r - The Hong Kong Polytechnic University

The 5th Cross-strait Conference on Structural and Geotechnical Engineering (SGE-5)
Hong Kong, China, 13-15 July 2011
ADSORPTION AND DESORPTION BEHAVIOR OF BIVALENT NICKEL AND
MANGANESE IONS ON LOESS SOIL
Y. Wang 1 , X. W. Tang 1, * , H. Y. Wang 1 and Z. F. Sun 1
1
MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, China.
* Corresponding author. Email: tangxiaowu@zju.edu.cn
ABSTRACT
Both nickel and manganese are trace heavy metals. Toxic effect will be caused by excessive intake of these
heavy metals. The control of heavy metal discharge into environment has been paid much attention recently.
Loess soil was used to study the behavior of removing Ni(II) and Mn(II) from aqueous solutions. The kinetic
data fit the pseudo-second order kinetics model very well, and the adsorption rate of Mn(II) was faster than that
of Ni(II). The adsorption capacity of loess soil for Ni(II) and Mn(II) was determined to be 13.84 and 7.65 mg g -1
respectively. The D-R model fit the isothermal data of Ni(II) and Mn(II) adsorption on loess soil best, and the
main adsorption mechanism was ion exchange for both the heavy metals. NTA had contribution to desorption of
heavy metals from loess soil. The maximum desorption ratio of Ni(II) and Mn(II) from loess soil was 63 % and
92% respectively, and heavy metal ions could be more easily desorbed from the loess soil loaded with less
heavy metal. These results have significant reference value for loess soil as a material removing heavy metals
and recycling use of heavy metal contaminated loess.
KEYWORDS
Loess soil, nickel, manganese, adsorption, desorption.
INTRODUCTION
1. Heavy metal contamination in environments has aroused a lot of public attention around the world.
Accumulation of excessive amounts of trace elements (such as nickel and manganese) in soils and waters
can result in severe toxic effects to human and ecosystems. Nickel and manganese can be released into
environments by many different ways such as mine smelting, industrial waste disposal, electroplating and
battery manufacturing processes (Kadirvelu et al. 2008). Heavy metal ions can easily be bioaccumulated and
spread along the food chain once entering soil or water. The level of heavy metals in environments needs
limiting to allowable value.
2.
Many researchers show interest in working on the technology of removing heavy metals from environment, and
adsorption method is popular due to its effectiveness and convenience. Chinese loess soil with abundant clay
minerals may be a potential promising material for removing heavy metals. Removal of Cu(II), Zn(II), Pb(II)
and Cd(II) from aqueous solutions using Chinese loess have recently been reported and the loess shows high
affinities for heavy metals (Tang et al. 2008ab; Li et al. 2009; Wang et al. 2009). In this study, adsorption
behavior of loess soil towards Ni(II) and Mn(II) was investigated. In order to recycle the loess soil contaminated
by heavy metals, NTA (nitrilotriacetic acid) which is environmental-friendly was used to desorb heavy metals
from loess soil.
MATERIALS AND METHODS
Preparation of Materials
Chinese loess soil samples were taken from the suburban area of Xi’an, located in northwestern China. The
loess soil was typical Quaternary loess on the Chinese Loess Plateau. The air-dried loess soil was oven-dried at
105 o C for 24 h for removing bulk water, cooled to room temperature, and then sealed in plastic bags for storage.
The basic parameters and chemical compositions of loess are summarized in Table 1 and 2. The reagent nickel
chloride hexahydrate (NiCl 2·6H 2 O) and manganese chloride tetrahydrate (MnCl 2·4H 2 O) used in this study were
of analytical grade. Ni(II) and Mn(II) stock solution (1 g L -1 ) was separately prepared in deionized water (DW).
Erlenmeyer flasks and centrifuge tubes were pre-treated, immersed in 0.01 M HNO 3 solution for 24 h firstly, and
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