Reduction of Metal Oxides by Pyrolysis of Waste Polymers

Yıl 2025, Cilt: 8 Sayı: 2, 36 - 41, 31.12.2025

Melek Cumbul Altay , Serafettin Eroglu

https://doi.org/10.55581/ejeas.1715362

Öz

This review evaluates the effectiveness of gaseous products derived from the pyrolysis of waste polymers (polyethylene (PE), polypropylene (PP), high-density polyethylene (HDPE) and waste tires) in reducing metal oxides (cobalt(III) oxide (Co₃O₄), nickel(II) oxide (NiO), bismuth(III) oxide (Bi₂O₃) and copper(II) oxide (CuO)). Owing to the high energy consumption and environmental impact of conventional reduction techniques, utilizing pyrolytic gases as an alternative reducing atmosphere is critical for sustainability and resource recovery. Experimental studies conducted using horizontal tube furnace systems have demonstrated that gas mixtures obtained from waste polymers — comprising mainly H₂, CH₄, C₂H₄ and aromatic hydrocarbons — can effectively reduce these metal oxides at relatively low temperatures. This review comparatively evaluates parameters influencing reduction efficiency, such as temperature, reactant ratio, heating rate, and gas composition, and provides detailed evaluations of product phases and microstructures through XRD, SEM, and EDS analyses. The findings reveal novel opportunities for waste management and sustainable metallurgy, establishing pyrolytic gases as a promising solution at scientific and industrial levels.

Anahtar Kelimeler

Metal Oxide , Pyrolytic Gas , Reactive Atmosphere , Reduction Process , Sustainable Metallurgy , Waste Polymer.

Atık Polimerlerin Pirolizi ile Metal Oksitlerin İndirgenmesi

Öz

Bu inceleme, atık polimerlerin (polietilen (PE), polipropilen (PP), yüksek yoğunluklu polietilen (HDPE) ve atık lastikler) pirolizinden elde edilen gaz halindeki ürünlerin metal oksitleri (kobalt(III) oksit (Co₃O₄), nikel(II) oksit (NiO), bizmut(III) oksit (Bi₂O₃) ve bakır(II) oksit (CuO)) indirgenme etkinliğini değerlendirmektedir. Geleneksel indirgeme tekniklerinin yüksek enerji tüketimi ve çevresel etkisi nedeniyle, pirolitik gazların alternatif indirgeme atmosferi olarak kullanılması, sürdürülebilirlik ve kaynak geri kazanımı için kritik öneme sahiptir. Yatay tüp fırın sistemleri kullanılarak yapılan deneysel çalışmalar, H₂, CH₄, C₂H₄ ve aromatik hidrokarbonlardan oluşan atık polimerlerden elde edilen gaz karışımlarının, bu metal oksitleri nispeten düşük sıcaklıklarda etkili bir şekilde indirgenebildiğini göstermiştir. Bu derleme, sıcaklık, reaktan oranı, ısıtma hızı ve gaz bileşimi gibi indirgeme verimliliğini etkileyen parametreleri karşılaştırmalı olarak incelemekte ve XRD, SEM ve EDS analizleri yoluyla ürün fazları ve mikro yapılar hakkında ayrıntılı değerlendirmeler sunmaktadır. Bulgular, atık yönetimi ve sürdürülebilir metalurji için yeni fırsatlar ortaya koyarak, pirolitik gazları bilimsel ve endüstriyel düzeyde umut verici bir çözüm olarak ortaya koymaktadır.

Anahtar Kelimeler

Metal Oksit , Pirolitik Gaz , Reaktif Atmosfer , İndirgeme Prosesi , Sürdürülebilir Metalurji , Atık Polimer

