| Summary: | Herein, a mixed fruit wastes of watermelon (Citrullus lanatus) rind (WR) and orange (Citrus sinensis) peel (OP) were utilized as an alternative precursor for producing a mesoporous activated carbon (WROPAC) with a relatively high specific surface area of 831.4 m2/g. A fast and convenient activation method of microwave assisted H3PO4 was applied to convert the feedstock (WROP) into WROPAC with 20 min of residence time and microwave power of 800 W. The adsorptive ability of WROPAC was evaluated towards removal of toxic cationic dye namely methylene blue (MB). A multivariable statistical optimization for the crucial adsorption variables, specifically A: WROPAC dosage (0.02–0.1 g/100 mL), B: solution pH (4–10), and C: contact time (20–120) was carried out and validated via Box-Behnken design (BBD). According to the BBD results, the best MB removal (90.3%) by WROPAC was achieved at 0.1g/ 100 mL WROPAC dosage, pH = 10 of dye solution pH, and 70 min of contact time with maximum adsorption capacity (qmax) of 225.2 mg/g at 25 °C. The adsorption kinetic and isotherm of MB adsorption by WROPAC were well described by a pseudo-second order (PSO) model and Freundlich model respectively. The adsorption mechanism of MB by WROPAC can be assigned to electrostatic forces, H-bonding, pore filling, and π-π stacking. This investigation shows the possibility of conversion mixed WR and OP wastes into mesoporous activated carbon (WROPAC) with potential application in wastewater treatment. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
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