Synthesis of allophane from rice husk ash and its use as a phosphate adsorbent: A novel approach. Issue 6 (December 2022)

• Record Type: Journal Article
• Authors: Ohta, Saki; Yoshida, Kazuma; Hongo, Teruhisa
• Is Part Of: Journal of environmental chemical engineering. Volume 10:Issue 6(2022)
• Publication Date: 2022-12
• Subjects: Rice husk ash -- Recycle -- Allophane -- Phosphate -- Adsorption; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2022.108634
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: There is a need to develop a recycling method for rice husk ash (RHA), as large amount of RHA is generated in rice husk-based power plants. Present study evaluated the RHA discharged from a rice husk-based power plant in Myanmar. It was found that RHA contained 91.65 mass % silica, of which 92.7 % Si could be extracted with 1.0 mol/L NaOH solution at 80 °C. Type I and II allophanes were successfully synthesized by adjusting the pH of the Si extract. The BET specific surface areas of type I and II allophanes were 334.2 and 150.2 m 2 /g, respectively. Both have bimodal pore structures in the micro- and meso-micro ranges, with the pore volume in the micro region being much larger for type I allophane. Both the adsorption rate and adsorption capacity for phosphate was higher for type I allophane than for type II. Langmuir adsorption isotherms revealed that the maximum adsorption capacities of the type I and type II allophanes were 35.1 and 4.3 mg/g, respectively. Graphical Abstract: ga1 Highlights: Allophane, an aluminosilicate material, was successfully synthesized from rice husk ash (RHA) for the first time. Type I and type II allophanes could be synthesized by changing the pH of Si source solution, respectively. Maximum phosphate adsorption capacities of type-I and type-II allophanes were 35.1 mg/g and 4.3 mg/g, respectively. Type-I allophane prepared from RHA can be a promising adsorbent for phosphate.