Biosorption of chromium, copper and zinc on rice wine processing waste sludge in fixed bed

Wine processing waste sludge (WPWS) has shown effective removal of heavy metals in batch studies, but the adsorption in a fixed-bed WPWS column has not been examined and the mass transport in this column remains unclear. This study aimed to investigate: (1) the retardation factor (R) and the dispersion coefficient (D) of WPWS, employing one-dimensional convective–dispersive model with breakthrough curve (BTC) and using chromium, copper and zinc as the adsorbates; and (2) explore the adsorption mechanism of WPWS column for heavy metals. The retardation factor for various metal treatments is shown in the following order: Cr(18.3) > Cu(13.0) > Zn(7.2), indicating their binding affinity toward WPWS. The dispersion coefficients were calculated to be 2.36 × 10−6, 5.89 × 10−7 and 6.83 × 10−7 m2 s−1 for Cr, Cu and Zn treatments, respectively. The high charge density for Cr3+ ion makes it longer for the Cr column to attain exhaustion state, about 4.0 and 8.2 times the time required for the Cr and Zn columns. However, the least retardation and adsorption amount for Zn can be attributed to its full orbital in electronic configuration.

Research Highlights
► Rice wine processing waste sludge (WPWS) can be recognized as a biosorbent. It is a mixture collected from the settling basin and final clarifier of wastewater treatment process. WPWS has been found to be an environmental friendly material for removal of heavy metals in water treatments.
► This study aimed to investigate: (1) the retardation factor (R) and the dispersion coefficient (D) of WPWS, employing one-dimensional convective–dispersive model with breakthrough curve (BTC) and using chromium, copper and zinc as the adsorbates; and (2) explore the adsorption mechanism of WPWS column for heavy metals.
► In this work, a mathematical model which involves one-dimensional convection–dispersion was employed to describe the solute transport in soil column. To predict the behavior of pollutants in column, determining the proper adsorption constants as well as the retardation factors is necessary.