<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.3 20210610//EN" "JATS-journalpublishing1-3.dtd">
<article article-type="research-article" dtd-version="1.3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xml:lang="ru"><front><journal-meta><journal-id journal-id-type="publisher-id">cvmet</journal-id><journal-title-group><journal-title xml:lang="ru">Известия вузов. Цветная металлургия</journal-title><trans-title-group xml:lang="en"><trans-title>Izvestiya. Non-Ferrous Metallurgy</trans-title></trans-title-group></journal-title-group><issn pub-type="ppub">0021-3438</issn><issn pub-type="epub">2412-8783</issn><publisher><publisher-name>НИТУ МИСИС</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.17073/0021-3438-2018-2-21-27</article-id><article-id custom-type="elpub" pub-id-type="custom">cvmet-744</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research Article</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="ru"><subject>Металлургия цветных металлов</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="en"><subject>Metallurgy of Non-Ferrous Metals</subject></subj-group></article-categories><title-group><article-title>ВЛИЯНИЕ ТЕРМИЧЕСКОЙ ОБРАБОТКИ НА ИЗВЛЕЧЕНИЕ МЕДИ ИЗ ЭЛЕКТРОННЫХ ОТХОДОВ</article-title><trans-title-group xml:lang="en"><trans-title>THERMAL TREATMENT INFLUENCE ON COPPER EXTRACTION FROM ELECTRONIC WASTE</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Ахметвалиева</surname><given-names>З. М.</given-names></name><name name-style="western" xml:lang="en"><surname>Akhmetvaliyeva</surname><given-names>Z. M.</given-names></name></name-alternatives><bio xml:lang="ru"><p>докторант </p><p>070010, Республика Казахстан, г. Усть-Каменогорск, ул. Серикбаева, 19</p></bio><bio xml:lang="en"><p>PhD candidate</p><p>070010, Republic Kazakhstan, Ust’-Kamenogorsk city, Serikbayev str., 19</p></bio><email xlink:type="simple">zakhmetyali@gmail.com</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Куленова</surname><given-names>Н. А.</given-names></name><name name-style="western" xml:lang="en"><surname>Kulenova</surname><given-names>N. A.</given-names></name></name-alternatives><bio xml:lang="ru"><p>канд. техн. наук, проф., зав. научно-производственным комплексом «Металлургия»</p></bio><bio xml:lang="en"><p>Cand. Sci. (Eng.), Associate prof., Head of research and production complex «Metallurgy»</p></bio><email xlink:type="simple">3007kulenova53@gmail.com</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Мамяченков</surname><given-names>С. В.</given-names></name><name name-style="western" xml:lang="en"><surname>Mamyachenkov</surname><given-names>S. V.</given-names></name></name-alternatives><bio xml:lang="ru"><p>докт. техн. наук, профессор</p><p>кафедра металлургии тяжелых цветных металлов </p><p>620002, г. Екатеринбург, ул. Мира, 17, оф. С-108</p></bio><bio xml:lang="en"><p>Dr. Sci. (Tech.), Prof., Department of metallurgy of heavy non-ferrous metals</p><p>620002, Ekaterinburg, Mira str., 17, оff. С-108</p></bio><email xlink:type="simple">svmamyachenkov@yandex.ru</email><xref ref-type="aff" rid="aff-2"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Анисимова</surname><given-names>О. С.</given-names></name><name name-style="western" xml:lang="en"><surname>Anisimova</surname><given-names>O. S.</given-names></name></name-alternatives><bio xml:lang="ru"><p>канд. техн. наук, доцент</p><p>кафедра металлургии тяжелых цветных металлов </p></bio><bio xml:lang="en"><p>Cand. Sci. (Tech.), Docent, Department of metallurgy of heavy non-ferrous metals</p></bio><email xlink:type="simple">osanis@mail.ru</email><xref ref-type="aff" rid="aff-2"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Фокина</surname><given-names>Е. Л.</given-names></name><name name-style="western" xml:lang="en"><surname>Fokina</surname><given-names>E. L.