Development of a multi-component agro-waste bio-adsorbent for heavy metal removal from real landfill leachate

Landfill leachate represents a complex wastewater stream containing both organic and inorganic pollutants, including heavy metals that pose serious ecological risks. Conventional biological treatments are often insufficient for stabilized leachates, necessitating alternative approaches such as bioadsorption using agro-waste materials (AWMs). This study evaluated four multi-component bio-adsorbent (MCB) blends composed of banana peel, coconut fiber, corn cob, rice husk, and sawdust, formulated according to specific pollutant-removal objectives (Max Cation, Cr Guard, Heavy Pollutants, and Universal Start). Raw leachate from the Talumelito landfill in Gorontalo, Indonesia, was characterized and treated using a modular column filtration system operated under continuous-flow conditions. Removal performance was assessed for total suspended solids (TSS), heavy metals (Fe, Cu, Cr, Pb), organic indicators (BOD, COD), and pH stabilization. The results revealed strong pollutant-specific performance, with Cr Guard achieving complete chromium removal (100%) but exhibiting unstable performance for Cu and pH. Max Cation and Heavy Pollutants blends effectively reduced Fe and TSS, whereas Universal Start provided consistent but moderate performance across multiple parameters. Notably, COD removal was negative across all blends, indicating competitive displacement or desorption of recalcitrant organics. BOD, Pb, and Cr were completely removed by all formulations, highlighting the affinity of AWMs for metals and biodegradable fractions. The findings suggest that MCBs are highly effective for heavy metal and particulate removal but inadequate for refractory organics, positioning them as pretreatment rather than stand-alone solutions. Their performance depends strongly on compositional design and pollutant context, underscoring the need for tailored formulations and integration into multi-stage treatment systems.