Study On Sonochemical Degradation Of Dyes Wastewater And Its Strengthened Approaches

Organic dyes are the largest group of pollutants in wastewater produced from textile and other industrial process. Since dyes are hardly removable due to their high toxicity, complex composition and biorefractory. Therefore, many researchers have paid more attention to the sonochemical technique recently, a kind of advanced-oxidation water treatment technology which is applied to degrade the toxic and biorefractory organic compounds. Sonochemistry degradation mechanism of dyes in US system was discussed in this paper, the effects of pH, ultrasonic energy intensity and sonication time on the process were investigated. Sonochemical degradation intermediates of dyes were found by means of Ultra Spectrograph and UV-Vis Spectrograph, the possible sonochemical degradation pathway was deduced, and available reaction kinetics model have been developed. Main work and innovation can be drawn as follows:(1) Sonochemical degradation of cationic dye Crystal Violet was studied in this paper. The decolorization rate of CV reached up to 97.8% in 50 min and COD removal was 80.8% in 80 min at: initial concentration 30 mg/L, pH8.0, ultrasonic energy intensity 47.5 W/cm² and medium temperature 25℃. The possible pathway of sonochemical degradation CV was deduced by means of UV-Vis Spectrograph, conjugate chromophores in the molecule of CV were broken to some small residual compounds firstly, main intermediates included benzene loop et al., final products were carbon dioxide acetic acid and so on. The degradation rate equation was established: dc/dt=-K₁c =(-10^-6ρ² + 0.0047ρ -0.0421)c, these results indicated that the process of ultrasound degradation of CV follows the first-order reaction.(2) Sonochemistry degradation of Butyl rhodamine B in US/Manganese Dioxide (MnO₂) system was studied. The decoloration rate of 10 mg/L dye solution reached up to 98.7% in 48 minutes at: pH3.0, ultrasonic energy intensity 40.7W/cm², and the feeding amount of MnO₂ is 1.6g/L. The results showed that the MnO₂ specific surface area after sonochemistry degradation was 11.5 times than before. The relationbetween reaction rate constant and pH was: K=-0.0056(pH)²+0.0043pH+0.0933,R²=0.9995.The structure of benzene loop was broken to some small residual compounds. The degradation rate equation was established: dc/d^/fcf(p)fi[OT)c===-(-0.0014ρ²+0.1254ρ-1.6044)·e^0.3189m·c, these results indicated that the process of ultrasound degradation of Butyl rhodamine B follows the first-order reaction.(3) Sonochemistry degradation of reactive brilliant red X-3B in US/magnesium (Mg) system was studied. The results indicated that the decoloration rate of 20 mg/ L dye solution reached up to 98.6% in 48 min under the conditions: pH3.5, ultrasonic energy intensity 54.3 W/cm², and the feeding amount of Mg 2.1g/L. Through Ultra Spectrograph and UV-Vis Spectrograph, the structure of benzene loop and naphthalene loop were broken to some small residual compounds. The degradation rate equation was established: dc/dt= - kf(ρ)f(m) c = - 0.0333 (ρ-24.60 )·e^1.0705·c, the process of ultrasound degradation of reactive brilliant red X-3B follows the first-order reaction.(4) Sonochemistry degradation of Direct fast blue B₂R_L in US/H₂O₂ system was studied. The table of four factors and ten levels was designed according uniform design table U10*(10⁸), imitate non-linearity regression equation by SPSS 11.0 for windows software. Optimum value of every factor was obtained by multi-differential analysis. Optimal decoloration rate reached up to 97.3%. The quantity of OH was determined by the iodometric method, the results showed that the quantity of ·OH increasing with time linearity in US/ H₂O₂ system.(5) This paper mainly studied and explored several technologies such as the methods of ultrasonic (US), US/H₂O₂ and US/MnO₂ for the treatment of practical dyes wastewater, the treatment performance was characterized with the COD removal and decoloration rate of dyes. Among the various treatment methods of practical dyes wastewater, US/MnO₂ synergetic technology appeared to be more efficient for the treatment of dyes wastewater in decoloration rate and mineralization degree, the decoloration rate reached up to 97.1% and the COD removal was 90.8% in 48 min. US/H₂O₂ synergetic technology appeared to be better, the decoloration rate reached up to 86.5% and the COD removal was 80.8% in 48 min.