In the initial evaluation of mercury sorption for the poly(S-r-limonene)-coated silica, 100 mL of an aqueous solution containing 5 ppm HgCl2 was added to 500 mg of the sorbent. After 1 minute, a 1 mL sample of the solution was obtained and any trace solids were removed by centrifugation before analysis by CVAAS. Remarkably, >90% of the mercury was removed from solution within this first minute (the average of triplicate experiments). No more than 20% of the mercury was removed by uncoated silica gel, indicating the key role of poly(S-r-limonene) in this rapid mercury uptake (Fig. ). In order to monitor mercury sorption over smaller time intervals for kinetic analysis, a revised protocol was developed. Accordingly, 500 mg of the poly(S-r-limonene)-coated silica was added to a 250 mL beaker followed by 100 mL of a 5 ppm aqueous solution of HgCl2 with stirring. Samples were drawn up into a syringe equipped with a syringe filter to separate the sampled water from the sorbent during the sampling. Samples were obtained every 10 seconds for the first minute, and then after 90, 120, 180, and 300 seconds. Sorption was again rapid: Over 90% of mercury was sequestered within the first minute and over 98% within 5 minutes. Kinetic modelling suggested that the maximum theoretical capacity of the sorbent for Hg 2+ was 1 mg/g (equivalent to 11 mg/g of the poly(S-r-limonene coating) under these conditions (see more details below). This result was important in that the sorbent proved to be fast and effective at low concentrations of inorganic mercury, such as those often encountered in the environment. Next, similar sorption experiments were carried out with varying pH and NaCl concentrations. These experiments were designed to help define under what conditions the sorbent is effective in aqueous media. The pH was adjusted to values of 3, 5, 9, and 11 (all 5 ppm in HgCl2) and compared to the unmodified 5 ppm solution of HgCl2 in water (pH = 6.99). For the effects of sodium chloride on mercury sorption, concentrations of 6.85 mM and 599 mM NaCl were evaluated-designed to mimic the salt concentrations in tap water and seawater, respectively. Sampling was carried out as describe above, with mercury concentration monitored over 300 seconds by CVAAS. The results are plotted in Figure . Key findings were that mercury sorption was most effective at pH = 7 or lower. However, mercury sorption slowed significantly at higher pH and bound less total mercury (see kinetic section below for additional details). The most dramatic change in sorption was at high concentrations of NaCl, with 599 mM NaCl significantly inhibiting mercury sorption. At this concentration of NaCl, only 30% of mercury was removed by the poly(S-r-limonene)-coated silica over 5 minutes, while 86% of mercury was removed when the concentration of NaCl was 6.85 mM. When no exogenous NaCl was added, 99% of the mercury was removed by 500 mg of the sorbent from a 100 mL solution of 5 ppm mercury. These results are summarized in Figure . Additional data is provided in Figures .