Ultrasound Technology In Aqueous Solution Of Atrazine And 2,4-d

Taking aqueous solution of atrazine and 2,4-D as objects, study their impact factors, synergistic effects and degradation kinetics systematiclly and on this basis of which by using various means, analyse and verify the intermediate products and degradation way of these two substances. Combine the ultrasound with Fenton technology and analyse the impact factor of the system in detail so as to detecting the optimum conditions of it. This study includ the following aspects:(1) By changing the initial pH, volume, concentration, ultrasonic reaction time, water quality, aeration, ultrasound parameters and so on, study various factors of atrazine and 2,4-D degradation rates. Studies show that:in 400kHz,40W ultrasound reactor, the concentration of 500mL atrazine solution (pH=5.73) was reduced from 10mg/L to 1.79mg/L; in 200kHz,90W ultrasound reactor, the concentration of 500mL 2,4-D solution (pH=4.41) was reduced from lOmg/L to 0.26mg/L; pH≤3.00 was benificial to the ultrasonic degradation rate to atrazine and 2,4-D; When pH≥4.00, the change of degradation following pH value increasing was small comparatively; the effect of initial concentration, the volumn and the reaction time was great:the effect of initial concentration of 2,4-D was relatively large than atrazine's. Increasing that from 1mg/L to 100mg/L, the degradation of 2,4-D was dropped by about 50%; when the volumn was enhanced to 500mL from 100mL, the degradation of these two substances were both decreased by about 35%; the ultrasonic degradation of two substances could be decribed by first-order; aeration was not conducive to ultrasonic degradation and the degradation of atrazine was more dependent on the hydroxyl radical oxidation than 2,4-D; the optimum frequency of atrazine degradation was 200kHz while 2,4-D was 800kHz; the optimum power of atrazine and 2,4-D were both 90W; the synergy effect of multi-frequency ultrasonic was relatively obvious in initial 20min. But the effect would gradually weakened with time; changing the water quality and adding all kinds of sodium salt had a very small effect to atrazine and 2,4-D degradation, which indicated that the adaptability of ultrasound degradation to the change of water quality was relatively strong. radical scavenger tert-butanol had a significant inhibitory to atrazine and 2,4-D in that when the concentration of tert-butyl alcohol was up to 500mg/L, the degradation of these two substances were both decreased by about 50%. So the degradation of these two substances is mainly depended on radical oxidation;(2) Study the ultrasonic degradation of atrazine and 2,4-D mechanism by COD, TOC, ion chromatography, GC-MS and other technologies. Studies show that:there were deamination reactions and dechlorination reactions during the ultrasound treatment; after 120min there was 0.141mM NO3-in atrazine solution and 0.064mM Cl" in 2,4-D solution while in atrazine solution there was only 0.12mM Cl" detected by Ion Chromatography; in this process atrazine was turned into de-isoropyl-atrazine and de-ethyl-atrazine.2,4-D was turn into 1, 4-phenol as well as 2,4-dichlorophenol; their mineralization rates were very low;(3) Analyse and study the effect of ultrasonic enhancement technologies, especially the Fenton. The results show that:the addition of metal oxides had a negative effect on the ultrasonic degradation, of which ZnO was particularly noteworthy. Ultrasound/CuO combined technology didn't achieve expected effect in that the heterogeneous catalytic system don't apply for low concentration, more complex refractory organic pesticide substances; the most pleasant concentraion of H2O2 for adding in ultrasound system is about 166.5mg/L, above which the degradation of atrazine and 2,4-D degradation would turn down; atrazine removal was observed to behave as pseudo-first-order kinetics in Fe2+/ultrasound system. The optimum frequency of this system is both 200kHz, the power is 90 W and the optimum concentration of Fe2+is between 0.01g and 0.03g.