污水处理中六价铬的测定方法

分析了银川地区水污染现状及其中的主要污染物，主要对六价铬的测定方法进行了探讨．在酸性溶液中，六价铬离子与二苯碳酰二肼反应，生成紫红色化合物，其最大吸收波长为540nm，吸光度与浓度的关系符合比尔定律．对不含悬浮物、低色度的清洁地面水可直接测定；对混浊、色度较深的水样，应加入氢氧化锌共沉淀剂并进行过滤处理；取9支50mL比色管，吸取标准液，绘制标准曲线．显色前，水样应调至中性，进行色度校正，参比溶液的水量水样要与待测液一致．测定时，要对仪器进行调零、调满，保证波长的透过率达到100％．根据水样吸收峰的特点，波长在540nm的吸收光谱，即可测定吸光度．要保证数据的准确性、精密性、完整性、代表性和可比性．只有坚持长期测定，才能从大量的数据中揭示其变化规律，预测其变化趋势，数据越多，预测的准确度就越高．

The current situation of polluted water quality in Yinchuan and method of determining Cr6+

In order to show the importance of water pollution prevention, on the base of accounting the water resource in Yinchuan, the current situation of water pollution and the main pollutants are analyzed. The method of determining Cr6+ is discussed. In acidity aqua, Cr6+ reacts with DPC, produces purplish red compound, and its biggest absorption wave-length is 540 nm. The relation of light absorption and density matches with the Bill law. The clean surface water with no float, low-color degree can be measured directly; the muddy water with deep-color degree should be provided with Zn(OH)2 to proceed percolation handles. Take nine pieces of 50 mL tube, absorbing the standard liquid, and drawing the standard curve. Before showing the color, the water should be adjusted to the neuter gender, and the color degree should be corrected, comparing aqua consistence with the measuring aqua. While measuring, in order to guarantee the rate of filter of wave-length to attain 100%, the instrument should be adjusted to the zero and full. According to the character of absorption peak, the absorption spectrum, whose wave-length is 540 nm, the light absorption can be measured. The accuracy, precision, completeness, representation, and comparison of data should be guaranteed. The shifting regulation can be revealed and the shifting trend can be predicted from a lot of data by long-term measurement. The more the data, the higher, the accuracy of prediction.