Application of Nostoc sp. for hexavalent chromium [Cr(VI)] removal: planktonic and biofilm

Abstract

ABSTRACT The bio-sorption is the using of biological biomasses, live or dead form, for heavy metals removal from polluted wastewater. In the current work, live planktonic Nostoc sp. cells were used for hexavalent Chromium [Cr(VI)] elimination from Cr-contaminated wastewater. Optimisation process was achieved in order to obtain the optimum conditions that help achieving the highest Cr(VI) removal efficiency. For instance, One Factor At a Time ‘OFAT’ experiments were performed for the determination of the coded factors levels (low/high levels) that can be included in the Full factorial design experiment ‘many interacted factors at a time’. Afterwards, a small reactor design was implemented to develop Nostoc sp. algal biofilm. After that, the algal biofilm was applied in the Cr(VI) removal process to facilitate harvesting and dewatering of the biomass after the treatment process. Results showed that, live planktonic Nostoc sp. achieved the highest Cr(VI) removal efficiency of 98.16%at 100 ppm after 7 days contact time. Furthermore, Nostoc sp. stated its great ability to form a biofilm on polystyrene substrate which achieved the highest Cr(VI) removal of ‘86.498%’ at a concentration of 100 ppm after 7 days contact time. Some characterisation techniques such as Fourier Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) analyses were applied on the developed biofilm of Nostoc sp. Isotherm and kinetics were investigated for the Cr(VI) removal process using Nostoc sp. biofilm.