Environmental Erosion Research

fa سنتز، مشخصه‌یابی و عملکرد مالچ ژئوپلیمری اسیدی بر پایه ضایعات صنعتی در خاک‌های شنی Synthesis, characterization and performance of acidic geopolymer mulch based on industrial waste in sand soils مدیریت و کنترل اثرات فرسایش محیطی مستخرج از پایان‌نامه / رساله / طرح پژوهشی فرسایش خاک و انتشار گرد و غبار در هوا و انتقال ذرات خاک و اثرات مرتبط با آنها، یکی از مشکلات بزرگ زیست محیطی محسوب میشوند. راهکارهای مختلفی برای تثبیت خاک و جلوگیری از پدیده گرد و غبار، از جمله تثبیت سطح خاک با استفاده از ژئوپلیمر، مطرح است. ضایعات صنعتی به عنوان پیشساز احتمالی برای تولید ژئوپلیمر برای استفاده سالمتر از مواد خام و منابع انرژی، از نظر زیست محیطی و اقتصادی، مورد توجه زیادی قرار گرفتهاند. بنابراین در مطالعه حاضر، امکان تولید مالچ ژئوپلیمری با استفاده از محلول اسید فسفریک به عنوان یک فعال کننده اسیدی و ضایعات کاشی و سرامیک (CTW) و باطله معدن آهن (IOT)، به عنوان محصولات جانبی صنعتی مورد بررسی قرار گرفت. ژئوپلیمر اسیدی با نسبتهای مختلف CTW و در پنج نوع ژئوپلیمر اسیدی شامل CTW100، CTW75IOT25، CTW50IOT50، CTW25IOT75 و IOT100 با استفاده از فعال کننده اسید فسفریک سنتز شد. نتایج مقاومت فشاری ماسه تیمار شده با سطوح 10 و 20 درصد ژئوپلیمرهای اسیدی نشان داد در تمام تیمارها بجز تیمار CTW100 افزایش سطح ژئوپلیمر از 10 به 20 درصد باعث افزایش معنیدار مقاومت فشاری ماسه شد. همچنین در سطح 20 درصد ژئوپلیمر، با افزایش درصد IOT ، مقاومت فشاری ماسه بهطور معنیداری افزایش یافت. در مطالعه حاضر دو ژئوپلیمر CTW25IOT75 و IOT100 که دارای بیشترین مقاومت فشاری بودند برای آزمایشهای اندازهگیری EC و pH خاک، تاثیر برجوانه زنی، جمعیت میکروبی خاک و مقاومت به فرسایش بادی انتخاب شدند. کاربرد ژئوپلیمرهای CTW25IOT75 و IOT100 در مقایسه با تیمار شاهد باعث کاهش معنیدار pH و نرخ فرسایش بادی و افزایش معنیدار جمعیت میکروبی ماسه شد و همچنین اثر منفی بر جوانهزنی بذرسورگوم نداشتند. بطور کلی نتایج نشان داد از دو ژئوپلیمر CTW25IOT75 و IOT100 می‌توان بعنوان مالچ ژئوپلیمری سازگار با محیط زیست استفاده کرد.   1. Introduction Wind erosion and dust emission pose significant environmental challenges, particularly in arid and semi-arid regions, affecting over 41 percentage of the Earth's land surface and nearly two billion people, primarily in developing nations (Komaei et al., 2023). Unsustainable agricultural practices, deforestation, and climate change have exacerbated soil degradation, leading to annual dust emissions of up to 3000 million tons, which adversely impact air quality, water resources, and agricultural productivity (de Farias et al., 2020). Traditional soil stabilization methods, such as Portland cement and lime, are energy-intensive and contribute substantially to CO₂ emissions (Shariatmadari et al., 2021). As an eco-friendly alternative, geopolymers—aluminosilicate-based materials activated by alkaline or acidic solutions—have emerged as sustainable binders for soil stabilization (Tchakouté et al., 2017). Acidic geopolymers, particularly those activated by phosphoric acid, exhibit superior mechanical strength and thermal stability due to the formation of Si-Al-P networks (Tchakouté et al., 2017) Industrial by-products, such as ceramic tile waste (CTW) and iron ore tailings (IOT), are promising precursors for geopolymer synthesis, offering both economic and environmental benefits (Behforouz et al., 2020). CTW, rich in amorphous silica and alumina, and IOT, containing iron oxides and aluminosilicates, are ideal for geopolymer production (Prates et al., 2023). This study investigates the feasibility of using CTW and IOT-based acidic geopolymers for sand dune stabilization, focusing on their compressive strength, microstructure, and ecological impact. 2. Methodology In this study, phosphoric acid was combined with different ratios of IOT and CTW, and five types of acidic geopolymers were prepared, including CTW100, CTW75IOT25, CTW50IOT50, CTW25IOT75, and IOT100. The compressive strength of sand treated with 10 and 20 percent levels of acidic geopolymers was determined, and finally the polymer with the highest compressive strength was selected for further tests. The surface morphology of the geopolymer selected based on the compressive strength results was obtained by SEM. The chemical composition and mineral phase composition of the geopolymers were also determined using XRF and XRD, respectively. The pH value, electrical conductivity (EC), seed germination, microbial population and wind erosion resistance of the geopolymer-treated sand were also investigated. 