</given-names></name></name-alternatives><bio xml:lang="ru"><p>вед. инженер</p><p>Институт наук о Земле</p><p>199034, г. Санкт-Петербург, Университетская набережная, 7-9</p></bio><bio xml:lang="en"><p>Senior engineer, Institute of Earth Sciences</p><p>199034, Saint Petersburg, University embankment, 7-9</p></bio><email xlink:type="simple">albite@yandex.ru</email><xref ref-type="aff" rid="aff-3"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="ru"><institution>Восточно-Казахстанский государственный технический университет (ВКГТУ) им. Д. Серикбаева</institution><country>Казахстан</country></aff><aff xml:lang="en"><institution>East Kazakhstan State Technical University (EKSTU)</institution><country>Kazakhstan</country></aff></aff-alternatives><aff-alternatives id="aff-2"><aff xml:lang="ru"><institution>Уральский федеральный университет (УрФУ) им. первого Президента России Б.Н. Ельцина</institution><country>Россия</country></aff><aff xml:lang="en"><institution>Ural Federal University (UrFU)</institution><country>Russian Federation</country></aff></aff-alternatives><aff-alternatives id="aff-3"><aff xml:lang="ru"><institution>Санкт-Петербургский государственный университет (СПбГУ)</institution><country>Россия</country></aff><aff xml:lang="en"><institution>Saint Petersburg State University</institution><country>Russian Federation</country></aff></aff-alternatives><pub-date pub-type="collection"><year>2018</year></pub-date><pub-date pub-type="epub"><day>18</day><month>04</month><year>2018</year></pub-date><volume>0</volume><issue>2</issue><fpage>21</fpage><lpage>27</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Ахметвалиева З.М., Куленова Н.А., Мамяченков С.В., Анисимова О.С., Фокина Е.Л., 2018</copyright-statement><copyright-year>2018</copyright-year><copyright-holder xml:lang="ru">Ахметвалиева З.М., Куленова Н.А., Мамяченков С.В., Анисимова О.С., Фокина Е.Л.</copyright-holder><copyright-holder xml:lang="en">Akhmetvaliyeva Z.M., Kulenova N.A., Mamyachenkov S.V., Anisimova O.S., Fokina E.L.</copyright-holder><license xml:lang="ru" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>Данная работа распространяется под лицензией Creative Commons Attribution 4.0.</license-p></license><license xml:lang="en" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>This work is licensed under a Creative Commons Attribution 4.0 License.</license-p></license></permissions><self-uri xlink:href="https://cvmet.misis.ru/jour/article/view/744">https://cvmet.misis.ru/jour/article/view/744</self-uri><abstract><p>Приведены результаты исследования влияния предварительной термической обработки измельченных электронных отходов при температуре 450 °С на степень извлечения меди при последующем выщелачивании материала растворами азотной кислоты. В качестве объектов исследования были выбраны отходы электронной промышленности, в частности автомобильные микросхемы и компьютерные печатные платы. Экспериментальным путем выявлено, что доля органической фазы в их составе колеблется в пределах 20–25 % от массы измельченного сырья. По результатам термогравиметрического и рентгенофлуоресцентного анализов установлено, что максимальная степень удаления органики и образование оксидных форм металлов наблюдаются в интервале температур 400–450 °С. Получена математическая модель процесса выщелачивания меди из электронных отходов растворами HNO3. Найдены оптимальные параметры проведения процесса: температура в системе 75 °С, продолжительность выщелачивания 150 мин, концентрация кислоты 4 М, обеспечивающие максимальное извлечение меди в раствор (98 %). Проведен сравнительный анализ процессов выщелачивания двух типов сырья (после термической обработки и без таковой). Экспериментально подтверждено, что для сырья после предварительного отжига наблюдается более полное выщелачивание меди из электронных отходов растворами азотной кислоты меньшей концентрации по сравнению с образцами без термической обработки. Доказано, что последняя обуславливает фазовые изменения в составе исследуемого объекта, а именно переход металлов в их оксидные формы, что положительно влияет на степень извлечения меди из электронных отходов при последующем азотно-кислом выщелачивании.