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90 AZERBAIJAN CHEMICAL JOURNAL № 3 2023 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 66.081: 54-71: 661.728.7
ADSORPTION OF Cu (II) IONS FROM WASHING SOLUTIONS OF TAILINGS
BY DOWEX MAC-3 H+ SORBENT
A.A.Heydarov, S.E.Bahramova, N.I.Abbasova, S.Kh.Kalantarova, A.A.Guliyeva
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education of the
Republic of Azerbaijan
Received 26.01.2023 Accepted 03.02.2023
In this article, the experimental results of the adsorption of Cu2+ ion with Dowex Mac-3H+, a cation exchange resin with weak acid character, were investigated. Factors affecting the adsorption of copper ions from sulfated solutions: the initial concentration of Cu2+ ion, the dose amount of the adsorbent, the concentration-time, and the pH of the solution were studied. The obtained results showed that Dowex Mac-3H+ resin shows a high volume capacity (322.6 mg/g) in the separation of Cu2+ ions from sulfated solutions. At the initial concentration of 0.5 g/l, for 4 hours, when 0.2 g of sorbent was taken, at pH 6, at room temperature, the adsorption rate of Cu2+ ions was maximal (98%). In the first 1 hour, sorption occurs at a high rate, and increasing the contact time does not affect the process much. Due to the increase in the concentration of OH- ions at higher pH values, it is observed that the Cu2+ ion changes to the Cu(OH)2 precipitate form. The values of the obtained experimental results fully correspond to the Langmuir and Freundlich isotherms. It can be seen from the adsorption isotherms of the Langmuir and Freundlich model that the adsorption of Cu2+ ions on the resin occurs according to the chemisorption mechanism.
Keywords: ore and waste, Cu2+ ions, Dowex Mac-3H+, sorption, Langmuir and Freundlich equations.
doi.org/10.32737/0005-2531-2023-3-90-97 Introduction
The presence of metal ions in industrial wastewater has attracted global attention due to its negative impact on the external environment and human health. Pollution of the environment with heavy metal ions poses a great threat to the biosphere. Heavy metal ions affect living and plant organisms and are included in food products. These ions, which fall into the water body, remain in solution for a long time as a potential source of danger. These metals are in the form of hydrated ions, oxyhydrates, and complex inorganic compounds in solution.
One of the dangerous ions is copper. The presence of copper ions in natural waters is due to waste and mining waters of the chemical and metallurgical industries. The presence of this ion in underground water is a result of water erosion of copper-containing minerals (chal-copyrite, chalcosine, covelline, malachite, etc.) in mountain rocks. The level of sanitary cleanliness of copper (II) ion in swimming pools is taken to be 0.008 mg/l. In our country, the solid
phase wastes from the beneficiation of Dashkasan iron and Gadabey copper ores and mine water from beneficiation also cause the above-mentioned problems. Removal of heavy metal ions from solutions can be carried out by chemical precipitation [1], extraction [2], sorption [3, 4], reverse osmosis [5], ion exchange [6] electrochemical [7], and liquid membranes [8] methods.
Due to its economic efficiency and simplicity in the removal of metal ions from mining and waste water, the adsorption method is more widespread. Small dispersed substances with a large surface area are used as sorbents: activated carbon [9], clays [10], natural ben-tonite [11], natural zeolite [12], non-ferrous metallurgical slags [13], synthetic sorbents [14], fuel oil combustion ash [15].
Due to the large volume and low value of these sorbents obtained by natural and man-made means, and due to the lack of regeneration, the sorption of copper ions from solutions was carried out using synthetic sorbents specially selected by us.
The form of copper present in the solution depends mostly on the hydrolysis process, complexation, and pH of the environment. All these factors are also important in finding the optimal conditions of sorption. The distribution of ionic forms of copper in solution depending on pH is depicted in Figure 1 [16].
Fig. 1. Percentage distribution of copper in ionic
forms in solution as a function of pH.
