Surface charge and adsorption properties of chrysotile asbestos in natural waters

Changes in surface-charge adsorption properties of chrysotile asbestos aging in water were studied in a series of constant-pH laboratory experiments. Chrysotile freshly suspended in an inorganic electrolyte has a positive surface charge below pH 8.9. Charge reversal occurs within about 2 weeks due to more rapid dissolution of chrysotile's outer magnesium hydroxide surface relative to the underlying silica component of the mineral. The inorganic anions NO_3^-, Cl^-, HCO_3^- , and SO_4^(2-) did not absorb. A constant- capacitance model can be used to relate surface charge to adsorption of protons over the pH range 7-9. At natural organic matter (NOM) concentrations at or below those encountered in natural waters, the particles can adsorb sufficient organic matter within 1 day to acquire a negative charge. Adsorption of NOM reached a maximum of 30 x 10^(-6) mg of C cm^(-2) after 21 h; catechol continued to adsorb over 5 days