3. Results The results of the compressive strength evaluation for sand treated with 10% and 20% levels of acid-geopolymers synthesized from IOT and CTW showed that in all treatments except CTW100, increasing the geopolymer percentage from 10% to 20% led to a significant increase in compressive strength. At the 20% level, with an increase in the proportion of IOT in the geopolymer composition, the compressive strength increased significantly. The highest compressive strength values were observed in the CTW25IOT75 (2.2 kg/cm²) and IOT100 (3.2 kg/cm²) treatments, which were above the minimum standard (2 kg/cm²) set by the Environmental Protection Agency. Accordingly, these two geopolymers were selected for further testing. X-ray diffraction (XRD) results of the IOT100 geopolymer revealed the formation of antigorite, chlorite, and iron phases. In the CTW25IOT75 geopolymer, albite, chlorite, and quartz phases were identified. Scanning electron microscopy (SEM) images confirmed a dense and cohesive structure in both geopolymers, indicating the presence of an aluminosilicate gel and the formation of compact tetrahedral phases with low porosity. These microstructural characteristics are the primary reason for achieving high compressive strength. The application of both geopolymers resulted in a significant decrease in the pH of the sand compared to the control sample. While the CTW25IOT75 geopolymer had no significant effect on EC, IOT100 caused a significant increase. However, the values of both parameters remained within the acceptable range of environmental standards. The results of the sorghum seed germination test showed that the application of these geopolymers had no negative effect on the germination percentage. Furthermore, the microbial population of the sand was significantly affected by the geopolymers, with the microbial population increasing by 400% and 275% in the CTW25IOT75 and IOT100 treatments, respectively, compared to the control. The most significant outcome was the geopolymers' remarkable effect on controlling wind erosion; the wind erosion rate in sand stabilized with either geopolymer was reduced to nearly zero compared to the control sample, which had no resistance.                                                                         4. Discussion & Conclusions The discussion centers on the critical role of acidic activation and precursor composition in developing the cohesive and dense microstructure of geopolymers, which is fundamental to their performance. The formation of a consolidated geopolymer matrix, as observed in SEM micrographs, is attributed to the phosphoric acid-driven reaction that creates aluminosilicate gels, effectively binding sand particles together (Nikolov, 2020). The high reactivity of IOT, characterized by their silica, iron oxide content, and high Si/Al ratio, facilitates the development of dense, compact tetrahedral structures with low porosity through reactions with the acidic activator. This dense structuring is a key factor in achieving excellent mechanical properties and is consistent with the mechanisms described in the literature for acid-based geopolymerization (dos Santos et al., 2019; Lazorenko et al., 2021). The observed microstructural integrity provides a scientific basis for the material's effectiveness, aligning with findings from other studies on acid-activated systems (de Carvalho et al., 2023; Kaze et al., 2021). The efficacy of the synthesized geopolymers is further discussed in the context of their environmental compatibility and functional performance beyond mere mechanical strength. The significant increase in microbial population in treated sand is theorized to be a direct result of the mulch's ability to retain moisture, thereby creating a more favorable habitat for microorganisms and mitigating moisture stress, which is a critical constraint in arid environments (Długosz et al., 2024; Qu et al., 2023). This highlights a beneficial ecological side effect of the treatment. Furthermore, the near-zero wind erosion rates observed are directly linked to the formation of a resistant and stable surface crust by the geopolymer, which effectively shields the soil from displacement by wind forces (Komaei et al., 2023; Shahnavaz et al., 2017). The absence of a negative impact on seed germination underscores the potential environmental safety of these materials for use in soil stabilization projects, as they do not introduce phytotoxic conditions (Banedjschafie et al., 2021; Abtahi, 2019).   باطله آهن, ضایعات کاشی و سرامیک, مقاومت فشاری, مقاومت به فرسایش بادی Iron waste, Tile and ceramic waste, Compressive strength, Wind erosion resistance. 66 87 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-1049-1&slc_lang=fa&sid=1 zahra barahooei زهرا براهویی zahrabarahooei097@gmai.com 10031947532846009932 0009-0002-1138-7194 No Department of Arid and Desert Areas Management, Faculty of Natural Resources and Desert Studies, University of Yazd, Yazd, Iran گروه مدیریت مناطق خشک و بیابانی، دانشکده منابع طبیعی و کویر شناسی، دانشگاه یزد، یزد، ایران Somayeh Ghasemi سمیه قاسمی s.ghasemi@yazd.ac.ir 10031947532846009933 10031947532846009933 Yes Associate Professor, Department of Arid and Desert Areas Management, Faculty of Natural Resources and Desert Studies, University of Yazd, Yazd, Iran گروه مدیریت مناطق خشک و بیابانی، دانشکده منابع طبیعی و کویر شناسی، دانشگاه یزد، یزد، ایران Somayeh Bakhtiari سمیه بختیاری Bakhtiari@sirjantech.ac.ir 10031947532846009934 10031947532846009934 No Department of Civil Engineering, Faculty of Civil Engineering, Sirjan University of Technology, Kerman, Iran گروه مهندسی عمران، دانشکده مهندسی عمران، دانشگاه صنعتی سیرجان، کرمان، ایران