In an acidic environment (up to pH =1.5-6.5), the ionic form of copper in solution is Cu . As a result of hydrolysis, some aquahydroxo complexes are also formed: [Cu(OH)]+, [Cu(OH)2]0, [Cu(OH)s]\ Cu2(OH)22-, [Cu(OH)4]2-, [Cu(OH) (H2O)3 ]+, [Cu(OH)s(H2O)]". At pH > 9, more than 40% of copper is in the form of [Cu(OH)2]0 and [CuCO3]0.
The form of presentation of the metal ion in the solution is the main factor and determines the mechanism of the process. Since the existing form of copper in mine waters is sulfate salts, copper is likely present in the form of Cu and Cu(OH)+
cations from pH-1 to pH-8.
From the analysis of literature materials, it became known that the sorption of Cu2+ ions from wastewater was carried out by researchers on various sorbents [9, 16, 18-22] (Table 1). As can be seen, the sorbent chosen by us shows a higher sorption capacity (322.6 mg/g).
The main goal of the research work is to evaluate the possibility of Cu2+ ions captured from man-made solutions with Dowex Mac 3H+ resin.
Experimental part
Characterization of the applied sorbent Dowex Mac 3H+ weak acid cation exchange resin was used as a sorbent. This material, which has a functional group of carbonic acid and a matrix of acrylic-divinylbenzene, is in the form of non-transparent spheres, and its color varies from white to amber. The structure of Dowex Mac 3H+ sorbent and the external view is as follows (Figure 2).
Adsorbent pH Copper (II) Reference
Activated carbon from palm bark 3 va 5 18.6 va 30.8
Chestnut bark 2 va 5 38.76 va 98.04 9
Activated carbon from pecan shells 3.6 95
Rice bran 5 33.58 16
Soybean husk 5 38.7
Activated carbon obtained from grapes 5 43.47
Orange peel 5 44.28 18
Activated carbon from palm bark 6 31.25
Polyazomethinamide 6 269.1 19
KU-2 5 179 20
Dowex HCR S/S 4.5 26.27 21
Dowex Marathon C 5.5 46.55
Natural zeolite (clinoptilolite) 5 20 22
Dowex Mac-3 6 322.6 Our study
Table 1. The maximum adsorption capacity of copper ions on the different adsorbents (mg/g)
a b
Fig. 2. External view (a) and the structure (b) of Dowex Mac 3H+.
Table 2. Physical and chemical properties of the adsorbent used in the research work
Adsorbent Dowex Mac-3
Molecular formula: C13H14O2
Type Type Weak acid cation
Form White, opaque, spherical beads
Matriks Macroporous
Matrix active group: Carboxyl group
Maximum operating temperature 1200C
pH range 4 - 14
Capacity 3.8 meq/ml
Particle size 12-50 mesh, 300-1200 ^m
Density 1.18 q/ml
In the literature [17] there is information about the selectivity of Dowex Mac 3H+ as a cation exchange resin in adsorbing Na+, Ca2+,
and Mg2+ ions.
Replacement of H2+ ions of the sorbent with copper ions in aqueous solutions is as follows:
Cu2+ + SO42" + 2(R-COO—H+) ^ (R-COO)2Cu2+ + 2H+ + SO42-
Methodology for determination of sorption quantities
Sorption was studied at
250C. The
adsorbent with a sample weight of 0.1-0.5 g is pounded and placed in a flask, the amount of CuSO4x5 H2O calculated according to the density is added to it, and the total volume is brought to 50 ml with distilled water. The required pH value was adjusted by adding NaOH and H2SO4 solutions.
Sorption was carried out at different pH values, with stirring in different time regimes. The concentration of Cu2+ ions in the solution at the initial and equilibrium moments was carried out by the atomic absorption spectrometer me-
thod, and sometimes by the iodometric method [18].
The percentage of Cu2+ ions separated from the solution was calculated by the formula 1:
e =
C0-C1
100%
(1).
C0 and C1 are the initial and post-sorption concentrations of Cu2+ ions in the solution (mg/l).
