Study On The Determination Of Chemical Oxygen Demand Using Flow Injection With On-line Nano-TiO₂-UV Photocatalytic Oxidation Spectrometric Detection

Based on pollution discharge quantity control actualizing in China, on-line COD monitoring became more important. So far, there are many kinds of auto-monitoring instruments, more than 20 of instruments certified by National Environment Protection Bureau in China. The design theory for these instruments is based on national standard method, that is traditional wet chemical method. However, the level of existing COD analysis technology is low, it can not meet requirement of discharge pollution quantity. Study and analysis the instrument that is more simple, fast, reliable, without the second pollution, with knowledge commercial right has a very important sense.This study, based on new think and discharged traditional method, determine COD using flow injection with on-line nano-TiO₂-UV photocatalytic oxidation spectrometric detection. The best analysis conditions are: the concentration of K₂Cr₂O₇ is 0.1mol/L, H₂SO₄ is 0.5mol/L, the flow rate is 0.50mL/min, ID of pump pipe is 0.8mm, sample bulk is 200uL, the lengthen of TiO₂-reaction pipe is 250cm, UV is 15W.The study uses three COD standard substance to examine the performance of the COD monitor system and found the absorbence is linear relationship with COD quantity when COD quantity in range of 10～100mg/L and 100～1000mg/L. for Na₂C₂O₄ standard substance, regression equations are Y=0.0019X + 0.1333...