Immobilization of Phaffia rhodozyma cells in biopolymer for enhanced Cr(VI) bioremediation

Abstract

The presented study investigated the use of Phaffia rhodozyma cells immobilized in natural biopolymer for improved bioremediation of toxic chromium compounds from aqueous solutions. Cells were immobilised in the shape of spheres (PRS) and flat coatings (PRC) with the use of sodium alginate. The bioremediation process was conducted through sorption and the reduction of Cr(VI). The biosorption was best described by the Langmuir isotherm model (R2 = 0.982, 0.985, 0.992 for Free cells, PRS and PRC, respectively) and for the kinetics, the Weber-Morris for unmodified cells and pseudo-second order model for PRS/PRC was the best fit according to the correlation coefficient (R2 >0.9). Fourier-transform infrared spectroscopy (FTIR) analysis showed that the sorption process is probably of chemical nature. The reduction of Cr(VI) to Cr(III) was carried out by the result of the difference between values obtained from colorimetry with the 1,5-diphenylcarbazide (DPC)–Cr(VI) complex and overall Cr concentration obtained from atomic absorbance spectrometry. The P. rhodozyma was able to detoxicate chromate up to 99%. The comparison of immobilization shapes showed that PRC has higher bioremediation properties than PRS by about 15% in terms of chromium removal from aqueous solutions. The 3 cycles of adsorption/desorption without decrease in efficiency showed that the PRS and PRC can be used multiple times for the removal of chromium ions from environment.