Metal-chelating character of wastewater generated from metal-complex dye manufacturing processes: Using chelated iron concentration to evaluate the removal efficiency of chelating functional group and treatment options

• Main Authors: Li-Wei Chang, 張立瑋
• Other Authors: Chi-Wang Li
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/16289395682446665980

碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 100 === In this study, Dye manufacturing processes wastewater (DMPW) is the effluent generated from synthesizing process of dyes, consisting of intermediated compounds, monomer structure, and dyes molecules. Coagulation is found to be an inefficient process for removing organic matters. Color of treated water is increased with the decreasing coagulation pH. Measured dissolved iron after coagulation allowed one to evaluate the content of functional groups of organics which can chelate iron from coagulant. Organic removal efficiency is also not very well when pre-precipitated ferric hydroxide was used as adsorbent. It is concluded that DMPW contains hydrophilic functional groups as the result that coagulation is not able to remove the most of the organic matters. One feature of DMPW is its metal-chelating ability. The C/chelated-Fe3+ molar ratio is used to explore the destruction of chelating functional groups after various treatment processes. The C/chelated-Fe3+ molar ratios of raw DMPW, biologically- treated DMPW, and thermo-persulfate treated DMPW are 15, 29, and 13, respectively. Since chelating functional groups and TOC were reduced after biological treatment, biological treatment process can be employed as a pretreatment process to improve degradation efficiency of DMPW. In this study, the chelating characteristic of DMPW was exploited with Homogeneous Fenton-like process being tested. The potential of chelating functional groups to enhance oxidation efficient in the Fe(III)/H2O2 system under neutral pH condition was compared with the same process at pH 3. Our results show that the trend of residual hydrogen peroxide concentration in neutral and acidic pHs were the same during a 3-hr reaction. A higher degree of organic matters and colour removal were observed at pH3. The removal efficiencies of TOC are 20% and 5% under pH 3 and pH 7 conditions, respectively, while the removal efficiencies of color are 70% and 10%, respectively. Under pH 7 condition, unchelated ferrous ions are oxidized to ferric ions gradually, and ferric ions form complexes (Fe2O3．nH2O) and precipitate as ferric hydroxide. The precipitated ferric ions could not be used efficiently in Fenton cycle.