Study On The Treatment Of Pulping Medium Wastewater By Micro-electrolysis Combined With FENTON Oxidation-flocculation

Micro-electrolysis combined with Fenton oxidation-flocculation technics had obvious advantage compared with micro-electrolysis and Fenton oxidation and flocculation separately. Using scrap iron from iron machining mills as main material, Fe/C micro-electrolysis process had significance of"using waste to treat waste", in which a lot of Fe2+ were generated, that could be used in the following Fenton oxidation in order to save materials and reduce cost, and Fe3+ generated from Fenton oxidation can be in flocculation. The combined process conquered the disadvantage of high cost and low efficiency using a single unit, having perfect meanings not only in theory but also in practice.In this paper effect of factors on treatment of pulping medium wastewater by micro-electrolysis combined with fenton oxidation and flocculation were studied. Combining between each technics was also studied. And the kinetic model of Fenton oxidation for pulping medium wastewater was established.Firstly, single factor experiments were designed to optimize four selected influence factors which were aeration, pH, Fe/C and reaction time. the optimum conditions were concluded in this experiment: aeration was 6L/min, pH=4, Fe/C=4, and the reaction time was 30min under which The COD and colour removal rate was about 60.0% and 80.0%, respectively, and the concentration of Fe2+ was 157mg/L which offered Fe2+ to Fenton oxidation and reduced the cost. The same result was observed from UV spectrum in micro-electrolysis.Then using Fe2+ generated from micro-electrolysis, three factors including pH, H2O2 quantity and reaction time were studied in Fenton oxidation and the optimum condition was concluded which was pH=4, H2O2 (concentration was 30%) amount was 3mL/L and reaction time was 15min when no additional Fe2+. Under optimum condition, the COD and colour removal rate was about 59.0% and 56.0% separately and the optimum ratio of H2O2 (volume) and FeSO4 (quantity) was 1/52. When the additional FeSO4 quantity was 10mg/L under the same ratio, the result was better, the COD and colour removal rate were 83.0% and 74.0%, respectively. The concentration of Fe3+ was 217mg/L after fenton oxidation which offered abundant flocculants to following flocculation technic and reduced the cost. According to UV spectrum analysis, the same result can be concluded. It also can be concluded that pH in Fenton oxidation and in micro-electrolysis was the same. According to correlativity of COD removal rate and the reaction time at different concentration oxidant and catalyzer, the kinetic reaction equation was fitted as follows: d[COD]/dt=17.477exp(-14418/RT)[H2O2]0.2081 [FeSO4]0.5277Using Fe3+ generated from micro-electrolysis and Fenton oxidation, different flocculants were studied in order to research the most efficient and economic flocculants. Compared with COD and colour removal rate and the dosage of PAM PAC and active silicic acid, the optimum flocculant was selected as PAM. When pH=7, the dosage of PAM was 1.5mL/L, the COD and colour removal rate achieved 51.6% and 88.0% respectively, the effluent COD reduced to 41mg/L and colour reduced to 4 which was in conformity with the first level of wastewater discharge standard. UV spectrum showed that micro-electrolysis combined with Fenton oxidation-flocculation had significant advantage for contamination reduction..