The Wettability And Adsorption Property Of Series Of Vermiculites Modified By Bis-N-heterocyclic Quaternary Ammonium Salts

Wettability is one of the important surface properties,and it is of great theoretical significance and practical value to understand the change of surface wettability in-depth.Based on the factors of wettability,this dissertation starts with the structure of bis-quaternary ammonium salt and chooses the vermiculite（Vt）as matrix,prepares and characterizes the microstructure of series of organo-vermiculites（organo-Vts）,and investigates the adsorption behavior and mechanism of the modifier on Vt.And the influences of the layer charge of Vt,and the head group,spacer group as well as alkyl chain length of bis-quaternary ammonium salts on the wettability and adsorption properties of organo-Vts are further explored.The structure-activity relationship between the structure of modifier,the wettability and adsorption property of organo-Vt is revealed.The main results are as follows:（1）Series of bis-imidazolium salts（EBMI,TBMI,HBMI,OBMI and DBMI）with different spacer length and short alkyl chain are synthesized,the adsorption of bis-imidazolium salts on Vt and its wettability alteration are explored.The results of characterization,adsorption experiment and molecular dynamics simulation show that series of bis-imidazolium salts are spontaneously adsorbed on Vt in the form of the monolayer.The saturated adsorptions of EBMI,TBMI,HBMI,OBMI and DBMI on Vt reach 0.159 mmol g^-1,0.156 mmol g^-1,0.145 mmol g^-1,0.114 mmol g^-1and 0.084 mmol g^-1 around 30 min at 25℃,respectively,which are sensitive to ionic strength and solution p H.The results of kinetics,isotherm and thermodynamics show that the adsorption processes conform to the second-order kinetic,Langmuir and statistical physics models,which are spontaneous endothermic processes.The capillary rise experiment results show that the change in wettability of organo-Vts is as follows:Vt<EBMI-Vt<TBMI-Vt<HBMI-Vt<OBMI-Vt<DBMI-Vt,which is related to the arrangements of bis-imidazolium salts in Vt layers,the hydrophobicity of bis-imidazolium salts with longer spacer as well as the interaction energies between the bis-imidazolium salts and Vt.（2）Series of bis-N-heterocyclic quaternary ammonium salts（BMMB,BMMH,BMMD,BPMH and BMPMH）are designed and synthesized,and reduced-charge vermiculites（Vt-1,Vt-2 and Vt-3）are prepared by Li⁺-saturated heating method.A series of organo-Vts and organo-reduced-charge vermiculites（organo-Vts-1/2/3）are prepared for exploring the wettability.The characterization results show that series of bis-N-heterocyclic salts are successfully intercalated into the Vt and Vts-1/2/3 with monolayer arrangement.The results of capillary rise tests indicate that the wettability of the organo-Vts and organo-Vts-1/2/3 gradually decreases with the layer charge decreasing:organo-Vts>organo-Vts-1>organo-Vts-2>organo-Vts-3.As the spacer length changes,the wetting properties of bis-morpholinium-based organo-Vts（organo-Vts-1/2/3）are in order of BMMD-Vts（Vts-1/2/3）>BMMH-Vts（Vts-1/2/3）>BMMB-Vts（Vts-1/2/3）,and difference in N-heterocyclic headgroups leads to the sequence of wettability alteration as follows:BMPMH-Vts（Vts-1/2/3）>BPMH-Vts（Vts-1/2/3）>BMMH-Vts（Vts-1/2/3）.In general,the layer charge of Vt,the spacer length and the structure of N-heterocyclic head group of the modifier have a synergistic effect on the wettability alteration.（3）bis-morpholinium gemini surfactants with different alkyl chain length（BMOB,BMDB and BMHB）are synthesized,and series of bis-morpholinium-based organo-Vts（BMOB-Vt,BMDB-Vt and BMHB-Vt）are prepared.The wettability and adsorption properties of BMOB-Vt,BMDB-Vt and BMHB-Vt are further investigated.The results of characterization and wettability experiment show that BMOB,BMDB and BMHB have been intercalated or loaded onto the Vt successfully,and the hydrophobicity of organo-Vts is enhanced with the alkyl chain of modifier increasing.Adsorption experiment results show that the adsorption of methyl orange（MO）/acid green 25（AG25）on BMOB-Vt,BMDB-Vt and BMHB-Vt reach maximum adsorption capacities of 108.68mg g^-1/67.38 mg g^-1,159.11 mg g^-1/135.40 mg g^-1 and 206.65 mg g^-1/161.13 mg g^-1,respectively,within 120 min.The kinetic,isotherm and thermodynamic results suggest that the adsorption processes conform to the pseudo-second-order kinetic model;The adsorption of MO is better fitted by Freundlich,while that of AG25 is suited with Langmuir;Almost all adsorption processes of organo-Vts towards MO/AG25 are exothermic and spontaneous,but AG25 on BMOB-Vt shows an endothermic and spontaneous process.Combined with the results of adsorption experiments and characterization of spent organo-Vts,the adsorption mechanisms can be confirmed that:the hydrophobic interaction works as the main driving force;the electrostatic interaction takes a synergistic effect;theπ-πstacking promotes the adsorption of MO.In binary-dyes adsorption system,MO and AG25 show a competitive adsorption on organo-Vts.（4）bis-pyrrolidinium and bis-piperidinium surfactants with long alkyl chain（BBHPyr and BBHPip）are synthesized,and organo-Vts（BBHPyr-Vt and BBHPip-Vt）are prepared for comparatively exploring their wettability and adsorption capacities.The characterization and wettability results show that both BBHPyr and BBHPip are successfully loaded onto Vt,and the hydrophobicity of organo-Vts enhances with the increase in the head groups of modifiers.Adsorption experiment results show that the adsorption of BBHPyr-Vt and BBHPip-Vt for bisphenol A（BPA）/acid black 1（AB1）reach the maximum experimental adsorption capacities of 143.72 mg g^-1/155.82 mg g^-1and 149.44 mg g^-1/179.94 mg g^-1 within 90 min/120 min at 25°C,respectively.The kinetic,isotherm and thermodynamic results indicate that all the adsorption processes can be better fitted by the pseudo-second-order kinetic model;The adsorption of BPA on these two organo-Vts is more suitable with Freundlich and double-layer statistical physics models,while that of AB1 well conforms with the Langmuir and one-layer statistical physics models;The adsorption processes of BBHPyr-Vt and BBHPip-Vt towards BPA are spontaneous exothermic,and the adsorptions of AB1 are spontaneous endothermic processes.Combined with the results of experiments and characterizations of spent samples,the adsorptions of BPA and AB1 on BBHPyr-Vt and BBHPip-Vt are mainly driven by the hydrophobic interaction,and theπ-πstacking between BPA molecules promotes its adsorption.In the binary-component system,there is a competitive adsorption of BPA and AB1 on the BBHPyr-Vt and BBHPip-Vt for some extent.