Mathematical Model of Lead Biosorption by Rhizopus nigricans Pellets in a Laboratory Batch Stirred Tank

A. Kogej and A. Pavko

Abstract
The aim of this work was to study the Pb2+-ions biosorption rate with the Rhizopus nigricans biomass in a batch stirred tank and to examine the process characteristics with a simple mathematical model. Self immobilized biomass in the form of 2.5Y±Y0.5Ymm pellets was used in a laboratory scale vessel of 100Yml working volume. Biomass concentrations from 25 to 200Yg of wet mass per liter of biomass suspension were used while the initial lead mass concentrations varied from 20 to 300YmgYl–1. Mathematical model is based on the assumption that the rate of biosorption determines the rate of the process. It combines the differential mass balance equation of the batch reactor and the biosorption rate equation, which is considered as a reversible reaction between metal ions and free binding sites on the biomass. On the basis of lead biosorption rate data and the applied mathematical model, the Langmuir adsorption mechanism was confirmed and the average adsorption rate coefficient kadsY=Y3Y×Y10–4 lYmg–1Ymin–1 was determined.

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Keywords
adsorption, Lead, batch stirred tank, mathematical model, Rhizopus nigricans