| Due to rich resources and special physical and chemical properties,the(chain)layered structure silicate minerals(CLSSMs)have been widely used in many fields.Organically modified CLSSMs and organic-inorganic fluorescent CLSSM composites have been a significant research field.However,further studies are needed on the adsorption mechanism of organic molecules on CLSSMs.In this thesis,several typical CLSSMs were applied to adsorb cationic surfactants,the effect of different structures of minerals on the adsorption performance were studied.Adsorption experiments of montmorillonite(MMT)and sepiolite(SEP)on organic cationic surfactants of different chain lengths were carried out,and the effect of chain lengths on the adsorption performance was discussed.By means of thermal analysis,it was found that the adsorption sites of short-chain organic cationic surfactants on expandable layered structure silicate minerals included layer surface and interlayer space;and that the adsorption sites on chain layered structure silicate minerals included surface and channels.For the adsorption of cationic surfactants onto MMT,it was found that the driving force of adsorption was mainly electrostatic attraction at low concentrations;while under the condition of high concentrations,the main driving force of adsorption was the hydrophobic interaction and repulsion between organic molecules.The longer the chain length,the easier the organic cations enter the interlayer,the greater the amount of adsorption.For the adsorption of cationic surfactants onto SEP,it was found that the adsorption was surface adsorption at low concentrations driven by electrostatic attraction;while under the condition of high concentrations,the surfactants could enter the channels of sepiolite caused by intermolecular forces.The longer the chain length,the less likely it is to enter the channel.Secondly,a series of new functional materials of organic luminescent molecules/CLSSMs were constructed.The adsorption behavior of lucigenin(BNMA)on typical CLSSMs was investigated.The relationship between the adsorption capacity and the luminescence properties of the composites were studied.The effect of adsorption sites on CLSSMs on the luminescent properties of BNMA were explored through experimental characterizations and molecular dynamics simulations.Unlike organic cationic surfactants,the adsorption of BNMA on layered structure silicate minerals was mainly caused by electrostatic attraction and ion exchanges,and the intermolecular forces have little impact on the amount of adsorption.Whereas,its adsorption on chain layered structure silicate minerals was mainly driven by surface electrostatic force.The adsorption of BNMA on MMT,kaolinite(KLN)and halloysite(HAL)conformed to the Langmuir adsorption isotherm,while its adsorption on rectorite(REC),SEP and palygorskite(PAL)corresponded to the Freundlich adsorption isotherm,and the adsorption kinetic results fitted Pseudo-second-order kinetics model well.By comparing the adsorption of BNMA on silicate minerals of different structures,it was found that the interlayer adsorption or pore adsorption was beneficial to the increase of the adsorption amount,but the surface adsorption of BNMA on the minerals was more conducive to the inhibition of fluorescentquenching.The inhibition of fluorescent quenching of BNMA by CLSSMs is firstly due to the surface-fixation of BNMA molecules,and secondly due to the dispersion of BNMA molecules by minerals.Comprehensively comparing the adsorption amount and the luminous intensity,halloysite was the most effective in inhibiting fluorescent quenching of BNMA out of the six minerals.Finally,the application of organic luminescent dyes/SEP composite was investigated.It was found that the content of phenol could be detected by the fluorescent quenching of BNMA/SEP and the detection limit could reach 0.1 ?mol/L.The test paper prepared by a combination of BNMA/SEP and rhodamine B/SEP could qualitatively detect the phenol concentration of the solution in the range of 5-500mmol/L. |
PDF Full Text Request