Isotherms and kinetic study of ultrasound-assisted adsorption of malachite green and Pb 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 Pb 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), Pb concentration (3-15mgL) 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 Pbions) was obtained at pH 6.0, 0.009g CuS-NRs-AC, 6.0min mixing by sonication and 15 and 6mgL for MG and Pb ions, respectively. High determination coefficient (R>0.995), Pred-R-value (>0.920) and Adju-R-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 for MG and Pb ions, respectively. This adsorbent over short contact time is good choice for simultaneous removal of large content of both MG and Pb ions from wastewater sample.