Experimental Study On The Synergistic Effect Of ICWPO And Photocatalytic Process On Dye Wastewater

Printing and dyeing wastewater is one kind of the main harmful industrial wastewater in China. In the past years, large numbers of persistent organic pollutants into wastewater with the widely application of new additives, the substrates in the wastewater tend to be anti-photolysis, anti-oxidation and biodegradation resistance. Currently, the feasible methods to the dye wastewater include biologic, chemical and physical-chemical technologies, and the traditional biochemical treatment is difficult to get a desirable result. Chemical oxidation has a bright prospect because of its high-efficiency and stability when it presents as the heterogeneous catalytic wet oxidation. However, the high cost and the harsh reaction conditions hinder its further applications. To enhance its effectiveness and practicality in the mild reaction conditions, researchers employed H2O2 reagent as an oxidant in the treatment of dye substrate, and created catalytic wet peroxide oxidation.The loaded active metals improve the catalytic activity, stability, and the specific adsorption performance of catalyst. And it can also accelerate the whole reaction efficiency. In recent few years, there has been an increasing interest in the combination of two or more active metal oxides for the composite metal oxides. It is of great importance on the heterogeneous reaction under normal temperature and pressure by preparing composite catalyst with sponge iron wrapped and active metals loaded.The magnetic or electrically conductive material will be induction heating with the high frequency AMF, while the non-magnetic materials are not heated directly. We combined the advanced organic wastewater treatment with high frequency AMF and applied composite catalyst having a magnetic core. In this process, the energy directly acts on the dispersive particles rather than the intermediate transfer pathway of aqueous phase. And the energy conversion is focused on the actual micro reaction sites by adding induction features of dispersed catalytic particles. In this work, we prepare specific composite catalysts presenting induction heating property and evaluate the performance of the new catalysts in the treatment of the dye substrate by iCWPO mode. And we combined this system with UV- Fenton to treat dye wastewater collaboratively. The main conclusions are as follows:(1) Three kinds of transition metals had been used as active component which were La, Mn, Ni to prepare the supported catalysts Mn-Ni/C、Mn-La/C、Ni-La/C、 Mn-Ni-La/C in which carbon coated sponge iron were used as carrier. To characterize the morphology and structure of catalyst, we conduct that, sponge iron, with good properties of magnetic thermal, has obvious fold and pore structure with large pore size and uneven distribution. And its main components are Fe and FexOy. Activated-carbon coated sponge iron is tightly arranged. As a result, the originated pore was covered by carbon layer, providing favorable conditions for loading active metals. The specific surface morphology of supported catalysts, whose surface are luster and rougher than original sponge iron, with significant stratification and uniform pore distribution.(2) We coated sponge iron with iron/carbon ratio (F/C) 4:1 three times. And the optimum preparation conditions of catalysts for the volume ratio of 1 to 1,0.02 mol/L La, Mn, Ni nitrate for metal pickling liquid, calcination at 300℃ for 2 h.(3) In iCWPO technology for low concentration wastewater treatment at normal temperature and atmospheric pressure system, the removal rate of direct blue D-3GL can be as high as 98.39%, the treatment efficiency of direct violet D-BL was 97.56% and direct Scarlet D-GLN’s removal rate reached 92.18%.The results showed that the catalyst of Mn-Ni-La/C has good catalytic activity at ambient temperature and pressure. This iCWPO system is economic and high-efficient, and promotes the degradation of dye molecules via the formed high micro-reaction interface temperature with lower power consumption, lower aqueous temperature and simple equipment.(4) Heterogeneous photocatalytic reaction system of UV/Mn2+-Fe3+/H2O2 was applied to treat azo dyes wastewater. UV, H2O2 and metal ions have good synergistic catalytic effect in a homogeneous reaction system. And the metal onions play a role of excitation and transmission function to continue the chain reaction until exhausted H2O2. Under 20 w UV irradiation, Mn2+ and Fe3+ concentration of 3mmol, H2O2 concentration of 10 ml/L and an irradiation time of 20 min, the removal capability on direct scarlet D-GLN was above 90%.(5) Combined iCWPO with UV/Mn2+-Fe3+/H2O2 system to treat high concentration refractory pollutants collaboratively, its synergy effect for treating azo dyes simulated wastewater was discussed. With the initial mass concentration of 600 mg/L,4 w UV irradiation time of 60 min, Mn2+and Fe3+ concentration of 1 mmol, H2O2 concentration of 5 ml/L,the removal rates of chromaticity and COD were 90.46% and 80.14% on direct violet D-BL, the treatment efficiency of chromaticity and COD could be reached as high as 94.83%、87.53% on direct blue D-3GL and the removal rates of chromaticity and COD could be reached as 91.35%、82.47% on direct Scarlet D-GLN. This comprehensive system can destruct the conjugated chromopgore of dye molecules completely, and improve the biodegradability of wastewater.