CC BY
4
SRSTI 53.37.91
https://doi.org/10.48081/DLCT7165
N. V. Oleinikova
Siberian Federal University, Russian Federation, Krasnoyarsk
STATUS AND PROSPECTS OF METALLURGICAL PROCESSING OF ELECTRONIC WASTE IN KAZAKHSTAN
This article provides an overview of the current state of the problem ofprocessing electronic waste in order to extract metals and other valuable components. Electronic waste is a source of potential danger to the environment, but at the same time a valuable raw material containing non-ferrous and ferrous metals. The content of some non-ferrous metals in electronic waste may exceed their content in mineral raw materials by several times. So, the content of printed circuit boards (PCBs) can reach up to 30 % of the weight ofprinted circuit boards, and tin up to 2—4 %. In addition, a ton of used smartphones can contain up to 30 grams of gold. It is also known that during the processing of secondary raw materials, the costs of obtaining metals are many times lower compared to the processing of mineral raw materials. Despite this, worldwide the percentage of recycling of electronic waste does not exceed 10 %. This fact requires a revision of traditional a PCBs to the processing of electronic waste and the formation of new, less costly and more environmentally friendly methods based on a review and analysis of existing a PCBs. To this end, the article considers examples of modern methods tested in laboratory conditions and already existing commercial technological solutions in the field ofprocessing. Based on the review of world experience, conclusions were drawn about the current state of the world and the prospects for recycling electronic waste in Kazakhstan.
Keywords: electronic waste, recycling, hydrometallurgy, pyrometallurgy, gold.
Introduction
The continuously growing consumption of electronic household a PCBs and gadgets until 2020 has led to an increase in the generation of electronic waste at the global level. Thus, studies conducted in 2017 assumed an annual growth rate of electronic waste generation of 3-4 % [1]. However, by 2019, the estimated growth in the generation of electronic waste has increased to 5-6 % [2]. In total, by the end of 2019, about 53.6 million tons of e-waste had been generated. The distribution of electronic waste by type in 2019 is shown in Figure 1. The COVID-19 pandemic has slightly reduced the pace of production of electronic equipment. However, such segments of the market as the production and sale of smartphones were practically not affected by the crisis. In 2016, the production of smartphones amounted to 3.7 million units. In 2021 - 6.26 million units. In 2022, the projected number of smartphone production is 6.56 million units, and by 2027, 7.69 million units.
The composition of electronic waste includes various materials: non-ferrous and ferrous metals, and non-metals. Many of the materials are toxic. Therefore, of particular
concern is the fact that worldwide, only 10 % of the waste generated is recycled [2]. Most of the waste that ends up in landfills harms the environment. As a result, a significant amount of metals falls out of circulation, creating economic risks associated with a shortage of materials necessary for the production of electronics.
electroi
Figure 1 - Distribution of electronic waste by type
1 - small equipment, 2 - large equipment, 3 - heat exchangers, 4 - screens and monitors, 5 - IT equipment, 6 - lamps [2]
Research methodology and methods
The low percentage of electronic waste recycling is associated with the difficulty of separating closely integrated materials and the impossibility of a PCBs traditional recycling schemes to them [3]. The amount of electronic scrap generated in Kazakhstan reaches 136 thousand tons per year. And only a small part of this amount is recycled. So in 2018, only 4561 tons were processed [4]. Of particular value for recycling are electronic waste, represented by electronic gadgets, computer and other IT equipment containing a large amount of noble and precious metals. Precious metals are used in the manufacture of contacts, and parts of electronic components of gadgets and computers. So, one ton of printed circuit boards of used smartphones can contain up to 350 g of gold [5]. In addition, 30 % percent of the weight of printed circuit boards is co PCBs. The average composition of PCBs of computer equipment and gadgets is presented in Table 1 [6].
