Simultaneous biosorption of micropollutants from aqueous effluents by rapeseed waste

Abstract

The simultaneous biosorption of a binary metal-dye mixture onto rapeseed waste (RS) resulted from oil press was investigated. Lead (Pb) and Reactive Blue 19 (Rb19) dye were used as model pollutants due to their low biodegradability and toxic effects, even at low concentrations. The biosorbent was minimally prepared before use and was characterized by using infrared spectroscopy before and after the simultaneous biosorption. The biosorption rates of each sorbate was determined using kinetic tests at three Pb:Rb19 molar ratios. The kinetic modelling revealed that the process is better described by a pseudo-second order rate of reaction. Freundlich isotherm model could explain the equilibrium data for the dye uptake, while Langmuir isotherm, followed by Freundlich model, could describe the biosorption of lead. Biosorption selectivity was determined at various initial concentrations of the pollutants in aqueous phase. At small to medium concentration ranges, the presence of Pb(II) ions determined an increase in the uptake of Rb19, as compared to its individual biosorption. By applying Boyd’s model, it was observed that film diffusion is the rate controlling step of the simultaneous biosorption process. Desorption was realized separately for each pollutant, as a function of the eluting pH. Through this approach, the waste biosorbent can be uploaded with two different type of micropollutants removed from wastewater, the sorbent being further reused or disposed in a controlled way, thus considering the circular economy principles. The practical implications of the simultaneous biosorption using RS waste were also discussed (reactor configuration, scale-up methodology and exhausted biosorbent management).