Hierarchical porous photosensitizers with efficient photooxidation.

Photosensitizers (PSs) with nano- or micro-sized pore provide a great promise in the conversion of light energy into chemical fuel due to the excellent promotion for transporting singlet oxygen (1O2) into active sites. Despite such hollow PSs can be achieved by introducing molecular-level PSs into porous skeleton, however, the catalytic efficiency is far away from imagination because of the problems with pore deformation and blocking. Here, very ordered porous PSs with excellent 1O2 generation are presented from cross-linking of hierarchical porous laminates originated by co-assembly of hydrogen donative PSs and functionalized acceptor. The catalytic performance strongly depends on the preformed porous architectures, which is regulated by special recognition of hydrogen binding. As the increasing of hydrogen acceptor quantities, 2D-organized PSs laminates gradually transform into uniformly perforated porous layers with highly dispersed molecular PSs. The premature termination by porous assembly endows superior activity as well as specific selectivity for the photo-oxidative degradation, which contributes to efficient purification in aryl-bromination without any postprocessing.

Ambient air pollutants concentration prediction during the COVID-19: A method based on transfer learning.

Research on the correlation analysis between COVID-19 and air pollution has attracted increasing attention since the COVID-19 pandemic. While many relevant issues have been widely studied, research into ambient air pollutant concentration prediction (APCP) during COVID-19 is still in its infancy. Most of the existing study on APCP is based on machine learning methods, which are not suitable for APCP during COVID-19 due to the different distribution of historical observations before and after the pandemic. Therefore, to fulfill the predictive task based on the historical observations with a different distribution, this paper proposes an improved transfer learning model combined with machine learning for APCP during COVID-19. Specifically, this paper employs the Gaussian mixture method and an optimization algorithm to obtain a new source domain similar to the target domain for further transfer learning. Then, several commonly used machine learning models are trained in the new source domain, and these well-trained models are transferred to the target domain to obtain APCP results. Based on the real-world dataset, the experimental results suggest that, by using the improved machine learning methods based on transfer learning, our method can achieve the prediction with significantly high accuracy. In terms of managerial insights, the effects of influential factors are analyzed according to the relationship between these influential factors and prediction results, while their importance is ranked through their average marginal contribution and partial dependence plots.

Preparation of a laminated structured polyethyleneimine cryogel for carbon capture.

A cryogel solid amine adsorbent with a laminated structure has been prepared by crosslinking polyethylenimine (PEI) with ethylene glycol diglycidyl ether (EGDE) at a low temperature via liquid nitrogen treatment and freeze-drying. The effects of cryogenic treatment on the morphology of the cryogels were investigated. The liquid nitrogen treatment and freeze drying were critical to create the layered structure. The fast formation of ice crystals at 77 K served as a template which directed the ordered lamellar structure of the PEI and EGDE cross-linked polymer networks. The PEI cryogel adsorbent showed excellent CO2 adsorption performance both in dry and wet conditions. In dry conditions, the PEI-gel-5-0.25 cryogel showed a 5.60 mmol/g of CO2 adsorption capacity at 75 °C. After being swelled with water, the PEI-gel-15-0.25 cryogel showed an extremely high CO2 adsorption capacity of 11.39 mmol/g at 25 °C. The adsorption behaviors of adsorbents with varied water contents were explained using kinetic simulations and intraparticle diffusion simulations. It was found that the presence of water can significantly enhance the diffusion process. The regeneration performance was examined in both dry and wet conditions. After 20 adsorption-desorption cycles, the adsorption capacity of the regenerated PEI cryogel had barely decreased, indicating reliable regeneration stability.

Preparation of a Fiber-Like 3D-Structured Adsorbent for CO2 Capture.

Solid amine adsorbents are promising materials to mitigate global warming. In this study, a commercially available melamine-formaldehyde sponge was adopted as a support to prepare a kind of solid amine adsorbent using polyethylenimine as a functional component and ethylene glycol diglycidyl ether as a cross-linker. The adsorbent, with abundant tunnels and a high amine loading amount, had a high adsorption capacity. When the amine loading was 89.6 wt%, the as-prepared adsorbent showed a high adsorption capacity of 7.29 mmol/g at 20 °C in the presence of water. The spent adsorbent could be easily regenerated by heating it at 90 °C, resulting in lower energy consumption. It has been proved by the Avrami model that physical and chemical adsorption coexist in the adsorption of CO2 on this adsorbent. Simulation with the intraparticle diffusion model has revealed that the rate-controlling step in the adsorption process was the gas film diffusion period when the adsorption temperature was below 30 °C, while it was the adsorption equilibrium period when the adsorption temperature was above 30 °C.

