Preparation Of Acrylic Ion Exchange Resin With High Mechanical Strength And Its Adsorption Behavior For Typical Pharmaceuticals

In recent years,pharmaceuticals and personal care products(PPCPs)have become important pollutants in the environment,posing potential threats to human health and stability of ecosystem.Resins as adsorbents have been used in the treatment of water or wastewater due to their high adsorption capacity,adjustable structure and reusability.Acrylic ion exchange resin(AER)has excellent removal capacity for some kinds of PPCPs.However,AER has poor mechanical strength and is susceptible to break up.For example,the internationally renowned magnetic acrylic ion exchange resin(MIEX(?))was confronted with resin loss due to its poor mechanical strength in China's 90,000 tons/day drinking water purification project in Huai'an,thus the water treatment cost increased by 0.09 yuan/ton.In this current work,the method of "implantation" of inorganic materials and the "interpenetration" of phenolic polymers were proposed to improve AER's mechanical strength,aiming at the development of AER with high mechanical strength.Then the adsorption properties of the resins on the target PPCPs were investigated and the adsorption mechanism was discussed.The main contents and conclusions were as follows:(1)From the perspective of resins mechanical strength and material stability,acrylic ion exchange resin implanted with inorganic materials(MAER)was prepared via a two-part procedure involving the in-situ formation of Fe3O4 and subsequent modification with SiO2.Due to the presence of Fe3O4,the sphericity rate after ball milling of MAER increased from 78.3%to 97.9%,and the mechanical strength of MAER was similar to that of styrene ion exchange resin with the highest mechanical strength in resin products.The subsequent modification of SiO2 could effectively prevent inorganic materials from falling off from the resins and ensure the stability of the materials.The FTIR and XPS analysis indicated that the formation of hydrogen bonding between the-OH groups on Fe3O4 and the-NH-groups on the resin matrix was beneficial to the improvement of mechanical strength of resin.Meanwhile,on the basis of optimizing the dosage of reagent and experimental conditions,the phenolic polymers were formed by polymerization between formaldehyde and phenol adsorbed in the AER by adjusting the ratio and catalyst.Thus the "interpenetration" between AER and phenolic polymers could be achieved,and phenolic-acrylic polymer resin(PFAER)with "interpenetrating" structure was prepared.The experimental results showed that when the ratio was increased from 1:1.0 to 1:2.2,the sphericity rate after ball milling of the resins was increased from 78.3%to 99.4%,and the mechanical strength of the resins was increased by about 27%compared with AER.(2)The removal of ibuprofen,clofibric acid,carbamazepine and humic acid by MAER was investigated.The study found that it could effectively adsorb the negatively-charged pollutants in water:ibuprofen,clofibric acid and humic acid,but have no effect on carbamazepine.Besides,it was noticeable that the released chloride from the MAER was around 49%less than that from the AER,suggesting that the adsorption of negatively-charged pollutants onto AER was caused by electrostatic interactions,while the adsorption onto MAER was caused by both electrostatic and non-electrostatic interactions.Further analysis by XPS showed that the hydrogen bonding between inorganic materials and PPCPs also greatly contributed to the interactions.Therefore,the amount of ibuprofen onto MAER could reach 0.26 mmol/g,which was 29.5%higher than that of AER.The Langmuir model and the Freundlich model could better describe the adsorption process.And the thermodynamic analysis indicated that the adsorption process was an endothermic and spontaneous process.The adsorption kinetics showed that the adsorption could reach equilibrium at 120 min.Besides,the effects of solution pH,inorganic salts and co-existing organic matter on the adsorption process were also discussed,and the reusability was investigated.(3)The adsorption behavior of ibuprofen by PFAER was also studied.The adsorption kinetics results showed that the adsorption reached equilibrium at 150 min.The adsorption of ibuprofen fitted the Langmuir model better,suggesting a monolayer-type adsorption of ibuprofen onto the homogeneous sorption sites on PFAER.When the solution pH was 4.2,the adsorption amount of ibuprofen reached the maximum(0.25 mmol/g).When the solution pH was higher than 4.2,the ibuprofen adsorption would be reduced due to the competition effect.And when the solution pH was lower than 4.2,there is no electrostatic interaction between the ibuprofen and the resin.With the concentration of sodium chloride or sodium sulfate in solution increased from 0 mg/L to 70 mg/L,the adsorption amount of ibuprofen decreased to zero due to the competition effect.When the concentration of humic acid in solution increased to 20 mg/L,the adsorption amount of ibuprofen decreased by approximately 10.2%,while the same concentration of tannic acid or gallic acid decreased by 14.5%and 20.2%,respectively.This phenomenon could be interpreted by the fact that tannic acid and gallic acid were more likely to diffuse into the pores of the resins due to their lower molecular weight and thus competed with ibuprofen.In this paper,the mechanical strength of AER was improved by two methods of"implantation" of inorganic materials and "interpenetration" of phenolic polymers.However,the two methods also had shortcomings.Although the modification of SiO2 could effectively prevent inorganic materials from falling off from the resins,this problem could not be completely avoided.Moreover,the "interpenetration" of phenolic polymers required the use of organic raw materials such as phenol and formaldehyde,leading to a large amount of organic matter was released during the cleaning process,and the preparation process was not environmentally friendly.Thus,these issues need to be further studied and solved.