Adsorption And Desorption Properties Of PCP On Surfactant Modified LDH And Photocatalysis Property Of Its Calcined Products

A series of surfactant-modified layered double hydroxides (LDH) were synthesized as hydrophobic organics (HIOCs) adsorber. Its 500～-800℃calcined products were also synthesized as HIOCs photocatalyzer. The main contents of this thesis are as follows:Dodecylbenzensulfonate modified LDH:DBS-NiRTi (R refer to Ni/Ti ratios:3,4,5,6) and DBS-MⅡMⅢ/Ⅳ(MⅡMⅢ/Ⅳ:Mg3Al,Zn2Fe and Zn6Ti), and sodium dodecylsulfate modified LDH (DS-Ni5Ti) were prepared by one-step coprecipitation method.Cyanate-intercalated LDH (CNO-Ni5Ti) was obtained by using urea hydrolysis route.XRD,FT-IR, SEM, CA, BET, UV and XPS techniques are used to investigate the structure characteristics, morphology, composition, contanct angle, surface areas and other physicochemical properties of as-prepared products.The basal spacings of DBS-NiRTi and DBS-MⅡMⅢ/Ⅳare slightly larger than DS-Ni5Ti (2.89nm) and greatly larger than CNO-Ni5Ti (0.73nm) corresponding with the larger size of DBS anion.Based on the basal spacings of DBS-NiRTi (2.99～3.54nm) and the size of DBS,it can be inferred that the interlayer configurations of DBS-NiRTi samples probably involve three anionic stacking models:loosely anti-parallel perpendicular monolayer arrangement, anti-parallel perpendicular interpenetrating monolayer arrangement and anti-parallel tilted interpenetrating monolayer arrangement. The greatly enhanced contact angles (113.6～144.2°)and reduced surface areas(1.18～11.9 m2/g) of DBS-LDH nanocomposites related to the closely staking hydrophobic DBS chains in the LDH interlayer.The Linear model fits well for pentachlorophenol (PCP) adsorption isotherms on surfactant-modified LDH (R2>0.96),implying a partitioning sorption process.The PCP adsoption capacity of DBS-MⅡMⅢ/ⅣLDH (QeDBS-Ni5Ti>QeDBS-Zn6Ti>QeDBS-Zn2Fe>QeDBS-Mg3Al) has positive correlation with layer cation electronegativity. The PCP adsorption capacity of NiTi LDH with different interlayer anions (QeDBS-NiRTi> QeDs-Ni5Ti>QeCNO-Ni5Ti) is due to the greatly enhanced hydrophobic property of DBS-NiRTi.Among the DBS-NiRTi series, the highest PCP adsorption capacity of DBS-Ni5Ti (22.23mg/g) is not only related to the content of organic matter but also due to its loosely stacked interlayer anion arrangement more favoring the adsolubilization of PCP in the hydrophobic interlayer region.The media pH effect of PCP adsorption on DBS-Ni5Ti reveals an adsolubilization mechanism mainly upon hydrophobic effect and the electrostatic interaction contribute a little.The temperature effect of PCP adsorption on DBS-Ni5Ti reveals an exothermic adsorption nature, the reduce of the free energy is the impetus of the PCP adsorption.The desorption study shows an irreversible sorption process and thus possibly enables the immobilization of PCP on DBS-NiRTi nanocomposites as an effectively route to avoid the secondary pollution of PCP in environment.An adsolubilization mechanism model is tentatively proposed.A series of mixed metal oxides were prepared using DBS-Ni5Ti as precursors after calcination at 500～800℃.The crystal phase of NiO, Ni2TiO4 and NiTiO3 are gradually appeared, the crystallinity and size is increased with the increase of tempreture. Photodegradation properties show the UV-light activity originating from the synergistic contribution of NiO,Ni2Ti04 and NiTiO3.The photodegradation properties of calcinated product were preliminary studied. The results show that the photodegradation capacity is increased with the increase of tempreture corresponding with the increased content of NiTiO3 nanopaticles.