close

Вход

Забыли?

вход по аккаунту

?

j.minpro.2017.10.003

код для вставкиСкачать
International Journal of Mineral Processing 169 (2017) 1–6
Contents lists available at ScienceDirect
International Journal of Mineral Processing
journal homepage: www.elsevier.com/locate/ijminpro
Competitive adsorption characteristics of rhenium in single and binary
(Re-Mo) systems using Purolite A170
Mohammad Bagher Fathi, Bahram Rezai ⁎, Eskandar Keshavarz Alamdari
Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran 158754413, Iran
a r t i c l e
i n f o
Article history:
Received 6 November 2016
Received in revised form 30 September 2017
Accepted 9 October 2017
Available online 10 October 2017
Keywords:
Rhenium
Purolite A170
Single and binary systems
Mechanism
a b s t r a c t
In this study adsorption of rhenium ions from single and bi-component solutions (Re-Mo) by Purolite A170 was
studied experimentally and described by isotherm, kinetic and thermodynamic modeling. Considering coefficient of determination (R2) and values of root mean squared error (RMSE) for the multicomponent isotherms,
the extended model of Freundlich isotherm was found to be successful. Moreover, fitting the time-dependent
data into different mechanisms showed that the data comply well with the pseudo-second order model. Results
from the binary systems demonstrated that the presence of the secondary metal ions in the system causes a decrease in the adsorption capacity of rhenium, which is mainly due to the competitive effects of metals for adsorption sites. Furthermore, evaluation of thermodynamic parameters showed that the reaction mechanisms are
different for both systems; however, due to negative values of ΔH, in competitive condition the adsorption of rhenium becomes more feasible with increasing the temperature.
© 2017 Published by Elsevier B.V.
1. Introduction
Rhenium with abundance concentration of 1 ppb on the Earth's (the
Clarke of rhenium being 7 ∗ 10−8%), is one of the rarest elements. Its
unique properties have been made it to be demanded in wide industries
metallurgy, petrochemical industry, aviation, medicine, defense and
chemical (Chekmarev et al., 2004; Nebeker and Hiskey, 2012). Limited
world-wide supply of this metal and its critical role in various fields of
modern industry has caused that the price of Re has been in fluctuating
in high level and is currently 2500 $/kg (Metalpages[WWWDocument],
2016).
Separation of rhenium from the solution could be achieved through
different methods such as precipitation, ion-exchange, and solvent extraction. But currently due to high affinity of perrhenate anions (ReO−
4
) to functionalized resins, preferred recovery technology is selective
sorption
by
ion
exchange
method
(Dąbrowska
and
Jermakowicz-Bartkowiak, 2008; Mal'tseva et al., 2012a; Zakhar'yan
and Gedgagov, 2013).
Previous studies have shown that in multicomponent systems,
amongst all the various involved metal ions (ferrous and nonferrous),
just molybdenum due having very similar chemical behavior with rhenium (the ionic radius of Re4+ and Mo4+ are 0.72 Å and 0.70 Å respectively), can be readily absorbed with the resin and may essentially
decrease rhenium loading. Hence, in the processing of bearing solutions,
separation of rhenium and molybdenum is the main problem (Blokhin
et al., 2011).
In a binary Re-Mo system, at pH range of 1–10, perrhenate ions have
a stable form of monomeric anion while the structure of Mo ions depends on pH values in the contacting solution tending to form anionic
and cationic species. Therefore, it seems that by selecting a proper adsorbent type and grain size and also pH range, these two elements can
be separated efficiently (Mal'tseva et al., 2012b; Kholmogorov et al.,
1999; Mikhaylenko and Blokhin, 2012).
Literature survey shows that thus far there is no investigation about
detection and description of governing phenomena on the processes of
Re-Mo joint presence systems processing using ion exchange method.
So, it could be of a great importance to study of a such system to discover the selective or successive adsorption and also mutual effect of metal
ion on the sorption of other metal ions, since the presence of other metal
ions can lead to synergism, antagonism or non-interaction mechanisms
(Chen et al., 2015; Nebeker and Hiskey, 2012).
The present study is undertaken to investigate the rhenium ions
competitive uptake behavior from the single (Re) and the binary (ReMo) metal ions solutions onto Purolite A170 (weak base/macroporous
resin) by the equilibrium, kinetics and thermodynamic relationships.
2. Experimental
2.1. Materials and reagents
⁎ Corresponding author.
E-mail address: rezai@aut.ac.ir (B. Rezai).
https://doi.org/10.1016/j.minpro.2017.10.003
0301-7516/© 2017 Published by Elsevier B.V.
