Functional Design Andverification Of Industrial Wastewater Heavy Metal Online Monitoring System Based On LIBS

The heavy metal pollutant in such environmental water as river,lake,etc.,will impose a severe threat over the ecological environment and human health,and excess emission of industrial wastewater is a major source of the heavy metal pollutant in the water,so long term on-line monitoring of the heavy metal elements in the industrial wastewater is of great significance for industrial emission reduction and control,and protection of water environment.LIBS is a simple,quick multi-element on-line analysis method,very suitable for on-line monitoring of water sample;but currently the technology still has some problems such as serious matrix effect,stability of measurement and poor repeatability,and there is no LIBS on-line monitoring equipment for heavy metals in wastewater.In order to realize LIBS technology based on-line monitoring of industrial wastewater heavy metal,the main research work and achievements obtained are as follows:(1)Anon-line monitoring method for aqueous heavy metal using LIBStechnology was proposed.Based on the preprocessing method of drying enriched liquid sample with graphite base,we researched the influence of coffee-ring effect on the enriching stability of liquid sample,designed the graphite flake by optimizing Spectroscopy quality and enhancing the effect of liquid sample addition to reduce the pulse stability of detecting Spectroscopy from 28.51%to 10.45%;designed the operating mode and overall structure of the on-line monitor for aqueous heavy metal.(2)Research on and design of the electromagnetic heating driving circuit for quickly enriching liquid sample.The operating principle of electromagnetic heating circuit was analyzed,key factors influencing electromagnetic heating performance was researched,a kind of high energy efficiency electromagnetic heating circuit was designed according to the result of the research.The result of theoretical analysis was tested and verified using the circuit.The results of the theory and experiment both showed that the ON time of the circuit oscillating switch(IGBT)is the main factor influencing electromagnetic heating power,when this factoris not more than 3 times the charge time coefficient of the coil,the heating power is linearly dependent on the opening time;the ON moment of IGBTis the main factor influencing the energy efficiency of the electromagnetic heating.With the increase of the parameter,the energy efficiency decrease gradually.(3)Functional design of the on-line monitor for aqueous heavy metalwas accomplished.In terms of mechanical structure,main functional modules such as substrate loading and unloading module,liquid sample quantitatively adding module,quickly heating enriching module,laser excitation detectionmodule,etc.were designed.By optimizing the flow path parameters of the sample and the working mode of the peristaltic pump,the relative standard deviation of the sample solution is reduced to 0.16%,and a new type of graphite sheet bonding method is developed.Judgement basis fordrying of the liquid samplewas confirmed,which improves the stability of the instrument.;in terms of circuit,with C8051F120 model MCU as core,the system control circui were designed,combined with the slave computer software,based on keil ?4.0 platform,the control of each function module and the cooperative work between the modules are realized.By means of data processing and human-machine interactionof the master computer,the automatic detection of water samples is realized.(4)The performance of the on-line monitor for aqueous heavy metalwas tested,and off-site verified.The detection limits of six heavy metal elements of Cd,Cr,Cu,Ni,Pb and Zn were 0.03,0.012,0.0047,0.033,0.071 and 0.038 mg/L respectively under the laboratory conditions.The calibration curves of each element had a good linearity in the 0?mg/L range.A normalized on-line calibration algorithm for reducing the difference of spectral change rate is proposed.The result of the experiment showed that the full-spectrum sum method reduced the RSD of Cd and Cr from 28.32%and 31.93%to 9.42%and 11.06%respectively,its combined calibrating effect is better than internally calibrating effect of single element.An continuous on-line detection experiment of water sample on site for above 90 hours was conducted to verify the continuous on-line monitoring capacity of the instrument;the result of the monitoring and the results of ICP-OES were compared,obtained error of detection of Cu and Zn were 5.50%and 27.54%respectively.The research results provide a technical means for on-line monitoring of heavy metals in industrial wastewater.