RECYCLING INDUSTRIAL WASTE INTO HIGH-PERFORMANCE CERAMICS

ABSTRACT

Industrial and energy production waste pose a significant risk to both the environment and public health. Instead of simply disposing of this waste in landfills, recycling and reusing them to create valuable, eco-friendly products can be a more sustainable solution. Ceramics, in particular, have shown promise in waste recycling efforts. Over the past 20 years, researchers have explored the use of alternative materials, such as fly ash, rice husk ash, blast furnace slag, sludge, glass waste, polished tile waste, and eggshells, in place of conventional raw materials like clay, quartz, and feldspar to create ceramics.

АННОТАЦИЯ

Отходы промышленных и энергетических производств представляют значительный риск как для окружающей среды, так и для здоровья населения. Вместо того, чтобы просто выбрасывать эти отходы на свалки, их переработка и повторное использование для создания ценных, экологически чистых продуктов может быть более устойчивым решением. Керамика, в частности, показала многообещающие результаты в усилиях по переработке отходов. За последние 20 лет исследователи изучили возможность использования альтернативных материалов, таких как летучая зола, зола рисовой шелухи, доменный шлак, шлам, отходы стекла, отходы полированной плитки и яичная скорлупа, вместо традиционного сырья, такого как глина, кварц. и полевой шпат для создания керамики.

Keywords: waste, fly ash, sewage sludge, tile, sanitaryware.

Ключевые слова: отходы, зола-уноса, осадок сточных вод, плитка, сантехническая керамика.

Introduction. This review aims to provide an up-to-date overview of recent advancements in waste-derived ceramics, including refractories, tiles, glasses, whitewares. The article discusses the limits of waste incorporation, manufacturing processes, and resulting ceramic properties. The investigation reveals that ceramic industries have a significant potential to utilize waste as a substitute for natural raw materials. The conversion of waste to value-added ceramics not only solves the problem of waste disposal but also helps conserve natural resources.

The evolution and significance of ceramics in modern society. The term "ceramic" originates from the Greek word for "pottery," but its meaning has expanded to encompass a wide range of inorganic, nonmetallic or metalloid solid compounds with a mixed type of bonding [1]. Compared to metals and other solids, ceramics possess unique properties such as high melting points, good chemical inertness, brittleness, high-temperature stability, and heat and electrical insulation abilities. Consequently, ceramics have diverse applications in contemporary society, including the manufacture of bricks, glass, tiles, tableware, sanitary ware, space and automotive components, abrasives, biomedical implants, and electronic devices [2].

However, the production of ceramics requires vast amounts of natural resources, with natural clay being the oldest and most commonly used raw material. Refractory industries also use specialized raw materials such as alumina, magnesite, chrome, and zircon, among others. The extraction of these materials has led to a depletion of natural resources and ecological damage. As such, researchers are seeking substitutes for natural ingredients to reduce the ecological impact of ceramic production.

As the global population grows, industrial production is expanding to meet the demands of people. However, this growth is causing two major problems for the ecosystem: pollution and the depletion of natural resources. To minimize these problems, industries are looking for ways to recycle their by-products and wastes. The ceramic industry is no exception, and researchers have been exploring the use of waste materials in ceramic production for the past two decades. Waste materials such as rice husk ash (RHA), fly ash (FA), blast furnace slag (BFS), waste marble powder, and glass waste have been identified as potential substitutes for natural raw materials in ceramics. Some studies have analyzed the benefits of these waste materials in ceramic formulations.

While some previous studies have focused on the use of waste materials in the production of specific ceramic products like tiles and bricks, there is no comprehensive review of the use of waste materials in the entire field of ceramics. This study aims to provide a complete summary of the current progress in the utilization of waste materials as a substitute for natural raw materials in the fabrication of different types of ceramics, including traditional and advanced fields. Table 1 presents various waste materials, such as FA, RHA, BFS, water treatment sludge, polished tile waste, and red mud, that have been recognized as potential substitutes for natural ingredients in the production of different ceramics. However, it is important to note that the characteristics and chemical composition of these wastes are greatly affected by the environmental conditions of their source materials and the processing parameters used during ceramic production [3].

Table 1.

