pH effects on the adsorption of saxitoxin by powdered activated carbon

Increasing occurrence of cyanotoxins in surface waters worldwide pose significant problems, including those for drinking water utilities. In this study, the removal of saxitoxin (STX) from three different powdered activated carbons (PACs) was studied. STX is one of the most toxic paralytic shellfish toxins (PSTs), albeit not the most prevalent. The results showed that a wide range of non-electrostatic and electrostatic interactions appeared to play a role in the sorption of STX on PAC, depending on the solution pH, NOM concentration, and other factors. A bituminous coal-based PAC, that was studied in greatest detail, showed a trend of increasing sorption capacity for STX with increasing pH. NOM appeared to significantly inhibit adsorption when the pH was nearly neutral (e.g. 7.05), yet it had less effect at higher pH levels of 8.2 and 10.7. (c) 2012 Elsevier B.V. All rights reserved.