Rhenium and Molybdenum standard stock solutions were prepared
by dissolving NH4ReO4 (Aldrich) and (NH4)6Mo7O24.4H2O (Aldrich),
2
M.B. Fathi et al. / International Journal of Mineral Processing 169 (2017) 1–6
respectively, in double-distilled water. In binary joint system the pH of
the solutions was kept approximately 2 in the studied temperature
range. The ion exchanger Purolite A170 (from Purolite) (in what follows, A170) was examined as sorbent. Physical and chemical properties
of the resin are provided in Table 1. All reagents were of analytical grade
and used without further purification. The pH was measured using pH
meter (Metrohm 827). The whole tests were perfumed using the
Ds311 incubator shaker. Concentration of metal ions in solutions was
determined using ICP-OES (Optima 7300 DV Perkin Elmer).
2.2. Method of the experiment
2.2.1. Resins treatment
The A170 anionite preliminary was converted to SO24 − form
(Abisheva and Zagorodnyaya, 2011; Mal'tseva et al., 2012a; Joo et al.,
2012). Weighed amount of resin was kept with 2 mol/l H2SO4 for 48 h
which subsequently led to the swelling of resin. Thereafter, the treated
resin was filtered and washed by deionized water till a constant value of
pH was achieved and later was dried by an oven at 323 ± 1 K duration
next 24 h. Before the resin extraction in aqueous solution for sorption of
meal ions, it was subjected to soak in water overnight.
2.2.2. Experimental procedure
The adsorption experiments were carried out under static condition
with flasks of 150 mL volume. Amount of adsorbed metal on anionites
was determined from the difference between its initial and final concentration in the solution (Blokhin et al., 2011). Experiments of equilibrium isotherms were conducted at 288 K. For single solutions, specified
amounts of the resins (about 0.1 g) were mixed with each of a series of
flasks with 50 mL of the ions solution having concentrations ranging
from 50 to 250 ppm. In natural deposits, generally it has been accepted
that rhenium is mainly carried by molybdenite through the isomorphous replacement of Mo and it has been known as molybdenum coproduct, accordingly always in this systems the concentration of Mo is
higher than Re (Maria-Ondina and Daniel, 2013). Hence, for binary solutions in order to get closer to real conditions, concentration of rhenium was varied over the range of 20 to 100 ppm, with Mo
concentration ratio of 5. The flasks were kept in a thermostated shaker
and stirred continuously for 24 h at shaking speed of 180 rpm to achieve
equilibrium state. Kinetics and thermodynamics investigations were
followed by adding 0.1 g of the adsorbent in 50 mL adsorbents solution
of 250mgl−1 rhenium and 500mgl−1 molybdenum concentration (in
binary system) at different temperatures, e.g. 299, 310 and 321 K. The
capacity of adsorbed metal was calculated from the mass balance equation as follows:
qe ¼
C 0 −C e
V
W
ð1Þ
where C0 and Ce are the concentrations of metal ion (mg/l) at t = 0 and
equilibrium, V is the total volume of solution (l) and W is the weight of
dry resins (gr) (Nur et al., 2014).
Table 1
Physical and chemical properties of A170 ion exchange resin.
3. Results and discussion
3.1. Adsorption isotherms
Equilibrium studies and development of appropriate isotherm
models are basic requirements to analysis and optimize of an adsorption
system (Srivastava et al., 2006). Generally, in multicomponent systems
due to complicated relations between metal ions and adsorbent, no single component isotherms can demonstrate nature of such interactions
at equilibrium state (Senthilkumar and Murugappan, 2015a). In the
present research, in order to assess the effects of the most serious adsorption competitor e.g. Mo, on Re uptake from the pregnant natural solutions, two systems namely single and binary Re-Mo, were examined.
3.1.1. Adsorption isotherms for single-component systems
Equilibrium data obtained from both Re and Mo single component
systems were analyzed separately, using linear forms of four the most
frequently applied isotherm models, namely, Langmuir, Freundlich,
Temkin and Dubinin–Radushkevich (Eqs.(2)–(5) respectively) (Lou
et al., 2013).
Langmuir :
Ce
Ce
1
¼
þ
qe qmax qmax KL
Freundlich : logqe ¼ logk f þ
Temkin : qe ¼
ð2Þ
1
logCe
n
ð3Þ
RT
RT
lnA þ
logC e
b
b
ð4Þ
Dubinin‐Radushkevich ðD‐RÞ : ln qe
1 2
1
¼ lnqm −β RT ln 1 þ
; E ¼ pffiffiffiffiffiffi
Ce
2β
ð5Þ
where qe is the equilibrium amount of metal adsorbed on resin
(mg·g−1), Ce is the equilibrium metal ions concentration in solution
(mg·l− 1), qmax is the monolayer maximum loading capacity of the
resin, KL is the Langmuir constant related to the energy of adsorption
(l·mg−1), KF is the Freundlich constant related to the adsorption capacity (l·mg−1), 1/n is the heterogeneity factor, A and b are the Temkin
constants, qm is the Dubinin-Radushkevich monolayer capacity
(mg·g−1) and β (mol2·kJ−2) is a constant with dimensions of energy,
and E is the mean free energy of adsorption per mole of the adsorbate
(kJ·mol−1).
