Adsorption Resin-grafted Polymer Brushes And Their Chloroform-adsorption Properties

Trihalomethanes (THMs) is a class of disinfection by-products (DBPs),whichis the highest content and most widely distributed in drinking water. With theoccurrence of numerous organic pollutants in water sources and the increasing ofchlorine in drinking water, it definitely causes the successive rise of somedisinfection by-products (DBPs) in water, such as THMs. THMs have receivedconsiderable attention for their potential threats to people’s health, which are knownto be carcinogenic and mutagenic. In present, the effective removal technologies forTHMs in water are focused on the membrane separation and adsorption methods.Among them, activated carbon, reverse osmosis membrane and macroporous resinare widely used, however, the shortcomings are high cost and low adsorptioncapacity. Therefore, it is essential to seek some economical adsorption materialswith good selectivity and high adsorption properties to remove THMs in water andfurther study the adsorption theories of THMs removal.In this dissertation, the ideal products-polymer brush adsorption materials,surface modified hypercrosslinked macroporous resins with methacrylates-grafted,were synthesized by e-atom transfer radical polymerization (ARGET ATRP).Furthermore, the low concentration chloroform-adsorption properties andmechanisms of the synthetic products were studied systematically with chloroformas the target pollutant. The main research and results of this dissertation were shownbelow:Based on the chemical structure of the adsorbent and adsorbate, polarity,adsorption sites and the hydrophobic effect of adsorption, combined with quantumchemical calculation methods, the matrix materials and the grafted monomers forTHMs-absorption in water were chosen. The chloromethylated polystyrene resinmatrix materials (HPD300), the addition means, the polymerization mechanisms andthe synthetic routes were designed. With HPD300as the grafted matrix and themacroinitiator, chlorine methyl as the functional group and three kinds ofmethacrylates as monomers, respectively, high grafting density polymer brusheswith thickness about4-7nm were slowly synthesized by ARGET ATRP methods,because monomer molecules can be easily controlled to "grafting from the surface"in the polymerization. The influence factors on the polymerization were studieddetailedly to determine the optimum conditions. The experimental results showedthat the layer thickness and the grafting density of the polymers had a linearrelationship to the average pore size and specific surface area of the polymer brushes, respectively. The method about indirectly characterization of the polymeraverage layer thickness and the grafting density was adopted by the measured valuesof the average pore diameter and specific surface area. An idea about controlling theaverage pore diameter and the specific surface area of the grafted resin by regulationof the reaction time was put forward, moreover, it was a breakthrough to achievehigh-density polymer brushes by the control of the pore structure parameters.The surface chemical compositions, chemical structures, microstructures andpore structure parameters of the matrix materials and the grafted products werecharacterized by a series of methods (infrared spectroscopy (FTIR), Scanning andtransmission electron microscopy (SEM、 TEM), X-ray diffraction (XRD) andphysical adsorption analyzer, etc.). And, it was pointed out that the polymer brushlayer thickness was related to the reaction time and the pore structure parameters.The conformations of the polymer brushes were characterizied bydeterminations of the grafting density, chain separation, mean-square end-to-enddistance and mean-square radius of gyration. The results showed that they wereconsistent with the conformations of the polymer brushesThe static and dynamic adsorption, adsorption dynamics and desorption andregeneration properties of the grafted products were tested, and the comparativeexperiments were carried out with the existing adsorbents. The results showed thatthe adsorption rate (efficiency) and the adsorption capacity of the grafted polymerbrush materials were significantly better than ungrafted resin and activated carbonsadsorption materials. Moreover, the polymer brushes with different functionalgroups had selective chloroform-adsorption properties, of which, HPD300-HEMAwas a kind of absorption material with excellent comprehensive properties. Thegrafted chloroform-adsorption materials can better meet the Freund lich empiricalequation.The frontier molecular orbital distribution and energy values, the equilibriumadsorption geometries and adsorption energies parameters were calculated throughthe thermodynamic parameters△H,△G,△S and the application of densityfunctional theories. The adsorption mechanisms of the graft products were revealed.The results showed that HPD300-HEMA had double features of physical adsorptionand chemical adsorption.Based on the above findings, the pore structure parameters of adsorptionmaterials can vary with molecular weight and the grafting density of the polymerbrushes by ARGET ATRP. Compared with the ungrafted resin, the adsorptionmaterials had greater special surface area, more reasonable pore size distributionand pore volume, the adsorbates on the polymer brushes were represented as three-dimensional structure, and the grafted products showed very high physicaladsorption capacity. The polymer brushes with a high density of functional groupscan produce multiple force when encounter the adsorbates, therefore,they generateda certain chemical adsorption with the selective adsorption capacity. The resultsabout THMs adsorption performance measurement of simulated and real watersamples showed that the perpared polymer brushes exhibited high adsorptionproperties.