RSM-CCD design of malachite green adsorption onto activated carbon with multimodal pore size distribution prepared from Amygdalus scoparia: Kinetic and isotherm studies

Abstract

In the present work, the activated carbon (AC) adsorbent with multimodal pore size distribution prepared from Amygdalus scoparia as low-cost and locally available source was applied for efficient adsorption of malachite green (MG) from aqueous media. The surface properties of the adsorbent were identified by various techniques such as FT-IR, BET and SEM analyses. The dependency of MG adsorption efficiency on the variables such as pH, initial dye concentration, adsorbent dosage and contact time was studied by central composite design (CCD) coupled with response surface methodology (RSM). A good agreement between experimental and predicted data was achieved that proved the efficiency of this model for prediction of real optimum point. Among the well-known previously isotherm models, the experimental equilibrium data were efficiently fitted by the Freundlich model, while maximum adsorption capacity of MG at 0.01 g of the adsorbent was 144.30 mg g−1. The kinetic data were efficiently interpreted by the combination of pseudo-second-order and intra-particle diffusion models. The advantage of the green adsorbent was that a small amount of the adsorbent (0.027 g) is applicable for high adsorption percentage of MG (>99.5%) within a reasonable time (75 min).