Production of large surface area activated carbon from a mixture of carrot juice pulp and pomegranate peel using microwave radiation-assisted ZnCl2 activation: An optimized removal process and tailored adsorption mechanism of crystal violet dye

In this study, carrot juice pulp (CJP) and pomegranate peel (PP) biomass wastes were used as alternative precursors for producing high surface area activated carbon (referred to as CJPPPAC) using microwave radiation assisted with ZnCl2 activation. The CJPPPAC has a large surface area (SA = 1202.2 m2/g), according to the Brunauer-Emmett-Teller analysis, and a mesoporous structure (average pore diameter of 3.0 nm). The adsorption characteristics of CJPPPAC were studied for the removal of a model of cationic dye (crystal violet; CV). The numerical desirability function of the Box-Behnken design (BBD) was used to optimize important adsorption variables (A: CJPPPAC dose (0.02–0.08 g); B: pH (4–10); C: time (2–6); and D: initial CV concentration (20–80 mg/L). The dye adsorption kinetics profile followed a pseudo-second-order (PSO) model, whilst the equilibrium adsorption was described by the Freundlich model. The maximum adsorption capacity (qmax) of CJPPPAC for the CV dye was identified to be 211.8 mg/g. The adsorption mechanism of CV dye onto the CJPPPAC surface occurs by a variety of mechanisms including electrostatic forces, pore diffusion, π-π stacking, and H-bonding. This work illustrates the applicability of CJP and PP as biomass precursors for the efficient production of CJPPPAC and its utility for wastewater treatment.