Control Of Clay Particle Wettability And Oleic Acid Aggregation Based On Organic Amine

Organic amine were used for hydrophobic modification of natural clay and gelation behaviors of organic amine in aqueous phase have been systematically studied.Molecular structure(number of chlorine atoms,alkyl chain length,modification degree)and environmental factors(pH,temperature,ionic strength)play a significant role in the adsorption process and aggregation behaviors.The thermal stability of ammonium modified particles and polyamine based lamellar gels were characterized by thermal analysis.Rheological properties of ammonium modified particle suspensions and polyamine based lamellar gels were tested.Moreover,the interfacial arrangement of modified particles and the morphology of polyamine based lamellar gels were characterized by freeze fracture electron microscopy,the interactions between different species in these systems are discussed in various conditions.The three aspects included in this dissertation are as follows:1.Organoclays were prepared by replacing exchangeable Na+ ions in Na-montmorillonite(Na-Mt)with dodecyltrimethylammonium bromide(DTAB)and cetyltrimethylammonium bromide(CTAB).Organic modification is important in order to obtain good affinity between organoclays and organic pollutants.Hydrophobic DTAB-montmorillonite(DTAB-Mt)and CTAB-montmorillonite(CTAB-Mt)were studied as adsorbents for 4-chlorophenol and 2,4-dichlorophenol.Adsorption was determined as a function of adsorbent dosage,pH,contact time,and temperature.It was found that pH and temperature had significant effects on the adsorption of chlorophenols.The Langmuir isotherm was the best choice to describe the adsorption behavior.The maximum adsorption capacities of CTAB-Mt for 4-chlorophenol and 2,4-dichlorophenol were 395.0 and 585.8 mg/g,respectively,whereas the maximum adsorption capacities of DTAB-Mt for 4-chlorophenol and 2,4-dichlorophenol were 331.1 and 458.2 mg/g,respectively.The kinetic data fitted the pseudo-second-order kinetic model.Thermodynamic parameters suggested that the adsorption process of chlorophenols onto organoclays was physisorption and exothermic.The adsorption mechanism is a complex process that involves a combination of partitioning and van der Waals forces.2.Rodlike sepiolite particles were in-situ modified in oil using dimethyldioctadecylammonium chloride(DODMAC).Hydrophobic modification was enhanced at high temperature due to DODMAC intercalation and the loss of zeolite water.High salinity solution(water)in paraffin oil(W/O)emulsion was prepared with the modified particles.Hydrophobic modification can influence interparticle interaction,their interfacial adsorption,and stability of particle-stabilized emulsions.Emulsions stabilized by rodlike particles are more stable than those prepared with spherical particles even at low concentrations.Moreover,interfacial adsorption of particles will be tuned by controlling the modification.Remarkable stability against coalescence was found at high temperature.The enhanced stability is due to the high viscosity of continuous phase.Moreover,modification of sepiolite particles at high DOMDAC concentrations enhances particle adsorption at water-oil interfaces and network in continuous phase,which improve the stability against sedimentation and coalescence of the W/O emulsions.3.The gelation behavior of diethylenetriamine(DETA)and oleic acid(OA)with different molar ratios in water was investigated.The gels were composed of lamellar phase and vesicles.Lamellar gels and rodlike micelles form successively with the increase of DETA/OA molar ratio.The lamellar gels exhibiting high thermal stability can be obtained over a wide range of molar ratios of polyamine to unsaturated fatty acid.Supra-amphiphile was constructed by DETA and OA,and self-assembly of supra-amphiphile through hydrophobic interaction and hydrogen bonding leaded to the formation of lamellar gels.Moreover,gel-sol transition can be triggered by tuning pH and ionic strength.This system has a good emulsification property.