The statistical adsorption capacity of the adsorbent (Qe) was calculated by the following formula (2):
.(Co-Ci>V
(2)
Here, Qe - adsorption capacity of adsorbent (mg/g); C0 and C1 - initial and final concentrations of copper ion in the solution, mg/l; V - solution volume, l; m - the weight of adsorbent, g.
The concentration of Cu2+ ions, pH, adsorption dose, and mixing time were evaluated in the studies. Copper ion sorption was tested under statistical conditions, first in individual sulfate solutions, and then in mine waters.
C
0
m
Result and discussion
Dependence of adsorption on medium pH
It was determined that the efficiency of sorption depends on the acidity of the environment. Figure 3 shows the pH dependence of Cu2+ ions sorption on Dowex Mac 3H+ type cation-exchange adsorbent.
As can be seen from the graph, the maximum value of adsorption occurs at the 5-7 pH value of the solution. It is not recommended to raise the pH above 7. Thus, copper begins to precipitate Cu(OH)2 at pH values above 7. Ammonium-acetate (pH 3.5-8) buffer solution was used in experiments to prevent precipitation. We have taken the normal acidity level as pH = 5.
This optimal value of pH coincides with
93
the research work conducted by Omar E. Abdel Salam [15].
Effect of Dowex Mac-3H+ adsorbent dosage on Cu2+ ions adsorption
The results of studies on the effect of the amount of adsorbent on the degree of adsorption at different concentrations of Cu2+ ions and the adsorption capacity of the sorbent are given in Figure 4 (a and b). As can be seen from Figure 4, the adsorption of Cu2+ ions from the solution increases to a certain extent in the initial moments, and then stabilizes. It is not advisable to take the sorbent after the limit of 4 g/l (m=0.2 g). This shows that the increase in the number of adsorbent particles ensures sufficient adsorption of Cu2+ ions.
M <D T3
5
o
6
o m
100 90 80 70 60 50 40 30 20 10 0
1.3 q/l -•-1 q/l -♦-0.77 q/l -■-0.5 q/l
solution pH
Fig. 3. Dependence of the degree of sorption on the pH of the solution at different concentrations of Cu2+ ion: time - 4 hours, mass of adsorbent - 0.2 g, temperature - 25 ± 10C.
0
1
2
5
6
7
100
n o
o
m
80
60
T3
40
20
0,2 0,4 0,6
Sorbent amount, g
<♦— 1,3 q/l
1 q/l ■a—0,77 q/l »3-0,5 q/l
0,8
a
-♦-0,5 q/l -■-0,77 q/l —a— 1 q/l 8 1,3 q/l
4 6 8 10 12 14 adsorbent dosage, g/l
16
Fig. 4. The effect of the amount of adsorbent on the degree of sorption (a); The effect of the adsorbent dose on the sorption capacity (b): t = 25 ± 10C, pH = 5, t - 30 min, V = 50 ml.
Effect of contact time on Cu ion adsorption
One of the other important factors affecting the sorption of copper ions is the contact time of the ions in the solution with the adsorbent. As can be seen from Figure 5, the rate of sorption is high in the first minutes. The concentration of Cu2+ ions in the solution decreases rapidly, and after 1 hour the rate of sorption decreases significantly. Further increase
1,4 Ht 1,2
u o1
ams 0,8 sn
. 2 0,6 + 0,4
<N °,4
uC0,2 0
in contact time does not affect the efficiency of sorption.
One of the main factors affecting the distribution of Cu2+ ions between solid and liquid phases is their initial concentration in solution. For this purpose, kinetic studies of the sorption process with different concentrations of Cu2+ ions in the solution were conducted. Keeping all parameters constant, the concentration of metal ions was changed between 0.51.3 g/l (Figure 6).
-♦-1,3 q/l -■-1 q/l —a—0,77 q/l -s-0,5 q/l
0 40 80
120 160 200 240 Sorption time, min
280 320 360
Fig. 5. The dynamics of reduction of Cu + ion in solution at different concentrations depending on time: mads = 0.2 g, t = 25 ± 10C, pH = 5, V-50 ml.
