The Design Of Automatic Instruments Based On Electrochemical And Colorimetric Principles For Heavy Metals Detection In Water

In order to monitor the pollution of heavy metals in water, this thesis introduces two kinds of automatic instruments for heavy metals monitoring based on different principles. Firstly,the situation of heavy metals pollution both in domestic and abroad as well as the harzards of several common heavy metals to human organs are introduced. Then, a review of the existing heavy metals detection methods is presented. For the purpose of on-site automated testing, we study the automatic detection instruments based on stripping voltammetry and spectrophotometric method. Through electrochemical workstation and spectrometer,the parameters of two methods was researched, the requirements of the instrument was confirmed. Hardware circuit and the corresponding embedded software was designed for the two instruments. Enrichment module was designed to inmprove the detection limt of the spectrophotometric instrumentReal sample testing indicated that the instruments based on stripping voltammetry can sensitively detect several heavy metals, Zn+, Cd2+,Pb2+ and Cu2+,the detection limits of which were 0.135μg/L、0.297μg/L 0.240μg/L,0.153μg/L, respectively.While the instruments based on spectrophotom-etry can detect 0.005mg/L Cu2+ with a dynamic range from 0.010mg/L to 10mg/L. The performance of both two instruments can meet the requirments for heavy metal detection of lakes.The innovation and detailed work of this thesis are as follows:1. Determining the detection parameters and verified the feasibility of the stripping voltammetry instrument and spectrophotometric instrument Firstly, effect of the parameters of DPS V such as pulse apmplitude,step voltage on peak current were explored. Secondly, the effect of pH, reaction time, dosage of DDTC, optical path on detection were optimized. Finally, We chose 100mm optical path and designed enrichment device to improve the detection limit.2. Optimizing the existing stripping voltammetry instrument The structure of existing instrument is too complex, the sampling system is redundant and the device of the circuit is obsolete. So we redesigned the instrument structure to simplify the water injection that could improve the stability of water avoiding cross contamination.Along with a new device to optimize the power system, we designed a set of embedded software for automatic detection. The result of testing is satisfying.3. Designing the instruments based on optical detection used for Cu2+ detection For the spectrophotometric instrument, peristaltic pumps are used with the advantages of small size and low-cost. A liquid quantity closed loop is designed to ensure the sampling accuracy and can detect in the abnormal situation. We also designed an optical intensity programmable system which can improve the detection precision. A hardware module was designed for electrochemical preconcentration, which decreased the lower limt of optical detection, and achieved good results in preliminary experiments.