Lead biosorption characterisation of Aspergillus piperis : contextualising the novel fungus within the larger mycoremediation corpus

Abstract

The Pb(II) adsorption capabilities of a heavy metal tolerant strain of fungus, Aspergillus piperis, were studied. Agar well diffusion was used with 2000 ppm of Cu(II), Fe(II), Pb(II), Mg(II), Mn(VI), Se(VI), Cd(II), and Zn(II) ions. Of the metals tested, A. piperis only exhibited substantial growth inhibition in Cd(II), while lesser inhibition was ob- served in Se(IV), Pb(II), and Zn(II). After five days the fungus had successfully grown in the presence of all the other metals. Optimal growth conditions were identified using a plating technique, and optimal adsorption conditions were identified using submerged fermentation and fractional factorial experimental design. The adsorption behaviour was then elucidated using isotherm and kinetic models, of which the one-surface Langmuir isotherm provided the best fit. The Langmuir maximum predicted adsorption capacity was 275.82 mg g-1, which is similar to the experimental Qmax of 267.41 mg g-1. Both these values are high when compared to other fungi tested for Pb(II) adsorption. Kinetic models suggested that internal mass transfer is the driving force behind the reaction rate. After adsorption, biomass surface characterisation was undertaken using ATR-FESEM, EDS, and FTIR suggesting that cation exchange is the underlying adsorption mechanism. The good adsorption performance as well as the relative ease in which this biomass can be manufactured indicate that A. piperis would be an excellent candidate for industrial Pb(II)-remediation.