Kaynakça

• IUCN (2024). Plastic pollution: Issues brief – May 2024 update. International Union for Conservation of Nature and Natural Resources. Retrieved from https://www.iucn.org/resources/issues-brief/plastic-pollution
• OECD. (2022). Global Plastics Outlook: Economic drivers, environmental impacts and policy options. Organisation for Economic Co-operation and Development. https://doi.org/10.1787/de747aef-en
• Lopez, G., Artetxe, M., Amutio, M., Alvarez, J., Bilbao, J., & Olazar, M. (2017). Recent advances in the gasification of waste plastics: a critical overview. Renewable and Sustainable Energy Reviews, 82, 576–596.
• Songül, E. E., & Altay, M. C. (2025). Plastik atıkların pirolizle katma değerli ürünlere dönüştürülmesi: Döngüsel ekonomi yaklaşımı. European Journal of Engineering and Applied Sciences, 8(1), 81–89. https://doi.org/10.55581/ejeas.1716406
• Hopewell, J., Dvorak, R., & Kosior, E. (2009). Plastics recycling: challenges and opportunities. Philosophical Transactions of the Royal Society B Biological Sciences, 364(1526), 2115–2126.
• Al-Salem, S. M., Lettieri, P., & Baeyens, J. (2009). Recycling and recovery routes of plastic solid waste (PSW): A review. Waste Management, 29(10), 2625–2643.
• Cotton, F. A., Wilkinson, G., Murillo, C. A., & Bochmann, M. (1999). Advanced Inorganic Chemistry (6th ed.). Wiley.
• Greenwood, N. N., & Earnshaw, A. (2012). Chemistry of the elements (2nd ed.). Oxford.
• Habashi, F. (1997). Handbook of extractive metallurgy (Vol. 1). Wiley-VCH.
• Altay, M. C., & Eroglu, S. (2021). Thermodynamic analysis and reaction of Co3O4 powder with pyrolytic gas derived from waste tires with and without waste polyethylene. JOM, 73(6), 1947–1956.
• Altay, M. C., & Eroglu, S. (2022). CO3O4 reduction behavior in the gas atmosphere generated by waste polyethylene pyrolysis: effects of temperature, time, heating rate and reactant ratio. Journal of Sustainable Metallurgy, 8(4), 1841–1852.
• Sandercock, P. M. L. (2012). Preparation of pyrolysis reference samples: evaluation of a standard method using a tube furnace. Journal of Forensic Sciences, 57(3), 738–743. https://doi.org/10.1111/j.1556-4029.2011.02030.x
• Cumbul Altay, M., & Eroglu, S. (2019). A novel way of using pyrolytic gas derived from waste rubber: pyrometallurgical reduction of NiO. Journal of Hazardous Materials, 367, 77–82.
• Suo, H., Peng, C., Wu, Z., Zhang, Y., Liu, C., Lou, L.-L., Liu, S., & Yu, K. (2025). Organic solid waste as sustainable fuels and reducing agents in low-carbon steelmaking technologies. Fuel, 392, 134825.
• Ji, M., Chen, L., Que, J., Zheng, L., Chen, Z., & Wu, Z. (2020). Effects of transition metal oxides on pyrolysis properties of PVC. Process Safety and Environmental Protection, 140, 211–220.
• Go, K., Son, S., & Kim, S. (2008). Reaction kinetics of reduction and oxidation of metal oxides for hydrogen production. International Journal of Hydrogen Energy, 33(21), 5986–5995.
• Altay, M. C., & Eroglu, S. (2023). H2-mediated reduction of GeO2 and chemical vapor deposition of polycrystalline Ge porous films. Thin Solid Films, 783, 140049. https://doi.org/10.1016/j.tsf.2023.140049
• Altay, M. C., & Eroglu, S. (2018). Reduction of Germanium Dioxide with Methane. JOM, 70(10), 2345–2350. https://doi.org/10.1007/s11837-018-3039-1
• Altay, M. C., & Eroglu, S. (2019). Use of waste polyethylene as a source of reducing agent for metal oxide reduction: a case study on NiO. JOM, 71(7), 2338–2344.
• Altay, M. C., & Eroglu, S. (2019). Feasibility of using polypropylene for metal oxide reduction. JOM, 71(11), 3923–3930.
• Altay, M. C., & Eroglu, S. (2021). Thermodynamics and reduction of Bi2O3 in waste tire-derived atmosphere. JOM, 73(3), 865–872.
• Altay, M. C., & Eroglu, S. (2021). Thermodynamics and synthesis of Cu Powder from CuO in waste tire-derived pyrolytic gas atmosphere. JOM, 73(4), 1004–1012.