Study On Treatment Of Amaranth Wastewater By Ozone Oxidation In A Rotating Zigzag Bed

Printing and dyeing wastewater usually contains a large amount of dyes and and their derivatives.It has the characteristics of darker color,higher COD value,poor biodegradability as well as toxicity and teratogenicity.Therefore,the treatment of printing and dyeing wastewater is one of the important challenges facing the textile industry,and the development of efficient treatment methods for printing and dyeing wastewater has also become a research hotspot in the field of industrial wastewater treatment.Rotating zigzag bed(rotating zigzag bed,referred to as RZB)is a new type of high gravity equipment,which has the advantages of longer gas-liquid contact time.This thesis combines it with the O3 oxidation process and applies it to the treatment of amaranth dye wastewater in order to seek an efficient printing and dyeing wastewater treatment process.This thesis used RZB as the reactor to study the influence of different operating conditions in the O3,O3/H2O2 and O3/Fe2+ processes on the degradation effect of the simulated amaranth wastewater.The suitable operating conditions were determined and the degradation mechanism was investigated.The research results are as follows:1.The O3 process was used to treat the amaranth wastewater in the onestage and two-stage RZB and the operating conditions were determined.Experiment results indicate that when the initial amaranth concentration was 500 mg/L,initial O3 concentration was 30 mg/L,pH was 6.5,RZB rotating speed was 800 rpm,gas flow rate was 1.0 L/min,and liquid flow rate was 0.3L/min,the amaranth decolorization,COD degradation,and ozone absorption percentages in the one-stage RZB reached 62.5%,10.6%,and 62.9%,respectively;the amaranth decolorization,COD degradation and ozone absorption percentages in the secondary two-stage RZB achieved 84.9%,15.8%,and 83.6%,respectively.2.The O3/H2O2 process was applied to the treatment of the amaranth wastewater in the one-stage and two-stage RZB and the suitable operating conditions were determined.The experimental results show that when the initial amaranth concentration was 500 mg/L,initial O3 concentration was 30 mg/L,molar ratio of ozone to hydrogen peroxide was 2,pH was 6.5,RZB rotating speed was 800 rpm,gas flow rate was 1.0 L/min,and liquid flow rate was 0.3L/min,the amaranth decolorization,COD degradation and ozone absorption percentages in the one-stage RZB reached 70.0%,11.3%and 65.5%,respectively;the amaranth decolorization,COD degradation and ozone absorption percentages in the two-stage RZB achieved 90.5%,16.4%,86.0%,respectively.3.The O3/Fe2+ process was employed for the treatment of the amaranth wastewater in the one-stage and two-stage RZB and the suitable operating conditions were determined.The experimental results reveal that when the initial amaranth concentration of amaranth was 500 mg/L,initial O3 concentration was 30 mg/L,Fe2+ concentration was 0.6 mmol/L,pH was 6.5,RZB rotating speed was 800 rpm,gas flow rate was 1.0 L/min,and liquid flow rate was 0.3 L/min,the amaranth decolorization,COD degradation and ozone absorption percentages in the one-stage RZB was 80.1%,11.5%and 69.8%,respectively;those data in the two-stage RZB reached 93.8%,16.9%,91.3%,respectively.4.By a comparison of the amaranth decolorization,COD degradation and ozone absorption percentages in the one-stage and two-stage RZB,it can be found that the two-stage RZB exhibited a better treatment effect.5.The degradation mechanism of amaranth was elucidated by UV-vis and LC-MS analyses of the amaranth wastewater degraded by the O3 process Firstly,O3 or ·OH attacks the "-N=N-" in the amaranth molecule,causing the chromophore group to break,and the solution gradually fades;secondly,the amino and sulfonic acid groups on the naphthalene ring in the molecule are destroyed and substituted,and finally the naphthalene ring and benzene ring are broken to form small molecular acids,which are eventually mineralized into CO2 and H2O.