Electrospinning Nanofibers For Adsorption Of Contaminant From Water

In recent years,the combined pollution became one of the most serious environmental problems in China.Adsorption was considered as a simple and efficient method to remove combined pollutants from water/wastewater.Various adsorbents including activated carbon,oxide minerals,biosorbents and polymeric adsorbents were investigated to remove combined pollutants from water.Among them,fibrous adsorbents arose people's significant interests due to their higher adsorption rate,better flexibility,and easy in separation.However,some shortcomings of fibrous adsorbents limited their wide applications in practice:1)most of them were prepared by modification of functional groups in non-homogeneous reactive system so that the functionalizing efficiency was relative low;2)In addition,adsorption mechanisms of multiple pollutants in their binary solutions were much more complexes than that in single solution.Thus,it is necessary to further study and illustrate these competition/synergistic adsorption mechanisms,which could help us improve the removal rate of multiple pollutants from their binary solutions;3)Although fixed-bed adsorption model is more widely applied in actual wastewater treatment,it is difficult to pack the soft and fluffy fibrous adsorbents into column symmetrically.And fibrous adsorbents are easy to twine together into knots and unfavorable to mass transfer in batch adsorption process.Thus,it is necessary to prepare bi-functional electrospun twin-nanfibrous membrane for simultaneous adsorption of BPA and Cu?II?and further illustrate these competition/synergistic adsorption mechanisms.Based on the above research background,we expected to prepare Sulfydryl-functionalized mesoporous polyvinyl alcohol/silica-based nanofiber?MNF-SH?and fibrous membrane?APAN/CS/PVA?for simultaneously/sequential removal of BPA,Cd?II?and Cu?II?from water/wastewater.The present work focused on the four main objectives:?1?Sulfydryl-functionalized mesoporous polyvinyl alcohol/silica-based nanofiber?MNF-SH?was prepared as efficient adsorbent to simultaneously/sequentially remove Bisphenol A and Cu²⁺ from their binary solutions.Mesoporous structure and sulfydryl groups of MNF-SH were observed.The specific surface area was 564.3 m2/g,and the pore volume was 0.495 cm3/g.The equilbrium adsorption capacity of Cu²⁺ and BPA were 5.431 mmol/g and 2.989 mmol/g,respectively.The adsorption mechanism of Cu²⁺ was chelating by sulfydryl groups,while hydrogen bonding and intermolecular force were the adsorption mechanism of BPA.Moreover,the coexistence of Cl-and NO₃^-increased the adsorption of Cu²⁺while decrease the adsorption of BPA;?2?APAN/CS/PVA-NM was prepared by amination reaction and electrospinning to simultaneously/sequentially remove Bisphenol A and Cd²⁺ from their binary solutions.SEM and TEM indicated that the average pore diameters of APAN/CS/PVA was 1.5?m.The adsorption of Cd²⁺ by APAN/CS/PVA-NM is mainly due to the chelating.However,the adsorption of BPA is not only due to the hydrogen bonding but also intermolecular forces.Different from traditional fibrous adsorbents,APAN/CS/PVA-NM can be used to remove BPA and Cd²⁺ in filtration model,and the filtration conditions?pH value,influent concentration and flow rate?showed a significant influence on the removal efficiency;?3?In the binary system of Cu and BPA,Cu²⁺ adsorption on MNF-SH was mainly attributed to the chelating interaction,while BPA adsorption was due to the intermolecular force and hydrogen bond.In addition,the loaded BPA on MNF-SH by intermolecular force,could act as bridge molecular to adsorb Cu²⁺,and showed synergistic effects on Cu²⁺ removal in simultaneous/sequential adsorption.However,the coexistence of Cu²⁺ or preload Cu²⁺ decreased the uptake of BPA because of competition for MNF-SH sulfydryl groups.;?4?In binary system of Cd and BPA,Cd²⁺ adsorption on APAN/CS/PVA-NM was mainly attributed to the chelating interaction,while adsorption of BPA was due to the intermolecular force and hydrogen bond.Cd and BPA competed for the adsorption sites?amino functional groups?of APAN/CS/PVA-NM.In addition,high concentration of BPA loaded on APAN/CS/PVA-NM by intermolecular force,could act as bridge molecular to adsorb Cd²⁺,and showed synergistic effects on Cd²⁺removal in simultaneous/sequential filtration.The highest adsorption capacity of APAN/CS/PVA-NM for BPA and Cd was achieved at pH 5.As pH was lower than 5,the H+ could compete with Cd for adsorption sites.BPA would transform into phenolic hydroxyl groups while pH was higher than 5,which was unfavorable BPA adsorption.