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Fig. 3. The concentrations of Cd, Ni, Zn, and Cu in the influent and the effluent solutions as a function of the cumulative volume of effluent studied for different influent electrolytes. The influent pH was 4.5 throughout the entire experiment. The concentrations of metals in the influent solution were designed to vary sequentially between a low level of 10 µg L-1 in Period 1, a high level of 30 µg L-1 in Period 2, and a low level of 10 µg L-1 in Period 3. When no background electrolyte was used a final zero-level of metal (0 µg L-1) was added as Period 4. The standard errors of means for the no-electrolyte, 0.01 M NaCl, and 0.01 M CaCl2 experiments are 0.30, 0.66, and 0.55 for Cd, 0.60, 0.79, and 0.87 for Ni, 0.73, 0.86, and 0.77 for Zn, and 0.86, 0.73, and 1.03 for Cu, respectively. Samples points below detection limits are not shown.
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