Adhesion of bacteria to pyrophyllite clay in aqueous solution

The aim of this study was to investigate the adhesion of bacteria (Escherichia coli) to pyrophyllite clay using batch and flow-through column experiments. Batch results demonstrated that pyrophyllite was effective in removing bacteria (94.5 +/- 2.0%) from aqueous solution (1mM NaCl solution; pyrophyllite dose of 1g/ml). At solution pH 7.1, negatively-charged bacteria could be removed due to their adhesion to positively-charged surfaces of pyrophyllite (point of zero charge=9.2). Column results showed that pyrophyllite (per cent removal of 94.1 +/- 2.3% ) was far more effective in bacterial adhesion than quartz sand (53.6 +/- 5.3%) under the given experimental conditions (flow rate of 0.3ml/min; solution of 1mM NaCl+0.1mM NaHCO3). Bacterial removal in pyrophyllite columns increased from 90 to 100% with decreasing flow rate from 0.6 to 0.15ml/min due to increasing contact time between bacteria and filter materials. In addition, bacterial removal remained relatively constant at 9497% even though NaHCO3 concentration increased from 0.1 to 10mM (flow rate of 0.3ml/min). This could be related to the fact that pyrophyllite remained positively-charged even though the solution conditions changed. This study demonstrates that pyrophyllite could be used as adsorptive filter materials in the removal of bacteria.