Adsorption of cadmium(II) from aqueous solution onto activated carbon
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abstract
The adsorption isotherm of cadmium on activated carbon was measured in a batch adsorber. Effects of temperature and solution pH on the adsorption isotherm were investigated by determining the adsorption isotherm at temperatures of 10, 25, and 40°C and at initial pH values from 2 to 8. Langmuir isotherm better fitted the experimental data since the average percent deviation was lower than with the Freundlich isotherm. It was noticed that the amount of Cd2 adsorbed was reduced about 3 times by increasing the temperature from 10 to 40°C. It was found that Cd2 was not adsorbed on activated carbon at pH of 2 or lower and that Cd2 was precipitated out as Cd(OH)2 at pH values above 9. Maximum adsorption capacity was observed at pH of 8 and the adsorption capacity was decreased about 12 times by reducing the initial pH from 8 to 3. According to the cadmium speciation diagram the predominant species below pH of 8 is Cd2 . Thus, cadmium was adsorbed on the activated carbon surface as Cd2 . It was concluded that the adsorption capacity is a strong function of pH and temperature.
The adsorption isotherm of cadmium on activated carbon was measured in a batch adsorber. Effects of temperature and solution pH on the adsorption isotherm were investigated by determining the adsorption isotherm at temperatures of 10, 25, and 40°C and at initial pH values from 2 to 8. Langmuir isotherm better fitted the experimental data since the average percent deviation was lower than with the Freundlich isotherm. It was noticed that the amount of Cd2%2b adsorbed was reduced about 3 times by increasing the temperature from 10 to 40°C. It was found that Cd2%2b was not adsorbed on activated carbon at pH of 2 or lower and that Cd2%2b was precipitated out as Cd(OH)2 at pH values above 9. Maximum adsorption capacity was observed at pH of 8 and the adsorption capacity was decreased about 12 times by reducing the initial pH from 8 to 3. According to the cadmium speciation diagram the predominant species below pH of 8 is Cd2%2b. Thus, cadmium was adsorbed on the activated carbon surface as Cd2%2b. It was concluded that the adsorption capacity is a strong function of pH and temperature.
