| At present, dye pollutant from dyestuffs and textile industry has become a major issue water pollution in many countries. Having high degradation rates, advanced oxidation processes as a valuable technology for the efficient degradation of dyes have received numerous attention. While some oxidation processes have some shortcoming, such as, high processing costs, and may bring secondary pollution. In the treatment of dye, due to the powerful simplicity to control, benign reaction conditions and oxidizing property, the Fenton reaction has special advantages. But the traditional Fenton reagents shows several shortcoming such as causing the secondary pollution and narrow working p H value, which limit its application. Therefore, there is urgent needs to develop recycleable and p H-tolerant Fenton-like catalytic materials to removing dyes from wastewater more efficient and eco-friendly.Due to the good chemical stability, cuprous oxide has been widely used as catalysts in green chemistry, organic synthesis and environmental treatment. Lately, cuprous oxide has received numerous attention using H2O2 as oxidant in some catalytic systems. We have developed a method to prepare the cuprous oxide having a particle diameter of less than 10 nm in DMSO solution. This method takes advantage of the property that a specific complex can generated between the DMSO and the copper ions. Based on this principle, a solid state reaction method for preparing nano cuprous oxide has been developed.The activity of Cu2 O on dye removal was studied using a ordinary azo dye Acid Red G(AR1) as the target in the presence of H2O2. Cu2O/H2O2 system exhibited good regeneration performance and wonderful ability on dye removal. The effects factors were discussed, such as temperature, p H, Na Cl, dye concentration and oxidant concentration. EPR analysis proved hydroxyl radical(HO?) not to be the dominated reactive species in the catalysis. This Cu2O/H2O2 catalytic system can ran at a wide p H range from alkaline to acidic and lower p H brought higher oxidation rate. This result is different from the general Fenton system which work only at the p H lower than 3. The Cu2O/H2O2 system can also efficiently degradate all sorts of dyes, including C. I. Reactive Red 2, C. I. Basic Green 4, C. I. Acid Red 1(AR1), and Rhodamine B.Our team note that dyes is mainly used for fiber dyeing in the textile industry, and the fixation and enrichment processes of dyes from solution to fiber in short time is the mechanism of dyeing.Our team proposed that a new method in previous study, “phase transfer in situ catalytic oxidation,” which is based on fiber supported MPcs(catalytic functional fiber), can be applied to eliminate various dyes. Because fibers have a high natural affinity to dyes by chemical and physical interaction, dyes can be adsorbed or enriched onto the fiber, and be oxidized effectively and rapidly in situ at the interior and surface of fiber. This method combines AOPs and common adsorption together.A novel catalytic fibers was constructed based on the combination of high catalytic activity of Fenton reagents Cu2 O and the fibers’ specific structural characteristics together. Since the prepared Cu2 O particles size is less than 10 nm, we mixed this Cu2 O with PAN in DMF solution, and prepared the heterogeneous catalyst Cu2O/PAN nanofibers(Cu2O/PANNF) by the electrostatic spinning method. The catalytic activity of catalytic fibers was investigated with H2O2 as oxidant and dyes as probe compounds.The activity of Cu2O/PANNF/H2O2 system on dye removal was investigated using AR1 as the target in the presence of H2O2. Cu2O/PANNF/H2O2 system also exhibited fine ability on dye degradation with good regeneration performance. The effects factors were discussed, including temperature, p H, Na Cl, dye concentration and oxidant concentration. EPR analysis proved peroxy radicals(HOO?) to be the dominated reactive species in the catalysis. This Cu2O/PANNF catalytic reaction can ran at a wide p H range from alkaline to acidic in the Cu2O/PANNF/H2O2 catalytic system and lower p H brought higher oxidation rate. This result was distinct from the traditional Fenton system. In repetitive test cycles, Cu2O/PANNF remains efficient with no significant decrease of catalytic activity and is stable, causes no secondary pollution. The Cu2O/PANNF/H2O2 system could proceed over a wider range of p H values from alkaline to acidic, indicating that it could enlarge the p H range effectively. The Cu2O/PANNF/H2O2 system can also efficiently degradate various dyes, such as C. I. Basic Green 4, C. I. Reactive Red 2, C. I. Acid Red 1(AR1), Rhodamine B.Furthermore, in dye removal, the Cu2O/PANNF showed high efficiency in the presence of Na Cl, which wasn’t similar to some ordinary Fenton catalytic reactions. For the current catalytic oxidation, the Na Cl is an accelerant and has positive effect on this systems. The positive effect of Na Cl was studied followed by the interaction between the Na Cl and PAN nanofibers, which revealed PAN carriers played the key role on the catalytic oxidation. In the presence of fibers, the Cu2O/PANNF catalysts system with Na Cl exhitited higher efficiency than the system without Na Cl mainly by enriching dyes. Therefore, for this system to be used practically, it is an outstanding advantage.Since the Cu2 O is embedded in PAN nanofibers, hydrogen peroxide was catalyzed by the Cu2 O in PAN matrix. PAN cyano has a significant impact on the cleavage of hydrogen peroxide for the strong electron-withdrawing properties. Catalyzed by Cu2 O, the hydrogen peroxide in water solution occurred homolytic bond cleavage to generate hydroxyl radicals. Due to the cyano group strong influence of the electron withdrawing, the hydrogen peroxide in PAN occurred heterolytic bond cleavage to generate peroxy radicals.This study provides a facile suspension and solid phase method for the synthesis of surfactants-free Cu2 O nanoparticles at high precursor quantity. Experimental results prove that DMSO played a surface passivation role in the formation of Cu2 O nanoparticles. In this reaction system, to reduce the amount of DMSO has little impact on the size of the product. The methods provide a useful reference for the preparation of other nanoparticles.With a full understanding of the interactions among PAN nanofibers, the additives and organic dyes, the study reveals the key role of PAN matrix in cooperative catalysis and further set a excellent example for the optimization and design of the catalyst via well controlling the supports. This study remove the obstacles that limits the widespread application of Fenton-like catalyst due to its difficult recovery and petty working p H value. |
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