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© IWA Publishing 2016 Water Science & Technology
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Adsorption of Cd, Cu and Zn from aqueous solutions onto ferronickel slag under different potentially toxic metal combination
SUPPLEMENTARY MATERIAL
FREUNDLICH AND LANGMUIR ADSORPTION MODELS Adsorption isotherms were determined by using the Freundlich and Langmuir models. The Freundlich isotherm is more widely used and deals with heterogeneous surface adsorption. The Freundlich equation (Bohn et al. ), in its original form, can be written as q¼
1 KCe n
(1)
where q (mg kg1) is the toxic metal concentration in the sorbent material (adsorption capacity), K is a constant related to the toxic metal adsorption capacity, Ce (mg L1) is the toxic metal concentration in solution, and n is an empirical parameter related to the intensity of adsorption, which varies with the heterogeneity of the material.
Figure S1
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Relative change in FTIR wave number identification of ferronickel slag.
Higher values for K indicate higher affinity for toxic metal, and values of the empirical parameter 1/n lie between 0.1 and 1, indicating favorable adsorption (Raji & Anirudhan ). The most widely used isotherm equation for modeling equilibrium is the Langmuir equation, which is valid for monolayer sorption onto a surface with a finite number of identical sites. The Langmuir equation (Bohn et al. ) in its original form can be written as
q¼
abCe 1 þ bCe
(2)
where Ce (mg L1) is the concentration of toxic metal in solution at equilibrium, q (mg kg1) is the mass of toxic metal adsorbed to the ferronickel slag, a (mg kg1) is the maximum adsorption capacity of toxic metal, and b is a constant related to the binding strength of toxic metal, which represents the inverse of the equilibrium concentration of adsorption at one-half saturation.
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Adsorption of metals from aqueous solutions onto ferronickel slag
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2016
ANALYSIS METHODS
Figure S2
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X-ray diffractogram for ferronickel slag.
Chemical composition and physical properties of the slags were analyzed as described below: for pH (1:5 water extraction), concentrations of Ca, Mg, Al, Ni, and Fe in the slags were analyzed by inductively coupled plasma (Perkin Elmer Optima DV 5300, USA), followed by acid digestion according to Vogel (). The uniformity of the particlesize distribution (the uniformity coefficient) was calculated as the ratio of d60 (60% of the slag by weight is smaller than d60) to d10 (10% of the slag by weight is smaller than
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Figure S3
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Adsorption of metals from aqueous solutions onto ferronickel slag
The speciation of each of the metals in the single- and multi-metal adsorption systems.
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Adsorption of metals from aqueous solutions onto ferronickel slag
Figure S6
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Simulation (3D diagram) for relationship of adsorbed toxic metals in the single-metal and multi-metal adsorption systems.
Table S1 Figure S4
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Maximum adsorption capacity of toxic metal on ferronickel slag at different temperature.
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Physico-chemical characteristics of ferronickel slag used in the study
Porosity (%)
34.0
Bulk density (g cm3) 2
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1.74
Specific surface (m g )
0.09
Uniformity coefficient (d60/d10)
3.00
Particle size (mm)
2.36
pH (1:5H2O)
7.5
SiO2 (%)
Figure S5
1
47.2
Fe2O3 (%)
2.6
Al2O3 (%)
0.4
CaO (%)
0.2
MgO (%)
14.4
Reduction rate of maximum adsorption capacity in single-metal and multi-
NiO (%)
metal adsorption isotherms for the three heavy metals (Cd, Cu, and Zn) on
CdO (%)
ND
CuO (%)
ND
ZnO (%)
ND
ferronickel slag in the batch experiment.
d10). Porosities were determined from the amount of water needed to saturate a known volume of slags (n ¼ 3), and the bulk density of the slags (g cm3) was based on the ratio of the dry weight to the bulk volume of the slags (n ¼ 3).
ND, not detected.
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Adsorption of metals from aqueous solutions onto ferronickel slag
REFERENCES Bohn, H., McNeal, G. & O’Connor, G. Soil Chemistry. Wiley Interscience, New York.
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Raji, C. & Anirudhan, C. Batch Cr(VI) removal by polyacrylamide grafted sawdust kinetic and thermodynamic. Water Research 32, 3772–3780. Vogel, A. I. A Text Book of Quantitative Chemical Analysis, 5th edn. ELBS Publication, London.
