Valorization of agricultural by-product Moringa stenopetala seed husks into activated carbon for Reactive Black and Basic Blue dye removal from textile wastewater

The presented experiment investigated the potential of Moringa stenopetala seed husks for producing activated carbon and evaluated its applicability as an adsorbent for removing Reactive Black 5 and Basic Blue 3 dyes from textile effluent. To produce the activated carbon, the MSSH was first impregnated with H₃PO₄ at a ratio of 3:1 (acid:biomass) followed by pyrolysis. Pyrolysis under N₂ for a duration of 1 h was compared at two temperatures of 400 ℃ and 500 ℃, achieving high BET surface areas of 1389 and 1693 m²/g, respectively. The activated carbon with the higher surface area (AC-500) was carried through for the conduction of adsorption studies at different pH, contact time, activated carbon doses, and initial dye concentrations. Experimental data were best described by the Langmuir isotherm model, indicating a monolayer coverage on the adsorbents’ surface. The maximum monolayer adsorption capacity was found to be 833 and 67 mg/g for Basic Blue 3 and Reactive Black 5, respectively, demonstrating a higher affinity of the carbon toward cationic dyes. In kinetic studies, the adsorption of the dyes well followed the pseudo-second-order kinetic model. In synthetic textile wastewater batch tests, 100% dye removal was achieved at pH 6 in 1 h with an adsorbent dosage of 3 g/L in dye concentrations up to 100 mg/L. The results of this study revealed that Moringa stenopetala seed husks can serve as a sustainable precursor for high-efficiency activated carbon-based dye removal from textile wastewater.