Chemical composition of wastes

Incorporating waste materials in porous insulation refractory. Refractories serve two main purposes: (i) to protect vessels from the corrosive and erosive effects of hot flue gases, molten salts, liquid metals, and slags, and (ii) to maintain the required temperature inside the vessel by preventing heat flow (insulation). To achieve the first purpose, high refractoriness and dense refractories are typically used because they come into direct contact with the furnace or kiln environments. For insulation purposes, furnaces are usually lined with refractories that have low thermal conductivity (σ), moderate refractoriness, and are porous and lightweight. Researchers are currently exploring ways to incorporate waste materials into insulation refractories.

Recently, researchers have been exploring the use of waste materials in the composition of insulation refractories. The third reference provides a comprehensive summary of studies investigating the impact of various waste materials on the behavior of insulation refractories. Results show that adding waste materials can improve the insulation behavior, porosity, and strength of insulation refractories up to a certain limit. For example, Ramezani et al. [4] studied the impact of waste serpentine on the insulating behavior of basic insulation refractories. They found that the addition of calcined waste serpentine improved the thermo-mechanical properties of the refractories, with the lowest thermal conductivity observed in specimens containing 43 wt.% dead-burned magnesia, 20 wt.% calcined alumina, 17 wt.% expanded perlite, and 20 wt.% calcined waste serpentine.

Hassan et al. [5] investigated the pore formation ability of waste bagasse in fireclay insulating bricks. They discovered that bagasse was a good replacement for petrochemical additives commonly used as pore creators in insulation bricks. Similarly, Sutcu et al. [6] utilized waste paper-processing sludge and sawdust as calcium oxide sources and pore formers, respectively, in anorthite-based insulating refractories. The addition of sawdust significantly increased the porosity and pore size in the anorthite matrix, leading to a decrease in thermal conductivity.

Tiles. Ceramic tiles are becoming increasingly popular in construction and building activities due to factors such as rapid urbanization, modernization, and population growth. The global ceramic tiles market size was valued at $343.9 billion in 2020, and is projected to reach $633.5 billion by 2030, registering a CAGR (compound annual growth rate) of 6.3% from 2021 to 2030. [7]. However, the manufacturing of ceramic tiles involves the consumption of vast amounts of natural resources such as clay, silica, feldspar, zircon sand, and alumina, which can lead to environmental issues. As a result, finding sustainable replacements for virgin raw materials is crucial for the industry in the coming years. Certain waste materials and industrial by-products have shown potential as replacements for these raw materials in the production of tiles. Table 2 highlights the types and amounts of waste materials used, the minerals they replace, firing temperatures, and categories of tiles produced using these sustainable alternatives [3].

The ceramic industry generates solid waste at various stages of processing, such as grinding of raw materials, polishing of fired products, and quality checks of final products. To manage this waste, the industry is adopting the practice of recycling waste as raw materials. El-Fadaly et al. [8] added ceramic industry waste (cyclone and filter dust) to the composition of floor tiles. Ke et al. [9] reused polished tile waste (up to 70 wt.%) as a raw material in porcelain tiles. Tarhan et al. [10] developed porcelain tiles using sanitaryware waste by replacing pegmatite (5 to 15 wt.%) or Na-feldspar (5 to 15 wt.%). In addition, ceramic sludge is produced by the wastewater treatment unit of tile plants, which can also be recycled for preparing floor and wall tiles. Amin et al. [11] examined the use of dried sludge powder (0 to 50 wt.%) mixed with basic composition for the preparation of wall and floor tiles. The study found that 10 wt.% sludge could be used for wall tiles and 20 wt.% sludge for floor tiles as a replacement, meeting internationally harmonized Egyptian standards.

Table 2.

