CC BY
7Chemical Journal of Kazakhstan
Volume 2, Number 78(2022), 5-15 https://doi.org/10.51580/2022-2/2710-1185.61
УДК 544.65:54.058:546.562
REMOVAL OF COPPER (II) IONS FROM SPENT SOLUTIONS BY GRANULAR GRAPHITE ELECTRODES
Nurdillayeva R.N.1*, Askarov A.K1, Zhylysbayeva AN.2, Bayeshov A.3
1 Khoja Akhmet Yassawi International Kazakh-Turkish University, Turkistan, Kazakhstan
2South Kazakhstan State Pedagogical University NJSC, Shymkent, Kazakhstan 3D.V.Sokolskiy Institute of Fuel, Catalysis and Electrochemistry JSC, Almaty, Kazakhstan E-mail: raushan.nurdillayeva@ayu. edu.kz
Abstract: The most abundant heavy non-ferrous metals in the industrial wastewaters and spent solutions are lead, copper, zinc, nickel, however, it depends on the type of the industry. This work proposes the concepts of an electrochemical method of divalent copper removal from the spent solutions with the help of granular graphite electrodes. The study has been conducted, changing the meanings of the five major parameters including the current density (i), the concentration of copper (II) ions (C), the surface area of graphite electrodes (S), the concentration of sulfuric acid in the solution (M) and the electrolysis duration (т), affecting Cu (II) ions removal percentage from the solution. The experimental results show that the current density, surface area of the granular graphite electrodes and the time are the main factors, which affect the removal percentage of Cu (II), while the changes in the sulfuric acid concentration in the solution have a minor effect. The highest copper removal value is 97% and 54 % current efficiency was observed in conditions: i =150A/m2, т = 1.5 h, [H2SO4] = 0.4 M, S = 150 cm2 which is considered as an optimal condition for copper removal process by granular graphite electrode.
Key words: copper (II) ions, granular graphite electrode, spent solutions, heavy non-ferrous metals, removal degree, current efficiency
Nurdillayeva Raushan Nurdillakyzy Candidate of Chemical Science, Professor, E-mail:
raushan.nurdillayeva@,ayu.edu.kz; ORCID ID:
https://orcid.org/0000-0001-9444-737X_
AskarovAkbarKhamdamovich Master student, E-mail: akbar.askarov@ayu.edu.kz;
_ORCID ID: https://orcid.org/0000-0001-6182-188X_
Zhylysbayeva Akkongyr Nurdillayevna Candidate of Chemical Science, Associate Professor, Email: zhylysbayeva.akkongyr@okmpu.kz; ORCID ID:
https://orcid. org/0000-0001-9114- 7582_
Bayeshov Abduali Doctor of Chemical Science, Professor, Academician of
the NAS RK, E-mail: bayeshov@mail.ru; ORCID ID: https://orcid.org/0000-0003-0745-039X_
1. Introduction
The industrial revolution with economic concerns has created some secondary problems such as heavy metal contaminated wastewater. And there has always been a need for a suitable, efficient, and cheap way of wastewater treatment with a high degree of success. Chemical precipitation, ion floatation, adsorption, coagulation, and some other chemical methods have been the most
Citation: Nurdillayeva R.N., Askarov A.K., Zhylysbayeva A.N., Bayeshov A. Removal of copper (II) ions from spent solutions by granular graphite electrodes. Chem. J. Kaz., 2022, 2(78), 5-15. DOI: https://doi.org/10.51580/2022-2/2710-1185.61
available methods for wastewater treatment [1].
Biopolymers and hydrogels are widely used for industrial applications because of their availability and safety. For instance, the modified biopolymer adsorbents, which are derived from chitosan, starch, and chitin, are proposed to be new material for water treatment from Cu2+ ions. Biosorption is highly effective for the aqueous solutions, containing low concentrations of Cu2+ and other metals because of its simplicity and high removal capacity [2]. Another adsorption method of wastewater treatment has been tested with magnetic/carbon nanocomposites by Andelescu A. and Nistor M.A. pH of the solution, a quantity of sorbent, the initial concentration of Cu (II), and temperature have been chosen as the main parameters. It has been observed that the removal efficiency of metal ions increases directly proportional to the absorbent's quantity and temperature, and inversely proportional to the initial metal concentration [3]. The adsorption experiments, using DTC-modified rGO-PDTC/Fe3O4nanocomposite, have achieved a high level of heavy metal removal. The spent nanocomposite after the adsorption and desorption process has been regenerated by the organic reaction. Nanocomposite has exhibited a good adsorption capability for the five cycles [4]. Manganese oxides are observed to be a good adsorbent for heavy metal ions, and they can be reused many times until the loss of the removal capacity. In his research, Yang X. used birnessite, which is the main manganese mineral. The research results have shown that the Cu2+ removal capacity of birnessite (44.3mg g-1) can be remarkably increased to 372 mg g-1 with the electrochemical redox reactions [5].