The calculated isotherm parameters are listed in Table 2. As shown
from the results, adsorption data of perrhenate ions lie well on
isotherm's model as R2 values for these plots are higher than 0.97; however, Freundlich and D-R isotherm models show the selectivity
Table 2
Isotherm constants for different models for Re and Mo adsorption on A170 from single
component system.
Resin type
Constants
Re
Mo
Langmuir
qmax (mg/g)
Kl(L mg−1)
R2
Kf((mg/g)/(mg/l)1/n)
n
R2
A(L mg−1)
b(J mol−1)
R2
qm(mg/g)
β(mo 2 kJ−2)
E(kJ/mol)
R2
166.67
0.67
0.985
53.83
2.09
0.993
8.76
83.86
0.978
0.006
3.37 ∗ 10−9
12.18
0.998
166.67
0.46
0.962
46.77
1.81
0.818
4.40
68.34
0.941
0.016
4.32 ∗ 10−9
10.755
0.846
Property
Description
Basic information
Structure
Matrix
Functional group
Ionic form
Macroporous
Polystryrene/divinylbenzene
Complex amine
OH (free base)
Freundlich
Physical/chemical
Bead size
Specific gravity
Moisture retention
Total capacity
0.6–1.2 mm
1.05
42–47% (in Cl− form)
1.3 meq/mL
Dubinin – Radushkevich (D-R)
Temkin
M.B. Fathi et al. / International Journal of Mineral Processing 169 (2017) 1–6
coefficient N 0.99. While for Mo, the Langmuir isotherm shows a better
fit to the adsorption data than the others.
The Langmuir model is the best-known isotherm for describing adsorption from aqueous solution. This model assumes that there is no interaction between the adsorbate molecules and due to homogenous
distribution of active sites on the adsorbent surface the adsorption is localized in amonolayer (Xiong et al., 2012; Xiong et al., 2013). In Table 2,
the maximum Langmuir monolayer capacities (Qm) for Re and Mo are
the same (166.67 mg/g), in contrast, for constant Kl, Re has higher
value (0.67) than Mo (0.46), which suggests that perrhenate ions have
highest affinity to bind to the A170 functional groups rather than molybdenum. The adsorption intensity of the metal ions on adsorbents
also can be determined by A constant in Temkin model. The obtained
values of A parameter in Table 2 revealing a higher A170-metal ion potential for Re compared to the Mo ion (Shahmohammadi-Kalalagh,
2011).
Another empirical equation is the Freundlich model with KF and 1/n
constants that incorporate all factors affecting the adsorption capacity
and an indication of the favorability of metal ion adsorption, respectively (Kadirvelu et al., 2008). For classification as favorable adsorption the
value of n should be within 1 b n b 10 also smaller the value of the 1/n,
the higher will be the affinity and the heterogeneity of the adsorbent
sites (Shahmohammadi-Kalalagh, 2011; Srivastava et al., 2006). From
Table 2, the first: n value changes are indicating the favorable adsorption of ions from aqueous medium, and the second: the A170 shows intensive affinity as well as heterogeneity for Re than that for Mo ions.
Meanwhile, the KF values indicate the higher uptake of rhenium than
that of molybdenum ions.
The value of E in D-R model is usually applied to distinguish the
physical and chemical adsorption of metal ions. When the value is
below 8 kJ/mol, the adsorption process can be considered as the physical adsorption while if it is located in the range of 8–16 kJ/mol, it is the
chemical adsorption and indicating ion-exchange mechanism (Liu and
Wang, 2013; Singha and Das, 2013). As shown in Table 2, its value for
both metals is above 8 kJ/mol that is confirming ion exchange mechanism and also chemical adsorption type in the process.
3.1.2. Adsorption isotherms for multi-component systems
In multicomponent solutions the interactions and competitions between different adsorbates to reach the adsorbent, complicate the process. To evaluate such systems, several methodologies have been
derived and developed from those of the single-component systems.
In the present work, since the adsorption behavior of the investigated
metals species in the single-component systems obeyed the Langmuir
and Freundlich models, their developed forms for multi component adsorption isotherms namely Extended Langmuir, Modified Langmuir, Extended Freundlich and Langmuir-Freundlich models (Eqs. (6)–(9))
were used to describe the nature of process.
