MECHANISM OF HUMIC-ACID COLOR REMOVAL FROM NATURAL-WATERS BY FUNGAL BIOMASS BIOSORPTION

Removal of humic acid (HA) colour from natural waters by biosorption o n Rhizopus arrhizus was studied. Experimental results demonstrated the dependence of adsorption on solution characteristics such as pH, ioni c strength, concentration of metal ions and temperature. The observed effects were attributed to the pH dependence of humic acid solubility and surface charge of humic acid and fungal biomass. The biosorptive c apacity of fungal cellular fractions was compared with the finding tha t chitin/chitosan was the major active component of R. arrhizus for hu mic acid uptake and this was confirmed by experiments on the effects o f culture age, growth medium composition and biomass pre-treatment wit h caustic solutions on fungal sorptive capacity. Desorption experiment s showed nearly all of the sorbed humic acid could be eluted, suggesti ng that the fungal biosorbents can be reused.