Analytical Sciences

Abstract − Analytical Sciences, 31(3), 177 (2015).

Fundamental Study on the Development of Fiber Optic Sensor for Real-time Sensing of CaCO3 Scale Formation in Geothermal Water
Takuya OKAZAKI,* Kenichiro IMAI,* Shin Y. TAN,** Yun T. YONG,** Faidz A. RAHMAN,*** Noriko HATA,* Shigeru TAGUCHI,* Akira UEDA,* and Hideki KURAMITZ*
*Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering for Research, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
**Department of Electronic Engineering, Faculty of Engineering and Green Technology, Universiti Tunku Abdul Rahman, Jalan Universiti, Bandar Barat, 39100 Kampar, Perak, Malaysia
***Department of Electrical and Electronic Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur, Malaysia
This study proposes an optical fiber sensor for calcium carbonate (CaCO3) scale formation in water. The sensor is easily fabricated by removing the cladding of a multimode fiber to expose the core towards the surrounding medium in order to detect refractive index change. A variation of the transmittance response from the high refractive index of CaCO3 which precipitated on the fiber core surface was observed. The proposed setup can be used to analyze the transmittance response over wide range of wavelength using white light as a source and also a spectroscopy detector. The curve of the transmittance percentage over time showed that a fiber core with 200 μm has higher sensitivity as compared to a fiber core with 400 μm. The findings from this study showed that the sensor detection region at near infrared (NIR) wavelengths showed better sensitivity than visible light (VIS) wavelengths. Field tests were conducted using natural geothermal water at Matsushiro, Japan in order to verify the performance of the proposed sensor. The optical response was successfully evaluated and the analytical results confirmed the capability of monitoring scale formation in a geothermal water environment.