Effects of pH on Metal Leaching from Activated Carbon Block Filters

Activated carbon block filters are commonly used in point-of-use water filtration systems, but limited studies have been done on the potential leaching of metals from these filters and their potential health risks to humans. This study aimed to investigate the effects of pH on metal leaching from activated carbon block filters. Commercially available activated carbon blocks were cut to similar size and weight and exposed to tap water whose pH was changed to between 4 and 9. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to measure metal concentrations. The results indicated that metals were leached significantly differently under different pH due to different mechanisms. Manganese was partially precipitated under alkaline conditions under basic pH conditions above 8. A sudden change in copper concentration after 70 hours could be attributed to many factors such as experimental conditions, operational errors, and differences in the activated carbon block itself. Concentrations of Zn at pH 4, 5, 6, 8, 9 in tap water did not change significantly during the 74 hours. The concentration of Zn at pH 7 decreased, which can be attributed to the adsorption effect on zinc under pH 7. The increasing concentrations of Na and K in tap water and the decreasing concentrations of Ca and Mg may be explained by ion exchange of cations in the tap water. The results of this study indicate that multiple mechanisms may affect metal leaching from activated carbon block filters and their health risks should be further investigated.