Valorisation of Rice Husk by Chemical and Thermal Treatments

Abstract:

In the industrial production of rice, large quantities of rice husk are generated constituting a residue with costs for the companies, which must be appropriately managed. The high grade of silica in the rice husk opens a possibility for its valorisation, through the production of amorphous silica with high porosity and potential application as ligand in construction materials, as catalyst support, as metals adsorbent, among others. In this research work a process was developed for the production of silica with amorphous properties from rice husk waste, and the products formed were characterised. The process involved three main operations: water washing for removal of some impurities, acid leaching with HCl or H₂SO₄ solutions for dissolution of contaminating metals and incineration for organics decomposition. The washing operation let a partial purification of the husk, allowing removal of 46-60% of contaminating metals such as K, Fe Mn and Zn. The leaching with 0.4M HCl and 0.2M H₂SO₄ allowed obtaining high metals removal efficiency, namely >99% for potassium, 85-90% for iron, >96% for manganese and >80% for zinc. The final composition of the leached husk was 0.003-0.006% K, 0.016-0.025% Fe, <0.001% Mn and <0.0007% Zn. The incineration of the rice husk after previous purification was performed at 540°C, by using samples obtained in the several chemical treatment conditions, and using different heating and cooling rates. As a result, a white colored final husk ash was produced, rich in quasi-amorphous silica (confirmed by X-ray diffraction). The analysis by scanning electron microscopy revealed that the organics removal allowed the formation of voids in the rice husk material, which became very porous and presented an alveolar morphology.

• Periodical: Materials Science Forum (Volumes 730-732)
• Pages: 659-664
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.730-732.659
• Online since: November 2012
• Authors: Rosário Madrid, Fernanda Margarido, Carlos A. Nogueira
• Keywords: Incineration, Leaching, Rice Husk, Valorisation

References

[1] N. Yalçin, V. Sevinç, Studies on silica obtained from rice husk, Ceram. Int. 27 (2001) 219-224.

DOI: 10.1016/s0272-8842(00)00068-7

[2] C. Real, M.D. Alcala, J.M. Criado, Preparation of sílica from rice husks, J. Am. Ceram. Soc. 79 (1996) 2012-2016.

[3] Y. Nakata, M. Suzuki, T. Okutani, M. Kikuchi, T. Akiyama, Preparation and properties of SiO2 from rice hulls, J. Ceram. Soc. Jpm. 97 (8) (1989) 842-849.

DOI: 10.2109/jcersj.97.842

[4] P.V. Della, I. Kuhne, D. Hotza, Rice husk ash as an alternate source for active silica production, Mater. Lett. 57 (4) (2002) 818-821.

DOI: 10.1016/s0167-577x(02)00879-0

[5] H. Biricik, F. Aköz, I. Berktay, A.N. Tulgar, Study of pozzolanic properties of wheat straw ash, Cement Concrete Res. 29 (1999) 637–643.

DOI: 10.1016/s0008-8846(98)00249-x

[6] K. Inoue, N. Hara, Thermal treatment and characteristics of rice husk ash, Inorg. Mater. 3 (1996) 312-318.

[7] M. Anwar, T. Miyagawa, M. Gaweesh, Using rice husk ash as a cement replacement material in concrete, Waste Manage. Series 1 (2000) 671-684.

DOI: 10.1016/s0713-2743(00)80077-x

[8] R.V. Krishnarao, J. Subrahmanyam, T.J. Kumar, Studies on the formation of black particles in rice husk silica ash, J. Eur. Ceram. Soc. 21 (1) (2001) 99-104.

DOI: 10.1016/s0955-2219(00)00170-9

[9] Rice husk ash market study Report ETSU U/00/00061/REP, DTI/Pub URN 03/668, Renewable Energy Programme.Contractor Bronzeoak Ltd, (2003)