Preparation And Performance Study Of Two New Ni (Ⅱ) Ion Imprinted Composite Membrane

Ni（Ⅱ）ion-containing wastewater has been heavily threatened the ecological environment and human health due to its persistent harmful effects.At present,several commonly used recovery methods for treating the nickel pollution in water bodies,including chemical precipitation,electrolysis,adsorption and membrane separation,etc.,but which of them have different defects.Therefore,it is necessary to find an adsorption separation material with high selectivity for Ni（Ⅱ）ions.Metal ion imprinted membranes（IIMs）are an emerging technology that combines the advantages of metal ion imprinting technology and membrane separation technology,and is an important branch in the development of metal ion imprinting technology.IIMs have certain selectivity and specificity for target ions,are more stable and resistant to harsh environments than general biological materials,which have advantages in low detecting limit,low price,easy scale-up,and energy-saving.Therefore,the study of IIMs has gradually attracted extensive attention from researchers at home and abroad.In this study,two novel Ni（Ⅱ）ion-imprinted composite membranes were prepared using the metal ion imprinting technology with Ni（Ⅱ）ions as template ions.The Ni（Ⅱ）ion-imprinted membranes and the corresponding non-imprinted membranes prepared under optimal experimental conditions were investigated for structural characterization and properties analysis.The specific studies are as follows:（1）Ni（Ⅱ）ion-imprinted composite membranes(Ni（Ⅱ）-IICM_1-16)and non-imprinted composite membranes(NICM_1-16)were prepared by surface imprinting method,which using Ni（Ⅱ）ions as template ions,a compound synthesized by independentdesignN-（1-（2,4-difluorophenyl）-2-（1H-1,2,4-triazol-1-yl）ethyl）acrylamide（NDTEA）as functional monomer,and N-isopropylacrylamide（NIPAM）as temperature-sensitive monomer.All of the experimental conditions were systematically optimized.Thereinto,Ni（Ⅱ）-IICM₈ performed an excellent adsorption properties for Ni（Ⅱ）,adsorption capacity and imprinting factor could be achieved 6.25mmol/g and 1.87.Subsequently,electron scanning microscopy（SEM）,nitrogen adsorption/desorption（BET）,thermogravimetric analysis（TG）and contact angle measurements were adopted for evaluating morphology and structural characterization of Ni（Ⅱ）-IICM₈.The results showed that Ni（Ⅱ）-IICM₈ with strong hydrophilicity,and which is a thermally stable adsorbent with a certain"stimulus responsiveness"to temperature.The adsorption behavior of Ni（Ⅱ）-IICM₈ for Ni（Ⅱ）is in accordance with the quasi-secondary kinetic model and Freundlich isothermal adsorption model,indicating that a chemisorption and multilayer adsorption involved.In addition,Ni（Ⅱ）-IICM₈ has good permeation selectivity for Ni（Ⅱ）ions while Cd（Ⅱ）,Cu（Ⅱ）and Pb（Ⅱ）coexist as competing ions,and the permeation process is well fitted with"facilitated permeation"mechanism.（2）A series of Ni（Ⅱ）ion-imprinted composite membranes（Ni（Ⅱ）-IICMs）and non-imprinted composite membranes（NICMs）were prepared in the aqueous phase by the optimization of the imprinting system using Ni（Ⅱ）ions as template ions,4-vinylpyridine as functional monomer,N,N-methylenebisacrylamide as crosslinker and potassium persulfate as initiator,and better experimental conditions for the preparation of Ni（Ⅱ）-IICMs were obtained.The better Ni（Ⅱ）-IICM₆,with an adsorption capacity of5.76 mmol/g and an imprinting factor of 1.67,was prepared under the better experimental conditions using scanning electron microscopy,thermogravimetric analysis,nitrogen adsorption/desorption and contact angle measurements for the structural characterization and performance study of Ni（Ⅱ）-IICM₆.The results showed that the adsorption behavior of the better Ni（Ⅱ）-IICM₆ is more in line with the quasi-secondary kinetics and Freundlich adsorption model,and belongs to the chemisorption of multilayer;when the temperature is 25℃and p H=5,it is favorable for the adsorption of Ni（Ⅱ）ions;under the coexistence of"competing ions"Cd（Ⅱ）and Pb（Ⅱ）,the better Ni（Ⅱ）-IICM₆ has good permeation selectivity for Ni（Ⅱ）ions,and its permeation process is in line with the"facilitated permeation"mechanism.