Study On The Preparation And Catalytic Performance Of Hierarchical Pore Melamine Resin-metal Composite Membrane

Phenolic pollutants mainly occured in the terrestrial and aquatic environments due to wide usage of pesticides,pharmaceutical products and chemical raw materials,which were synthesized and manufactured in great part by phenolic micro-pollutants compounds.Chlorophenol organic compounds are harmful to human beings directly or indirectly.The catalytic reduction method has the advantages of high efficiency,good economy and elimination of second-pollution on the removal of chlorophenols compounds.It shows great potential for practical environmental protection.Hierarchical porous materials loaded with noble metal nanoparticles are often used to catalytically degrade phenolic contaminants in water due to their high surface area and high mass transfer efficiency,but they they often have difficulty in recovery.Membrane separation has the advantages of simple operation and low cost and has been widely used in the field of catalysis,particular in membrane reactor.In this article,through combining the advantages of advanced hierarchical porous polymers?ah-PMF?and membrane,a new type of hierarchical porous melamine resin filled metal composite membrane?ah-PMF-NF?was successful prepared by high internal phase emulsion polymerization.On the one hand,the lower-level micropores structure within the material significantly increases the surface area of the material,providing a large number of adsorption sites for metal ions.On the other hand,the higher-level macroporous and mesoporous structures assist the mass transport of the material in the course of the reaction.Hierarchical porous catalytic membranes?Pd@ah-PMF-NF and Ag@ah-PMF-NF?were prepared by adsorption and reduction of palladium ion and silver ion.Two typical phenolic pollutants,p-nitrophenol?4-NP?and p-chlorophenol?4-CP?,were selected as target pollutants.The catalytic performance of the catalytic membrane was studied by static immersion and dynamic filtration.The preparation method of catalytic membrane?Pd@ah-PMF-NF and Ag@ah-PMF-NF membrane?was proposed.The catalytic membrane was applied to catalytic degradation of phenolic pollutants?4-NP and 4-CP?in water.The catalytic membrane was characterized by scanning electron microscope?FESEM?,surface area analyzer?BET?thermogravimetric analyzer?TG?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?.The results show that the Pd@ah-PMF-NF and Ag@ah-PMF-NF composite catalytic membranes was found to exhibit good catalytic activity in the hydrogenation of 4-NP to 4-AP with a conversion of 99%within half an hour in the presence of sodium borohydride at room temperature under continuous flow reaction conditions,the reaction rate constant reached 2.78×10^-3s^-1 and 4.7×10^-3 s^-1,respectively.For 4-CP,the conversion rate of Pd@ah-PMF-NF composite catalytic membrane reached 99%under continuous flow reaction conditions and room temperature in 5 hours.Compared to melamine resin powders,the Pd@ah-PMF-NF composite catalytic membranes show excellent features such as superior activity,convenient recovery,and reusability when it was used for catalyzing environmental pollutants.