Table 1 - Average concentration of metals in PCB (wt.%)
Cu Fe Al Sn Ni Zn Pb Ag
31,2 2,4 4,12 2,1 0,2 2,3 0,73 0,01
It should be noted that electronic waste exceeds mineral raw materials in terms of the content of valuable elements. This circumstance makes the recycling of electronic waste attractive from an economic point of view. Below are examples of modern methods tested in laboratory conditions and already existing commercial technological solutions in the field of processing. An analysis of the a PCBs technological solutions in this area will allow us to identify the best methods from the point of view of environmental friendliness and economics.
Results and discussion
A typical processing scheme for a computer system unit is shown in Figure 2, where at the first stage the case is separated from the printed circuit board, and then the electronic components are separated from the printed circuit board. The same recycling principle a PCBs to smartphones. The case, as a rule, contains ferrous metals and plastic. For the processing of printed circuit boards after their pre-treatment, pyro and hydrometallurgical methods are used.
Second stage other radiator CPU components
Figure 2 - Scheme of processing computer system blocks
Today, pyrometallurgy has evolved into a simple, promising and efficient e-waste recycling method, mainly used to extract non-ferrous metals such as co PCBs and precious metals [7]. Despite its widespread use, pyrometallurgical methods have a number of disadvantages. Disadvantages include an inability to recover iron, aluminium, organics and glass components, high energy consumption, release of toxic by-products such as dioxins and halogen compounds, and its primary use for processing only high quality printed circuit boards containing high concentrations of gold. The essence of recycling lies in the melting of the crushed mass of printed circuit boards. The resulting material is drained in the form of a cone to separate the heaviest metals. Modern commercial technologies offered on the free market by some companies are based on this principle. A typical processing scheme is shown in Figure 3.
Figure 3 - A typical scheme for the processing of electronic equipment,
offered on the market [8]
In a number of works, alternative pyrometallurgical methods of processing have been considered. The authors carried out high-temperature processing of printed circuit boards at a temperature of 900 °C to obtain metal microparticles [9]. The release characteristics of gold and silver were studied by heat treatment of incinerated waste PCB in a chlorine gas flow at a temperature of 1000 °C [10].
Hydrometallurgical methods involve the use of various acids to bring valuable components into solution. Printed circuit boards are usually shredded to a size of < 0.1mm. Various acids are used as reagents. The extracted metals from the solution are precipitated by cementation, electrolysis, and other methods. Comparison and characteristics of some hydrometallurgical methods are shown in Table 2.
able 2 - Main characteristics of hydrometallurgical methods for processing PCB
[11] [12] [13] [14] [15]
Presentment No No No No C4HsNO;T/Zb=3/10, 50 aC:16 L
Reagents HCL 2 шо1Л HCL 2 шо1Л 25 % HNOj;75 SBCl HiSO^ C11S04 1 nool/l HNO]
TfZh±: °C 10/1; 4; 75 10/1; 4; 75 20/1; 6; BO 10/1; 3; 65 35/1; 3; 60
Mixing speed. 500 500 550 500 Ultrasound
Precipitation Cementation Cementation Electrolysis 1.5 A; 1 hour EfcO: NaOH additive for Cu precipitation, filter for tiaPCBing Sn and Pb
Regeneration reagents No No No Yes No
Hydrometallurgical methods compare favorably with pyrometallurgical methods by lower energy costs. The main problem of hydrometallurgical methods is the lack of reagent regeneration. Therefore, the question of storage and disposal of toxic waste solutions will arise. Against this background, the method using H2SO4, CuSO4 as reagents looks the most promising, since it includes the regeneration of the reagent.
Conclusions
Thus, based on the foregoing, we can conclude that the optimal scheme for processing electronic waste should include, at the first stage, physical methods for separating black. Non-ferrous metals and non-metals. Ferrous metals are recycled using traditional methods. Recycling of the non-metal part should include separation of plastic, glass and other items for separate recycling. The extraction of non-ferrous and precious metals must be carried out by hydrometallurgical methods with the indispensable regeneration of reagents. This will eliminate the problem of storage and disposal of toxic waste solutions. A promising waste recycling scheme is shown in Figure 4.
