Comparative Evaluation of Fresh and Mature Moringa oleifera Seeds as Chemically Activated Adsorbents for Sustainable Turbidity Removal

The growing environmental and health concerns associated with conventional inorganic coagulants in wastewater treatment have accelerated interest in sustainable, plant-based alternatives. In this study, Moringa oleifera seeds, both fresh and mature, were evaluated as natural precursors for the synthesis of low-cost, eco-friendly adsorbents. Adsorbents were prepared by chemical activation with 0.6 M sulphuric acid at a 1:8 (w/v) impregnation ratio, followed by thermal treatment at 400°C for 2 and 4 hours. Physicochemical characterisation using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) confirmed the development of active functional groups (hydroxyl, carbonyl, ether), an amorphous carbonaceous structure, and enhanced surface porosity, particularly in fresh seed-derived adsorbents. Turbidity removal from synthetic kaolin wastewater, measured by a nephelometric method, revealed that both fresh and mature seed adsorbents achieved high efficiency under optimal conditions, with 11% (w/v) dosage at 4 h activation yielding removals of 93.50% and 93.99%, respectively. Across a range of dosages, however, fresh seeds consistently outperformed mature seeds, attributed to their higher protein content, better preservation of functional biomolecules, and greater surface reactivity due to reduced lignification. These findings highlight the potential of Moringa oleifera seeds, particularly in their fresh form, as effective, renewable adsorbents for turbidity removal. The work underscores the importance of activation optimisation in maximising performance and supports the integration of plant-based adsorbents into sustainable water treatment strategies aligned with global clean water and sanitation goals (SDG 6).