</p></abstract><trans-abstract xml:lang="en"><p>The paper provides the results of studying the influence of preliminary thermal treatment of crushed electronic waste at a temperature of 450 °C on the copper extraction degree during subsequent material leaching by nitric acid solutions. Electronic industry waste, in particular automobile microcircuits and computer printed circuit boards, was chosen as a research object. It was experimentally determined that the percentage of the organic phase in the research object composition varies within 20–25 % of the crushed raw material mass. The results of thermogravimetric analysis (TGA) and X-ray fluorescence analysis (XRF) show that the maximum degree of organic removal and formation of metal oxides are observed in a temperature range of 400–450 °C. A mathematical model of copper leaching from electronic waste by HNO3 solutions was obtained. The optimum parameters for the process were found – the temperature in the system is 75 °C; leaching duration is 150 min; acid concentration is 4 M with a maximum copper extraction to the solution of 98 %. A comparative analysis of leaching processes for two types of materials (after thermal treatment and without it) was carried out. It was experimentally confirmed that copper leaching from electronic waste by nitric acid solutions with lower concentrations is more complete for materials after preliminary thermal treatment as compared to raw material leaching without thermal treatment. It was proved that preliminary thermal treatment leads to phase changes in the composition of the research object, namely, the transition of metals to their oxide forms, which positively affects the degree of copper extraction from electronic waste at subsequent nitric acid leaching.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>комплексный термический анализ</kwd><kwd>термическая обработка</kwd><kwd>электронные отходы</kwd><kwd>печатные платы</kwd><kwd>медь</kwd><kwd>выщелачивание</kwd><kwd>азотная кислота</kwd></kwd-group><kwd-group xml:lang="en"><kwd>complex thermal analysis</kwd><kwd>thermal treatment</kwd><kwd>electronic waste</kwd><kwd>printed circuit boards</kwd><kwd>copper</kwd><kwd>leaching</kwd><kwd>nitric acid</kwd></kwd-group></article-meta></front><back><ref-list><title>References</title><ref id="cit1"><label>1</label><citation-alternatives><mixed-citation xml:lang="ru">Park Y.J., Fray D.J. Recovery of high purity precious metals from printed circuit boards. J. Hazard. Mater. 2009. No. 164. P. 1152—1158.</mixed-citation><mixed-citation xml:lang="en">Park Y.J., Fray D.J. Recovery of high purity precious metals from printed circuit boards. J. Hazard. Mater. 2009. No. 164. P. 1152—1158.</mixed-citation></citation-alternatives></ref><ref id="cit2"><label>2</label><citation-alternatives><mixed-citation xml:lang="ru">Shamsuddin M. Metal recovery from scrap and waste. J. Metals. 1986. No. 38. P. 24—31.</mixed-citation><mixed-citation xml:lang="en">Shamsuddin M. Metal recovery from scrap and waste. J. Metals. 1986. No. 38. P. 24—31.</mixed-citation></citation-alternatives></ref><ref id="cit3"><label>3</label><citation-alternatives><mixed-citation xml:lang="ru">Cui J., Zhang L. Metallurgical recovery of metals from electronic waste: A review. J. Hazard. Mater. 2008. No. 158. P. 228—256.</mixed-citation><mixed-citation xml:lang="en">Cui J., Zhang L. Metallurgical recovery of metals from electronic waste: A review. J. Hazard. Mater. 2008. No. 158. P. 228—256.</mixed-citation></citation-alternatives></ref><ref id="cit4"><label>4</label><citation-alternatives><mixed-citation xml:lang="ru">Wong M.H., Wu S.C., Deng W.J., Yu X.Z., Luo Q., Leung A.O.W., Wong C.S.C., Luksemburg A.S., Wong A.S. Export of toxic chemicals — a review of the case of uncontrolled electronic waste recycling. J. Environ Pollut. 2007. No. 149. P. 131—140.</mixed-citation><mixed-citation xml:lang="en">Wong M.H., Wu S.C., Deng W.J., Yu X.Z., Luo Q., Leung A.O.W., Wong C.S.C., Luksemburg A.S., Wong A.S. Export of toxic chemicals — a review of the case of uncontrolled electronic waste recycling. J. Environ Pollut. 