| Lithium(Li)is a strategic energy source used in medicine,electronics,mobile phones,automotive and aviation industries.The vigorous development of lithium-ion battery electronic products has also increased the demand for lithium in the world,making the rational development and utilization of lithium more important.With the increasing stock of lithium in salt lakes,the consumption of lithium extraction from salt lakes is relatively small,and obtaining lithium from salt lakes has received widespread attention.Surface imprinting technique(SIT)is to establish a target recognition system on or near the surface of the carrier.The binding sites of the imprinted polymer outer layer will improve the mass transfer and reduce the permanent retention of the template,and improve the adsorption efficiency.The development of lithium ion imprinted polymers by SIT can improve the selectivity of lithium and the stability of materials,and reduce some energy consumption,investment and operation costs,which will help to achieve sustainable and renewable society.In this paper,three new lithium ion imprinted polymers were developed by SIT.The related properties of the materials were characterized by FT-IR,SEM,BET and TGA.The adsorption,selectivity and regeneration ability of the materials were studied.The adsorption mechanism of the materials was studied according to the kinetics and isothermal adsorption model.The main conclusions are as follows:(1)The optimal synthesis process of MCM-41@Li-IIPs using MCM-41 molecular sieve as the carrier was as follows:EGDMA was 3.8 mL,and MAA was 0.17 mL.At pH is 7 and 25 ℃,the maximum adsorption capacity of MCM-41@Li-IIPs(1450.59 μmol/g)was higher than that of MCM-41@Li-NIPs(786.67 μmol/g).Langmuir model and pseudo-second-order kinetic model could better explain the adsorption behavior of adsorbent,indicating that the material tends to be monolayer adsorption,mainly chemical adsorption.Compared with MCM-41@Li-NIPs,the Li+selectivity coefficient of MCM-41@Li-IIPs was higher,and the relative selectivity separation factor was greater than 1.After six cycles,the adsorption capacity of MCM-41@Li-IIPs for Li+decreased slightly and maintained a stable structure.(2)Li-IIPs were obtained using activated carbon as the carrier.The surface activity of activated carbon was purified by 10%(v/v)HCl and 32.5%(v/v)HNO3,and then oxidized activated carbon was hydrolyzed by 3-(trimethoxysilyl)propyl methacrylate(KH-570).The optimal KH-570 dosage of modified activated carbon was 15 mL.At pH is 6 and 25℃,both imprinted and non-imprinted lithium reached adsorption saturation,and the maximum adsorption capacity of Li-IIPs(2267.76 μmol/g)was higher than that of Li-NIPs(1548.51μmol/g).Radushkevich-Dubininin(DKR)and quasi-first-order kinetic model could better explain the adsorption behavior of adsorbents,indicating that the adsorption of materials follows the pore filling mechanism and multi-layer characteristics involving van der Waals bonds.At the same time,the average free energy of Li-IIPs was 6.9 kJ/mol,indicating that the adsorption process of the material was a physical adsorption process.The relative selectivity separation factors between Li-IIPs and Li-NIPs were greater than 1.3.After eight adsorption-desorption cycles,the adsorption capacity of Li-IIPs was 88.3%of the initial adsorption capacity.(3)UiO-66-NH2@Li-IIPs were synthesized with Zr-based organic frameworks(MOFs)as the carrier.At pH is 6 and 25℃,both imprinted and non-imprinted lithium reached adsorption saturation,and the maximum adsorption capacity of UiO-66-NH2@Li-IIPs(2194.56 μmol/g)was higher than that of UiO-66-NH2@Li-NIPs(1051.48 μmol/g).Langmuir model and quasi first order kinetic model could better explain the adsorption behavior of adsorbent.The relative selectivity separation factors between UiO-66-NH2@Li-IIPs and UiO-66-NH2@Li-NIPs were greater than 1.After five cycles,the adsorption capacity of UiO-66-NH2@Li-IIPs decreased by only 21.4%. |
PDF Full Text Request