Name of wastes used in the compositions of tiles

Sewage sludge (SS) is a waste product discharged from water treatment plants that typically ends up in landfills. However, SS contains pollutants such as pathogenic microorganisms, heavy metals, and organic contaminants, which contribute to secondary environmental pollution [12]. This has resulted in increasing social and environmental pressure to develop recycling technologies for SS [13]. Several studies have explored the use of SS in various sectors, including the production of ceramic tiles. Li et al. [14] observed a gradual decrease in compressive strength and slight improvement in bending strength when dried SS was added to tile compositions. Zhou et al. [15] developed split tiles using crude SS from wastewater treatment plants without any pretreatment. Their optimal formulation contained 60 wt.% crude SS, 20.6 wt.% feldspar, 15.2 wt.% quartz, and 14.2 wt.% kaolin and met the required properties of fine-grade split tiles as per ISO: 13006:1998. Cremades et al. [16] proposed utilizing SS up to 70 wt.% for the preparation of glazed tiles. Amin et al. [17] prepared floor tiles by mixing dry SS powder (0 to 30 wt.%) with a standard composition for floor tiles. According to ISO standards, the maximum permitted limit of SS addition is 7 wt.% for 1150°C fired samples. These studies demonstrate the potential for utilizing SS in the ceramic industry, but further research is needed to optimize the use of SS in ceramic tile production while minimizing its impact on the environment.

The process of blasting and crushing rocks during rock mining results in the production of waste material known as granite dust waste. This waste contains a significant amount of SiO₂ and Al₂O₃, along with some fluxes (Na₂O & K₂O) and coloring compounds (Fe₂O₃) [18]. However, this waste material can be used as an alternative to conventional raw materials in ceramics. For instance, granite waste can be used as a replacement for sand due to its low plasticity, which reduces the possibility of dimensional defects. Additionally, it can substitute for feldspathic ingredients that form glassy phases at lower temperatures during the manufacture of floor tiles [19].

Researchers such as Pazniak et al. [20] have studied the effects of incorporating granitic and basalt waste into porcelain tiles. They found that using granitic and basalt rock waste as a substitute for feldspar shows potential as fluxes in the tile industry. A sample containing 5 wt.% basalt sintered at 1150°C showed properties similar to those of industrial porcelain tiles. Similarly, Sultana et al. [21] developed roof tiles using hard rock dust (10 to 50 wt.%) mixed with clay.

The production of ceramic sanitaryware involves fixtures and components related to sanitation, such as water closets, washbasins, faucets, and bathtubs. The global sanitaryware market is projected to have a compound annual growth rate (CAGR) of 5.0% from 2018 to 2025, leading to an increased demand for natural ingredients like feldspar, quartz, kaolin, and different types of clays. To ensure sustainable production in compliance with environmental regulations, industries are turning to waste or by-products. However, there is limited research on the utilization of waste for sanitaryware products. Some studies have investigated the incorporation of wall tile waste, glass waste, and galvanized waste into fireclay or porcelain sanitaryware compositions. The addition of such waste has resulted in lower thermal expansion coefficients, decreased water absorption, improved strength, and energy savings.

Recycling waste for ceramic production: benefits and challenges. In light of environmental, ecological, and economic concerns, scientists and technology developers are working to find ways to utilize waste materials to create value-added products. This includes ceramic researchers who are exploring ways to recycle industrial by-products or waste to create ceramics. While many research articles have been published on this topic in recent years, industrially produced ceramics from waste ingredients are not yet widely used. Although some tile industries have started using waste materials for tile production, the number is limited due to various factors such as the compatibility between natural raw materials and waste, characteristics of the final product, availability of waste, transportation costs, constant chemical composition, and pre-treatment of waste. Therefore, more research is needed to transfer technology from academia to industry for the commercialization of waste-derived ceramics. This transfer of technology presents various challenges, including ethical concerns, knowledge gaps, and risks of unsustainability. As such, more encouragement is needed for industrial manufacturing to recycle waste materials. The government can play a role in increasing interest by creating laws and policies to promote sustainable production, which not only benefits the ceramic industry but also helps protect the environment and society from pollution.

Conclusion. The production of toxic and hazardous wastes is continuously increasing, causing difficulties in the form of dumping and pollution. The valorization of these wastes as substitutes for primary natural resources can provide numerous benefits, including conservation of resources, cost-effectiveness, and improved health and safety. Recycling waste for ceramic production is particularly beneficial because it consumes a large amount of natural raw materials. Even a small amount of waste incorporation can have a significant impact on waste absorption. While there have been many research studies on waste utilization for ceramics, technological transfer to commercial production is still limited.

