The Organic Modification Of Vermiculite And Its Adsorption Performance Study On Antibiotics And Environmental Hormones

With the rapid development of industry and the improvement of human's living,the various types of antibiotics and environmental hormones are widely used and gradually accumulate in the environment,causing serious harm to the ecological environment and human health.The removal of these pollutants has become the focus of attention.Vermiculite is one of clay minerals who have a rich source,a low cost,stable physical and chemical properties and is friendly to environment.It has broad application prospect in adsorption removal of pollutants.However,the adsorption capacity of natural vermiculite for organics is limited due to the hydrophilicity of surface.It is suggested that appropriate organic modification can introduce organic functional groups into vermiculite and increase the hydrophobicity of surface,then modified vermiculite can be used as a good adsorbent for the organic pollutants in environment.The dissertation mainly includes the following content:1.Phosphatidylcholine modified vermiculite(PC-VER)was prepared with phosphatidylcholine(PC)as the organic modifier.Some characterization methods such as XRD,FTIR,TG-DTG,SEM/EDS,BET and Zeta potential were used to analyze the change in the crystal structure and physicochemical properties before and after the modification.The adsorption performance of oxytetracycline(OTC)and ciprofloxacin(CIP)on VER and PC-VER were studied by batch experiments.The results showed that:(1)PC molecules only adsorbed on the surface of VER and cannot inserted into the interlayer.However,if the solution containing water,PC molecules not only adsorbed on the surface but also intercalated into the interlayer of VER,thus the interlayer spacing greatly expanded;(2)After modified by PC,the surface morphology of VER becomes more smooth and density and the specific surface area decreased.The thermal stability and hydrophobicity of VER increased.Moreover,the negative charge in surface reduced and possess positive charge under low pH value;(3)The adsorption amount of OTC and CIP on PC-VER was higher than that on VER,the maximum adsorption capacity increased from 36.80 and 36.87 mg·g-1to 66.40 and 93.72mg·g-1,respectively.The adsorption process was in accord with pseudo-second-order modeland Langmuir adsorption isotherm,and the increase of temperature was unfavourable for the adsorption;(4)The adsorption efficiency on VER decreased with the increase of pH value,and the coexisting cations could significantly inhibit the adsorption(Ca2+> Na+).However,the adsorption of OTC(CIP)on PC-VER was not affected(significant influenced)by pH;(5)Cu2+and Zn2+ could form complexes with OTC and then promoted the absorption,and inhibited the adsorption of CIP due to the competition;(6)The main adsorption mechanism of OTC and CIP by VER was electrostatic adsorption.Also,the surface complexation on the edges made part of contribution to the adsorption.The adsorption of OTC on PC-VER was mainly controlled by hydrophobic interaction and the CIP adsorption was more controlled by the electrostatic adsorption.2.Betaine modified vermiculites(BS-VER,SB-VER,PBS-VER)were synthesized with dodecyl dimethyl(N-carboxylate)betaine(BS),dodecyl dimethyl(3-sulphonate)betaine(SB)and dodecyl dimethyl(N-phosphate)betaine(PBS)as the organic modifiers.Some characterization methods were used to investigate the difference in the combination mode between three kinds of betaine and VER,and analyze the change in structure and properties after the modification.The adsorption performance of bisphenol A(BPA)and tetrabromobisphenol A(TBBPA)on BS-VER,SB-VER and PBS-VER were studied.The results showed that:(1)SB molecules only adsorbed on the surface of VER;BS molecules mainly adsorbed on the surface and rarely intercalated into the interlayer of VER;PBS molecules could be bonded into VER via both of adsorption and intercalation and greatly expanded the interlayer spacing;(2)After modification,the surface roughness of VER reduced and the specific surface area decreased significantly,the thermal stability also increased.The loading capacity of modifiers on three organic vermiculites and its hydrophobic performance followed the order PBS-VER > BS-VER > SB-VER;(3)BS-VER and SB-VER were negatively charged in the range of pH 2-10 and carried more negative charges than VER,while PBS-VER possessed a positive potential value at low pH and carried less negative charges than VER in other cases;(4)The adsorption amounts of VER to BPA and TBBPA were scarce,and the absorption efficiency of modified vermiculites followed theorder PBS-VER > BS-VER > SB-VER.The adsorption was not affected by pH when the pH value at 2-8;(5)The adsorption of BPA and TBBPA on three modified vermiculites were very fast and could achieve balance within 30 min.The pseudo-second-order model and Langmuir adsorption isotherm could well describe the adsorption process.The affinity between PBS-VER and pollutants was strongest than BS-VER and SB-VER,the maximum adsorption capacity can reach 92.67 mg·g-1(BPA)and 88.87 mg·g-1(TBBPA);(6)PBS-VER was easier to be desorbed and had good reusability.Furthermore,PBS-VER could remove ionic(methylene blue and orange G)and molecular(BPA)organic pollutants simultaneously and effectively due to the function of amphoteric hydrophilic groups and alkyl chains.