Preparations And Applications Of Polymeric Quaternary Ammonium Salt And N-halamine Modified Activated Carbons

Activated carbon (AC) has been widely used as an adsorbent in airpollution control and water treatment because of its large specific surface area,developed microporous structure, and a large number of chemical groups on thesurface. However, the drawback of carbon materials is their excellentbiocompatibility with bacteria. Bacteria may breed on carbon during the purificationprocess, thus eventually causing the carbon materials themselves to becomepollutants. Therefore, it would be advantageous if AC has the ability of killing air-orwater borne bacteria. In this thesis, two kinds of modified activated carbons werefirstly prepared by polymerizing cetyldimethyl[3-(trimethoxysilyl)propyl] ammoniumchloride and5,5-dimethyl-3-(3-triethoxysilylpropyl)hydantoin in situ.First, polysiloxane quaternary ammonium salt modified activated carbon(AAC) was prepared and analyzed by elemental analysis, x-ray photoelectronspectroscopy, zeta potential determination, and field emission scanning electronmicroscope. The results show that the surface potential of modified activated carbonshifted from-33.4mV to+43.8mV and the variation of its specific surface area wasrelated to the addition of acid and amount of quaternary ammonium groups graftedon the surface of activated carbon. The iodine adsorption value of Modified activatedcarbon increased from508.4mg/g to543.9mg/g and its methylene blue adsorptionvalue increased substantially from46.3mg/g to650.4mg/g. By comparing theadsorption of phenol and dichromate on modified activated carbon with one onuntreated activated carbon, we found that the adsorption capacity of phenol onmodified activated carbon did not decline and the adsorption capacity of dichromateon modified activated carbon increased substantially. With0.80g of untreatedactivated carbon added in20mL dichromate solution (100mg/L Cr6+), the removalrate was19%. However, under the same conditions, the removal rate for modified activated carbon was99%. Under continuous flowing water condition, it was foundthat polysiloxane quaternary ammonium salt absorbed on activated carbon leachedaway slowly in early time, but the quaternary ammonium salt content on activatedcarbon was kept constant at0.55×10-4mol/g after96h, which means thatpolysiloxane quaternary ammonium salt was firmly absorbed on activated carbon.The study indicates that the existence of polysiloxane quaternary ammonium salt onthe surface of activated carbon not only endues the activated carbon antimicrobialproperty, but also increases its adsorption capacity for some pollutants in water.Secondly, polysiloxane hydantoin modified activated carbon (MAC) wasprepared and analyzed by x-ray photoelectron spectroscopy, zeta potentialdetermination, and field emission scanning electron microscope. After chlorination,polysiloxane hydantoin on the surface of activated carbon was transferred topolysiloxane N-halamine which is biocidal. It was found that5,5-dimethyl-3-(3-triethoxysilylpropyl)hydantoin is easily hydrolyzed and thenpolymerized on the surface of activated carbon in situ under acidic condition. Theantimicrobial results showed that polysiloxane N-halamine modified activated carbonhad excellent antimicrobial property and could kill E.coli and S. aureus within10min.For the stability of polysiloxane N-halamine modified activated carbon in the air, itwas found that the absorbed hypochlorite on the surface of activated carboncompletely decomposed after6days, but the oxidative chlorine percentage(Cl+%) ofpolysiloxane N-halamine on activated carbon decreased only from0.38%to0.37%after21days, which means that polysiloxane N-halamine modified activated carbonhas very good stability in the air.