Characteristics of isothermal adsorption and desorption of aluminum ion to/from humic acids

The freeze-thaw cycle is one of the important processes that affected heavy metal behaviors in soil. However, information regarding the adsorption and desorption behavior of heavy metals in soils under different freeze-thaw conditions is relatively less. Therefore, different freeze-thaw conditions including unfrozen, 15 freeze-thaw cycles at 60% water content, and 15 freeze-thaw cycles at 100% water content were investigated. Then the adsorption and desorption behaviors of Pb and Cr in freeze-thaw soils were studied. Results showed the Pb and Cr adsorption amount mostly decreased with increasing water-soil ratio, and the soil performance of Pb and Cr adsorption at same water-soil ratios showed variation under different freeze-thaw conditions. The Pb isothermal adsorption was higher for most freeze-thaw treatments compared to the control. The soil performance of Cr isothermal adsorption showed variation under different freeze-thaw conditions. Most electrostatic binding of Pb and Cr were stronger under unfrozen and freeze-thaw conditions than unfrozen conditions. Most Pb and Cr adsorption kinetics patterns of freeze-thaw treated soils were rapid than unfrozen conditions. These results implied that freeze-thaw cycles could change the soil adsorption and desorption patterns of Pb and Cr. Therefore, further studies are urgently needed to investigate Pb and Cr immobilization mechanisms in soils during freeze-thaw cycles. Hence, these findings provided useful information on Pb and Cr immobilization process in soils that underwent freeze-thaw cycles to offer an additional insight into predicting Pb and Cr behaviors in cold and freezing environments.

Download Full-text

Study on Characters of Nitrogen Adsorption and Desorption of Sediment in Ganjiang River

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.212-213.391 ◽

2012 ◽

Vol 212-213 ◽

pp. 391-394

Author(s):

Qiu Lin Ouyang ◽

Gui Qing Gao ◽

Su Su Liu ◽

Xiao Ling Shi

Keyword(s):

Theoretical Basis ◽

Poyang Lake ◽

Nitrogen Adsorption ◽

Sediment Concentration ◽

Isothermal Adsorption ◽

Desorption Process ◽

Adsorption And Desorption ◽

Nitrogen Desorption ◽

Adsorption Of Nitrogen ◽

Desorption Capacity

Sediment has the function of adsorption and desorption of the nitrogen in water body. This study provides the theoretical basis of calculating the nitrogen content discharged into the Poyang Lake. The results show the nitrogen adsorption of sediment reaches balance basically in about 4~ 6h, the adsorption capacity is increased with the increment of the initial concentration of nitrogen, and decreased with the increment of sediment conentration.The isothermal adsorption of nitrogen by sediment can be fitted preferably by Henry and Langmuir equation.The adsorption and desorption process can be fitted by Langmuir equation.The nitrogen desorption of sediment reaches balance basically in about 8~14h.The nitrogen desorption capacity of sediment is decreased with the increment of sediment concentration.

Download Full-text

Adsorption and desorption of uranium(VI) onto humic acids derived from uranium-enriched lignites

Water Science & Technology ◽

10.2166/wst.2017.608 ◽

2017 ◽

Vol 77 (4) ◽

pp. 920-930 ◽

Cited By ~ 3

Author(s):

Yangyang Zhang ◽

Yilian Li ◽

Yu Ning ◽

Danqing Liu ◽

Peng Tang ◽

...

Keyword(s):

Adsorption Capacity ◽

Humic Acids ◽

Uranium Content ◽

Hydroxyl Groups ◽

Order Kinetic ◽

Adsorption And Desorption ◽

Complex Interactions ◽

Order Kinetic Model ◽

Pseudo Second Order ◽

Ph Level

Abstract Humic acids (HAs) were extracted and characterized from three kinds of uranium-enriched lignites from Yunnan province, China. Batch experiments were used to study the adsorption and desorption behavior of uranium (VI) onto these HAs and a commercial HA. The results showed that the optimum pH level at which all the HAs adsorbed uranium(VI) ranged from 5 to 8. The high uranium content of the HAs was released into the solution at the pH values between 1 and 3; when the HA dosage was 2.5 g L−1, the maximum concentration of uranium was 44.14 μg L−1. This shows that HAs derived from uranium-enriched lignites may present a potential environmental risk when used in acidic conditions. The experimental data were found to comply with the pseudo-second-order kinetic model, and the adsorption isotherms fit the Langmuir and Freundlich models well. The desorption experiments revealed that the sorption mechanism was controlled by the complex interactions between the organic ligands of the HAs and uranium(VI). The uranium present in the HAs may not affect the adsorption capacity of the uranium(VI), but the carboxylic and phenolic hydroxyl groups in the HAs play a significant role in controlling the adsorption capacity.

Download Full-text