Flocculation of quartz by microorganisms

摘要

The adsorption behaviour of Escheichia coli (wildtype and genetically modified strain Sip) , Arthrobacter nicotianae, Bacillus licheniformis and Pseudomonas maltophilia onto quartz mineral was investigated. Zeta potentials of the studied microbes and quartz were firstly separately measured at different pH values. Effect of bacterial treatment on the quartz surface was then investigated by analyzing zeta potentials of quartz incubated with bacterial cells. Flocculation behaviour of bio-treated and untreated quartz was compared. Of the tested microorganisms, only E. coli strain Sip brought about significant changes to the quartz surface: The IEP (isoelectric point) for quartz was shifted from pH < 2 to pH 4. 3 and the mineral particles became positively charged at acidic pH. Moreover, the settling velocity (an indication of flocculation) of the bio-treated quartz reached its maximum. The results obtained from the study together with the classical DLVO theory would explain the significant changes observed in the mineral surface property.