC and SO. The values of coefficient of determination (R-2) for SO and IC were 0.9608 and 0.9796, respectively, indicating the favorable fitness of the experimental data to the second order polynomial regression model. The isotherm data were well correlated with Freundlich model. The maximum monolayer adsorption capacities of 87.5 and 69.90 mg g(-1) at room temperature for IC and SO in the investigated binary system expressed the high efficiency of the novel adsorbent for water cleanup within a short time. The investigation of correlation between time and rate of adsorption revealed that IC and SO adsorption onto the CuS-NPs-AC followed pseudo-second-order and intra-particle diffusion simultaneously.