• International Journal of Technology (IJTech)
  • Vol 11, No 1 (2020)

Synthesis of Amorphous Silica from Rice Husk Ash: Comparing HCl and CH3COOH Acidification Methods and Various Alkaline Concentrations

Synthesis of Amorphous Silica from Rice Husk Ash: Comparing HCl and CH3COOH Acidification Methods and Various Alkaline Concentrations

Title: Synthesis of Amorphous Silica from Rice Husk Ash: Comparing HCl and CH3COOH Acidification Methods and Various Alkaline Concentrations
Donanta Dhaneswara, Jaka Fajar Fatriansyah, Frans Wensten Situmorang, Alfina Nurul Haqoh

Corresponding email:


Cite this article as:
Dhaneswara, D., Fatriansyah, J.F., Situmorang, F.W., Haqoh, A.N., 2020. Synthesis of Amorphous Silica from Rice Husk Ash: Comparing HCl and CH3COOH Acidification Methods and Various Alkaline Concentrations. International Journal of Technology. Volume 11(1), pp. 200-208

3,631
Downloads
Donanta Dhaneswara - Departement of Metallurgical and Materials Engineering, Faculty of Engineering, Universitas Indonesia
-
Jaka Fajar Fatriansyah Department of Metallurgical and Materials Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia
Frans Wensten Situmorang Departement of Metallurgical and Materials Engineering, Faculty of Engineering, Universitas Indonesia
Alfina Nurul Haqoh Departement of Metallurgical and Materials Engineering, Faculty of Engineering, Universitas Indonesia
Email to Corresponding Author

Abstract
Synthesis of Amorphous Silica from Rice Husk Ash: Comparing HCl and CH3COOH Acidification Methods and Various Alkaline Concentrations

High purity silica has been successfully synthesized from rice husk ash (RHA) by alkaline extraction using the reflux process followed by acidification. For this study, rice husk was burned in an electric furnace at 700°C for 5 hours to produce RHA. The RHA was refluxed using sodium hydroxide with concentrations of 1.25×10-3 M (equal to 5% NaOH) and 2.5×10-3 M (equal to 10% NaOH). The acidification process was performed using hydrochloric acid (HCl) 1 M and acetic acid (CH3COOH) 1M to produce silica gel. Then, the silica gel was heated to 120°C for 12 hours to produced silica. The characterization of silica was determined using energy-dispersive X-ray analysis, Fourier-transform infrared spectrometry, the Brunauer–Emmet–Teller method, and X-ray diffraction. The results show HCl acidification produced silica of a higher purity than that produced by CH3COOH acidification. The higher concentration of sodium hydroxide led to higher purity of silica. Based on X-ray diffraction, the silica extracted from RHA was found to be amorphous, and Fourier-transform infrared spectrometry revealed bending and stretching vibrations of Si-O and Si-O-Si. The silica extracted by HCl acidification had a surface area of 236 m2/g, a total pore volume of 0.54 cc/g, and an average pore diameter of 9 nm. The silica extracted by CH3COOH acidification had a surface area of 204 m2/g, a total pore volume of 0.43 cc/g, and an average pore diameter of 8.4 nm.

Acidification; Reflux; Rice husk ash; Silica gel; Xerogel

Introduction

Rice husk accounts for a significant amount of agricultural waste in many rice-producing countries. In 2015, Indonesia produced about 75 million tons of paddy, and rice husk accounts for 20–22% of the weight of paddy (Saleem et al., 2014). The accumulation of rice husk waste can pose a threat to the environment if it is not properly controlled. Rice husk is separated from rice grains during the milling process because it is low in nutrients (Lee et al., 2017). Due to its poor nutrient composition, rice husk is usually used as an animal food ingredient and as a low-cost burning fuel, which is ineffective and can lead to air pollution. Nevertheless, compared to other biomass fuels, rice husk contains unusually high levels of cellulose, lignin, and ash, which are its major constituents. The actual composition varies, but the typical composition is as follows: 38% cellulose, 22% lignin, 20% ash, 18% pentosanes, and 2% other organics (Chandrasekhar et al., 2003). Rice husk ash (RHA) contains amorphous silica in the range of 20–25 wt.%.

