Influence of pH and Metal Concentration on Cu adsorption by two soils of contrasting feature
The influence of soil pH and soil copper concentration on the adsorption of the metals by the soil particles was studied in batch conditions. The metal was introduced into the soil through the application of copper based fungicide. Copper adsorption was studied by means of adsorption isotherms using Cu concentrations range of 3.25 g/l to 4.5 g/l and solution pH of 3, 4, 5 and 6. Results indicated that the four solution pH were significantly (P < 0.05) different in their effects on the adsorption of the metal to the two soils. The two soils are also significantly different in their adsorption capacity. The adsorbed copper increased with increase in solution pH and copper concentration with the maximum adsorption occurring at pH of 6 and copper concentration of 4.00 g/l. However, concentrations 4.25 g/l and 4.50 g/l were not significantly different in their effects on the amount of copper adsorbed by the two soils. The amount of copper adsorbed per unit mass of the soil on the average increased from 15.25mg/g at pH 3 to 26.13 mg/g at pH 6 while it increased on the average from 19.20 mg/g at copper concentration of 3.25 g/l to 21.30 mg/g at copper concentration of 4.50g/l. Regression analysis revealed a strong correlation between adsorbed copper and solution pH within individual copper concentrations. From the isotherm analysis, sorption of copper to the two soil types considered was best described by Langmuir equation.
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