2007. No. 149. P. 131—140.</mixed-citation></citation-alternatives></ref><ref id="cit5"><label>5</label><citation-alternatives><mixed-citation xml:lang="ru">Veit H.M., Bernardes A.M., Ferreira J.Z., Tenório J.A., de FragaMalfatti C. Recovery of copper from printed circuit boards scraps by mechanical processing and electrometallurgy. J. Hazard. Mater. 2006. No. 137. P. 1704—1709.</mixed-citation><mixed-citation xml:lang="en">Veit H.M., Bernardes A.M., Ferreira J.Z., Tenório J.A., de FragaMalfatti C. Recovery of copper from printed circuit boards scraps by mechanical processing and electrometallurgy. J. Hazard. Mater. 2006. No. 137. P. 1704—1709.</mixed-citation></citation-alternatives></ref><ref id="cit6"><label>6</label><citation-alternatives><mixed-citation xml:lang="ru">Anindya A. Minor elements distribution during the smelting of WEEE with copper scrap: PhD Thesis. Australia, Melbourne: RMIT University, 2012.</mixed-citation><mixed-citation xml:lang="en">Anindya A. Minor elements distribution during the smelting of WEEE with copper scrap: PhD Thesis. Australia, Melbourne: RMIT University, 2012.</mixed-citation></citation-alternatives></ref><ref id="cit7"><label>7</label><citation-alternatives><mixed-citation xml:lang="ru">Dhawan N., Kumar M., Kumar V., Wadhwa M. Recovery of metals from electronic scrap by hydrometallurgical route. In: Proc. Global Symposium on Recycling, Waste Treatment and Clean Technology (REWAS) (Cancun, Mexico, 12— 15 October 2008). P. 693—698.</mixed-citation><mixed-citation xml:lang="en">Dhawan N., Kumar M., Kumar V., Wadhwa M. Recovery of metals from electronic scrap by hydrometallurgical route. In: Proc. Global Symposium on Recycling, Waste Treatment and Clean Technology (REWAS) (Cancun, Mexico, 12— 15 October 2008). P. 693—698.</mixed-citation></citation-alternatives></ref><ref id="cit8"><label>8</label><citation-alternatives><mixed-citation xml:lang="ru">Dhawan N., Kumar V., Kumar M. Recovery of metals from electronic scrap by hydrometallurgical route. In: Extraction and Processing Division (EPD) Congress: The Minerals, Metals and Materials Society. USA, Warrendale, 2009. P. 1107—1109.</mixed-citation><mixed-citation xml:lang="en">Dhawan N., Kumar V., Kumar M. Recovery of metals from electronic scrap by hydrometallurgical route. In: Extraction and Processing Division (EPD) Congress: The Minerals, Metals and Materials Society. USA, Warrendale, 2009. P. 1107—1109.</mixed-citation></citation-alternatives></ref><ref id="cit9"><label>9</label><citation-alternatives><mixed-citation xml:lang="ru">Delfini M., Ferrini M., Manni A., Massacci P., Piga L., Scoppettuolo A. Optimization of precious metal recovery from waste electrical and electronic equipment boards. J. Environ. Prot. 2011. No. 2. P. 675—682.</mixed-citation><mixed-citation xml:lang="en">Delfini M., Ferrini M., Manni A., Massacci P., Piga L., Scoppettuolo A. Optimization of precious metal recovery from waste electrical and electronic equipment boards. J. Environ. Prot. 2011. No. 2. P. 675—682.</mixed-citation></citation-alternatives></ref><ref id="cit10"><label>10</label><citation-alternatives><mixed-citation xml:lang="ru">Hagelüken C. Recycling of electronic scrap at Umicore’s integrated metals smelter and refinery. World Metall. — Erzmetall. 2006. No. 59. P. 152—161.</mixed-citation><mixed-citation xml:lang="en">Hagelüken C. Recycling of electronic scrap at Umicore’s integrated metals smelter and refinery. World Metall. — Erzmetall. 2006. No. 59. P. 152—161.</mixed-citation></citation-alternatives></ref><ref id="cit11"><label>11</label><citation-alternatives><mixed-citation xml:lang="ru">Lehner T. Integrated recycling of non-ferrous metals at Boliden Ltd. Ronnskar smelter. In: IEEE Int. Symp. on Electronics and Environment. 1998. P. 42—47.</mixed-citation><mixed-citation xml:lang="en">Lehner T. Integrated recycling of non-ferrous metals at Boliden Ltd. Ronnskar smelter. In: IEEE Int. Symp. on Electronics and Environment. 