Qihan Li

Preparation of an ion-imprinted fiber for the selective removal of Cu2+.

A novel Cu(2+)-imprinted fiber (IIF) was prepared by grafting acrylic acid (AA) onto the surface of a polypropylene (PP) fiber and subsequently modified with polyethylenimine (PEI). An examination by infrared spectroscopy and scanning electron microscopy confirmed that the ion-imprinted polymer was successfully introduced onto the surface of a PP fiber. The modification of PP fibers with AA was beneficial to the grafting of PEI onto the fibers. The highest grafting degree of PEI could reach 120 wt % under optimal grafting conditions. This IIF showed excellent tensile and chemical stability in acid solution, which qualified the IIF for practical applications. Besides having a high adsorption capacity for Cu(2+) (120 mg/g), the IIF adsorbent showed a high selectivity for Cu(2+) as compared with that of the non-ion-imprinted fiber (NIF). The dynamic adsorption results indicated that IIF can thoroughly remove Cu(2+) from the solution in a relatively short contact time. The effective treatment volume was about 910 bed volumes. The selectivity coefficient of IIF for Cu(2+) with respect to Zn(2+) could reach 76.4. IIF also has good regeneration performance and could maintain almost the same adsorption capacity for copper ions after 10 adsorption-desorption cycles.

Preparation and Characterization of a Solid Amine Adsorbent for Capturing CO2 by Grafting Allylamine onto PAN Fiber

Solid amine adsorbents using synthetic fibers instead of silica as the matrix are expected to offer more benefits for the adsorption of CO(2) because of high external surface area, low pressure drops, and flexibility of the matrix fibers. A novel kind of solid amine-containing fibrous adsorbent (PAN-AF) was prepared by preirradiation grafting copolymerization of allylamine onto polyacrylonitrile (PAN) fiber, using the redox system of (NH(4))(2)S(2)O(8)/NaHSO(3) as initiator. The effects of the reaction conditions such as reaction time, temperature, monomer concentration, amount of the initiator on grafting degree were studied. The results showed that the optimal conditions for the grafting copolymerization were using 50% allylamine monomer (V/V) and 1.5% (W/V) initiator and reacting at 100 degrees C for 10 h. FTIR was employed to characterize the corresponding changes on the surface chemical structure of PAN and PAN-AF. Thermal gravimetric analysis was used to evaluate the thermal stability of the materials. Equilibrium adsorption capacities for CO(2) and regeneration behaviors of PAN-AF were determined. Adsorption capacity for CO(2) of PAN-AF with 60.0 wt % grafting degree was 6.22 mmol CO(2)/g PAN-AF. PAN-AF could be completely regenerated by heating in boiling water for 30 min. The CO(2) adsorption performance of the regenerated PAN-AF was almost the same as that of the fresh adsorbent after several cycles, which revealed that PAN-AF exhibited good regenerating stability. The high speed and effective regeneration process proves that PAN-AF has great potential in industrial applications for CO(2) capture.

Structure design of a hyperbranched polyamine adsorbent for CO2 adsorption

An amino-terminated hyperbranched polymer (HBP-NH2) has been prepared through the Michael addition reaction between amines and methyl acrylate (MA) at 0 °C, followed by self-condensation of the addition reaction products at 100 °C and 140 °C. A novel CO2-“imprinted” hyperbranched polymeric adsorbent (IHBPA) with a high amino density was conveniently prepared by using glutaraldehyde to crosslink HBP-NH2 which had pre-adsorbed CO2. Through comparing the adsorption capacities of the IHBPA with HBPA, which was prepared with a similar procedure to that of IHBPA but without CO2 pre-adsorption, it could be found that the pre-adsorbed CO2 on HBP-NH2 would occupy the reactive sites of amino groups, and play the role of “imprinting” in the preparation of the adsorbent. The adsorption capacity of the IHBPA could thus be improved. After reducing the imino groups of the IHBPA to alkyl amine by NaBH4, the adsorption capacity of the reducing solid amine adsorbent (IHBPA-R) can be further improved. The prepared solid amine adsorbents also showed promising regeneration performance, which could maintain almost the same adsorption capacity for CO2 after 10 adsorption and desorption recycles. The high CO2 adsorption capacity (7.65 mmol g−1) of IHBPA-R can be attributed to its high amino density, terminal amine and hyper-branched structures.

The use of ZnCl2 activation to prepare low-cost porous carbons coated on glass fibers using mixtures of Novolac, polyethylene glycol and furfural as carbon precursors

Abstract Using ZnCl 2 as an activation agent, low-cost porous carbons were prepared using mixtures of Novolac, polyethylene glycol (PEG) and furfural in alcohol as carbon precursors that were coated onto glass fiber mats. The morphology, microcrystalline structure, pore structure, surface chemistry, mechanical strength and adsorption properties of the porous carbons were characterized. Results show that the addition of furfural and PEG to the carbon precursors greatly improves pore development. The specific surface area of the porous carbons is as high as 2023 m 2 /g when PEG and furfural are added, otherwise it is only 404 m 2 /g. It is found that the addition of PEG to the precursors can increase the solubility of ZnCl 2 in alcohol, and thus facilitate the activation of the carbon precursors. The formation of a crosslinked structure of furfural with Novolac is responsible for the improvement in the thermal stability of the precursors and the increase in the carbon yield, which favors the increase in the surface area and the reduction of the production cost. The porous carbons have similar adsorption performance and microcrystalline structure to conventional activated carbon fibers.

Effect of the pH of the preparation medium on the microstructure and electrocatalytic activity of carbon nanotubes decorated with PtSn nanoparticles for use in methanol oxidation

Abstract Carbon nanotubes (CNTs) decorated with PtSn nanoparticles (PtSn/CNT) were prepared by the microwave-assisted ethylene glycol reduction method and characterized by atomic adsorption spectroscopy, X-ray diffraction and transmission electron microscopy. Results indicated that the loading efficiency of the metal catalyst, and the degree of alloying and morphology of the PtSn nanoparticles were significantly affected by the solution pH value of the metallic ions in the ethylene glycol. The required composition of the PtSn/CNT catalysts could be obtained by adjusting the pH value to about 5, which is almost the isoelectric point of the acid-treated CNTs. The size of the PtSn nanoparticles decreased with the pH value in the range 2 to 7, but they became large and agglomerated when the pH value was greater than 7. Electrocatalytic activity tests indicated that the PtSn/CNTs prepared at pH 5 had the best catalytic performance towards methanol oxidation. The improvement in catalytic activity was mainly attributed to a high loading efficiency and control of particle shape and size distribution.