Potential of Various Immobilization Matrices in Heavy Metal Ions Removal Using Nostoclinckiabeads: A Comparative Study

Abstract

This article reports the potential of removal of heavy metal ions of hexavalent chromium Cr(VI) and bivalent Cobalt Co (II) by different immobilization matrices containing dead cyanobacterial biomass of Nostoclinckia. Nostoclinckia was pre-treated by successive washes in distilled water, dried and then crushed to increase the surface area of biomass which was then immobilized in different immobilization matrices like Calcium alginate, polyvinyl alcohol alginate and polyvinyl alcohol alginate glutaraldehyde that was stable and easy to handle. The immobilized beads of Nostoclinckia was used to study the adsorption of metals (Cr VI & Co II) from simulated wastewaters under varying range of contact time (5-180 minutes), pH (1-6) and initial metal ion concentration (10-50mg/l) in a batch adsorption system. Experimental results showed that the different matrices pose impact on the different variable parameters like the optimum pH for biosorption of Cr (VI) ions was found to be 2.0 in alginate immobilized biomass while it was 4.0 polyvinyl alcohol alginate and polyvinyl alcohol alginate glutaraldehyde immobilized biomass. Similarly the maximum biosorption of Co (II) occurred at pH 3.0 in alginate biosorbent while it was 5 in polyvinyl alcohol alginate and polyvinyl alcohol alginate glutaraldehydebiosorbent. Similarly values of optimized contact times and initial metal ion concentrations were different for same biomass concentration immobilized in different matrices. From the results it can be concluded that the immobilization matrices affects the optimum values of different parameters in same conditions. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isothermic constants. Freundlich model was fitted best in case of both metals. Alginate immobilized biomass was suited most for removal of hexavalent chromium (R 2 =0.992) while PVA-A is found to have very high adsorption capacity for Co (II) as shown by (R 2 =0.9978).