Palygorskite-based Composites With Enhanced Adsorption-photocatalytic Performance

The palygorskite minerals possess many extraordinary properties,such as huge specific surface area,high adsorption capacity,abundant surface active sites and so on.Therefore,based on theirs structure and morphology characteristics,the integrated system between mineral resource and material is established,which has attracted more and more attention on the research and development of silicate minerals in recent years.In china,palygorskite mineral resources are rich,but the level of theirs comprehensive utilization is too lower.Consequently,focused on the palygorskite mineral with a rod-like or fibrous microstructure,the thesis proposes the low cost preparation of palygorskite-based functional composites with high-performance.The main research results are as follows:1.Preparation of acidified palygorskite and its study on adsorption performance.The acidification of 6 mol L-1 hydrochloric acid resulted in stepwise dissolution of the octahedral cations in the crystal structure of palygorskite,but most of silicon oxygen tetrahedron still existed.The plate-like or massive aggregates were dissociated in the structure.The resulted crystal bundles were long and loose,which formed numberous void channels and effectively enlarged specific surface area.With electrostatic and ion exchange interaction,acidified palygorskite could adsorb more than 75%of aniline in solution.The whole adsorption process belonged to homogeneous monolayer adsorption,and it was a spontaneous chemical adsorption process.2.Synthesis of BiOI/acidified palygorskite composite and its research on adsorption-photocatalysis performance.The BiOI/acidified palygorskite photocatalytic functional composites had higher purity.The BiOI microspheres were uniformly dispersed on the surface of acidified palygorskite nanofibers,and there was strong interaction between the two crystals.Acid palygorskite could effectively increase specific surface area and acidity of the composite,thus greatly improved its adsorption properties.The catalyst had a strong absorption in visible region,and the absorption band edge was gradually blue shifted with the increase of the amount of acidified palygorskite.When the mass percentage of acidified palygorskite was 50%,the photocatalytic activity of the catalyst was excellent,and the removal rate of TOC was 88%.3.Preparation of Al-MCM-41 mesoporous material from palygorskite and its study on adsorption performance.Using acidified palygorskite as raw material,mesoporous molecular sieve Al-MCM-41 with highly ordered pore structure was successfully prepared.When the mass ratio of CTAB to SiO2 was 0.1,pH value of the gel was less than 7,the crystallization temperature was 110?,the crystallization time was 12 h,the structure rearrangement of palygorskite occured with hydrothermal and calcination treatment.The as-synthesized Al-MCM-41 material with obvious mesoporous features contained Al,Si and O elements.The BET specific surface area of the sample was up to 997 m2 g-1,and the pore volume was 0.82 cm3 g-1.The mesoporous molecular sieve Al-MCM-41 owned excellent adsorption performance for removal of basic fuchsin.The Langmuir adsorption isotherm and pseudo-first-order model could represent the whole adsorption process.4.In situ self-assembled synthesis of Ag-AgBr/Al-MCM-41 and its research on adsorption-photocatalysis performance.With acidified palygorskite as raw material,while mesoporous molecular sieve Al-MCM-41 was synthetized,the photocatalytic Ag-AgBr active particles were successfully installed into Al-MCM-41.The Ag-AgBr/Al-MCM-41 composites with excellent adsorption-photocatalytic performance were obtained.A large number of Ag-AgBr active grains were self-assembled on the surface of Al-MCM-41 and partly into their mesoporous channels,which did not destroy the highly ordered mesoporous features of the original carrier.50%Ag-AgBr/Al-MCM-41 sample had BET specific surface area of160.69 m2 g-1,and pore volume of 0.27 cm3 g-1.The composite photocatalytic system had strong absorption in the visible region,which could greatly inhibit the carrier recombination.The composites possessed higher adsorption-photocatalytic activity,which could remove 98%of fuchsin,99%of crystal violet and 90%of aniline in water.