In recent times, rice husk has been utilized in various applications such as in the manufacture of fertilizer (due to its high lignin content), in the preparation of activated carbon, and as an industrial fuel for gasification or combustion boilers (Namdeo, 2018). Scientists are particularly attracted to the potential of rice husk as a raw material for silica-based materials, as well as pure silicon, silica nitride, silicon tetrachloride zeolite, and amorphous silica (Sun and Gong, 2001).

Controlled combustion of rice husk produces ash that contains high purity amorphous silica. Amorphous silica can be obtained from RHA when the rice husks are burned at a temperature of 700°C, and this is transformed into crystalline silica when it is burned at a temperature of over 850°C (Fernandes et al., 2016). This silica has many applications as a filler, adsorbent, catalyst support, a component of star gels, and a source for producing superior quality silicon and its compounds.

Silica is a basic raw material that is widely used in semiconductors, ceramics, polymers, and several industries, such as the rubber industry and pharmaceuticals (Fernandes et al., 2016). In particular, silica can be used for gas adsorption (Dhaneswara et al., 2019, Fatriansyah et al., 2019) and heavy metal remediation in water (Dhaneswara et al., 2018). In mesoporous form, silica can be used too in gas adsorption application (Wilson and Mahmud, 2015).

Since silica can be produced from RHA, several reports have addressed the extraction of silica from rice husk. This process not only produces valuable silica but also reduces pollution problems caused by the uncontrolled combustion of rice husk.

Many researchers have developed methods for extracting silica from rice husks. Riveros and Garza (1986) reported that silica can be recovered from rice husk by acid leaching. Later, Kalapathy et al. (2000) discovered the alkaline extraction sol-gel method for recovering silica from rice husk, which is based on the fact that silica can be dissolved in alkaline solution. Because silica has high solubility in a solution with a pH above 10, it can dissolve in alkaline solution to form sodium silicate (Qomariyah et al., 2019). Acidification is also a necessary part of the process to produce silica gel. This process has numerous advantages; it is not as costly or as damaging to the environment as the quartz fusing method (Todkar et al., 2016). It has been reported that the character and purity of silica are more affected by chemical treatment than by thermal treatment (Daifullah et al., 2004).

This study aims to synthesize amorphous silica using rice husk waste as a raw material of SiO2. A simple reflux process using an alkaline solution (sodium hydroxide) was followed by acidification to form silica gel. Then, the effects of various alkaline concentrations and the two acidification methods were investigated by examining the physical, structural, and mechanical properties of the amorphous silica obtained from rice husk waste. 


Conclusion

This study demonstrates that high purity silica can be obtained from rice husk using a simple alkaline-acidification process. Amorphous silica with a purity of 98–99% was obtained from rice husk by alkaline extraction using a reflux process followed by acidification. In this study, the silica extracted from rice husk by acidification using HCl had the highest purity and the largest surface area (236.2 m2/g). Moreover, dissolving the silica in a higher concentration of alkaline solution also had a significant effect, resulting in a higher surface area but a smaller total volume and average diameter. Fourier-transform infrared spectra characterization shows that the synthesized silica has both Si-O-Si and Si-O bonds, and the XRD pattern shows that it has an amorphous structure. Silica with a large surface area can be used for various applications, such as catalysts and adsorbents.

Acknowledgement

This research was funded by the Directorate of Research and Community Services (DRPM), Universitas Indonesia, through Hibah PTUPT under contract no. NKB-1729/UN2.R3.1/HKP.05.00/2019.

References

Anuar, M.F., Fen, Y.W., Zaid, M.H.M., Matori, K.A., Khaidir, R.E.M., 2018. Synthesis and Structural Properties of Coconut Husk as Potential Silica Source. Results in Physics, Volume 11, pp. 1–4

Aripin, H., I Made, J., Mitsudo, S., I Nyoman, S., Priatna, E., Busaeri, N., Sabchevski, S., 2017. Formation and Particle Growth of TiO2 in Silica Xerogel Glass Ceramic during a Sintering Process. International Journal of Technology, Volume 8(8), pp.1507–1515

Chandrasekhar, S., Satyanarayana, K.G., Pramada, P.N., Raghavan, P., Gupta, T.N., 2003. Processing, Properties and Applications of Reactive Silica from Rice Husk—An Overview. Journal of Materials Science, Volume 38, pp. 3159–3168

