Sorption Behavior of Aluminum in Black and Albic Soils and Its Response to Environmental Conditions

In order to study the transport activity and pollution risk of exogenous aluminum into soil, the adsorption behavior of aluminum in the black and albic soils as well as the affecting factors including pH, organic matter, electrolyte, and temperature were evaluated using batch equilibrium method. Results showed that the equation of pseudo-second-order could be used to describe the adsorption kinetics of aluminum and Langmuir equation could well describe the thermodynamic characteristics of aluminum adsorption in the two soils, respectively. Soil adsorption of aluminum is an endothermic process. The amount of adsorption of aluminum increased with increasing the temperature, which agreed with that aluminum adsorption in the black and albic soils was the process of endothermic according to the thermodynamic parameters. The amounts of aluminum adsorbed by the soils was higher in the range of pH 4 to 6; however, the amount of Al adsorbed with the soils decreased when the pH of the adsorbent solution was lower than 4 or higher than 6. The adsorption capacity of saturated adsorption decreased by 21.9% when the contents of organic matter in black and albic soils decreased by 33.2%. Adsorption experiments with NaCl and Na2SO4 as supporting electrolytes showed that aluminum adsorptions decreased with increasing concentration of Na+. The adsorption capacity of aluminum in black soil was higher than that in albic soil under any conditions.