Study Of Adsorption And Degradation Of Typical Dye In Dyeing Wastewater Using Noval Catalyst

The printing and dyeing wastewater contains many organic pollutans, which have the teratogenic, carcinogenic and mutagenic effects, and is difficult to biodegrade. Treatment of printing and dyeing wastewater is a significant environmental concern. The treatment of printing and dyeing wastewater has been a difficult problem in the water treatment industry. Because of its strong oxidation ability and fast reaction rate, Fenton oxidation has become the most promising treatment technology for the refractory orgnic wastewater.However, the homogeneous Fenton process has some drawbacks, including pH dependence of the system(2.5–4.0), the formation of iron sludges and large consumption of hydrogen peroxide. Thus,development of the heterogeneous Fenton catalysts represent a possible solution to overcoming the problems associated with homogeneous catalysis.In the present work, alkaline lignin, the byproduct from the production of pulp and paper industry, are used as the raw materials for preparation of new lignin-based magnetic carbon material(LMC) by impregnation and calcination method, developing the new route of value-added utilization of lignin. LMC can be used as a heterogeneous Fenton catalysts for catalytic degradation of dyeing wastewater.Firstly, LMC was prepared by simple impregnation and calcination method. Through the construction of different degradation system for Rhodamine B(RhB), it was found that the heterogeneous Fenton oxidation reaction system in the presence of LMC and H2O2 had the highest catalytic degradation performance for RhB. The effect of Fe2+concentration, oxalic acid concentration, immersion time, calcining temperature, and calcining time on the catalytic activity of LMC has been investigated, and the optimal preparation conditions of LMC catalyst was confirmed. The results showed that optimalconditions were: Fe2+ concentration 107 mmol/L, oxalic acid concentration 321 mmol/L,impregnation time 4 h, calcination temperature 900 ℃, calcination time 2 h. The degradation rate of RhB is nearly 100% using the LMC prepared under these optimal conditions. The surface morphology and phase composition of LMC were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS). The results show that the calcination temperature and calcination time have the important effect on the catalytic activity of LMC, and there are many kinds of iron oxides in the LMC microporous materials, such as FeO, Fe2O3, Fe3O4 and FeOOH.Secondly, the catalytic degradation of the simulated dye wastewater of RhB has been studied used LMC as heterogeneous catalyst, and the effect of pH, LMC dosage, H2O2 concentration and dye concentration has been investigated. The results show that the suitable degradation conditions for the dyeing wastewater were pH value 3, catalyst concentration 1 g/L, hydrogen peroxide concentration 8.56 mmol/L, RhB solution initial concentration 100 mg/L. The degradation rate of RhB is nearly 100% within 15 minutes under these optimal conditions. The recyclability of LMC catalyst was also tested. Only slightly decrease in activity was observed after the catalyst was recycled five times, and the dissolved iron ion concentration in aqueous solution was lower than pollutant emission limit value for industrial wastewater in EU, indicating that LMC can function as a stable catalyst.Finally, the mechanism of degradation of RhB has been explored. The degradation of RhB on LMC undergoes 3 steps, including: the formation of hydroxyl radical by the reaction of H2O2 and the iron oxides on the surface of LMC; the degradation of RhB with hydroxyl radical to small moleculars or CO2 and H2 O. In addition, the preparation cost of LMC catalyst is 7787 yuan per ton, having a good economic advantage in the actual industrial application process.