Figure 4 - Perspective processing schemee-waste
REFERENCES
1 Balde, C. P., Forti, V., Gray, V., Kuehr, R., Stegmann, P. 2017. The Global E-waste Monitor 2017: Quantities, Flows, and Resources. United Nations University, International Telecommunication Union, and International Solid Waste Association, Bonn, Geneva, and Vienna, p. 116.
2 Forti, V., Balde, C.P., Kuehr, R., Bel, G. 2020. The Global E-waste Monitor 2020: Quantities, Flows and the Circular Economy Potential. United Nations University, United Nations Institute for Training and Research - co-hosted SCYCLE Programme, International Telecommunication Union, and International Solid Waste Association Bonn, Geneva and Rotterdam, p. 120.
3 Ahirwar, R., & Tripathi, A. K. (2021). E-waste management: A review of recycling process, environmental and occupational health hazards, and potential solutions. Environmental Nanotechnology, Monitoring & Management, 15, 100409.
4 Extended Producer Responsibility in Kazakhstan Green Action Task Force Review and recommendations [electronic resource]https://www.oecd.org/environment.
5 Hsu, E., Barmak, K., West, A., Park, A. H. A. Advancements in the Treatment and Processing of Electronic Waste with Sustainability: A Review of Metal Extraction and Recovery Technologies. Green Chemistry. - 2019. 21. - 919-936. - doi: 10.1039/ C8GC03688H.
6 Sapinov, R. V., Sadenova, M. A., Kulenova, N. A., Oleinikova, N. V. Improving Hydrometallurgical Methods for Processing Tin containing Electronic Waste // Chemical engineering transactions. - 2020. - Vol. 81. - P. 1021-1026.
7 Ghimire, H., Ariya, P. A. E-Wastes: Bridging the Knowledge Gaps in Global Production Budgets, Composition, Recycling and Sustainability Implications. // Sustain. Chem. -2020. - P. 1. - 154-182
8 NETMUS, 2021. Equipment, catalog. https://netmus.ru/katalog-tipovyh-resheniy
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10 Sakusabe, K., Kato, T., Okawa, H., Sugawara, K. Recovery of Gold and Silver from an Incinerated Spent Printed Circuit Board Using Chlorination. Journal of Chemical Engineering of Japan. 2018. - 51. - 704-710.
11 Moosakazemi, F., Ghassa S., Mohammadi, M. R. T. Environmentally friendly hydrometallurgical recovery of tin and lead from waste printed circuit boards : Thermodynamic and kinetics studies. // Journal of Cleaner Production. - 2019. 228. - 185-196.
12 Moosakazemi, F., Ghassa, S., Soltani, F., Tavakoli Mohammadi, M. R.
Regeneration of Sn-Pb solder from waste printed circuit boards : A hydrometallurgical aPCBroach to treating waste with waste // Journal of Hazardous Materials . - 2020. -385.- 121589.
13 Silva, M. S. B., Melo, R. A. C., Lopes-Moriyama, A. L., Souza, C. P.
Electrochemical extraction of tin and coPCBer from acid leach ate of printed circuit boards using coPCBer electrodes. Journal of Environmental Management. - 2019. -246.- 410-417.
14 Guo, X., Qin, H., Tian, Q., Li, D. Recovery of metals from waste printed circuit boards by selective leaching combined with cyclone electrowinning process. Journal of Hazardous Materials. - 384. - 2020.
15 Tatariants, M., Yousef, S., Skapas, M., Juskenas, R., Makarevicius, V., Lukosiüté ,S. I., Denafas, G. Industrial technology for mass production of SnO2 nanoparticles and PbO2microcube/microcross structures from electronic waste. // Journal of Cleaner Production. - 2018. 203. Р. 498-510.
Material received on 16.09.22.
*Н. В. Олейникова
Ci6ip федералды университет^ Ресей Федерациясы, Красноярск к. Материал 6araaFa tyctí 16.09.22.