Daifullah, A.A.M., Awwad, N.S., El-Reefy, S.A., 2004. Purification of Wet Phosphoric Acid from Ferric Ions using Modified Rice Husk. Chemical Engineering and Processing: Process Intensification, Volume 43(2), pp. 193–201

Dhaneswara, D., Fatriansyah, J.F., Mahagnyana, A.B., Delayori, F., Putranto, D.A., Adriyani Anwar, S.U.A., 2018. The Role of Modification SBA-15 Mesoporous Silica with CPTMS in Cd Adsorptions. In: International Conference on Chemistry and Material Science, Volume 299(1), pp. 1–11

Dhaneswara, D., Fatriansyah, J.F., Yusuf, M.B., Abdurrahman, M.H., Kuskendrianto, F.R., 2019. Study of Si Surface Adsorption Towards Hydrogen Molecule. In: IOP Conference Series: Materials Science and Engineering, Volume 547(1), pp. 1–7

Fatriansyah, J.F., Dhaneswara, D., Abdurrahman, M.H., Kuskendrianto, F.R., Yusuf, M.B., 2019. Modeling of Nitrogen Adsorption Phenomena in Amorphous Silica using Molecular Dynamics Method. AIP Conference Proceedings, Volume 2169(1), pp. 030001-1–030001-8

Fernandes, I.J., Calheiro, D.F., S?nchez, A.L., Camacho, A.L.D., de Campos Rocha, T.L.A., Moraes, C.B.A.M., de Sousa, V.C., 2016. Characterization of Silica Produced from Rice Husk Ash: Comparison of Purification and Processing Methods. Materials Research, Volume 20(2), pp. 512–518

Kalapathy, U., Proctor, A., Shultz, J., 2000. A Simple Method for Production of Pure Silica from Rice Hull Ash. Fuel and Energy Abstract, Volume 42(1), pp. 257–262

Lee, J.H., Kwon, J.H., Lee, J.W., Lee, H.-S., Chang, J.H., Sang, B.I., 2017. Preparation of High Purity Silica Originated from Rice Husks by Chemically Removing Metallic Impurities. Journal of Industrial and Engineering Chemistry, Volume 50, pp. 79–85

Mukherjee, D., Roy, A.B., 1991. Predator Mediated Co-Existence of Three Competing Species with L-V Type Interactions. Ecological Modelling, Volume 58(1–4), pp. 285–301

Namdeo, M., 2018. Magnetite Nanoparticles as Effective Adsorbent for Water Purification: A Review. Advances in Recycling & Waste Management, Volume 2(3), pp. 126–129

Okoronkwo, E.A., Imoisili, P.E., Olusunle, S.O.O., 2013. Extraction and Characterization of Amorphous Silica from Corn Cob Ash by Sol-Gel Method. Chemistry and Materials Research, Volume 3(4), pp. 2225–2956

Qomariyah, L., Widiyastuti, W., Winardi, S., Kusdianto, K., Ogi, T., 2019. Volume Fraction Dependent Morphological Transition of Silica Particles Derived from Sodium Silicate. International Journal of Technology, Volume 10(3), pp. 603–612

Riveros, H., Garza, C., 1986. Rice Husk as a Source of High Purity Silica. Journal of Crystals Growth, Volume 75(1), pp. 126–131

Saleem, M., Rustam, M., Naqvi, H.J., Jabeen, S., Akhtar, A., 2014. Synthesis of Precipitated Silica from Corn Cob by using Organic Acids. Science International (Lahore), Volume 27(1), pp. 265–269

Sun, L., Gong, K., 2001. Silicon-based Materials from Rice Husks and Their Applications. Industrial and Engineering Chemistry Research, Volume 40, pp. 5861–5877

Todkar, B.S., Deorukhkar, O.A., Deshmukh, S.M., 2016. Extraction of Silica from Rice Husk. International Journal of Engineering Research and Development, Volume 12(3), pp. 69–74

Wilson, L.D., Mahmud, S.T., 2015. The Adsorption Properties of Surface-modified Mesoporous Silica Materials with ß-Cylodextrin. International Journal of Technology, Volume 6(4), pp. 533–545