Rice Husk Ash as Raw Material for the Synthesis of Silicon and Potassium Slow‑Release Fertilizer

Abstract

Rice husk ash (RHA) is a waste material produced in large quantities in many regions worldwide, and its disposal can be problematic. This work describes a method for using RHA to synthesize silicon and potassium slow-release fertilizer. The extraction of silica from RHA was accomplished by alkaline leaching with KOH. Different KOH concentrations and reaction times were evaluated and the best production of K 2 SiO 3 solution was achieved using 6 mol L -1 and 6 h, respectively. The fertilizer was synthesized by the reaction of K 2 SiO 3 with KAlO 2 in aqueous medium, followed by calcination at 500 °C. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses indicated that the fertilizer composition was similar to mineral kalsilite. Solubility essays indicated lower K + and Si 4+ release percentage in neutral medium. Kinetic mechanisms of release tests can be well explained by the pseudo-second order model. The proposed synthesis seems to be a viable process offering economic and environmental benefits.Keywords: rice husk ash, silicon, potassium, slow-release fertilizer IntroductionNowadays, one of the most important goal of agronomic management is the development of environmentalfriendly fertilizers, which promote a sustainable nutrient management to ensure growth crop yield.1 One method of reducing fertilizer nutrient losses involves the use of slowrelease fertilizers, which have been designed to gradually release nutrients to plants at a rate to coincide with the requirement of crops. The advantages of using slow-release fertilizers instead of the conventional type are various, such as the increased efficiency of the fertilizer, the continuous supply of nutrients for a prolonged period and a decrease of nutrient losses by volatilization and leaching out to surface and ground water. 2,3 Potassium (K) is known as one of the most required nutrient during plant growth. K plays an important role in the energy state of the plant, translocation and storage of assimilates and maintenance of water in plant tissues. 4 For many crops, silicon (Si) is also an important nutrient and its availability to plants is often associated to increase of crop yield. 5Plants under intensive cultivation that require high absorption of Si, such as rice, sugar cane, and grasses in general, can quickly deplete the soluble Si content of soil. This element, therefore, needs to be replaced by fertilization. The application of Si fertilizer can influence plants in two ways: (i) by improvement of the fertility and chemical properties of the soil, and (ii) by direct effects on plant growth and development.6 Positive effects that have been reported include improved plant structure, such as upright leaves and stems, 7 and increased resistance to fungi and insects due to deposition of Si under the plant cuticle. 8 The high Si content of rice husk ash (RHA) has led to interest in its use as a source of Si for plants and for the production of numerous Si-based materials.9 RHA is generated after burning the rice husk, which is a waste from the ric...

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“…França et al investigated silica extraction from rice husk ash using KOH solution with various concentration and showed that 32.3% recovery from ash was achieved using 1.0 M solution for 6 hr. [45]. The difference between biological treatment and thermal treatment was not too far or less than 50%, it means that biological process could be an alternative to the thermal one in a series of extraction procedures.…”

“…3Bio Journal of Biological Science, Technology and Management 2(2): [39][40][41][42][43][44][45][46] Nyuanti et al Management recommendation to manage invasive species for A. riparia is aimed to reduce the environmental, economic, and social impacts of invasive species. This particular management approach is recommended by [10] especially for invasive species with high risk categories.…”

“…3Bio Journal of Biological Science, Technology and Management 2(2):[39][40][41][42][43][44][45][46] Nyuanti et al…”

Potential Slow Release Fertilizers Based on K2MgSiO4 Obtained from Serpentinite

“…3 Therefore, these reports evidence the need to prospect fertilizer technologies which release K in a controlled process according to plant demands aiming to improve fertilizer efficiency, including the reduction of both on K loss and the need of split application. 4,5 In fact, several studies have been performed into using different materials as slow-release K-fertilizer, such as rice husk ash for the synthesis of silicon and potassium, 6 K-feldspar (KAlSi 3 O 8 ) 7 and chrysotile/K 2 HPO 4 . 8 Serpentinite, a metamorphic rock with general approximate formula [Mg 3 Si 2 O 5 (OH) 4 ], is found in different places on the surface of the world with global reserves estimated in hundreds of millions kg.…”

Preparation of Microcapsules of Slow-Release NPK Compound Fertilizer and the Release Characteristics

“…9 Therefore, due to its abundance, nontoxicity, low cost and biodegradability, biomass has been widely used as SRF material. França et al 10 used rice husk ash as the raw material to prepare a slow-release fertilizer containing silicon and potassium. Wen et al 11 reported the synthesis of a corncob-based semi-interpenetrating polymer network slow-release nitrogen fertilizer.…”