title: Adsorption behavior and mechanism of Cd(II) on loess soil from China.
abstract: Cadmium is a toxic heavy metal that has caused serious public health problems. It is necessary to find a cost effective method to deal with wastewater containing Cd(II). Loess soils in China have proven to be a potential adsorbent for Cd(II) removal from wastewater. The adsorption capacity of loess towards Cd(II) has been determined to be about 9.37 mg g(-1). Slurry concentration, initial solution pH, reaction time and temperature have also been found to significantly influence the efficiency of Cd(II) removal. The adsorption isotherms and kinetics of loess soil from China can be best-fit with the Langmuir model and pseudo-second order kinetics model, respectively. The thermodynamic analysis revealed that the adsorption process was spontaneous, endothermic and the system disorder increased with duration. The natural organic matter in loess soil is mainly responsible for Cd(II) removal at pH < 4.2, while clay minerals contribute to a further gradual adsorption process. Chemical precipitation dominates the adsorption stage at pH > 8.97. Further studies using X-ray diffraction, Fourier transform infrared spectra of Cd(II) laden loess soil and Cd(II) species distribution have confirmed the adsorption mechanism.
authors.affiliation: MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Yuhangtang Road 388, Hangzhou 310058, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Tang
authors.forename: Yunmin
authors.initials: Y
authors.lastname: Chen
authors.forename: Liangtong
authors.initials: L
authors.lastname: Zhan
authors.forename: Zhenze
authors.initials: Z
authors.lastname: Li
authors.forename: Qiang
authors.initials: Q
authors.lastname: Tang
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000032:analysis* / Q000737:chemistry; D002681:China; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009930:Organic Chemicals; D012722:Sewage; D012987:Soil; D012989:Soil Pollutants / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D009930:Organic Chemicals; D012722:Sewage; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D002104:Cadmium