The practical use of fibrous materials in heavy metal treatment has been shown in the research of Du Z. and Zheng T. Raw jute fiber and carboxyl-modified jute fiber have been taken as two types of sorbents and have been compared in the same process conditions. The results have shown that the CMJF has exhibited 4.2 times higher adsorption capacity [6]. Magnetic chitosan/graphene oxide nanocomposite (MCGON) can be used as an adsorbent of Cu2+ from the aqueous solutions. MCGON has a high specific area, large pore volume, small particle size, and strong saturation magnetization. MCGON exhibited an adsorption capacity of 217.4 mg/g-1. The process has been practical and efficient due to the adsorbent's high saturation capacity [7].
Due to the use of the electrolysis-enhanced micro-electrolysis fluidized bed technology processes, it has been detected that copper is mostly removed in optimum conditions: flow rate - 22 mm/s, current-voltage -12V, initial pH=4, time-30 min [8]. Reusable and capable hollow magnetic polydopamine nanoparticles have been fabricated as an effective way of heavy water removal from the sewage and industrial effluents. The experiment results have shown that the heavy metal removal value has been above 70% and stayed the same after reusing the Fe3O4@PDA 5 times. Fe3O4@PDA nanoparticles have been introduced as a beneficial method of Cu (II) and Pb (II) recovery [9]. Cu (II)
removal value reached a high of 99,9% by using mechanically activated CaCO3. The sediment of treated wastewater Cu4(SO4) (OH)6*H2O has been used as a copper-based antibacterial agent [10].
The advanced methods of treating Cu (II), containing the wastewater experiments by combining the internal micro-electrolysis (IME) and electrocoagulation processes have been conducted by Fu Chen, Zhanbin Luo. The effects of pH, time, current density, and Fe/C mass ratio have been tested during the experiment. As a result, by IME, 92% of Cu, 88% of Pb, and 72% of Zn have been removed within 30 min at initial pH=3. As a result of the coagulation process 99% of Cu, 99% of Pb, and 98% of Zn have been removed [11].
The electrochemical methods of wastewater treatment can be grouped into three categories as the transformation methods, separation methods, and combined methods. These methods are compact and efficient as they do not require a lot of space and have a high value of metal removal [12]. Our previous research results reveal the effectivity of the electrochemical method via using the granular graphite electrodes in wastewater treatment from Pb (II) ions [13]. Electrolytic recovery of copper from wastewater has been experimented and the effects of temperature, current density, anode material, organic contaminants have been measured. As a result of the 2D and 3D electrodes comparison, it has been observed that 2D electrodes used about 27.3 kWh while 3D electrodes used only 5.86 kWh for the same amount of copper recovery (1.443kg) [14]. I.A. Khattab and M.F. Shaffei have done some research for the electrochemical removal of Cu2+ from the effluent wastewater. A direct current has been used as a power supply and a graphite material has been used as an electrode. The experiment has been conducted in an electrolyte with an initial Cu2+ concentration of 100-350 mg/l and 750 ml/min flow rate. 0.5 M NaCl has been used as a supporting electrolyte and the pH value of the electrolyte has been 3. The current density range has been between 100-500 A/m2. As a result, under the optimal conditions (current density-500 A/ m2, electrolysis time = 30 min, pH = 3, initial [Cu] = 100 mg/l) removal percent has reached 96% [15].
Heavy metal-containing wastewater can be regenerated by two-stage electrochemical treatment. It is determined that the process of bioleaching heavy metals from sediment emits the processed water with a high level of dissolved metals and sulfate. The model cell with a platinum anode with an effective electrode area of 10 cm2 and a graphite cathode with an effective area of 10 cm2 has been used to achieve a high level of heavy metal treatment. The treatment process has consisted of two stages. The main load of heavy metals has been eliminated by cathode in the first stage and excessive sulfuric acid which is 3-4 g/l has been decreased to about 1 g/l with help of anode. The pH level has risen from 3.0 to 4-5. As a result of electrolyte with a time duration of 5.5 hours, an electric current density of 0.1 A/m2, more than 99% of Cu, Pb, Zn, and Cd have been removed [16].
Although it is possible to achieve a high value of Cu (II) ions removal, some methods cannot be widely used for the industrial purposes. The main reasons are high price and low efficiency. As the electrochemical way of Cu (II) ions removal with granular graphite electrodes has a high removal value and high current efficiency, it can be a promising approach for the effective treatment of industrial spent solutions.
