• Vol 11, No 2 (2020)
  • Chemical Engineering

Synthesis of Nano-silica from Boiler Ash in the Sugar Cane Industry using the Precipitation Method

Nastiti Siswi Indrasti, Andes Ismayana, Akhiruddin Maddu, Sasongko Setyo Utomo

Corresponding email: nastiti.indrasti@gmail.com

Cite this article as:
Indrasti, N.S., Ismayana, A., Maddu, A., Utomo, S.S., 2020. Synthesis of Nano-silica from Boiler Ash in the Sugar Cane Industry using the Precipitation Method. International Journal of Technology. Volume 11(2), pp. 422-435
Nastiti Siswi Indrasti Department of Agroindustrial Technology, Institut Pertanian Bogor (IPB) University, Jl. Raya Dramaga, Bogor 16680, Indonesia
Andes Ismayana Department of Agroindustrial Technology, Institut Pertanian Bogor (IPB) University, Jl. Raya Dramaga, Bogor 16680, Indonesia
Akhiruddin Maddu Department of Physics, Institut Pertanian Bogor (IPB) University, Jl. Raya Dramaga, Bogor 16680, Indonesia
Sasongko Setyo Utomo Department of Agroindustrial Technology, Institut Pertanian Bogor (IPB) University, Jl. Raya Dramaga, Bogor 16680, Indonesia
Email to Corresponding Author


Boiler ash is a second layer by-product of the combustion of fuel, usually an agro-waste, in any industry. In the sugarcane industry, boiler ash is obtained from the combustion of bagasse. The boiler ash of the sugarcane industry contains 49.69% silica, which can be transformed into nano-silica using the precipitation method, which is easier and cheaper than other methods. Precipitation pH and aging time are the main factors that influence nano-silica’s characteristics. The objectives of this research were to determine the effect of various precipitation pH levels and aging times on the characteristics of nano-silica and to identify the potential applications of nano-silica based on these characteristics. An increase in precipitation pH affected the number of the crystal phase and the intensity of the diffraction peaks. An increase in aging time also affected the intensity of the diffraction peaks and the number of crystal phases. The degree of crystallinity varied from 66.40% to 93.53%, the crystal size ranged from 37.77 nm to 56.87 nm, the particle size ranged from 214.04 nm to 698.24 nm, and the polydispersity index (PDI) ranged from 0.21 to 0.83. The nano-silica in this research had polygonal morphology. Increases in precipitation pH and aging time increased the number of siloxane groups, creating nano-silica dominated by a crystalline form with three crystal phases: tridymite, quartz, and cristobalite. Nano-silica have various potential applications based on their characteristics, including as filler for membranes, composite resin, rubber airbags, and supplementary cementitious material.

Boiler ash; Characteristics; Nano-silica; Precipitation; Silica


Boiler ash is a second layer by-product from the combustion of fuel, usually an agro-waste, in any industry. Sugar-cane bagasse ash (SCBA) is a by-product of bagasse combustion in the sugar cane industry. SCBA is mostly fine particulate silica with minor alumino-silicates and is produced when bagasse is burned for the co-generation of heat and electricity at a sugar mill (Arif et al., 2017). Silica also can be extracted from various sources, such as rice husk ash (Dhaneswara et al., 2020), fly ash tiles (Yadav et al., 2020), bamboo leaves (Dileep and Narayanankutty, 2020), coal fly ash (Lee et al., 2017), corn cob ash (Okoronkwo et al., 2013), mud, the fly ash of the palm oil industry, and natural sand (Munasir et al., 2013).  

Boiler ash from the sugar cane industry is 49.69% silica, while furnace ash is 78.75% silica (Ismayana et al., 2017). The synthesis of silica from boiler ash not only produces valuable silica but also reduces pollution problems caused by the uncontrolled combustion of the ash (Dhaneswara et al., 2020). The development of nanoscale particles (nanoparticles) has recently become the object of attention for researchers due to their unique properties, such as their very small size, high surface area, and surface activity (Dileep and Narayanankutty, 2020). One of the nanoparticles focused upon in current research is nano-silica. In some applications, nano-silica has been used as an adsorbent, catalyst support material, a semiconductor, thermal insulation, and a ceramic filler (Adam et al., 2011).

The high content of silica-induced boiler ash is transformed into nano-silica, and its characteristics and utilization are more extensive because of the larger surface area. There are several methods for synthesizing nano-silica, such as microemulsion, thermal decomposition, the sol-gel method (Okoronkwo et al., 2013), ultrasonication (Ismayana et al., 2017), and precipitation (Mahdavi et al., 2013).

The precipitation method has many advantages; it is easy and cheap, operates at a low process temperature, uses a low amount of energy, and produces nano-silica of high purity and good quality (Mahdavi et al., 2013). It is also safe and environmentally friendly (Shahmiri et al., 2013). The main factors that influence the nano-silica produced through the precipitation method are precipitation pH and aging time. Various combinations of precipitation pH and aging time result in nano-silica with different characteristics. According to Singh et al. (2012), an increase in pH increases crystal size. Allaedini and Muhammad (2013) found that the crystal size of a nanoparticle is closely linked to the diffraction pattern, the crystalline phase, the particle size, and the degree of crystallinity. In addition, a longer aging time causes a higher degree of crystallinity (Jalilpour and Fathalilou, 2012).

   The objectives of this research were to synthesize nano-silica from the boiler ash in the sugarcane industry using the precipitation method and to determine the effect of pH precipitation and aging time on the characteristics of the nano-silica. This research also aimed to identify potential applications based on the characteristics of the nano-silica produced.


The precipitation method produced nano-silica with polygonal morphology. Precipitation pH and aging time affected the characteristics of the nano-silica, including the particle size, PDI, crystal size, crystallinity degree, and crystal phase. The combination of various precipitation pH and aging times resulted in nano-silica with different characteristics. Overall, the nano-silica in this research had a semi-crystalline to crystalline form with three crystal phases: tridymite, quartz, and cristobalite. Nano-silica has several potential applications, namely, as filler for DMFC membranes, ultrafiltration membranes, rubber airbag launchers, composite resin, and SCM.


       This research was supported by the General Directorate of Strengthening Research and Development of the Ministry of Research, Technology, and Higher Education of the Republic of Indonesia through the Grant of Competence (Hibah Kompetensi) Scheme (Grant Number: 011/SP2H/LT/IV/2017 and Contract Addendum: 011/SP2H/LT/DRPM/VIII/2017).

Supplementary Material
R3-CE-1741-20200401110747.jpg Diffractogram of Nano-Silica
R3-CE-1741-20200401110816.pdf Particle Size Distribution of Nano-Silica
R3-CE-1741-20200401111321.pdf FTIR of Nano-Silica
R3-CE-1741-20200401111732.png Morphology of Nano-Silica 100x
R3-CE-1741-20200401111832.PNG Morphology of Nano-Silica 5000x

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