Modeling of copper biosorption by Arthrobacter sp. in a UF/MF membrane reactor

Copper biosorption by Arthrobacter sp. has been studied in this work. The p rocess has been realized inside of a ultrafiltration/microfiltration (UF/MF ) reactor in order to confine cells. A mathematical model has been develope d that is able to predict experimental data under different operating condi tions. The model takes into account different phenomena, which might occur during the process, such as a dependence of equilibrium parameters on pH, a partial cell disruption, and a change in the membrane retention properties at high biomass concentrations. Experimental tests have been performed und er different operating conditions: a full factorial design has been impleme nted with pH (levels: 4, 5, and 6 units) and biomass concentration (levels: 1 and 5 g/L) as factors. A simple mathematical model based on metal mass b alance taking into account the effect of pH on the Langmuir equilibrium ads orption parameters well fitted experimental data at low pH values and bioma ss concentrations. A more complex mathematical model, which considers a par tial cell disruption during the biosorption trial, was proposed to understa nd and analyze the anomalous system behavior at pH = 6 and biomass concentr ation equal to 5 g/L. The effect of mechanical stress on biomass performanc es was also examined by using a discontinuous system (test tube trials) sim ulating the membrane reactor apparatus. In this alternative system biosorpt ion trials were carried out in test tubes in such a way to avoid or at leas t minimize the disruption due to mechanical stress. Experimental results ob tained by using this system can be modeled up to pH = 5 without considering cell disruption phenomenon, while at pH = 6 possible chemical reactions of biomass constituents could happen.