Exploring barley bagasse as affordable biosorbent for efficient copper and zinc removal from synthetic solutions and effluent

This study explored the use of barley bagasse (BB), a byproduct of the brewing industry, to adsorb copper and zinc in synthetic solutions and raw dairy farm effluents. Adsorption, which was assessed in batch, followed the Freundlich isotherm and fitted well with pseudo-second-order kinetics and the Elovich model. This means that it was multilayered (i.e., it occurred on energetically heterogeneous adsorption surfaces) and controlled by chemisorption, and that more than one adsorption mechanism was involved. In terms of diffusion mechanisms, it was governed by both film and intraparticle diffusion. The effective adsorption of metals onto the BB surface was confirmed using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray fluorescence (XRF) analysis. The process remained stable in time (24 h) and was efficient between pH 4 and 8. Adsorption efficiency ranged from 1.40 to 2.40 mg metal/g BB, regardless of whether the medium contained only one or both metals, and was similar in the synthetic solutions and the raw effluent. The highest removal percentage obtained was 45%, and the metal levels remaining in the effluent after adsorption were below legally established limits. For these reasons, BB could be a suitable alternative for wastewater treatment.