Sorption and sorption reversibility of cadmium on calcite in the presence of phosphate and sulfate
- 標題
- Sorption and sorption reversibility of cadmium on calcite in the presence of phosphate and sulfate
- 作者
- R.D. van der Weijden, J. Meima, R.N.J. Comans
- 文件屬性
- 國外期刊
- 知識分類
- 基礎研究
- 出版年
- 1997
- 刊名
- Marine Chemistry
- 點閱數
- 2637
摘要
The influence of phosphate and sulfate on the sorption of cadmium on calcite was studied in laboratory experiments at I = 0.7, pH 7.4–9.5 and PCO2 = 10−3.5 atm. The fast initial sorption of cadmium decreased with increasing phosphate and sulfate concentrations. Since total phosphate and total sulfate sorption increase with decreasing pH, due to lower carbonate concentrations, the effects on the sorption of cadmium are most pronounced in the pH range 8.3–7.4. Phosphate and sulfate also affect the sorption reversibility of cadmium. The short term (t < 24 h) sorption reversibility at pH 8.3 decreases, because a relatively greater percentage of sorbed cadmium is present at the high affinity sites in the presence of phosphate. The short term reversibility at pH 7.4 does not change, because, both in the absence and in the presence of phosphate, the greater amount of cadmium is sorbed at the high affinity sites. The long term (t > 144 h) sorption reversibility of cadmium increases in the pH range 7.4–8.3 and with increasing phosphate (or sulfate) concentrations. The main cause for this is a decreased recrystallization rate of calcite and therefore a smaller amount of cadmium is lattice bound. Based on the reduction of the...