Synthesis and characterization of a thermosensitive solid amine biomass adsorbent for carbon dioxide adsorption.

A thermosensitive solid amine fiber SF-AM-co-NIPAM-HBP-NH2 was synthesized by grafting temperature-sensitive monomer N-isopropyl acrylamide (NIPAM) as well as acrylamide (AM) onto the surface of substrate sisal fiber, and further aminating with hyperbranched amine. FTIR, 13C NMR, SEM, EA and TGA were used to confirm the structure and chemical properties of the grafted fibers. Swelling ratio and CO2 adsorption-desorption experiment were investigated to verify the thermo-sensitivity of the grafted fibers and their CO2 adsorption-desorption behavior. Compared with conventional solid amine adsorbents regenerated around 140 °C, SF-AM-co-NIPAM-HBP-NH2 (1:1) with NIPAM could be regenerated at a much lower temperature of 60 °C, while still maintain a high CO2 adsorption capacity (2.61 mmol/g), comparable to that of SF-AM-HBP-NH2 (2.73 mmol/g) before NIPAM introduction. Its excellent regeneration property and the effect of energy consumption reduction make it possible to be used for CO2 adsorption in industrial process.

Preparation of a Solid Amine Microspherical Adsorbent with High CO2 Adsorption Capacity.

Amine-skeleton solid-amine materials are promising adsorbents for CO2 capture from flue gas. Here, a novel solid-amine microsphere was synthesized by cross-linking the skeleton poly(ethylenimine) (PEI) with ethylene glycol diglycidyl ether in a facile one-pot W/O emulsion system. The material had a remarkable CO2 adsorption capacity of 7.28 mmol/g in the presence of moisture at 20 °C, 0.1 bar. The highest ratio of breakthrough capacity to saturation capacity was ca. 84%. According to kinetic simulation, the Avrami kinetic model could better describe the adsorption process of CO2 under different temperatures, in which the value of R2 was above 0.99 and n was between 1 and 2, indicating that both physical and chemical adsorption mechanisms were performed during adsorption. Moreover, the material had a high swelling speed. Equilibrium was established within 30 s, and the swelling ratio was 271% at equilibrium. The saturated adsorbent could be easily regenerated with a regeneration efficiency of 94.63% after six cycles. The PEI microsphere appears to be a promising candidate material for CO2 capture from flue gas.

Adsorption behavior of Au(III) and Pd(II) on persimmon tannin functionalized viscose fiber and the mechanism.

A novel bio-adsorbent (DAVF-PT) was prepared by the introduction of persimmon tannin (PT) on the surface of viscose fiber (VF) through condensation reaction. The adsorbent was applied to the adsorption of Au(III) and Pd(II) from aqueous solution. Batch adsorption experiment found that the adsorption performance of DAVF-PT for Au(III) and Pd(II) was closely related to pH of solution, initial metal ion concentration as well as co-existing metal ions. The adsorption isotherms data of Au(III) and Pd(II) on DAVF-PT could be best explained by the Langmuir equation, and the fitted maximum adsorption amounts for Au(III) and Pd(II) were 535 mg/g and 214 mg/g, much higher than those similar adsorbents reported in the literatures. The thermodynamic study revealed that adsorption reaction was an endothermic, spontaneous and entropy increase process. Furthermore, the kinetics data of Au(III) and Pd(II) adsorption on DAVF-PT obeyed the Pseudo-second-order equation, indicating that the chemical adsorption was the mainly rate-limiting step. The EDS, XPS and XPD analysis confirmed that the gold and palladium ions were reduced to metallic state following adsorption, while the phenolic group was simultaneously converted into quinone group, indicating the potential use of this novel fiber-based adsorbent in the recovery of precious metal ions from wastewater.