References:

1. R.A.Rahimov. Keramika va olovbardosh materiallar: O'quv qo'l. O'zR Oliy va o'rta-maxsus ta'lim vazirligi; - T.: «O'zbekiston faylasuflari milliy jamiyati» nashriyoti, 2008. - 144 b.
2. Августиник А.И. Керамика. Изд. 2-е, перераб. и доп. Л., Стройиздат (Л е-нингр. отд-ние), 1975, 592 с. ил.
3. Sk.S.Hossain & P.K.Roy (2020) Sustainable ceramics derived from solid wastes: a review, Journal of Asian Ceramic Societies, 8:4, 984-1009, DOI:10.1080/21870764.2020.1815348.
4. Ramezani A., Emami S.M., Nemat S. Effect of waste serpentine on the properties of basic insulating refractories. Ceram Int. 2018;44(8):9269–9275.
5. Hassan A.M., Moselhy H., Abadir M.F. The use of bagasse in the preparation of fireclay insulating bricks. Int J Appl Ceram Technol. 2019; 16(1):418–425.
6. Sutcu M., Akkurt S., Bayram A., et al. Production of anorthite refractory insulating firebrick from mixtures of clay and recycled paper waste with sawdust addition. Ceram Int. 2012;38(2):1033–1041.
7. Ceramic Tiles Market. 2021. Available at. https://www.alliedmarketresearch.com/ceramic-tiles-market. Accessed on 2022 Dec 30.
8. El-Fadaly E.,Bakr I.M., Breka M.R.A. Recycling of ceramic industry wastes in floor tiles recipes. J Ame Sci. 2010;6:241–247.
9. Ke S.,Wang Y., Pan Z., et al. Recycling of polished tile waste as a main raw material in porcelain tiles. J Clean Prod. 2016;115:238–244.
10. Tarhan B., Tarhan M., Aydin T. Reusing sanitaryware waste products in glazed porcelain tile production. Ceram Int. 2017;43(3):3107–3112.
11. Amin S.K., Elmahgary M.G., Abadir M.F. Preparation and characterization of dry pressed ceramic tiles incorporating ceramic sludge waste. Ceram-Silik. 2019;63:11–20.
12. Ruan T., Liu R., Fu Q., et al. Concentrations and composition profiles of benzotriazole UV stabilizers in municipal sewage sludge in China. Environ Sci Technol. 2012;46(4):2071–2079.
13. Yilmaz D.D., Temizgul A. Assessment of arsenic and selenium concentration with chlorophyll contents of sugar beet (Beta vulgaris var saccharifera) and wheat (Triticum aestivum) exposed to municipal sewage sludge doses. Water Air Soil Pollu. 2012;223(6):1–10.
14. Li S.Z., Shi Z., Xie M. Production and performance of tiles made from wastewater treatment sludge. J Chin Ceram Soci. 2007;35:251–254.
15. Zhou J., Li T., Zhang Q., et al. Direct-utilization of sewage sludge to prepare split tiles. Ceram Int. 2013;39(8):9179–9186.
16. Cremades L.V., Cusid J.A., Arteaga F. Recycling of sludge from drinking water treatment as ceramic material for the manufacture of tiles. J Clean Prod. 2018;201:1071–1080.
17. Amin S.K., Hamid E.M.A., El-Sherbiny S.A., et al. The use of sewage sludge in the production of ceramic floor tiles. Hbrc J. 2018;14(3):309–315.
18. Pazniak A., Barantseva S., Kuzmenkova O., et al. Effect of granitic rock wastes and basalt on microstructure and properties of porcelain stoneware. Mater Lett. 2018;225:122–125.
19. Torres P., Manjate R.S., Cuaresma S., et al. Development of ceramic floor tile compositions based on quartzite and granite sludges. J Eur Ceram Soc. 2007;27(16):4649–4655.
20. Pazniak A., Barantseva S., Kuzmenkova O., et al. Effect of granitic rock wastes and basalt on microstructure and properties of porcelain stoneware. Mater Lett. 2018;225:122–125.
21. Sultana M.S., Ahmed A.N., Zaman M.N., et al.Utilization of hard rock dust with red clay to produce roof tiles. J Asian Ceram Soci. 2015;3(1):22–26.