Adsorption of Cr(VI) on ureolytic mixed culture from biocatalytic calcification reactor

Ca-rich water and wastewater have caused problems in water use, wastewater reuse and the operations of reactors treating Ca-rich wastewater. Nowadays, reuse of wastewaters is fast gaining importance as water sources have been polluted. Therefore, the concept of biocatalytic calcification reactors (BCR) based on urea hydrolysis, pH increase and calcite production has been studied to remove Ca from wastewaters. This biological process produces significant amounts of waste sludge. In the present study, Cr(VI) adsorption on the ureolytic mixed culture (UMC) waste by-product from BCR was investigated to evaluate its potential for metal removal. The biosorption process was investigated using equilibrium batch tests and the data were fit to the Langmuir, Freundlich and Temkin isotherm models. The Cr(VI) ion concentration dependence of sorption (1–100 mg/L) could be fit to the Langmuir isotherm model. Monolayer adsorption capacity, qm (mg/g), of the adsorbent was 8.67 and the Langmuir constant b (L/mg) was 0.881. Based on the obtained results, the waste UMC appears to be a potential biosorbent for the removal of Cr(VI) from wastewater, although its adsorptive capacity is lower than those of other biosorbents.

Data fit to the Langmuir adsorption isotherm for the Cr(VI) biosorption on living ureolytic mixed culture compared to Freundlich and Temkin models. From the slope and intercept of the line in figure, the Langmuir constants were found as qm = 8.67 mg/g and b = 0.881 L/mg.Figure optionsDownload as PowerPoint slideHighlights
► Cr(VI) biosorptions in excess of 8% was obtained for 100 mg/L Cr(VI) at the equilibrium times of 120 min.
► Biosorption isotherms were modeled with the Langmuir, Freundlich, and Temkin isotherms. Based on the correlation coefficients, Langmuir models better described the Cr(VI) biosorption isotherms compared to Freundlich and Temkin models.
► It was found that the living UMC are a potential adsorbent for removal of Cr(VI) from aqueous solutions although its adsorptive capacity is lower than other biosorbents.