Extended Langmuir : qe;i ¼
Modified Langmuir : qe;i ¼
q max;i KL;i Ce;i
1þ
q max;i KL;i
1þ
Extended Freundlich : qe;i ¼
C
ei
ηi
N
∑ j¼1 KL; j Cej η
j
K F;i Cne;ii þxi
N
∑ j¼1 Cxe;ii þ yi Cze;i j
1
Langmuir‐Freundlich : qe;i ¼
ð6Þ
N
∑ j¼1 KL; j Ce; j
aC
ð7Þ
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2
n ð∑i¼1 Xobs;i −Xmodel;i
RMSE ¼
n
one metal ion in binary and single systems respectively. Three possible
types of behavior may be stated: qe;mix =qe N1, synergism (sorption of target species will be promoted by the presence of other metal ions);
qe;mix
=qe ¼ 1, no net interaction effect is observed and qe;mix =qe b1, antagonism (the effect of the mixture is less than that of each individual adsorbates in the mixture)(Mahamadi and Nharingo, 2010; Srivastava et al.,
2006; Zhu et al., 2012). Under the investigated conditions, the qe;mix =qe
values of Re in Re-Mo binary system were ≈ about 0.85which is implying inhibitory effect of molybdenum ions on binding of the perrhenate
ions due to their competition for occupying vacant sites on adsorbent
with rhenium ions and accordingly perrhenate ions adsorption is
suppressed.
3.2. Adsorption Kinetic
Analysis of ion exchange kinetics and thermodynamic parameters,
such as diffusion coefficient, energy and entropy of activation, or free
energy change are of importance as they provide valuable insight into
the reaction pathways and into the mechanism of the reaction. In the
present work the evaluation of essential parameters for rhenium uptake
from both single and binary systems have been done with variation of
Re and Mo sorption as a result of temperature changing. Modeling of
Table 3
Multi-component isotherm parameter values for the simultaneous adsorption of Re and
Mo adsorption on A170.
Extended Langmuir
Re
Mo
Modified Langmuir
RMSE
R2
ηi
RMSE
R2
8.72
75.89
Negative
Negative
58.23
185.7
1.307
26.13
0.9876
0.2903
Extended Freundlich
Re
Mo
ð9Þ
where, qe,i is the equilibrium amount of component i adsorbed
in the system, Ce,i is the equilibrium concentration of component i, Ce,j
ð10Þ
where Xobs,i are the observed values and Xmodel,i are the modeled values
(Fouladgar et al., 2015).
Fitting parameters, correlation coefficients (R2) and RMSE are given
in Table 3.
It is evident from the data that the Extended Freundlich model with
higher coefficients of determination R2 and lower values of RMSE is the
most convenient model to predict the isotherm of Re-Mo binary system.
Mutual interference effects of metal ions on adsorption capacity can
be probe using qe;mix =qe , where qe, mix and qeare the sorption capacity for
ð8Þ
=mi
i e;i
1=
m
N
∑ j¼1 b j Ce; j j
(j = 1, 2, …, N; N is the number of the components) is the equilibrium
concentration of each component, KL(i,j) and (KF(i,j),ni) are the Langmuir
and Freundlich constants for component i and j, respectively and qmax,i
is the maximum adsorption capacity of component i. The parameters
qmax,i, ni and KL,F(i,j) are obtained from the single adsorption isotherm.
The other parameters (ηi,j, xi, yi,zi, ai,bj, mi,j) can be obtained from the optimized fitting method (Al-Asheh et al., 2000; Senthilkumar and
Murugappan, 2015b; Srivastava et al., 2006; Sukpreabprom et al., 2015).
This procedure was performed in MATLAB program. RMSE (root of
mean square errors) was also used to evaluate quality of the fitting.
RMSE is given as:
Adsorbate
3
xi
yi
zi
RMSE
R2
−0.4815
−7.774
0.8481
1.74E-06
1.155
−5.727
0.8794
5.078
0.9944
0.9732
Langmuir-Freundlich
Re
Mo
ai
mi
mj
bi
bj
RMSE
R2
54
47
0.5287
4.302
0.7497
4.438
0.3447
12.61
0.6756
−19.96
1.288
15
0.9879
0.7661
4
M.B. Fathi et al. / International Journal of Mineral Processing 169 (2017) 1–6
batch kinetic adsorption performed using linear form of pseudo-firstorder, pseudo-second-order, Elovich and intra-particle diffusion equations (Eqs.(11)–(14)).(Lou et al., 2013):
k1
t
Pseudo first‐order equation : log qq ‐qt ¼ logqe −
2:303
Pseudo second‐order equation :
Elovich equation : qt ¼
t
1
1
¼
þ t
qt k2 q2e qe
ð11Þ
ð12Þ
1
1
ln ðαβÞ þ ln t
β
β
ð13Þ
Intra‐particle diffusion equation : qt ¼ ki t0:5
ð14Þ
where in Eqs. (11) and (12), qt and qe are the amount of adsorbate
(mg g−1) at any time (t) and at equilibrium, respectively, and k1 is the
rate constant of pseudo first-order model (h− 1). k2 (mgg− 1 h−1) is
the rate constant for pseudo-second-order. In Eq. (13), α
(mg g−1 h−1) is the initial sorption rate constant, and β (mg g−1) is related to the extent of surface coverage and chemisorptions energy of activation and in Eq. (14), ki (mg g−1 h-0.5) is the intra-particle diffusion
rate constant.