100
M e
^ 50 n o ti
tpr
o S
100 200
Sorption time, min
-♦-1,3 q/l -•-1 q/l —a—0,77 q/l -■-0,5 ql
300 400
Fig. 6. Effect of time on the sorption of Cu + ions from solutions of different concentrations: t= 25 ± 1°C, pH = 5, m - 0.2 g, V-50 ml.
b
0
2
0
As can be seen, the rate of sorption of Cu2+ ions in the solution at relatively low starting concentrations (C0=0.5 g/l) has high values. As the initial concentration of metal ions in the solution increases, the sorption capacity of the sorbent (Qe, mg/g) increases (Figure 7).
At first, qe increases rapidly. During 90 minutes, this increase occurs at a high rate, then stabilizes. This indicates that sorbent has a limited number of active centers. The stabilization of sorption capacity can be explained by the filling of sorption centers.
Langmuir and Freundlich isotherms
The results of the investigated Cu2+ ions sorption capacity correspond to the theoretical models of Langmuir and Freundlich
QmKLC
qe
1+K.Ce
- = -•Ce+ Q e
Langmuir equality (1)
(2)
QmKL
qe = KCe
1/n
Freundlich equality (3)
Here, qe is the concentration of adsorbed metal ions per unit mass of adsorbent (mg x g-1); Ce - equilibrium density of the substance dissolved in the volumetric solution (mg x l-1); Q0 - is the concentration of the solid substance that completely covers the adsorption centers, KL - constant related to free adsorption energy; KF and n are constants according to the Freundlich theory model. The Langmuir isotherm shows that the free energy of adsorption does not depend on the degree of surface filling.
The values of Q0 and KL can be plotted and found by the linear form of the Langmuir model equation (Eq. 2) In working out the experimental results, these equations are considered as isotherms used in describing the sorption of components from the liquid phase to the surface of the adsorbent (solid phase) due to their simplicity. The linear dependencies of the obtained experimental results in the Langmuir and Freundlich equations are graphically shown in Figure 8.
Ln qe = - lnCe +lnKF
(4)
a ioo 50
o
0,5 ql
0
100
2°°orption time0
min
400
Fig. 7. Effect of sorption time on sorption capacity in solutions of different concentrations: 0.2 g sorbent, pH =5, m= 0.2 g, V= 50 ml.
1,2 1 0,8 0,6 0,4 0,2 0
Ce/Qe
y = 0,0033x + 0,2122 R2 = 0,9327
♦
100
Ce
200
300
2,4 2,35 2,3 2,25 2,2 2,15 2,1 2,05
log Qe
y = 0,3047x + 1,6205 R2 = 0,9975
1,5 log Ce 2
2,5
Fig. 8. Freundlich (a) and Langmuir (b) isotherms.
a
0
1
Table 2. Characterization of Cu2+ ions sorption by Dowex Mac 3 H+ resin according to Langmuir and Freundlich models
Langmuir constants KL = 0.0154 Qm (mg/g) = 322.6 R2 = 0.9327
Freundlich constants KF = 1.93 1/n = 0.2857 R2 = 0.9975
As can be seen from the curves in the figure, the experimental results of the adsorption of copper ions in the studied conditions correspond to the Langmuir and Freundlich models. According to these equations, the sorption characteristics of Cu2+ ions by Dowex Mac 3H+ resin are given in Table 2.
Conclusion
As a result of research, the adsorption isotherm of Cu2+ ion in aqueous solutions with Dowex Mac 3 H+ resin was obtained under statistical conditions. It was found that the maximum adsorption occurs in an acidic environment (pH=5-6.5). Adsorption constants were calculated as a result of kinetic studies. From the experimental results, it was found that Dowex Mac 3 H+ resin shows a high volume capacity (322.6 mg/g) in the separation of Cu2+ ions from sulfated solutions. It can be seen from the adsorption isotherms of the Langmur and Frendlich model that the adsorption of Cu2+ ions on the resin occurs according to the chemisorption mechanism.