PVAm Nanofibers Fabricated by Rotary Jet Wet Spinning and Applied to Bisphenol A Recognition.

Poly(vinylamine) (PVAm) is an important polymer with the highest content of primary amine groups of any polymer. PVAm has a great potential in selective separation and smart materials. It is difficult to fabricate pure PVAm nanofibers by electrospinning and rotary jet spinning (RJS) without additional polymers. In this work, rotary jet wet spinning (RJWS) was applied to fabricate molecular imprinting nanofibers (MINFs) with polyelectrolyte for the first time. Initially, optimal parameters of spinning are investigated, including coagulation bath, solution viscosity, and rotation speed. The PVAm aqueous solution is sensitive to alcohol. To demonstrate RJWS application, PVAm-based MINFs for bisphenol A (one endocrine disruptor) recognition are prepared by adding dummy template, cross-linking, and template elution. The association constant (8.6 mg/L), equilibrium time (30 min), and binding sites utilization rate (80%) of MINFs are evaluated. Its adsorption amount and selectivity are little lower than those of MIPs prepared by bulk polymerization; however, its adsorption speed is faster than that of MIPs.

Synthesis of porous polymer based solid amine adsorbent: Effect of pore size and amine loading on CO2 adsorption.

A series of porous polymers was synthesized by a suspension polymerization of divinylbenzene (DVB) and ethylene glycol dimethyl acrylate (EGDMA), which was further functionalized with polyethyleneimine (PEI) for CO2 capture. The results showed that the synthesized DVB and EGDMA (DE) copolymers were an effective support for loading PEI because of its larger pore size and specific surfaces area. It was found that DE (30, 10) loaded with 30wt% PEI exhibited a higher CO2 adsorption amount of 3.28mmol/g at 25°C under dry condition. The CO2 adsorption capacity would decline gradually as the temperature continuously raised, for the reaction between CO2 and amine groups was an exothermic reaction. The kinetics study showed that Avrami kinetic model could accurately describe the whole CO2 adsorption process, suggesting that both physical adsorption and chemical adsorption were involved with the CO2 adsorption process. The intraparticle diffusion and Boyd's film diffusion models were applied to investigate the CO2 diffusion mechanism, the intraparticle diffusion model could well distinguish the rate-limiting step during CO2 adsorption process. This solid amine adsorbent could be regenerated with nitrogen stream at 75°C, and it kept stable CO2 adsorption capacity after eight adsorption-desorption cycles. All these features indicated that this porous polymer based adsorbent has a high potential for CO2 capture and separation from flue gas.

Preparation and Properties of A Hyperbranch-Structured Polyamine adsorbent for Carbon Dioxide Capture.

A fibrous adsorbent with amino-terminated hyperbranch structure (PP-AM-HBP-NH2) was prepared by grafting hyperbranched polyamine (HBP-NH2) onto the acrylamide-modified polypropylene (PP) fibers. The grafting of AM on PP fibers provided the active sites for introducing HBP-NH2 onto the PP fibers. This kind of "grafting to" procedure to synthesize hyperbranch-structured fiber could overcome the disadvantages of stepwise growth procedure, avoiding the complicated synthesis process and the requirement of strict experimental conditions. The grafted HBP-NH2 was three-dimensional dentritic architecture and had a large number of pores existing within the grafted polymers, which is favorable for CO2 molecules to diffuse into the HBP-NH2. Therefore, the as-prepared PP-AM-HBP-NH2 fibers showed a high adsorption capacity (5.64 mmol/g) for CO2 in the presence of water at 25 °C, and the utilization efficiency of alkyl amino groups could reach 88.2%, demonstrating that the hyperbranched structure of adsorbents can greatly promote adsorption capacity and efficiency. This could be attributed to better swelling properties and lower mass transfer resistance to CO2 of the hyperbranched adsorbent. PP-AM-HBP-NH2 also showed excellent regeneration performance, and it could maintain the same adsorption capacity for CO2 after 15 recycle numbers as the fresh adsorbent.

Solid Amine Adsorbent Prepared by Molecular Imprinting and Its Carbon Dioxide Adsorption Properties.

