Through selecting the soil from tea garden in Mengshan as the research object

effect of citric acid on adsorption-desorption of Cu2+ by soil micro-aggregates was investigated using the methods of equilibrium liquid adsorption and the NaNO3 solution as desorption. The results showed that: the adsorption of Cu2+ by raw soil and different sizes fractions of the micro-aggregates increased

with the concentration of Cu2+ increased. Influenced by free ferric oxide

cation exchange capacity and organic matter

the adsorption capacity of Cu2+ was diminishing as the following sequence: (＜0.002 mm)＞（0.053—0.002）mm＞raw soil＞（2—0.25）mm＞（0.25—0.053）mm; The low concentration of citric acid (0 to 1 mmol/L) was beneficial to the adsorption of Cu2+

while the high concentration of citric acid (＞1 mmol/L） inhibited the adsorption. Adsorption capacity reached the maximum when the concentration of citric acid was 0.5 mmol/L. Easy desorption rate increased with the concentration of Cu2+ increased

and the order of desorption was opposite to adsorption. The increase in concentration of citric acid would increase the desorption of Cu2+. The fitting of 3 equations (Langmuir

Freundlich

and Temkin) to the isothermal adsorption process reached a significant level (p＜0.01)

and the fitting effect of Langmuir equation was the best. The adsorption of Cu2+ on the soil micro-aggregates after adding citric acid was mainly absorbed by single layer.