Thermochemical treatment of mixed mandarin peel and algae via microwave and H3PO4 activation: process optimization and adsorption mechanism for methylene blue dye

Herein, blended mandarin (Citrus reticulata) peel (MP) and algae (AG) biomass were thermochemically treated (TCTMPAG) to yield a cost-effective and renewable adsorbent for removal of methylene blue (MB), a known toxic cationic dye. The preparation included microwave irradiation, in conjunction with H3PO4 activation at 800 W for 15 min in a nitrogen atmosphere. The adsorption characteristics of TCTMPAG were studied by assessing its capacity to remove methylene blue (MB) dye from aqueous media. The Box-Behnken design (BBD) was used to optimize key adsorption factors, namely A: TCTMPAG dosage (0.02–0.12 g/0.1 L), B: pH (4–10), and C: contact period (30–420) min. The BBD model determined that the highest elimination of MB (98.4