A carbon dioxide imprinted solid amine adsorbent (IPEIA-R) with polyethylenimine (PEI) as a skeleton was conveniently prepared by using glutaraldehyde to cross-link carbon dioxide-preadsorbed PEI. As confirmed by FTIR, FT-Raman, and 13 C NMR spectroscopy, CO2 preadsorbed on PEI could occupy the reactive sites of amino groups and act as a template for imprinting in the cross-linking process. The imino groups formed from the cross-linking reaction between glutaraldehyde and PEI could be reduced by NaBH4 to form CO2 -adsorbable amino groups. The adsorption results indicated that CO2 imprinting and reduction of imino groups by NaBH4 endowed the adsorbent with a higher CO2 adsorption capacity. Compared with PEI-supported mesoporous adsorbents, the solid amine adsorbent with PEI as a skeleton can avoid serious pore blockage and CO2 diffusion resistance, even with a high amine content. The solid amine adsorbent with PEI as a skeleton showed a remarkable CO2 adsorption capacity (8.56 mmol g-1 ) in the presence of water at 25 °C, owing to the high amine content and good swelling properties. It also showed promising regeneration performance and could maintain almost the same CO2 adsorption capacity after 15 adsorption-desorption cycles.

Preparation and characterization of amine-functionalized sugarcane bagasse for CO2 capture.

A low-cost solid amine adsorbent for CO2 capture was prepared by using sugarcane bagasse (SB), a dominant agro-industrial residue in the sugar and alcohol industry as raw materials. In this preparation process, acrylamide was grafted on SB, and the grafted fiber was then aminated with different type of amine reagents to introduce primary and secondary amine groups onto the surface of SB fibers. The graft and amination conditions were optimized. The prepared solid amine adsorbent showed remarkable CO2 adsorption capacity and the adsorption capacity of the solid amine adsorbent could reach 5.01 mmol CO2/g at room temperature. The comparison of adsorption capacities of amine fibers aminated with various amination agents demonstrated that fibers aminated with triethylenetetramine would obtain higher adsorption capacities and higher amine efficiency. These adsorbents also showed good regeneration performance, the regenerated adsorbent could maintain almost the same adsorption capacity for CO2 after 10 recycles.

Design, synthesis, and characterization of 1,3,5-tri(1H-benzo[d]imidazol-2-yl)benzene-based fluorescent supramolecular columnar liquid crystals with a broad mesomorphic range.

A new kind of supramolecular columnar liquid crystal T-A with a broad mesomorphic range (up to 164.9 °C), good thermal stability, and strong fluorescence is designed and formed by the H-bonding between 1,3,5-tri(1H-benzo[d]imidazol-2-yl)benzene (T) and serial gallic acid derivatives (A). Two components are easily available because of simple routes, common reactions, high yields, commercial starting materials, and inexpensive catalysts. The introduction of the 1,2,3-triazole structure into component A makes the textures different and is slightly disadvantageous for the T-A complexes.

Design of a viscose based solid amine fiber: effect of its chemical structure on adsorption properties for carbon dioxide.

A solid amine fiber VF-AM-TETA was designed with viscose (VF) substrate for efficient CO2 capture, where its hydroxyl groups could serve synergizing effect in CO2-amine reaction. When grafting modification and subsequent amination were applied to VF, effect of structures of grafting monomers as well as amines on its CO2 adsorption properties was taken into account. Amines with different 1° and 2° amine ratios were investigated as amination agents in terms of amine efficiency, so as to afford the fibrous adsorbent with maximum effective reactive amine sites for CO2 capturing. Results suggested that higher content in primary amine can facilitate CO2 adsorption onto the fiber by stronger basicity and smaller steric hindrance. Consequently, optimal chemical structure provided VF-AM-TETA with satisfactory adsorption capacity of 4.08 mmol/g when amine content was 8.74 mmol/g. Constant adsorption behavior within 6 adsorption-desorption cycles indicated its desirable regeneration performance in practical use due to excellent mechanical properties of VF-AM-TETA.

Surface molecular imprinting on polypropylene fibers for rhodamine B selective adsorption.

