Study on adsorption of Co~(2+), Cd~(2+) on humic acid

The humic acid (HA), extracted from soils by alkali and acid was used to study the adsorption mechanism of Co2+, Cd2+. The results show that the best pH ranges from 6 to 7 and the adsorption procedure is exothermic reaction. The adsorption of Co2+ on HA fits for Langmuire and Freundlich adsorption equation, the amount of adsorption at the temperature of 19℃、 35℃、 45℃ are 12.51, 9.52, 8.30 mg/g respectively. The adsorption of Cd2+ on HA fits for Langmuire and Freundlich adsorption equation at the temperature of 19℃、 35℃, the amount of adsorption are 33.90, 33.30 mg/g respectively; however, at 45℃ it mainly fits for Freundlich adsorption equation. The adsorption of Co2+ ,Cd2+ on HA is in the way of forming complex compound through second order complex reaction.