国家标准规定的Ⅰ级水是分析实验室常用的试验用水, 为快速、 准确的实现纯水水质分析, 为分析实验室设备自动化、 智能化提供科学依据, 采用全波段(200900 nm)紫外-可见光谱分析技术, 设计了基于紫外-可见光谱国标Ⅰ级水净化系统(NSGI-WPS)。 该系统以树莓派为核心控制器, 光谱探测器、 电导率传感器为采集模块, 改良的硅钼蓝分光光度法为可溶性硅测定方法, 实现了对分析实验室用水254 nm吸光度、 电导率和可溶性硅含量的同时在线检测。 在痕量硅含量的测定试验中, 为了消除噪声干扰对试验的影响, 系统采用Savitzky-Golay平滑去噪法对光谱进行预处理, 通过窗口宽度和多项式次数的不同组合形式, 获得了80组平滑后的光谱数据, 将其分别与0.004, 0.006, 0.008, 0.010和0.012 mg·L^-1硅标准溶液浓度进行一元线性回归分析后, 得到单波长吸光度与硅标溶液浓度的相关光谱。 试验结果表明, 当窗口宽度为17, 多项式次数为2时, 相关光谱的特征峰宽度最宽, 特征峰区间为796824 nm, 特征峰峰值所处波长与平滑后的显色溶液吸收光谱峰值波长一致。 通过比较不同硅标准溶液的显色溶液吸收光谱分布, 发现硅标液浓度与吸收光谱呈线性正相关, 因此, 试验选取812.638 nm为最优特征波长。 为了建立可溶性硅含量与显色溶液吸光度的关系模型, 以加入的硅标准溶液浓度为横坐标 x, 812.638 nm处显色溶液的吸光度为纵坐标y, 绘制了其工作曲线, 曲线的决定系数 R²=0.999 6, 表明了模型具有较强的拟合能力。 此外, 编写的NSGI-WPS系统管理软件实现了参数的实时处理和自动控制, 对未达到分析实验室国标Ⅰ级水用水规格的纯水通过反渗透(RO)、 连续电去离子技术(EDI)、 混合床离子交换树脂和紫外光氧化等技术处理, 实现了对纯水的严格控制。 通过对比分析自来水、 Ⅲ级水、 Ⅱ级水在净化前后各参数变化, 发现净化后各参数数值下降显著, 其中, 电导率最高下降幅度可达99.94%, 各参数的相对平均偏差均小于2%。 试验结果表明, 基于紫外-可见光谱分析法的NSGI-WPS系统具有净化能力强、 准确性高、 鲁棒性好等优点, 经过检测、 分析和净化后的纯水满足分析实验室国标Ⅰ级水用水要求。 本文为紫外-可见光谱分析法在纯水净化系统中的应用做出了探索性研究。

The Grade Ⅰ water specified in national standards is the water commonly used in analytical laboratory. In order to analyze the quality of pure water quickly and accurately to provide scientific basis for the automation and intelligence of the equipment in analytical laboratory, this paper designed a national standard Grade Ⅰ water purification system (NSGI-WPS) based on ultraviolet-visible spectroscopy (UV-VIS) by full-band (200900 nm) UV-VIS analysis technology. The system collects modules with Raspberry Pi as the core controller and spectral detector and conductivity sensor as the sensors. As a method for the determination of soluble silicon, the improved silicon-molybdenum blue spectrophotometry realized the simultaneous on-line detection of the 254 nm absorbency, conductivity and the content of soluble silicon of the water used in analytical laboratory. In order to eliminate the impacts of noise interference on the determination test on the content of trace silicon, the system adopted Savitzky-Golay smoothing de-noising method to pretreat the spectrum. 80 groups of spectral data after smoothing were obtained via the different combinations of window width and the degree of polynomial and received unitary linear recursive analysis with the concentration of silicon standard solution 0.004, 0.006, 0.008, 0.010 and 0.012 mg·L^-1 respectively, after which the correlation spectrum between single wavelength absorbency and concentration of silicon standard solution was obtained. The results showed that when the window width is 17 and the degree of polynomial is 2, the characteristic peak of the correlation spectrum is the widest; the interval of the characteristic peak is 796824 nm; and the wavelength of the characteristic peak is consistent with that of the peak of absorption spectra of chromogenic solutions after smoothing. It was found by comparing the distribution of the absorption spectrum of chromogenic solution of different standard silicon solutions that the concentration of silicon standard solution is positively correlated to absorption spectra. Therefore, 812.638 nm was selected as the optimal characteristic wavelength in the test. In order to establish the relationship model between the content of soluble silicon and the absorbency of chromogenic solution, the working curve of the model is drawn with the concentration of the silicon standard solution added as the x-coordinate and the absorbency of the chromogenic solution at 812.638 nm as the y-coordinate. The determination coefficient of the curve R²=0.999 6, indicating that the model has strong fitting ability. In addition, the system management software written for NSGI-WPS realized the real-time processing and automatic control of parameters. The pure water not up to the specifications on National Standard Grade Ⅰ Water used in analytical laboratory was strictly controlled by means of reverse osmosis (RO), continuous electrode ionization (EDI), mixed bed ion exchange resin and UV photooxidation and other techniques. By comparing and analyzing the changes of various parameters of tap water, grade Ⅲ water and grade Ⅱ water before and after purification, it was found that the values of all parameters decreased significantly after purification, among which, the maximum electrical conductivity decreased by 99.94%, and the relative average deviation of all parameters was less than 2%. The test results showed that NSGI-WPS based on UV-Vis has such advantages as strong purification capacity, high accuracy and good robustness, and the purified water after detection, analysis and purification meets the requirements on National Standard Grade I Water used in analytical laboratory. This paper made an exploratory study on the application of UV-Vis analysis in pure water purification system.