2. Experimental part
The necessary methods and appropriate methods were selected for conducting the research. A direct current was used to study the rules of the copper (II) ions removal process. A rod graphite electrode was taken as the anode and a granular graphite electrode as the cathode for the electrolyzer with a volume of 200 ml (Figure 1). A model solution containing 1g/l of Cu2+ ions, acidified with 0.2 M of sulfuric acid was used as an electrolyte. Current density (i), electrolysis time (t), the surface area of a granular graphite electrode (S), the molar concentration of sulfuric acid (M), and concentration of Cu (II) ions were taken as the main parameters affecting the electrolysis during the study.
1- rectifier; 2- amperemeter; 3-model solution; 4- rod graphite anode; 5- bed graphite electrode; 6- granular graphite cathode.
Figure 1 - Model of the electrolyzer used for research.
A voltammeter CTA-1 was used to determine the low concentrations of Cu2+ ions in a solution from 0.001mg/l and above, with high accuracy. The process of determining the mass concentration of Cu2+ ions in electrolyzed solution with a CTA-1 analyzer was shown in Figure 2.
Figure 2 - The expression of reduction maximum of Cu2+ ions during voltametric analysis: 1-voltametric curve of background solution; 2- voltametric curve of sample solution containing Cu2+ ions
3. Results and discussions
The research work is based on the removal of copper (II) ions by the electrolytic reduction from the spent solutions to metallic copper at the granular graphite cathode:
Cu2+ + 2e- ^ Cu0
E0= +0.34 V
The effect of current density on the copper (II) ions removal degree has been investigated by direct current. The current density interval was 50-250 A/m2. It has been observed that an increase in current density has resulted in a steady rise in the removal of Cu2+ ions from electrolytes (Figure 3). Despite the high removal level at a high current density, an erosion of graphite electrode and a reduction of current efficiency have been noted at a high 200-250 A/m2. This is due to an increase in the hydrogen emission rate which is electrolyzed at the same time with a copper at the cathode at high current densities. Therefore, the current density of 150 A/m2 has been assumed to be an optimal value.
%
100 -, 80 60 40
20 -
0 -I-.-1-.-1-1-.
50 100 150 200 250 i, A/m2
—•— Cu (II) removal —•— Current efficiency
t= 0.5 h., [H2SO4] =0.2 M, S=100 cm2, [Cu2+] = 1 g/l Figure 3 - Influence of the current density on the copper removal degree.
The dependence of copper (II) ions removal degree from the solution on the initial Cu2+ ions concentration has been studied. As a result of electrolysis carried out for 0.5 hours at a current density of 150 A/m2 and the initial copper (II) ions concentration between 0.5 and 2.5 g/l, it has been observed that the removal percentage of Cu2+ ions decreases as the concentration increases. However, it has been revealed that the value of current efficiency increases directly proportional to the initial copper (II) ions concentration (Table 1).
Table 1 - Influence of the initial copper (II) ions concentration on the copper removal degree, i = 150A/m2, t = 0.5 h., [H2SO4] =1.0 M, S=100 cm2
[Cu2+] g/l 0.5 1.0 1.5 2.0 2.5
Copper (II) ions removal percentage, % 62.5 ± 0.5 55.5 ± 0.4 42.0 ± 0.2 36.5 ± 0.2 31.8 ± 0.2
Current efficiency, % 35.0 ± 0.2 70.6 ± 0.5 80.6 ± 0.4 81.8 ± 0.4 89.1 ± 0.5
The result of experiments, which have been conducted to study the influence of the concentration of the sulfuric acid in the solution has shown that an increase in the acid concentration results in a slight growth of copper (II) ions removal level. This circumstance can be attributed to the high electrical conductivity of sulfuric acid with increasing acid concentration (Table 2).
Table 2 - Influence of sulfuric acid concentration on the copper (II) ions removal degree, i = 150 A/m2, t = 0.5 h., [Cu2+] =1.0 g/l, S=100 cm2
[H2SO4], M 0.2 0.4 0.6 0.8 1.0
Copper (II) ions removal percentage, % 55.5 ± 0.3 58.6 ± 0.2 62.8 ± 0.2 65.1± 0.3 66.4 ± 0.4
Current efficiency, % 62.2 ± 0.4 65.6 ± 0.3 70.4 ± 0.3 72.9 ± 0.4 74.4 ± 0.4
The influence of the duration of electrolysis has been studied by direct current under the conditions of current density 150 A/m2, [H2SO4] = 0.2 M, [Cu2+] = 1.0 g/l and surface area of granular graphite electrode has been 100 cm2. As a result of the experiment, it has been found that as the electrolysis duration increases, the degree of copper (II) ions removal also increases. The maximum value of copper (II) ions removal degree has been 96.3% in 2.5 hours of the electrolysis process (Figure 4). After the electrolysis for 0.5 hours duration, the current efficiency of copper (II) ions removal has reached 62%, while the current efficiency of copper (II) ions removal after the electrolysis for 2.5 hours has been 21%. The reduction of current efficiency can be attributed to the decrease in the initial copper (II) ions concentration in the solution over time.
