Effect of adding four metal ions on distribution of anthracene on kaolin colloid

In order to understand the effect of metal ions on distribution and adsorption of anthracene on soils (water/soil = 10), Fe3+, Cu2+, Zn2+ and Ca2+ were added in the colloid solution of contaminated kaolin to probe the varies of anthracene concentrations in supernatants after 180 r/min of shaking at 28℃. The adsorption equilibrium time and equilibrium concentration of Fe3+, Cu2+, Zn2+ and Ca2+ by kaolin were about 24 h and (20 ± 3) mg/g, respectively. When contents of metal ions added were more than 30 mg/g for kaolin, the lowest concentration of kaolin colloid was (40±3)mg/L in supernatant. The total colloid concentrations in supernatants increased from 52 mg/L to 133 mg/L for adding Fe3+, 52 mg/L to 110 mg/L for adding Cu2+ or Zn2+, and 52 mg/L to 73 mg/L for adding Ca2+, respectively. Meanwhile, the increasing trends of anthracene in the supernatants were similar to those of total colloid concentrations, which were from 30 ng/L to 73 ng/L for adding Fe3+, 28, 35ng/L to 65, 66 ng/L for adding Cu2+ or Zn2+, and 40 ng/L to 50 ng/L for adding Ca2+, respectively. Thus, the sequences of the increase of anthracene in supernatants were the same as those of the charge densities of metal ions (Fe3+ Cu2+, Zn2+). However, adding Ca2+ at pH 6.5 only led to a minor increase of anthracene in supernatant.