| Textile and dyeing wastewaters are important sources of the refractory organic wastewaters. More than2000chemicals (dyes and agents) are used in textile industry, and20%of these are discharged in textile industrial effluents without pretreatment. Large amounts of inorganic salts (such as copper sulfate) and surfactants exist simultaneous with dyes in water, which come from the processes of the solidation of color and uniform the blooming. Textile effulents with low penetrations, high toxicity. and high COD has been focused on, not only for toxic to human beings but also for the resistant of photosynthesis.Advanced oxidation processes (AOPs) have been considered a green efficient method, coping with organics in wastewater. Fenton is a kind of AOPs, consisting of Fe2+species and hydrogen peroxide. Under acidic conditions, H2O2can be catalyzed decompose, generating hydroxyl radicals(-OH), which is the most oxidizing chemical species except fluorine atoms. Hydroxyl radical is such a powerful species for the non-selectively in water to oxidize organics, and the oxidation potential has been estimated as2.78and1.90V at pH0and14. respectively. Hydroxyl radicals can also abstract one hydrogen atom from hydrocarbons and other organic substrates, under the condition that the hydrogen bond to be broken has bond energy lower than109kcal/mol. which is the energy of the H-O bond energy.-OH is considered a general oxidant which is able to attack any kind of organics. Fenton is considered a benignity process, with a minimum dosage of reagents used and all transition metals used in Fenton process were environmental friendly, but with drawbacks of the comsumption of a large amount of Fe salts, iron sludge generated after the reaction as a kind of second pollution. Also, catalyst used in Fenton is hard to be recovered and reused, leading to a waste of reagents. Heterogeneous Fenton established using solid catalyst is a promising alternative to solve or minimize these problems in traditional Fenton system.Heterogeneous Fenton has been focused on for waterwater treatment. It is effect in dissolving the disadvantages of traditional Fenton, such as the impossible of the recycling of catalysts, generation of iron sludge, and small pH window. Heterogeneous Fenton catalyzed by metal loaded catalysts has already been focused on, but with drawbacks of slow reaction rate and the introduction of extra energies, such as sonic, ultraviolet. In this study, Ferrocene(Fc) and FeFe-LDH were occupied as catalyst to establish new heterogeneous Fenton systems. Fc which possesses electron donor-acceptor conjugated structure is of good oxidation redox character, catalytic activity and stability. FeFe-LDH with layered structure is of large surface area, and it can be easily prepared. The ferrous and ferric ion in FeFe-LDHs is of good catalytic activity. Thus, both Fc and FeFe-LDH can be used as catalyst to establish heterogeneous Fenton processes. The main research contents and conclusions are listed as follows:(1) Fc was verified to be of good reversible redox characteristic, and H2O2can be catalyzed to decompose, forming hydroxyl radicals(-OH), effectively. Based on the characters of Fc mentioned above, Fc was occupied to establish the new heterogeneous Fenton-Fc/Fenton. The optimal condition was determined to be pH3,0.372g/L Fc,23.58mmol/L H2O2at30??100%discoloration was reached at120min, with63.75%COD removed.(2) Mechanism of Fc/Fenton reaction and the degradation pathways of Methylene Blue was proposed, and the reaction active energy was determined to be82.708kJ/mol. pH decreased as MB degraded and Benzothiazole was detected. MB degraded in three pathways simultaneously:Cl was first removed from MB, and the the residual structure decomposed in two ways:oxalic acid and benzothiazole generated after the removal of methyl and the broken of C-N and S-C Benzenesulfonic acid and phenol generated after the broken of C-N in residual structure, the oxidation of S and the removal of methyl and amino; macromolecular compounds generated as the connection of-OH and-SO3to the residual structure. Finally, all the intermediates were oxidized to CO2and H2O.(3) The effects of inorganics including NaCl, Na2S, Na2SO4, Na2CO3, CUSO4and surfactants including PVA, SDBS and Tween-80on the efficiency of Fc/Fenton was investigated. The results indicated that the degradation of MB in Fc/Fenton was accelerated with the addition of low concentrations of CUSO4and PVA, but resisted with the addition of NaCl, Na2S. Na2SO4, Na2CO3, SDBS and Tween-80.(4) Two methods were proposed in order to enhance the efficiency of Fc/Fenton. The results indicated that the degradation of MB can be accelerated with the presence of low concentraitons of Oxalic acid or adding H2O2in multi-steps.(5) The mechanisms of the adsorptive removal of MB and the simultaneous adsorptive removal of MB and Cu2+on to ferrocene mofied cation exchange resin(FMCER) were proposed. The adsorption capacity of MB was improved a lot and the pH window for the adsorption of MB onto resin was expanded from2-4to2-12. MB and Cu2+in water can be removed effectively using FMCER. The adsorption of MB and Cu2+on FMCER were physicosorptive, and4-5is optimum.(6) FeFe-LDH, which can catalyzed the decompositon of H2O2to from·OH was synthesized, was used as catalyst to establish a new kind of heterogeneous Fenton. The degradation of MB in FeFe-LDH/Fenton indicated that FeFe-LDH is of good stability and high efficiency. The catalysis activatity was improved as the [Fe2+]/[Fe3+] increased in preparation. The optimal condition was pH3, and the degradation of MB can be accelerated by increasing the dosage of FeFe-LDH.(7) Mechanism of the degradation of MB in FeFe-LDH/Fenton process was proposed. pH of solution decreased as MB degraded, and Pleiocarpamine. DL-Norleucine and Benzothiazole that have rarely been detected previously were observed. MB decomposed through three pathways simultaneously. Cl and methyl were first removed from MB, and then C-N and S-C in the residual structure broken: phenol and DL-Norleucine generated; oxalic acid and benzothiazole generated; DL-Norleucine reacted with benzothiazole after-NH3been removed, to from pleiocarpamine. |
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