3.2.1. Kinetics of single and binary component adsorption
The kinetic models parameters and selectivity coefficient (R2) are
summarized in Table 4. As seen from the R2 values, in all studied conditions the second order kinetic equation is more applicable than others.
Moreover, in both systems based on comparison of adsorption capacities for experimental and calculated values, it can be deduced that
there are not any significant differences between them. The pseudosecond order model demonstrates that the adsorption reaction is the
rate determining step. Comparing of the qe and k2 values for the
pseudo-second order, in both systems, approves the competitive inhibition in the mixture of ion solutions.
Identifying the ion exchange process rate limiting step and involved
likely mechanism is commonly performed through the intra-particle
diffusion model (Wu et al., 2009). The rate constants for rhenium uptake from both systems corresponding to this model are shown in
Figs. 1 and 2, in which the slope of each portion determines its rate. As
seen from Fig. 1, in single system, there are 3 stages in adsorption of rhenium on A170 including: (1) diffusion of the ions from the bulk solution
to the film surrounding the adsorbent, (2) their diffusion from the film
to the adsorbent surface and (3) diffusion from the surface to the internal sites (Igwe and Abia, 2006; Lou et al., 2013; Qiu et al., 2009). Comparison of slopes show that the sharper portion is belong to arriving of
adsorbates ions to adsorbents surrounding film by shaking (180 rpm).
However, in Fig. 2, it is clear that in binary system, perrhenate ions adsorption is limited just in two stages and third portion has been omitted
that is attributed most likely to shield-shaped inhibitions of
multicharged molybdenum anions that adsorbed on the resin surface
and prevent the rhenium ions penetration into the bead (Mikhaylenko
and Blokhin, 2012). Behavior of rhenium ions sorption/desorption
Fig. 1. Intra-particle diffusion equation for the adsorption of Re from single system on the
A170 resin at the different temperature. Initial concentration of metal ions = 250 mg L−1,
resin dosage = 0.1 mg, pH = 2.
within grains of A170 was demonstrated by Mal'tseva et al. (2012a,
2012b). In their works the kinetics of the process were analyzed by
the limited-volume method. The results confirmed that in both cases
(sorption/desorption), the rate is limited by internal diffusion
(Mal'tseva et al., 2012a, 2012b).
3.3. Selectivity investigation of A170 toward Re & Mo
The magnitude of A170 affinity for studied metal ions was determined by separation percentage (rt) Eq. (15).
rt ¼ 100
ðC0 −Ct Þ
C0
ð15Þ
where C0 and Ct are the concentrations of the metal ions at t = 0 and
time t, respectively (Rahmani et al., 2010).
Comparing rt values for Re and Mo ions in binary system shows that
in all studied conditions the rhenium separation percentage values are
always higher (≈ 26%) than for molybdenum values. This is in accordance with results of (Virolainen et al., 2015), who concluded that, the
complex amine functional group in the A170 resins favor more univalent anions (ReO−
4 ) than larger and multivalent ions (polymeric oxy anions of molybdenum).
Differences between average values of rt for the rhenium in the both
systems show a decrease of the perrhenate ions uptake in the presence
of the Mo ions by a factor of 63.28%. This difference indicates that in
spite of the A170 preference for the adsorption of Re ions, in the presence of a competitor ion, adsorption of this ion is affected by competitive inhibition and shield preventing effects.
3.4. Thermodynamics study
Temperature variations impact on thermodynamic constants of Re &
Mo ions adsorption on the A170, including changes in the enthalpy
Table 4
Kinetic parameters of Re adsorption on to the PuroliteA170 from single (Re = 250 ppm) and binary (Re = 250 ppm-Mo = 500 ppm) system.
Pseudo first-order
Pseudo second-order
Elovich
Intraparticle diffusion
T (K) System qe (exp) (mg g−1) qe (mg g−1) K1 (h−1) R2
Model
qe (mg g−1) K2 (mg g−1 h−1) R2
α (mg g−1 h−1) β(gmg−1) R2
Ki (mg g−1 h-0.5) R2
299
124
100.67
124
100.67
124
100.67
40.79
2.847
43.28
2.715
56.75
2.587
3.05
2.21
3.07
2.17
2.94
2.15
310
321
Single
Binary
Single
Binary
Single
Binary
116.5
100
117.4
98.75
119
98.2
55.53
26.78
63.62
26.84
54.76
26.84
0.012
0.006
0.011
0.006
0.01
0.006
0.992
0.996
0.988
0.997
0.987
0.992
0.00035
0.00022
0.00036
0.00021
0.00037
0.00029
0.999
0.987
0.999
0.995
0.999
0.996
0.056
0.135
0.057
0.136
0.06
0.136
0.986
0.985
0.985
0.995
0.984
0.983
0.922
0.962
0.92
0.965
0.917
0.945
M.B. Fathi et al. / International Journal of Mineral Processing 169 (2017) 1–6
5
weakening the randomness of the system due to occurrence of reaction
via an arrangement of metal ions at the surface of the sorbent.
