Enhancement of the surface properties of oil palm calyx biomass by redox initiated graft copolymerization with methacrylic acid for the adsorption of dyes

Abstract

Modified biomass from oil palm calyx, an agro-waste, was utilized for the removal of methylene blue (MB) and malachite green (MG) from industrial effluent mimic. Graft copolymerization technique was adopted for the modification process, using methacrylic acid as the functional monomer and Fenton’s reagent as the initiator. Optimum grafting condition was established by varying the Fenton’s reagent composition, grafting time, temperature and biomass mass. About 30 % grafting yield was attained at a 1:200 [Fe²⁺]/[H₂O₂] Fenton’s reagent composition, 60℃, 60 min and 1 g biomass mass. Characterization results indicated a successful incorporation of carbonyl group (CO), from the carboxyl group of methacrylic acid, on the surface of the biomass material. Adsorption process showed high dye removal efficiency (over 98 %) at pH 6, 30 mg/L concentration, 90 min and, 50 mg copolymer mass. The sorption data best followed the pseudo-second-order kinetic model (with R² > 0.93) and the Redlich-Peterson isotherm (R² > 0.94). The negative ΔGº values, obtained at 303 – 333 K for the sorption of MB and MG, indicated feasibility and spontaneity, while those of ΔHº and ΔSº were indication of exothermicity and a process occurring with reduction in randomness at the dye/copolymer interface. Aggregation of the outcome of the various tests portrayed the copolymer as an adsorbent of high physicochemical qualities with good dye adsorbing efficiency. This submission, thereby, highlights the advantages of graft copolymerization technique in the improvement of adsorbent’s properties for wastewater treatment.