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1、The catalyst of environmental catalysisMolecular chemisorption at manganese oxide/liquid interfaces has attracted increased interest due to its importance in the development of heterogeneous catalysts, microbial fuel cells and selective adsorption. Recently, inexpensive manganese oxide based catalys
2、ts instead of noble metal catalysts have been investigated in the catalytic wet oxidation (CWO) of phenolic wastewater. However, the adsorption of organic compounds on manganese oxide surfaces, which plays an important role in electron transfer and oxygen reduction, has not fully been explored. Phen
3、ol has attracted more attention in wastewater treatment because of its toxicity and wide occurrence in wastewater. Several conversion processes, currently under development for the production of synthetic fuel from coal, discharge substantial amounts of phenol (0.2-0.5g/L). Moreover, phenol is taken
4、 as a model compound for the study of adsorption and oxidation because phenol is an intermediate product in the oxidation of higher-molecular-weight aromatic compounds and phenol also converts to a series of intermediates on oxidation.Cryptomelane-type manganese oxide is an octahedral molecular siev
5、e (OMS) composed of 2x2 edge-shared Mn06 octahedral chains, which are corner shared to form onedimensional tunnels. Potassium ions and water are located in the tunnels (designated K-OMS-2). Mixed-valent manganese ions (Mn2+ and Mn3+) are situated in the octahedral sites of cryptomelane. Transition m
6、etal ions can be incorporated into the framework or tunnel sites. Sizes and charges of M determine which sites are occupied. The synthetic counterpart of metal ion doped cryptomelane is known asoctahedral molecular sieve M-K-OMS-2 (M doped metalions). In recent years, some work has been published on
7、 the syntheses of cryptomelane-type manganese oxides and their applications in the oxidation of benzene, carbon monoxide, and other hydrocarbons. K-OMS-2 was found to possess excellent hydrophobicity and strong affinity for volatile organic compounds in the oxidation of benzene. Little has been repo
8、rted on doping effects on the adsorption of substrates or on catalytic properties.This research focuses on structure-property relationships for doped cryptomelane. These doped porous cryptomelane materials have high surface areas (40-100m2/g), more oxygen vacancies compared with undoped K-OMS-2, and
9、 more surface bonded OH groups. The substitution of framework Mn2+ with bivalent (Cu2+) and trivalent ions (Co3+) can create more oxygen vacancies to maintain an overall charge. Surface bonded OH groups on OMS-2 react with solute molecules and increase the adsorption of phenolic compounds. Solute mo
10、lecules tend to attach to oxygen vacancies. Subsequently, electron and/or oxygen transfer between the metal oxide surfaces and solutes take place at these sites.Doped K-OMS-2 materials have dual roles in the removal of aqueous phenol, including adsorption and oxidation of phenol at moderate temperat
11、ures (298-423 K), pressures (80-150 psi), and pH (6-9). When phenol is adsorbed, phenol is oxidized to CO2 and H2O in the catalytic wet oxidation with oxygen. The advantages of this process over microbial activated sludge processes are that this process withstands high phenol loading rates and the f
12、luctuations in phenol loading and does not produce any biological sludge. We show that the chemisorbed phenolic compounds on doped K-OMS-2 can reach up to 2-5 times the weight of doped K-OMS-2. Compared with activated carbon (AC) adsorption, phenolic compounds on K-OMS-2 can be oxidized by oxygen or
13、 air with the catalysis of doped K-OMS-2 at 573 K. The products are CO2 and H2O. Doped K-OMS-2 adsorbent and catalysts are regenerated.The overall results in this research showed that doped M-K-OMS-2 catalysts had increased activity over that of undoped K-OMS-2 catalysts. Doped K-OMS-2 shows potenti
14、al application in the removal of aqueous phenol. Structure activity relationships provide some scientific background for the development of highly efficient and low cost heterogeneous catalysts for applications in wastewater treatment.Doping Effect on Adsorption and Oxidation of Phenol. M-K-OMS-2 do
15、ped with Co3+, Ce4+, and Cu2+ have greater adsorption of phenol and higher catalytic activity than that of undoped K-OMS-2. These doped OMS-2 catalysts have high BET surface areas (40-63 m2/g). High surface area generally increased the adsorption and activity. Other doping and structure factors desc
16、ribed here showed greater effects on the adsorption and oxidation than surface area. Although XRD patterns reveal that Co3+, Ce4+, and Cu2+ doped K-OMS-2 materials have the same 2x2 tunnel structure as K-OMS-2, the dopants make a distinct difference in the ability to adsorb and oxidize phenol. These metal ion dopants greatly enhance the adsorption properties and catalytic activities of the doped K-OMS-2 materials.Considering the structures, the doped ions either locate in the frame work to r