4. Conclusions
Fig. 2. Intra-particle diffusion equation for the adsorption of Re from binary (Re-Mo)
system on the A170 resin at the different temperature. Initial concentration of metal
ions Re = 250 mg L−1, Mo = 500 mg L−1 resin dosage = 0.1 mg, pH = 2.
(ΔH), entropy (ΔS) and free energy (ΔG) were calculated using the following equations:
Kad ¼
Ca
Ce
ð16Þ
ΔG ¼ −RT ln Kad
ð17Þ
ΔG ¼ ΔH−TΔS
ð18Þ
The adsorption mechanism of rhenium on Purolite A170 from single
and Re - Mo jointed systems was studied by isotherms, kinetics and
thermodynamic modeling. In single systems, the Langmuir maximum
adsorption capacity of Re and Mo were found the same
(166.67 mg/g). For binary system, adsorption of the Re ions were described well by Extended Freundlich isotherm.
Investigation of mutual interference effects of Mo ions on Re adsorption capacity indicated that due to trend of molybdenum ions for occupying vacant sites on adsorbent, always the adsorption of perrhenate
ions is suppressed.
Kinetic studies showed that the adsorption of the discussed metal
ions from the both systems follows a second-order kinetic model with
R2 N 0.98. The fit of the data to this model denotes that the adsorption
reaction is the rate limiting step of the overall adsorption process. The
value of thermodynamic parameters also suggested that the adsorption
of perrhenate ions from single component system is spontaneous and
endothermic in addition the process follows the dissociative mechanism while for binary condition it is spontaneous and exothermic meanwhile it obeys an associative mechanism as revealed by negative values
of entropy.
Acknowledgments
ln Kad
ΔS ΔH 1
−
:
¼
R
R T
ð19Þ
where R is the gas constant, T is the reaction temperature (K), Kad is adsorption equilibrium constant, Ca and Ce are concentration of Re(VII) on
the adsorbent and solution at equilibrium (mg L−1) respectively. Δ H
can be calculated by the slope of the linear Van't Hoff plot (lnKad versus
(1/T) acc. to Eq. (19)) (Xiong et al., 2013).
Table 5 shows thermodynamic constants of studied both systems related to rhenium adsorption. The positive value of ΔH in single system
reveals energy is adsorbed as ion exchange proceeds, and the reaction
is endothermic but in competitive state, the negative value of enthalpy
implies two phenomenon: (1) the adsorption process is exothermic,
due to dissociating of the hydrated metal ions into free ions that are
then exchanged, and (2) the overcoming of the dehydration energy of
rhenium ions during adsorption was exothermic (Liu et al., 2014).
The negative variation of Gibbs free energies show that the adsorption of Re from both systems are spontaneous over the temperature
range 299–321 K·The value of ΔS is an indication of whether or not
the reaction follows an associative or dissociative mechanism. Positive
values of ΔS generally imply a dissociative mechanism, whereas negative values indicate an associative mechanism (Khan et al., 2014). Dissociative mechanism can be attributed to the exchange of the metal ions
with more mobile ions present on the exchanger, which would cause increase in the entropy (Xiong et al., 2012) as well as it can be raised from
the release of water molecule produced by ion exchange reaction (Lee
et al., 2007). In the present study, positive value of entropy for nocompetitive condition, shows the increased randomness at the solid/solution interface during the adsorption process and it reconfirms the dissociative mechanism whereas for other case negative sing, indicates
Table 5
Thermodynamic parameters of Re(VII) adsorption onto the A170 from single
(Re = 250 ppm) and binary (Re = 250 ppm - Mo = 500 ppm) system.
System
ΔH (kJ/mol)
ΔS (J mol−1 K−1)
ΔG(kJ/mol)
Single
Binary
3.34
−4.37
27.31
−8.86
T = 299 K
−4.94
−1.72
T = 310 K
−5.16
−1.63
T = 321 K
−5.35
−1.53
The authors gratefully acknowledge financial support from the National Iranian Copper Industries Co. (NICICO). They also wish to express
their gratitude to Dr. Azadmehr and Engineer M. Torabi for their help
and support.
Funding
This work was supported by the National Iranian Copper Industries
Co. (NICICO).
References
Abisheva, Z., Zagorodnyaya, A.N., 2011. Rhenium of Kazakhstan, (review of technologies
for rhenium recovery from mineral raw materials in Kazakhstan). Book of
Processings, p. 208.