100 80 60 40 20 0
0.5 1.0 1.5 2.0 2.5 t, h
—removal, % —•— CO, %
i = 150 A/m2, [H2SO4] = 0.2 M, [Cu2+] = 1.0 g/l, S= 100 cm2
Figure 4 -Influence of electrolysis duration on the copper (II) ions removal degree.
The following research work has been carried out to determine the influence of the surface area of a granular graphite electrode on the copper (II) ions removal percentage at a current density of 150 A/m2 with an electrolysis duration of 0.5 hours (Figure 5). It has been observed that copper (II) ions removal value is proportionate to the surface area of the electrode. The results have shown that electrolysis with the participation of the granular graphite electrodes with a surface area of 50 cm2 has had a 76.2% current efficiency, and the current
efficiency decreases as the surface area of granular graphite electrode increases. The efficient surface area of granular electrodes decreases as volume increases in size.
- Cu (H) removal ♦ Current efficiency
i = 150 A/m2. [H2SO4] = 0.2 M. [Cu2+] = 1.0 g/1. i = 0.5 h.
Figure 5 -Influence of the surface area of the granular graphite electrode on the copper (II) ions
removal degree.
By comparing the obtained results, the values obtained as the optimal point of each parameter are - i =150 A/m2, S=150 cm2, t=1.5 h, [H2SO4] = 0.4 M, [Cu2+] =1.5 g/l. Electrolysis by the given values has shown 97% copper (II) ions removal degree, and 54% current efficiency.
4. Conclusion
As a result of the scientific research, the influence of the main factors affecting the degree of copper removal from electrolytes has been determined. It has been noted that:
- Cu2+ removal percentage decreases and current efficiency raises as the initial concentration of Cu2+ ions increases;
- Cu2+ ions removal percentage and a current efficiency raise as the concentration of sulfuric acid in the solution increases;
- The removal percentage of Cu2+ ions increases, and current efficiency reduces as the duration of electrolysis gradually increases;
- The removal percentage of Cu2+ ions increases, and current efficiency decreases as the surface area of granular graphite electrode expands;
- The removal percentage of Cu2+ ions rises, and the current efficiency reduces as the current density increases. Comparing the results, it has been found
that the method of using granular graphite electrodes is a very effective way of cleaning the spent solutions with a high copper concentration.
The results of the study have shown that with the help of granular graphite electrodes it is possible to remove 97% of copper (II) ions from a solution and make the spent solution suitable for technical use.
The results of scientific research can be used in the cleaning areas of the high Cu2+ ions containing solutions.
Funding: The research has been conducted at Khoja Akhmet Yassawi International Kazakh-Turkish University as part of initiative research work (the State Registration number No 0120RKI0185, registered at NCSTE RK).
Acknowledgements: The research has been carried out in the research laboratory of Ecology and Chemistry Department of the Natural Science Faculty of Akhmet Yassawi University.
Conflict of Interest: The authors have no Conflict of Interest declared between the authors requiring disclosure in this article.