ЦАЗАЦСТАН РЕСПУБЛИКАСЫНДАFЫ ЭЛЕКТРОНДЫЦ ЦАЛДЬЩТАРДЫ ЦАЙТА ЭЦДЕУ ЖАFДАЙЫ ЖЭНЕ БОЛАШАFЫ
Бул мацалада металдар мен басца да цунды KOMnoHeHmmepdi алу ушт электронды цалдыцтарды ецдеу мэселестщ агымдагы жай-куйте шолу жасалады. Электрондыц цалдыцтар элеуеттi экологиялыц цауттщ Kesi болып табылады, бiрац сонымен бiрге цурамында mycmi жэне цара металдар бар багалы шитзат. Электрондыц цалдыцтардагы кейбiр тyстi металдардыц мeлшерi олардыц минералдыц шитзаттагы мелшертен бiрнеше есе жогары болуы мумкт. Сонымен, баспа платаларыныц (PP) мазмуны баспа платаларыныц салмагы бойынша 30 % дешн, ал цалайы 2—4 % дешн жетуi
мумкт. Сонымен цатар, бiр тонна пайдаланылган смартфонныц цурамында 30 грамга детн алтын болуы мумкт. Сондай-ац, цайталама шитзатты вцдеу кезтде металдарды алуга кететт шыгындар минералды шитзатты вцдеуге цараганда бiрнеше есе темен болатыны белгiлi. Осыган царамастан, дуние жузтде электронды цалдыцтарды цайта ецдеу пайызы 10 %-дан аспайды. Бул факт электрондыц цалдыцтарды ецдеудщ дэстyрлi эдютерт цайта царауды жэне цолданыстагы эдiстердi царастыру мен талдау негiзiнде жаца, аз шыгынды жэне экологиялыц таза эдiстердi цалыптастыруды талап етедi. Осы мацсатта мацалада зертханалыц жагдайларда сыналган заманауи эдктердщ мысалдары жэне ецдеу саласындагы бурыннан бар коммерциялыц технологиялыц шешiмдер царастырылады. Элемдж тэжiрибенi шолу негiзiнде элемтц цазiргi жагдайы жэне Цазацстандагы электрондыц цалдыцтарды кэдеге жарату перспективалары туралы цорытындылар жасалды.
Кiлттi сездер: электронды цалдъщтар, цайта вцдеу, гидрометаллургия, пирометаллургия, алтын.
*Н. В. Олейникова
Сибирский федеральный университет, Российская Федерация, г. Красноярск Материал поступил в редакцию 16.09.22.
СОСТОЯНИЕ И ПЕРСПЕКТИВЫ ПЕРЕРАБОТКИ ЭЛЕКТРОННЫХ ОТХОДОВ В РЕСПУБЛИКЕ КАЗАХСТАН
В данной статье представлен обзор современного состояния проблемы переработки электронных отходов с целью извлечения металлов и других ценных компонентов. Электронные отходы представляют собой источник потенциальной опасности для окружающей среды, но в то же время ценное сырье, содержащее цветные и черные металлы. Содержание некоторых цветных металлов в электронных отходах может в несколько раз превышать их содержание в минеральном сырье. Так, содержание печатных плат (ПП) может достигать до 30 % от массы печатных плат, а олова до 2-4 %. Кроме того, тонна бывших в употреблении смартфонов может содержать до 30 граммов золота. Известно также, что при переработке вторичного сырья затраты на получение металлов во много раз ниже по сравнению с переработкой минерального сырья. Несмотря на это, во всем мире процент утилизации электронных отходов не превышает 10 %. Этот факт требует пересмотра традиционных ПХД в сторону переработки электронных отходов и формирования новых, менее затратных и более экологически чистых методов на основе обзора и анализа существующих ПХД. С этой целью в статье рассмотрены примеры современных методов, апробированных в лабораторных условиях, и уже существующие коммерческие технологические решения в области переработки. На основе обзора мирового опыта сделаны выводы о современном состоянии мира и перспективах утилизации электронных отходов в Казахстане.
Ключевые слова: электронные отходы, рециклинг, гидрометаллургия, пирометаллургия, золото
