Mesoporous Activated Carbon from Sunflower (Helianthus annuus) Seed Pericarp for Crystal Violet Dye Removal: Numerical Desirability Optimization and Mechanism Study

Abstract

In this work, sunflower (Helianthus annuus) seed pericarp (SSPC) was converted into mesoporous activated carbon (SSPCAC) via microwave-assisted ZnCl₂ activation to be a cost-effective and renewable adsorbent for crystal violet (CV) dye removal. The obtained SSPCAC exhibits a preferable surface area of 641 m²/g with mesoporous characteristics. A statistical optimization by Box-Behnken Design (BBD) with Response Surface Methodology (RSM) was adopted to achieve the optimal operational conditions for CV dye including SSPCAC dose, solution pH, and contact time. Moreover, desirability functions confirm the maximum CV removal of 91% was attended at SSPC-AC dose (0.083 g/100 mL), solution pH (9.8), and contact time (5.38 min). Thus, the equilibrium data were best described by the Langmuir isotherm model with a maximum adsorption capacity of 111.9 mg/g at 25 ⁰C. Thus, the adsorption kinetics were well described by a pseudo-second order (PSO) model. The adsorption mechanism of CV onto SSPCAC surface can be assigned to the electrostatic attraction, hydrogen bonding, pore filling, and pi-pi interactions. This research highlights the potential of sunflower seed pericarp as a renewable precursor for activated carbon production with promising applications in toxic dye removal from wastewater.