Blended tropical pineapple peel and crown fruit wastes as precursor for activated carbon by microwave-assisted H₃PO₄ activation: process optimization for methylene blue dye removal

A blended tropical pineapple (Ananas comosus) peel and crown (PPC) fruit wastes were utilized as an alternate source material for producing mesoporous-activated carbon through H₃PO₄ activation employing microwave pyrolysis. Diverse techniques including BET, XRD, FTIR, and SEM–EDX were employed to characterize the PPC-AC. The efficacy of PPC-AC as an adsorbent was assessed for removing (MB) cationic dye from an aqueous medium. Optimization of adsorption process parameters—adsorbent dose (A: 0.02–0.1 g/100 mL), solution pH (B: 4–10), and contact time (C: 40–360 min)—was conducted using RSM-BBD. The adsorption process adhered to pseudo-second-order (PSO) kinetics and Freundlich isotherm models. PPC-AC demonstrated a peak adsorption capacity of 39.5 mg/g for MB dye. The adsorption mechanism of MB dye was attributed to various interactions including electrostatic, H-bonding, and π–π interaction. This investigation showcases the efficacy of a renewable biomass resource for generating activated carbon with advantageous adsorption properties for cationic dyes.