From Renewable Biomass to Water Purification Systems: Oil Palm Empty Fruit Bunch as Bio-Adsorbent for Domestic Wastewater Remediation and Methylene Blue Removal

Abstract

Oil palm empty fruit bunch fibers (OPEFBF), in three size ranges (small: 250–450 µm, medium: 450–600 µm, large: 600–800 µm), were investigated as a filter-bed material in biofilters for the removal of organic matter and nutrients. After saturation, these fibers (post) were used in the removal of methylene blue through batch processes. The batch adsorption tests included optimizing the adsorbent dosage (0.5–32.0 g/L) and contact time (2.5–60.0 min). Experimental data were fitted to various kinetic/isotherm models. Instrumental characterization of both raw and post fibers was conducted. Post fibers underwent morphological/compositional changes due to the presence of microorganisms and their byproducts. Efficiencies reached up to 94% for chemical oxygen demand (COD), 88.4% for total nitrogen and 77.2% for total phosphorus. In batch adsorption, methylene blue removal exceeded 90%, underscoring the effectiveness of small raw OPEFBF and large post OPEFBF. Kinetic models indicated that raw OPEFBF better fit the pseudo-first-order model, while post OPEFBF better fit the pseudo-second-order model. Both types of OPEFBF showed a good fit with the Freundlich model (higher R2, lower χ2 and SSE). Particularly, large post OPEFBF stood out as the most efficient adsorbent, achieving a maximum adsorption capacity of 12.02 mg/g for methylene blue. Therefore, raw/post OPEFBF could be an alternative to remove contaminants from wastewater.