1998. P. 42—47.</mixed-citation></citation-alternatives></ref><ref id="cit12"><label>12</label><citation-alternatives><mixed-citation xml:lang="ru">Park Y.J., Fray D.J. Recovery of high purity precious metals from printed circuit boards. J. Hazard. Mater. 2009. No. 164. P. 1152—1158.</mixed-citation><mixed-citation xml:lang="en">Park Y.J., Fray D.J. Recovery of high purity precious metals from printed circuit boards. J. Hazard. Mater. 2009. No. 164. P. 1152—1158.</mixed-citation></citation-alternatives></ref><ref id="cit13"><label>13</label><citation-alternatives><mixed-citation xml:lang="ru">Sheng P.P., Etsell T.H. Recovery of gold from computer circuit board scrap using aqua regia. Waste Manage. Res. 2007. No. 25. P. 380—383.</mixed-citation><mixed-citation xml:lang="en">Sheng P.P., Etsell T.H. Recovery of gold from computer circuit board scrap using aqua regia. Waste Manage. Res. 2007. No. 25. P. 380—383.</mixed-citation></citation-alternatives></ref><ref id="cit14"><label>14</label><citation-alternatives><mixed-citation xml:lang="ru">Quinet P., Proost J., Van Lierde A. Recovery of precious metals from electronic scrap by hydrometallurgical processing routes. Miner. Metall. Process. 2005. No. 22. P. 17—22.</mixed-citation><mixed-citation xml:lang="en">Quinet P., Proost J., Van Lierde A. Recovery of precious metals from electronic scrap by hydrometallurgical processing routes. Miner. Metall. Process. 2005. No. 22. P. 17—22.</mixed-citation></citation-alternatives></ref><ref id="cit15"><label>15</label><citation-alternatives><mixed-citation xml:lang="ru">Kulandaisamy S., Prrabhakar Rethinaraj J., Adaikkalam P., Srinivasan G.N., Raghavan M. The aqueous recovery of gold from electronic scrap. JOM. 2003. No. 55. P. 35—37.</mixed-citation><mixed-citation xml:lang="en">Kulandaisamy S., Prrabhakar Rethinaraj J., Adaikkalam P., Srinivasan G.N., Raghavan M. The aqueous recovery of gold from electronic scrap. JOM. 2003. No. 55. P. 35—37.</mixed-citation></citation-alternatives></ref><ref id="cit16"><label>16</label><citation-alternatives><mixed-citation xml:lang="ru">Macaskie L.E., Creamer N.J., Essa A.M.M., Brown N.L. A new approach for the recovery of precious metals from solution and from leachates derived from electronic scrap. Biotechnol. Bioeng. 2003. No. 96. P. 631—639.</mixed-citation><mixed-citation xml:lang="en">Macaskie L.E., Creamer N.J., Essa A.M.M., Brown N.L. A new approach for the recovery of precious metals from solution and from leachates derived from electronic scrap. Biotechnol. Bioeng. 2003. No. 96. P. 631—639.</mixed-citation></citation-alternatives></ref><ref id="cit17"><label>17</label><citation-alternatives><mixed-citation xml:lang="ru">Моисеева Н.Г. Исследование и разработка технологии комплексной переработки отходов электронной промышленности: Автореф. дис. ... канд. техн. наук. Москва: МИСиС, 1997; Moiseeva N.G. Issledovanie i razrabotka tekhnologii kompleksnoi pererabotki otkhodov elektronnoi promyshlennosti [Research and development of technology of the complex waste processing of the electronic industry]: Abstr. Diss. of Cand. Sci. (Eng.). Moscow: MISIS, 1997.</mixed-citation><mixed-citation xml:lang="en">Моисеева Н.Г. Исследование и разработка технологии комплексной переработки отходов электронной промышленности: Автореф. дис. ... канд. техн. наук. Москва: МИСиС, 1997; Moiseeva N.G. Issledovanie i razrabotka tekhnologii kompleksnoi pererabotki otkhodov elektronnoi promyshlennosti [Research and development of technology of the complex waste processing of the electronic industry]: Abstr. Diss. of Cand. Sci. (Eng.). Moscow: MISIS, 1997.</mixed-citation></citation-alternatives></ref><ref id="cit18"><label>18</label><citation-alternatives><mixed-citation xml:lang="ru">Лолейт С.