Biosorption of Mercury Ion (Hg2+) using Live and Dead Cells of Rhizopus oryzae and Aspergillus niger : Characterization, Kinetic and Isotherm Studies

Mercury ions (Hg2+) are usually being discharged into water bodies without proper treatment. It is toxic, non-biodegradable and persistent naturally which leads to serious environmental problems. Through microbial approach, this study compares the efficiency of two types of fungi: R. oryzae and A. niger of common biosorption fungi in absorbing Hg2+ based on FTIR analysis, kinetic and isotherm studies. Both fungi were prepared into two forms which are live and dead biomass; and the Hg2+ was prepared at 10 and 100 ppm. FTIR analysis has identified existing functional group of hydroxyl, carboxylic and amino functional groups from both fungi, which are important in attracting Hg2+ ion. On average, 60-90% of Hg2+ was removed by both live and dead biomass of R. oryzae and A. niger at 10 and 100 ppm. Meanwhile, the highest sorption was achieved by dead cells of R. oryzae which is up to 90.38% at 100 ppm. In terms of kinetic studies, experimental data fitted to the Pseudo-second-order kinetic model, with correlation coefficient, R2 (0.9997), and Langmuir isotherm, which means the absorption process occurs on the homogenous surface that corresponds to the monolayer formation. Through these findings, the dead cells of A. niger and R. oryzae are better in sorption of Hg2+ compared to the live cells. Meanwhile, the rate of biosorption by R. oryzae is higher compared to A. niger. However, both fungi are excellent in biosorption of Hg2+ ions and could be an alternative to current physico-chemical methods used.