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TULLANTILARIN YUMA MOHLULLARINDAN Cu (II) iONLARININ DOWEX MAC-3H+
SORBENTi iLO ADSORBSiYASI
A.0.Heydarov, §.E.Bahramova, N.LAbbasova, S.X.Kabnt3rova, A.A.Quliyeva
Bu maqalada Cu2+ ionun zaif turçu xassali kationdayiçdirici qatran olan Dowex Mac-3H+ ils adsorbsiyasinin tacrubi naticalari araçdinlmiçdir. Mis ionunun sulfatli mahlullardan adsorbsiyasina tasir edan amillar: Cu2+ ionunun ilkin qatiligi, adsorbentin doza miqdan, kontant muddati, mahlulun pH-i oyranilmiçdir. Alinan naticalar gostardi ki, Dowex Mac-3H+ qatrani Cu2+ ionunun sulfatli mahlullardan ayrilmasinda yuksak hacm tutumlulugu gostarir (322.6 mq/q). 0.5 q/l ilkin qatiliqda, 4 saat muddatinda, 0.2 q sorbent goturuldukda, pH-in 6 qiymatinda, otaq temperaturunda mis ionlannin adsorbsiya daracasi maksimal (98%) olmuçdur . ilk 1 saatda sorbsiya yuksak suratla baç verir va toxunma zamaninin artinlmasi prosesa o qadar da tasir etmir. pH-in daha yuksak qiymatlarinda OH- ionlannin qatiliginin artmasi sababindan Cu2+ ionunun Cu(OH)2 çokuntu formasina keçdiyi muçahida olunur. Alinmiç tacrubi naticalarin qiymatlari Langmur va Frendlix izotermlarina tam uygun galir. Lanqmur va Frendlix modelinin adsorbsiya izotermlarindan gorunur ki, Cu2+ ionunun qatran uzarinda adsorbsiyasi xemosorbsiya mexanizmi uzra baç verir.
Açar sozlsr: filiz va tullantilar, Cu2+ ionu, sorbsiya, Dowex Mac-3H, Langmur va Frendlix izotermbri.
АДСОРБЦИЯ ИОНОВ Cu(II) ИЗ ОТХОДОВ МОЮЩИЕ РАСТВОРЫ СОРБЕНТОМ
DOWEX MAC-3H+
А.А.Гейдаров, Ш.Э.Бахрамова, Н.И.Аббасова, С.Х.Калантарова, А.А.Гулиева
В данной статье исследованы экспериментальные результаты адсорбции иона Cu2+ слабокислотным катионитом Dowex Mac-3H+. Изучены факторы, влияющие на адсорбцию иона меди из сульфатированных растворов: начальная концентрация иона Cu2+, количество дозы адсорбента, время концентрирования, рН раствора. Полученные результаты показали, что смола Dowex Mac-3H+ демонстрирует высокую объемную емкость (322.6 мг/г) при выделении иона Cu2+ из сульфатированных растворов. При исходной концентрации 0.5 г/л, за 4 часа, когда было взято 0.2 г сорбента, при значении рН 6.5, при комнатной температуре скорость адсорбции ионов меди была максимальной (98%). В первый час сорбция происходит с высокой скоростью, и увеличение времени контакта не сильно влияет на процесс. Полная адсорбция иона Cu2+ происходит при pH > 6. При более высоких значениях рН наблюдается переход иона Cu2+ в форму осадка Cu(OH)2 с увеличением концентрации ионов OH-. Значения полученных экспериментальных результатов полностью соответствуют изотермам Ленгмюра и Френдлиха. Из изотерм адсорбции модели Ленгмура и Френдлиха видно, что адсорбция иона Cu2+ на смоле происходит по хемосорбционному механизму.
Ключевые слова: руды и отходы, ион меди (II), сорбция, Dowex Mac-3H+, уравнения Ленгмюра и Френдлиха.
