نوع مقاله : پژوهشی
نویسندگان
1 استادیار سازمان تحقیقات، آموزش و ترویج کشاورزی، موسسه تحقیقات برنج کشور، رشت، ایران
2 دانشجوی دکتری مدیریت منابع خاک – فیزیک خاک و حفاظت خاک، دانشکده کشاورزی، دانشگاه گیلان، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Objectives
This study was conducted to address the growing need for sustainable utilization of agricultural waste and the development of environmentally friendly nanomaterials for land management applications. The primary objectives included: 1) extraction and synthesis of silica nanoparticles from the abundantly available rice husk, as an agricultural by-product, using a controlled acid-leaching and calcination process, 2) characterization of the morphological, structural, and moisture properties of the nanosilica thus produced using advanced analytical techniques including Fourier-transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM), 3) evaluation of the quality, structural stability, and physicochemical characteristics of rice husk-derived nanosilica and assessemt of its potential for application as a sustainable material in soil improvement, land management, and environmental technologies.
Material and Methods
The study was carried out using rice husk as the primary raw material collected from the Rice Research Institute of Iran. Prior to processing, the rice husk samples were washed thoroughly with distilled water and dried at ambient temperature. The dried samples were then subjected to acid leaching using a 10% HCl solution under continuous heating for two hours to remove metallic impurities. After repeated washing and drying at 100°C for 24 hours, the treated samples were calcined at 700°C for two hours to obtain silica-rich ash. Subsequently, the silica powder thus obtained was treated with 0.5 N potassium nitrate solution under continuous stirring for one hour to induce partial crystallization. The resulting material was filtered, dried at 105°C for four hours, and finally calcined at 800°C for eight hours to produce porous semi-crystalline silica nanoparticles.
The structural properties of the synthesized nanosilica were characterized using Fourier-transform infrared spectroscopy (FTIR) to identify functional groups and confirm the silica bonding structures. Morphological characteristics and particle size distribution were determined using field emission scanning electron microscopy (FESEM) at a magnification of 200 kx. Particle dimensions and shape factors were determined using the ImageJ software. Specific surface area was estimated based on geometric relationships between particle diameter and density. Moisture content was determined using the oven-drying method. Production yield was calculated as the ratio of final nanosilica mass to that of initial rice husk ash. Statistical measures, including mean, standard deviation, coefficient of variation, skewness, and frequency distribution, were calculated using XLSTAT software to evaluate data consistency and reproducibility.
Results
The FTIR analysis confirmed the successful synthesis of silica nanoparticles through identification of characteristic absorption bands corresponding to Si–O–Si and Si–OH functional groups. A strong absorption peak observed at 1017 cm⁻¹ represented the asymmetric stretching vibration of Si–O–Si bonds while that near 808 cm⁻¹ corresponded to the symmetric stretching vibration of the siloxane framework. Moreover, a broad absorption band around 3400 cm⁻¹ indicated the presence of surface hydroxyl groups and the water molecules adsorbed, confirming the hydrophilic nature and high surface activity of the synthesized nanosilica.
FESEM images revealed that the silica nanoparticles exhibited a nearly spherical morphology with a highly uniform particle distribution and minimal aggregation. Particle sizes ranged from 8 to 24 nm, with an average particle diameter of 15.56 nm. The observed morphology confirmed the successful conversion of rice husk into highly pure nanosilica with a homogeneous porous structure. Statistical analysis demonstrated a low standard deviation (2.96 nm) and a coefficient of variation of 0.194, indicating high reproducibility and uniformity of the synthesis process.
The estimated specific surface area of the synthesized nanosilica was approximately 178.5 m² g⁻¹, reflecting the presence of a highly porous nanostructure with abundant active surface sites. The calculated particle shape factor was 0.95, indicating a highly spherical morphology and excellent geometric uniformity. Moisture analysis showed an average moisture content of 1.84%, with a standard deviation of 0.09 and a coefficient of variation of 4.9%, confirming the stability and consistency of the nanoparticles produced. Furthermore, the production process yielded approximately 70 g of nanosilica from 200 g of dried rice husk, corresponding to a production efficiency of approximately 35%.
Conclusion
This study demonstrated the successful production of high-quality silica nanoparticles from rice husk through a controlled acid-leaching and thermal treatment process. The synthesized nanosilica exhibited desirable physicochemical characteristics, including an amorphous to semi-crystalline structure, spherical morphology, narrow particle size distribution, high specific surface area, and low moisture content. The presence of active Si–OH functional groups and the high surface area indicate significant potential for adsorption, ion exchange, and environmental applications.
The findings revealed that the combined acid treatment and controlled calcination at 800°C represent an efficient and sustainable approach for producing high-purity nanosilica from agricultural waste materials. The nanoparticles thus obtained exhibited excellent structural stability, high surface activity, and favorable morphological characteristics that make them a suitable candidate for soil amendment, environmental remediation, nutrient management, and sustainable land management applications.
In addition to providing an environmentally friendly strategy for agricultural waste recycling, this study contributes to the advancement of green nanotechnology and circular economy principles. Nevertheless, further investigations are recommended to evaluate the long-term behavior, environmental interactions, and biological impacts of rice husk-derived nanosilica in soil-plant systems under field conditions. Overall, the present research demonstrates that rice husk-derived nanosilica enjpys a substantial potential as a multifunctional nanomaterial for sustainable agriculture, environmental protection, and clean technology development.
کلیدواژهها [English]
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