Valorization of winemaking residues as biochar for removing Ni(II) from real industrial painting process effluent in a fixed-bed column

In this work, the adsorption of nickel ions from a real effluent from a metal-mechanic industry was investigated in a fixed-bed column using biochar. Biochar was prepared from winemaking residues originating from the Beifiur® composting process. The use of wine industry residues as precursor materials for biochar production is established in biomass residue valorization using the existing logistics and the lowest possible number of manipulations and pre-treatments. The results found in the work showed that the optimal conditions for nickel adsorption in fixed-bed columns were bed height (Z) of 7 cm, initial nickel concentration (C₀) of 1.5 mg L⁻¹, and flow rate (Q) of 18 mL min⁻¹. In this condition, the maximum adsorption capacity of the column was 0.452 mg g⁻¹, the mass transfer zone (Z_m) was 3.3 cm, the treated effluent volume (V_eff) was 9.72 L, and the nickel removal (R) was 92.71%. The Yoon-Nelson and BDST dynamic models were suitable to represent the breakthrough curves of nickel adsorption. Finally, the fixed-bed column adsorption using biochar from winemaking residues proved to be a promising alternative for nickel removal from real industrial effluents.