Al-Asheh, S., Banat, F., Al-Omari, R., Duvnjak, Z., 2000. Predictions of binary sorption isotherms for the sorption of heavy metals by pine bark using single isotherm data.
Chemosphere 41, 659–665.
Blokhin, A., Maltseva, E., Murashkin, J.V., Pleshkov, M., Mikhaylenko, M., 2011. Sorption
recovery of rhenium from acidic sulfate and mixed nitrate-sulfate solutions containing molybdenum, 7th International symposium on technetium and rhenium-science
and utilization. Book of Abstracts.
Chekmarev, A.M., Troshkina, I.D., Nesterov, Y.V., Maiboroda, A.B., Ushanova, O.N., Smirnov,
N.S., 2004. Associated rhenium extraction in complex processing of productive solutions of underground uranium leaching. Chem. Sustain. Dev. 12, 113–117.
Chen, Y.-G., He, Y., Ye, W.-M., Jia, L.-Y., 2015. Competitive adsorption characteristics of Na
(I)/Cr (III) and Cu (II)/Cr (III) on GMZ bentonite in their binary solution. J. Ind. Eng.
Chem. 26, 335–339.
Dąbrowska, J., Jermakowicz-Bartkowiak, D., 2008. Modificated polymers towards rhenium sorption and desorption. Proceedings of the XXIII International Symposium on
Physico-chemical Methods of Separation, pp. 6–9.
Fouladgar, M., Beheshti, M., Sabzyan, H., 2015. Single and binary adsorption of nickel and
copper from aqueous solutions by γ-alumina nanoparticles: equilibrium and kinetic
modeling. J. Mol. Liq. 211, 1060–1073.
Igwe, J., Abia, A., 2006. A bioseparation process for removing heavy metals from waste
water using biosorbents. Afr. J. Biotechnol. 5.
Joo, S.-H., Kim, Y.-U., Kang, J.-G., Kumar, J.R., Yoon, H.-S., Parhi, P., Shin, S.M., 2012. Recovery of rhenium and molybdenum from Molybdenite roasting dust leaching solution
by ion exchange resins. Mater. Trans. 53, 2034–2037.
Kadirvelu, K., Goel, J., Rajagopal, C., 2008. Sorption of lead, mercury and cadmium ions in
multi-component system using carbon aerogel as adsorbent. J. Hazard. Mater. 153,
502–507.
Khan, M.D.A., Akhtar, A., Nabi, S.A., 2014. Kinetics and thermodynamics of alkaline earth
and heavy metal ion exchange under particle diffusion controlled phenomenon
using polyaniline-Sn (IV) iodophosphate nanocomposite. J. Chem. Eng. Data 59,
2677–2685.
6
M.B. Fathi et al. / International Journal of Mineral Processing 169 (2017) 1–6
Kholmogorov, A., Kononova, O., Kachin, S., Ilyichev, S., Kryuchkov, V., Kalyakina, O.,
Pashkov, G., 1999. Ion exchange recovery and concentration of rhenium from salt solutions. Hydrometallurgy 51, 19–35.
Lee, I.-H., Kuan, Y.-C., Chern, J.-M., 2007. Equilibrium and kinetics of heavy metal ion exchange. J. Chin. Inst. Chem. Eng. 38, 71–84.
Liu, J., Wang, X., 2013. Novel silica-based hybrid adsorbents: lead (II) adsorption isotherms. Sci. World J. 2013.
Liu, W., Zhang, P., Borthwick, A.G., Chen, H., Ni, J., 2014. Adsorption mechanisms of thallium (I) and thallium (III) by titanate nanotubes: ion-exchange and co-precipitation.
J. Colloid Interface Sci. 423, 67–75.
Lou, Z., Zhao, Z., Li, Y., Shan, W., Xiong, Y., Fang, D., Yue, S., Zang, S., 2013. Contribution of
tertiary amino groups to Re (VII) biosorption on modified corn stalk: competitiveness
and regularity. Bioresour. Technol. 133, 546–554.
Mahamadi, C., Nharingo, T., 2010. Competitive adsorption of Pb 2+, Cd 2+ and Zn 2+
ions onto Eichhornia crassipes in binary and ternary systems. Bioresour. Technol.
101, 859–864.
Mal'tseva, E.E., A.A.B., Murashkin, Yu V., 2012a. Kinetics of rhenium sorption from weakly
basic macroporous and gel anion exchangers purolite A170 and purolite A172 from
sulfuric acid solutions. Russ. J. Appl. Chem. 85, 5.
Mal'tseva, E.E., A.A.B., Murashkin, Yu V., 2012b. Specific features of rhenium desorption
from weakly basic anion exchangers purolite A170 and purolite A172 with ammonia
solutions. Physicochemical Studies of Systems and Processes. 85.
