利用光纖光譜儀檢測水中餘氯含量之研究

氯是自來水公司用來消毒汙水的化學藥品，但氯會和水中的有機物產生四個生成物，分別為氯仿、一溴二氯甲烷、二溴一氯甲烷和溴仿，稱為「總三鹵甲烷」，而美國早在三十年前就將總三鹵甲烷列為致癌物質。為了檢測水中的餘氯，本論文研發一種具新穎性的光學檢測方法：反射式光纖光譜餘氯檢測法，當光進入光纖時會產生全反射，與待測溶液的餘氯進行多次互相作用，可提升感測效率。優點為：檢測時，不需加入任何穩定氧化染色劑，且能檢測到低濃度的餘氯。利用特殊波長850 nm的LED燈，將光源導入1x2耦合式光纖，一邊連接光譜儀，另一邊連接自製光纖感測器。其中，光纖感測器總長度約70 mm，前後各環剝20 mm，利用研磨機將光纖兩端進行研磨，使其端面平整光滑。透過光譜儀接收後進行分析，可得知不同濃度餘氯的光強度變化。本論文總共做了三十組餘氯檢測實驗，餘氯檢測的範圍從0 ppm – 6 ppm。三十組餘氯檢測實驗的斜率都是負的，且R2都高於0.85，代表三十組餘氯檢測實驗的線性回歸解釋能力相當高，而大部分的數據都落在1 %的誤差範圍裡，若將1 %以外的數據組去除，趨勢線R2會從0.5066增加到0.7113，平均斜率從原本的-0.004/ppm變成-0.0032/ppm，最終方程式為y = -0.0032x + 0.9997，此方法對於餘氯檢測的良率是相當高的，確實有機會應用於水質檢測領域。

關鍵字

餘氯；光學檢測；光纖；光譜儀

並列摘要

Chlorine is the chemical substance, which was used to disinfect sewage by the water company. Chlorine can produce four products include chloroform, Monobromo-dichloro-methane, Dibromo-monochloro-methane and bromoform, which are called "total trihalomethanes" with organic matter in water. Thirty years ago, The total trihalomethanes was listed of carcinogens by United States. In order to measure the residual chlorine in the water, this thesis develops a novel optical detection method: Reflective fiber optic spectral residual chlorine detection method. When the incident light was guided to the fiber, it will produce total reflection and multiple interactions with the residual chlorine to improve the sensing efficiency. The advantage during the detection process, the stable oxidation dye is not added, and it can detect the low concentration of residual chlorine. The experimental setup, we used a central wavelength is 850 nm of the LED as the incident source and then guided the light source into the 1x2 coupled fiber, one side connects the spectrometer, the other side connects the sensing fiber. The total length of the fiber sensor is about 70 mm, strip 20 mm at each end. The fiber ends were polished and make sure the ends surface be smooth. The spectrometer for data acquisition, the light intensity changes of different concentrations of residual chlorine can be known. This thesis was preformed 30 sets of residual chlorine measurement experiments. The residual chlorine detection ranges from 0 ppm to 6 ppm. The slopes of the 30 groups of residual chlorine measurement experiments were all negative, and the R2 was higher than 0.85, which means that the linear regression interpretation ability of the 30 groups of residual chlorine measurement experiments is high. Most of the data in the 1% error range. Remove the data group other than 1%, the trend line R2 will increase from 0.5066 to 0.7113, and the average slope will be change from -0.004/ppm to -0.0032/ppm. The final equation of linear fit is y = -0.0032x + 0.9997. The yield of this method for residual chlorine detection is quite high and it has an opportunity to be used in water quality testing.