ЦОЛДАНЫЛFАН ЕР1Т1НД1ЛЕРД1 МЫС (II) ИОНДАРЫНАН ТУШРШ1КТ1 ГРАФИТТ1 ЭЛЕКТРОДТАР К0МЕПМЕН ТАЗАЛАУ
Нурдтлаева Р.Н.1*, Аскаров АХ.1, Жылысбаева АН.2, Баешое А3
1Кожа Ахмет Ясауи атындагы Халыщаралыщ цазац-mYpiK ynrnepcumemi, TYpKlcman, Казащстан 2ОцmYcmiк Казацстан мемлекеттт педагогикалъщ ynueepcumemi КЕАК, Шымкент, Казахстан 3Д.В.Сокольский атындагы Жанармай, катализ жэне электрохимия институты АК, Алматы, Казащстан
E-mail: raushan.nurdillayeva@ayu.edu.kz
Туйшдеме. 0ндiрiс TYpiHe карай колданылган ертндшер мен акаба сулар курамында ец коп кездесетш ауыр жэне TYCTi металдар коргасын, мыс, мырыш, никель болып табылады. Бершген зерттеу жумысында TYЙipшiктi графит электродтар комепмен колданылган ертндшерден мыс (II) иондарынан тазартудыц электрохимиялык эдю усынылды. Зерттеуде колданылган epiтiндi курамындагы мыс (II) иондарыныц тазалану дэрежесше эсер ететш непзп бес параметрдщ, оныц шшде ток тыгыздыгы (i), мыс (II) иондарыныц концентрациясы (С), графит электродтарыныц бeттiк ауданы (S), epiтiндiдeгi куюрт кышкылыныц концентрациясы (M) жэне электролиз узактыгы (т) мэндepiн озгерте отырып жасалды. Тэж1рибе нэтижeлepi ток тыгыздыгы, TYЙipшiктi графит электродтарыныц бeттiк ауданы жэне электролиз уакытыныц epiтiндiнiц мыс (II) иондарынан тазалану дэрежесше ец коп эсер ететш факторлар екендт, ал ертндщеп куюрт кышкылыныц концентрациясы айтарлыктай эсер eтпeйтiндiгi коpсeттi. Мыс (II) иондарынан тазалану дэрежесшщ ец жогары мэнi 97% жэне ток бойынша шыгымы 54 % мэш кeлeсi шарттарда аныкталды: - i =150А/м2, т = 1.5 саг., [H2SO4] = 0.4 M, S = 150 cм2 жэне осы мэндер колданылган epiтiндiнi мыс (II) иондарын TYЙipшiктi графит электродтары катысында тазалаудыц оцтайлы жагдайы peтiндe белгшенд^
ТYЙiндi сездер: мыс (II) иондары, TYЙipшiктi графит электроды, колданылган ертндшер, ауыр TYeri металдар, тазалану дэрежеа, ток бойынша шыгым.
Нурд'тлаева Раушан Нурдтлацызы Химия г^гл^гмдарыныц кандидаты, профессор
Аскаров Акбар Хамдамович Магистрант
Жылысбаева Ащоцыр Нррдтлацызы Химия г^гл^гмдарыныц кандидаты, доцент
Баешое Эбдуэлг Химия г^гл^гмдарыныц докторы, профессор, КР ¥ГА
академиг1
ОЧИСТКА ОТРАБОТАННЫХ РАСТВОРОВ ОТ ИОНОВ МЕДИ (II) ГРAНУЛИРОВАННЫМИ ГРАФИТОВЫМИ ЭЛЕКТРОДАМИ
Нурдиллаева Р.Н.1*, Аскаров АХ1, Жылысбаева АН.2, Баешое А.3
1Международный казахско-турецкий университет имени Ходжи Ахмеда Ясави, Туркестан, Казахстан
2НАО Южно-Казахстанский государственный педагогический университет, Шымкент, Казахстан
3АО Институт топлива, катализа и электрохимии им. Д.В. Сокольского, Алматы, Казахстан E-mail: raushan.nurdillayeva@ayu. edu.kz
Резюме. Наиболее распространенными тяжелыми цветными металлами в отработанных растворах и сточных водах в зависимости от типа промышленности являются свинец, медь, цинк, никель. В данной работе предложено электрохимический способ очистки ионов меди (II) из отработанных растворов с помощью гранулированных графитовых электродов. Исследование было проведено с изменением значений пяти основных параметров, включая плотность тока (i), концентрацию ионов меди (II) (C), площадь поверхности графитовых электродов (S), концентрацию серной кислоты в растворе (M) и продолжительности электролиза (т) влияющую на степень извлечения ионов Cu (II) из раствора. Результаты экспериментов показывают, что плотность тока, площадь поверхности графитовых электродов и время являются основными факторами, влияющими на степень очистки Cu (II), в то время как изменения концентрации серной кислоты в растворе оказывают незначительное влияние. Наибольшее значение очистки от ионов меди 97% и выход по току 54 % установлено в условиях: i =150 А/м2, т =1,5 ч, [H2SO4] = 0,4 М, S = 150 см2, что предложено оптимальным условием для процесса очистки меди гранулированными графитовыми электродами.
Ключевые слова: ионы меди (II), гранулированные графитовые электроды, отработанные растворы, тяжелые цветные металлы, степень очистки, выход по току
Нурдиллаева Раушан Нурдиллакызы Кандидат химических наук, профессор
Аскаров Акбар Хамдамович Магистрант
Жылысбаева Акконыр Нурдиллаевна Кандидат химических наук, доцент
Баешов Абдуали доктор химических наук, профессор, академик НАН РК
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