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

[Display omitted] •This work devoted to the investigation of adsorption of malachite green and Pb2+ ions by CuS-NPs-AC.•An experimental design methodology was used to optimize the parameters.•The MG and Pb2+ ions adsorption data was best followed by Langmuir and pseudo-second order models.•The novel sorbent was characterized by SEM, TEM, EDX and XRD analysis.•The adsorption was assisted by ultrasound and performed at pH 6.0. 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.