Removal of hexavalent chromium from synthetic wastewater using alginate immobilized cyanobacteria: Experiment and mathematical modeling

Abstract

The present study aims at removal of Cr(VI) using immobilized Limnococcus limneticus from synthetic wastewater. Four different methods were followed to immobilize test cyanobacterial strain onto calcium alginate bead and named as Cyanobacteria Immobilized Calcium alginate Bead (CICB). Based on the preparation method, they were termed as CICB1, CICB2, CICB3, and CICB4. Effect of input variables such as pH (5-11) and concentrations of sodium alginate (20-40 g/L), calcium chloride (14.7-44.1 g/L), and amount of algal dosage (0.957-2.871 g/L) on the efficacy of beads in removal of Cr(VI) were examined. Comparative study showed that CICB1 was least efficient and maximum removal was obtained with CICB2, in which maximum cyanobacterial biomass was used. The effect of initial concentration (IC) of Cr(VI) on removal was studied using both CICB3 and CICB4 individually. The removal gradually decreased with increase in IC of Cr(VI) for both the beads. Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and Fourier Transform Infrared studies of CICB3 and CICB4 were done. To understand the molecular transport mechanism of Cr(VI) within the solution, mesoscale simulations using computational fluid dynamics were used for predicting the removal of hexavalent chromium.