Isotherms and kinetic study of ultrasound-assisted adsorption of malachite green and Pb2+ ions from aqueous samples by copper sulfide nanorods loaded on activated carbon: Experimental design optimization.

Copper sulfide nanorods loaded on activated carbon (CuS-NRs-AC) was synthesized and used for simultaneous ultrasound-assisted adsorption of malachite green (MG) and Pb2+ ions from aqueous solution. Following characterization of CuS-NRs-AC were investigated by SEM, EDX, TEM and XRD, the effects of pH (2.0-10), amount of adsorbent (0.003-0.011g), MG concentration (5-25mgL-1), Pb2+ concentration (3-15mgL-1) and sonication time (1.5-7.5min) and their interactions on responses were investigated by central composite design (CCD) and response surface methodology. According to desirability function on the Design Expert optimum removal (99.4%±1.0 for MG and 68.3±1.8 for Pb2+ions) was obtained at pH 6.0, 0.009g CuS-NRs-AC, 6.0min mixing by sonication and 15 and 6mgL-1 for MG and Pb2+ ions, respectively. High determination coefficient (R2>0.995), Pred-R2-value (>0.920) and Adju-R2-value (>0.985) all are good indication of best agreement between the experimental and design modelling. The adsorption kinetics follows the pseudo-second order model and adsorption isotherm follows the Langmuir model with maximum adsorption capacity of 145.98 and 47.892mgg-1 for MG and Pb2+ ions, respectively. This adsorbent over short contact time is good choice for simultaneous removal of large content of both MG and Pb2+ ions from wastewater sample.