A surface molecular imprinted fiber (MIF-B) for rhodamine B (RhB) was prepared by bonding polyethylenimine (PEI) onto polypropylene (PP) fibers and subsequently cross-linking with epichlorohydrin (ECH) in the presence of RhB. The chemical structures of composites in each synthetic step were traced by FTIR analyses. The MIF-B exhibited excellent static and dynamic adsorption properties for RhB. Its adsorption isotherm for RhB followed Langmuir model. The competitive adsorption results indicated that the MIF-B had much higher selectivity for RhB over a structural analog (rhodamine 6G) with a selectivity coefficient (K(c)) of 74.1. The MIF-B proved to be a pH-sensitive material. Poly(acrylic acid) (PAA) and PEI chains grafted on PP would stretch or shrink in response to pH, resulting in the change in size and shape of binding sites of the MIF-B. Basic condition could induce the lightly cross-linked MIF-B to swell and expand its surface area, thus providing more memory cavities and internal binding sites constructed by imprinting process and ultimately leading to higher binding capacity and better RhB recognition.

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.

Preparation of amine group-containing chelating fiber for thorough removal of mercury ions.

An aminated chelating fiber (AF) with high adsorption capacity for mercury ions was prepared by grafting copolymerization of acrylonitrile onto polypropylene fiber, followed by aminating with chelating molecule diethylenetriamine. Effects of reaction conditions such as temperature, reaction time, bath ratio and dosage of catalyst on the grafting yield were studied. Chemical structure, tensile strength and thermal stability of AF were characterized. The adsorption performances for mercury were evaluated by batch adsorption experiments and kinetic experiments. The results show that AF is effective for the removal of mercury over a wide range of pH. The chelating fiber also shows much higher adsorption capacities for mercury, the equilibrium adsorption amount could be as high as 657.9 mg/g for mercury. The high adsorption capacity of Hg(2+) on AF is resulted from the strong chelating interaction between amine groups and mercury ions. Two amine groups coordinate with one mercury ion could be speculated from the adsorption capacity and amine group content on AF. The kinetic adsorption results indicate that the adsorption rates of AF for mercury are very rapid. Furthermore, the residual concentration was less than 1 microg/L with feed concentration of mercury below 1mg/L, which can meet the criterion of drinking water, which indicates that the chelating fiber prepared in this study could be applied to low-level Hg contaminated drinking water purification.

CO2 capture by polyethylenimine-modified fibrous adsorbent.

This work focuses on developing a novel adsorbent for CO2 capture, by coating polyethylenimine (PEI) on glass fiber matrix and using epichlorohydrin (ECH) as cross-linking agent. The physicochemical properties of the fibrous adsorbent were characterized. The CO2 adsorption capacity was evaluated. Factors that affect the adsorption capacity of the fibrous adsorbent were studied. The experimental results show that this fibrous PEI adsorbent exhibits a much higher adsorption capacity for CO2 compared with another PEI fiber prepared in our previous work, which employed epoxy resin as the cross-linking agent. A CO2 adsorption capacity as high as 4.12 mmol CO2/g of adsorbent was obtained for this fibrous PEI adsorbent at 30 degrees C, equal to 13.56 mmol CO2/g of PEI, with a PEI/ECH ratio of 20:1. The adsorbent can be completely regenerated at 120 degrees C.

Preparation and characterization of a strong basic anion exchanger by radiation-induced grafting of styrene onto poly(tetrafluoroethylene) fiber.

A novel anion-exchange fiber with strong basic groups has been prepared by grafting styrene onto poly(tetrafluoroethylene) fibers via irradiation. Experiments were carried out to analyze the effects of synthesis conditions on the grafting degree and to characterize the physicochemical properties of the anion-exchange fibers. The experimental results showed that preirradiation grafting styrene onto poly(tetrafluoroethylene) fiber could significantly reduce the waste of raw material and the formation of homopolymer, although the grafting degree was relatively low. The grafting reaction could be effectively enhanced through the addition of magnesium powder into the reaction system. The optimal temperature and time for preirradiation grafting were 80 degrees C and 6 h, respectively. The experimental results also showed that the anion-exchange fibers had excellent mechanical properties and thermal stability at a temperature up to 420 degrees C. The fibers were stable in acidic, alkali, and oxidative solutions. The static ion-exchange capacity of the fibers was as high as 6.08 mmol/g. The static adsorption capacities for Cr(2)O(2-)(7) and MnO(-)(4) ions were 214.08 and 290.98 mg/g, respectively.