Application of two sites non-equilibrium sorption model for the removal of Cu(II) onto grape stalk wastes in a fixed-bed column

Grape stalk wastes generated in the wine production process were used for the removal of Cu(II) from aqueous solutions. Column experiments were performed and the code CTXFIT (two-site non-equilibrium sorption model) was used in order to fit the experimental data and to determine the sorption and transport parameters. The effects of both inlet metal concentration and the particle size were evaluated. The retention capacity of the compacted bed was affected by the initial metal concentration as well as the transport and sorption parameters. Columns with higher inlet concentration were fast saturated leading to shorter breakthrough and exhaustion times. The maximum retardation factor (R) was observed for the particle size of 0.35–0.5 mm. A clear decrease in that parameter was observed for larger particle size, and for the small particle sizes high flow resistance was observed and lower values of R were reported. The recovery of the metal in desorption experiments was close to 85%.