Maria-Ondina, F., Daniel, D.O., 2013. Molybdenite as a rhenium carrier: first results of a
spectroscopic approach using synchrotron radiation. J. Miner. Mater. Charact. Eng.
2013.
Metalpages[WWWDocument], 2016. (URL).
Mikhaylenko, M., Blokhin, A., 2012. Ion exchange resins tailored for effective recovery and
separation of rhenium, molybdenum and tungsten, Preprint 12–156. SME Annual
Meeting, Feb. 19–22, 2012, Seattle, Washington.
Nebeker, N., Hiskey, J.B., 2012. Recovery of rhenium from copper leach solution by ion exchange. Hydrometallurgy 125, 64–68.
Nur, T., Loganathan, P., Nguyen, T., Vigneswaran, S., Singh, G., Kandasamy, J., 2014. Batch
and column adsorption and desorption of fluoride using hydrous ferric oxide: solution chemistry and modeling. Chem. Eng. J. 247, 93–102.
Qiu, H., Lv, L., Pan, B.-C., Zhang, Q.-J., Zhang, W.-M., Zhang, Q.-X., 2009. Critical review in
adsorption kinetic models. J. Zheijang Univ. Sci. A 10, 716–724.
Rahmani, A., Mousavi, H.Z., Fazli, M., 2010. Effect of nanostructure alumina on adsorption
of heavy metals. Desalination 253, 94–100.
Senthilkumar, G., Murugappan, A., 2015a. Multicomponent adsorption isotherm studies
on removal of multi heavy metal ions in MSW leachate using fly ash. Int. J. Eng.
Res. Technol 4.
Senthilkumar, G., Murugappan, A., 2015b. Kinetic modeling and multicomponent isotherm studies on adsorption of multi heavy metal ions in MSW leachate by alcoffine.
Int. J. ChemTech Res. 8, 324–343.
Shahmohammadi-Kalalagh, S., 2011. Isotherm and kinetic studies on adsorption of Pb, Zn
and Cu by kaolinite. Caspian J. Environ. Sci. 9, 243–255.
Singha, B., Das, S.K., 2013. Adsorptive removal of cu (II) from aqueous solution and industrial effluent using natural/agricultural wastes. Colloids Surf. B: Biointerfaces 107,
97–106.
Srivastava, V.C., Mall, I.D., Mishra, I.M., 2006. Equilibrium modelling of single and binary
adsorption of cadmium and nickel onto bagasse fly ash. Chem. Eng. J. 117, 79–91.
Sukpreabprom, H., Arqueropanyo, O.-A., Naksata, W., Sooksamiti, P., Janhom, S., 2015. Single and binary adsorption of Cd (II) and Zn (II) ions from aqueous solutions onto bottom ash. Korean J. Chem. Eng. 32, 896–902.
Virolainen, S., Laatikainen, M., Sainio, T., 2015. Ion exchange recovery of rhenium from industrially relevant sulfate solutions: single column separations and modeling. Hydrometallurgy 158, 74–82.
Wu, F.-C., Tseng, R.-L., Juang, R.-S., 2009. Initial behavior of intraparticle diffusion model
used in the description of adsorption kinetics. Chem. Eng. J. 153, 1–8.
Xiong, C., Chen, X., Liu, X., 2012. Synthesis, characterization and application of
ethylenediamine functionalized chelating resin for copper preconcentration in tea
samples. Chem. Eng. J. 203, 115–122.
Xiong, Y., Xu, J., Shan, W., Lou, Z., Fang, D., Zang, S., Han, G., 2013. A new approach for rhenium (VII) recovery by using modified brown algae Laminaria japonica adsorbent.
Bioresour. Technol. 127, 464–472.
Zakhar'yan, S., Gedgagov, E., 2013. Anion-exchange separation of rhenium and selenium
in schemes for obtaining ammonium perrhenate. Theor. Found. Chem. Eng. 47,
637–643.
Zhu, Y., Hu, J., Wang, J., 2012. Competitive adsorption of Pb (II), Cu (II) and Zn (II) onto
xanthate-modified magnetic chitosan. J. Hazard. Mater. 221, 155–161.
Mohammad Bagher Fathi is Ph.D. candidate of mineral processing in Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
Bahram Rezai is a Lecturer at the Department of Mining and Metallurgical Engineering
Amirkabir University of Technology. His research interest is hydrometallurgical separation
& purification techniques particularly ion exchange, liquid-liquid extraction (LLX), which
includes optimization of the current technology and development of new techniques.
Eskandar Keshavarz Alamdari is a Lecturer at the Department of Mining and Metallurgical Engineering Amirkabir University of Technology. His research fields are Thermodynamics, Kinetics, simulation, Hydrometallurgy and Pyrometallurgy.
Документ
Категория
Без категории
Просмотров
2
Размер файла
386 Кб
Теги
003, 2017, minpro
1/--страниц
Пожаловаться на содержимое документа