Equilibrium and kinetics of biosorption of cadmium(II) and copper(II) ions by wheat straw.
Biosorption equilibrium and kinetics of Cd(2+) and Cu(2+) ions on wheat straw, Triticum aestivum, in an aqueous system were investigated. Among the models tested, namely the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, the biosorption equilibrium for both Cd(2+) and Cu(2+) was best described by the Langmuir model. The Langmuir biosorption capacity for Cd(2+) was about 27% higher than that for Cu(2+). It was also found that biosorption of Cd(2+) and Cu(2+) by wheat straw followed second-order kinetics. The equilibrium amount of metal ions adsorbed onto the wheat straw increased with increasing of pH from 4.0 to 7.0, and the effect was more pronounced for Cd(2+) than for Cu(2+). The equilibrium adsorbed amount also increased with the initial concentration of the metal ions, as expected. On the other hand, an increase of temperature from 25 to 30 degrees C only enhanced the biosorption of Cd(2+) and Cu(2+) slightly. The apparent temperature independence and the strong pH dependence of the amount of metal ions adsorbed along with moderate mean free energies of biosorption (between 8.0 and 12.9 kJ mol(-1)) altogether indicate that biosorption of Cd(2+) and Cu(2+) by wheat straw might follow a chemisorption mechanism.
Dang
V B H
VB
Department of Environmental Engineering, University of Technology, Ho Chi Minh, Vietnam.
Doan
H D
HD
Dang-Vu
T
T
Lohi
A
A
D000042:Absorption; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000493:pharmacokinetics*; D003198:Computer Simulation; D003300:Copper / Q000378:metabolism*; D007477:Ions; D007700:Kinetics; D008954:Models, Biological; D035261:Plant Components, Aerial / Q000378:metabolism*; D014908:Triticum / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics*; D018508:Water Purification / Q000379:methods*
D007477:Ions; D014874:Water Pollutants, Chemical; D002104:Cadmium; D003300:Copper