И. Разработка экологически чистых технологий комплексного извлечения благородных и цветных металлов из электронного лома: Автореф. дис. ... докт. техн. наук. М.: МИСиС, 2010; Loleit S.I. Razrabotka ekologicheski chistykh tekhnologii kompleksnogo izvlecheniya blagorodnykh i tsvetnykh metallov iz elektronnogo loma [Development of environmentally friendly technologies of complex extraction of precious and non-ferrous metals from the electronic scrap]: Abstr. Diss. of Dr. Sci. (Eng.). Moscow: MISIS, 2010.</mixed-citation><mixed-citation xml:lang="en">Лолейт С.И. Разработка экологически чистых технологий комплексного извлечения благородных и цветных металлов из электронного лома: Автореф. дис. ... докт. техн. наук. М.: МИСиС, 2010; Loleit S.I. Razrabotka ekologicheski chistykh tekhnologii kompleksnogo izvlecheniya blagorodnykh i tsvetnykh metallov iz elektronnogo loma [Development of environmentally friendly technologies of complex extraction of precious and non-ferrous metals from the electronic scrap]: Abstr. Diss. of Dr. Sci. (Eng.). Moscow: MISIS, 2010.</mixed-citation></citation-alternatives></ref><ref id="cit19"><label>19</label><citation-alternatives><mixed-citation xml:lang="ru">Колмакова А.А. Физико-химические закономерности процессов вскрытия электронного лома, содержащего благородные металлы смесью азотной и серной кислот: Автореф. дис. ... канд. техн. наук. Красноярск: ГУЦМиЗ, 2004; Kolmakova A.A. Fizikokhimicheskie zakonomernosti protsessov vskrytiya elektronnogo loma, soderzhashchego blagorodnye metally smes’yu azotnoi i sernoi kislot [Physicochemical regularities of the electronic scrap processing containing noble metals by a mixture of nitric and sulfuric acids]: Abstr. Diss. of Cand. Sci. (Eng.). Krasnoyarsk: State University of Non-ferrous metals and gold, 2004.</mixed-citation><mixed-citation xml:lang="en">Колмакова А.А. Физико-химические закономерности процессов вскрытия электронного лома, содержащего благородные металлы смесью азотной и серной кислот: Автореф. дис. ... канд. техн. наук. Красноярск: ГУЦМиЗ, 2004; Kolmakova A.A. Fizikokhimicheskie zakonomernosti protsessov vskrytiya elektronnogo loma, soderzhashchego blagorodnye metally smes’yu azotnoi i sernoi kislot [Physicochemical regularities of the electronic scrap processing containing noble metals by a mixture of nitric and sulfuric acids]: Abstr. Diss. of Cand. Sci. (Eng.). Krasnoyarsk: State University of Non-ferrous metals and gold, 2004.</mixed-citation></citation-alternatives></ref><ref id="cit20"><label>20</label><citation-alternatives><mixed-citation xml:lang="ru">Fisher R.A. The Design of experiments. New York: Hafner publishing company, 1971.</mixed-citation><mixed-citation xml:lang="en">Fisher R.A. The Design of experiments. New York: Hafner publishing company, 1971.</mixed-citation></citation-alternatives></ref><ref id="cit21"><label>21</label><citation-alternatives><mixed-citation xml:lang="ru">Гмурман В.Е. Теория вероятностей и математическая статистика. М.: Высш. школа, 1972; Gmurman V.E. Teoriya veroyatnostei i matematicheskaya statistika [Theory of probability and mathematical statistics]. Moscow: Vysshaya shkola, 1972.</mixed-citation><mixed-citation xml:lang="en">Гмурман В.Е. Теория вероятностей и математическая статистика. М.: Высш. школа, 1972; Gmurman V.E. Teoriya veroyatnostei i matematicheskaya statistika [Theory of probability and mathematical statistics]. Moscow: Vysshaya shkola, 1972.</mixed-citation></citation-alternatives></ref><ref id="cit22"><label>22</label><citation-alternatives><mixed-citation xml:lang="ru">Горский В.Г., Адлер Ю.П. Планирование промышленных экспериментов. М.: Металлургия, 1974; Gorskii V.G., Adler Yu.P. Planirovanie promyshlennykh eksperimentov [Planning of industrial experiments]. Moscow: Metallurgiya, 1974.</mixed-citation><mixed-citation xml:lang="en">Горский В.Г., Адлер Ю.П. Планирование промышленных экспериментов. М.: Металлургия, 1974; Gorskii V.G., Adler Yu.P. Planirovanie promyshlennykh eksperimentov [Planning of industrial experiments]. Moscow: Metallurgiya, 1974.</mixed-citation></citation-alternatives></ref></ref-list><fn-group><fn fn-type="conflict"><p>The authors declare that there are no conflicts of interest present.</p></fn></fn-group></back></article>
