Influence Factors and Kinetics Analysis of Nitrate Reduction by UV/C2H5OH/N2 Process
The rapid growth of nitrate concentration in surface water and ground water has become a global problem.The research on nitrate removal by using simple organic matter activated by UV to produce reductive active substances is in the ascendant.Common UV-activated substrates include formic acid and formate,oxalic acid and oxalate,etc.But these substances have certain toxicity.Therefore,ethanol,which has not been reported before,is selected as the activated substrate to investigate the efficiency of ultraviolet activated ethanol to reduce nitrate and the influence of alcohol dosage,nitrate concentration,pH,UV intensity and other factors.The results showed that under the conditions of nNO3-∶nC2H5OH=5∶7,UV intensity of 175 W and reaction for 90 minutes,the nitrate nitrogen reduction rate and total nitrogen removal rate were 100％and 86.8％respectively;the nitrate nitrogen reduction rate increased with the increase of UV light intensity,but the total nitrogen removal rate decreased;The initial pH value had no obvious effect on the reduction rate of nitrate nitrogen,but when pH value was ≤ 2,the total nitrogen removal rate could reduce;The increase of humic acid concentration in water could reduce nitrate reduction rate and total nitrogen removal rate.With nitrogen in the system,the nitrate reduction process of the system conformed to the first-order reaction kinetics,and the reaction rate constants were between 0.031 4～0.165 7 min-1.And electron paramagnetic resonance spectrometer(EPR)proved that the active substance in the system was CO2.
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