查看更多>>摘要：A reduced graphene oxide (rGO)-Gd2MoO6-ZnO nanocomposite was synthesized using a hydrothermal method, in which rod-shaped ZnO and plate-like Gd2MoO6 were decorated on rGO sheets. The as-prepared photocatalyst was characterized using X-ray diffraction, optical studies, photoluminescence measurements, surface morphology, chemical states, and photocurrent density studies. A stable photocatalytic performance was achieved using the synergetic Gd2MoO6-rGO-ZnO composite catalyst during the reduction of Cr(VI) to benign Cr(III) compared with the performance achieved using bare and binary composite catalysts. The effects of various parameters, such as different weight ratios and solution pH, were investigated. An optimized pH of 4 was used for the effective reduction of Cr(VI) to Cr(III). The maximum photocatalytic reduction performance (94.5%) was achieved within 160 min. Photocurrent density and PL emission measurements confirmed the fast charge transfer and effective charge separation over Gd2MoO6-rGO-ZnO, which improved the Cr(VI) reduction. A photocatalytic Cr(VI) reduction mechanism for Gd2MoO6-rGO-ZnO was proposed.
查看更多>>摘要：Polyacrylonitrile (PAN) has been mostly used as a base polymer for asymmetric membrane synthesis with the aim of pervaporation (PV) applications, since it has a superior hydrophilicity and the ability to become hydrolyzed with an alkaline solution. Nonetheless, PAN and hydrolyzed PAN membranes have shown moderate permeate fluxes along with a mechanical softness. In this study, we aimed to improve the PV performance by exploring the possible effect of the hydrolysis of a novel mixed matrix membrane based on PAN and kaolin. Specifically, 15% PAN was used as a dope solution along with varying concentrations (2, 5, 7, and 10%) of kaolin to synthesize mixed matrix membranes using a non-solvent-induced phase separation technique. The 2% kaolin addition maximized the hydrophilicity and water sorption capacity of the membrane by developing wellorganized, deep channel structures with increased porosity, membrane thickness, and surface roughness. The tensile strength was also the highest with the 2% kaolin addition. Further hydrolysis of the 2% kaolin-embedded PAN caused an extra enhancement of its hydrophilicity with a decrease of pore size due to the amplified carboxylic group density. PV performance tests under different salt concentrations confirmed that the hydrolyzed PAN membrane with a 2% kaolin intercalation had an outstanding permeation flux of 82 kg m-2h- 1 and 59 kg m2h-1 as well as a salt rejection of 99.93% and 99.91% with a 3.5% and 10% NaCl solution, respectively, at a 65 degrees C feed temperature.
查看更多>>摘要：Metal-organic frameworks (MOFs) as molecular sieve membrane materials have received extensive attention on the gas separation application. However, the membrane separation performance is extremely limited by its intrinsic stability of frameworks. The successful preparation of high-quality gas separation membranes with excellent stability remains a grand challenge. ZIF-302 is based on hydrophobic ligand in-situ design with a high-stabile chabazite (CHA) topology. Herein, we synthesized uniform ZIF-302 nanocrystals with exceptional stability by introducing a modulator. Correspondingly, the continuous dense ZIF-302 polycrystalline membranes were also prepared for the separation of H-2, N-2, CO2, CH4 and other gases. The permeance of H-2 and separation factor for H-2/CH4 mixtures at 35 degrees C and 1 bar were 2.8 x 10(-8) mol m(-2) S-1 Pa-1 and 51.5, respectively, exceeding the Robeson upper bound in 2008. Furthermore, the separation performance of the super-hydrophobic ZIF-302 membranes for humidified mixed gases can maintain more than 168 hat 35 degrees C, indicating reliable longterm operational stability. Therefore, the CHA-type ZIF-302 polycrystalline membrane is promising for actual industrial gas separation.
查看更多>>摘要：In this work, we report on a regenerable and robust adsorptive membrane with superb dynamic adsorption capacity towards dyes prepared by a controllable mussel-inspired co-deposition of dopamine (DA) and polyethyleneimine (PEI) on a polyvinylidene fluoride (PVDF) microfiltration membrane. The DA oxidative selfpolymerization occurred to form polydopamine for high adhesion with the PVDF membrane. On the other hand, the PEI provided a large number of amino groups with high adsorption ability, and had both Michael addition and Schiff base reaction with DA to induce covalent interaction for high stability. In addition, the codeposition process was controlled to happen on the membrane surface and inside the membrane bulk pores simultaneously. By these ingenious designs, the prepared adsorptive membrane thus showed high dynamic adsorption capacity (up to 188 mg g-1) and ultra-high removal ratio (>99.9%) towards typical anionic dye of methyl blue. Not only that, the membrane could separate rapidly and selectively anionic dyes from dye mixtures. More importantly, the adsorptive membrane showed highly regenerative ability in NaOH solution (after 6 recovery cycles, the treating efficiency maintained higher than 95%), and good durability with robust resistance in acidic and alkaline environments. This work affords an innovative strategy and insight in fabricating the adsorptive membrane using mussel-inspired co-deposition for organic dye removal in water.
查看更多>>摘要：Low cost and high performance NaA zeolite membranes have been successfully prepared on 100-cm-long coarse macroporous alumina supports using industrial grade reagents and chemicals. A simple and efficient sandpaper polishing method can effectively reduce the support surface roughness and the formation process of NaA zeolite membranes was investigated on inexpensive coarse supports by secondary growth, which was more conducive to the preparation of high performance membranes. For separation of a 90 wt% EtOH/H2O mixture at 348 K, the scaled-up NaA zeolite membrane showed a permeation flux of 4.67 kg m(-2) h(-1) and a high separation factor of more than 10,000. Simultaneously, these membranes were used for pervaporation (PV) dehydration of a dimethoxymethane/water (DMM/H2O) mixture for the first time, which exhibited a permeation flux of 0.89 kg m(-2) h(-1) and together with a separation factor of more than 23,000 at 313 K for dehydration of a 96 wt% DMM/H2O mixture. Moreover, the membrane also showed a superior long-term stability for running over 10 d. Importantly, the study on the recovery of permeation flux of scaled-up NaA zeolite membranes after long-term PV experiment to produce high-concentration DMM product (water content was less than 0.1%) found that the permeation flux was recovered to more than 85% of the fresh membranes after the membranes was cleaned using PV test with a methanol aqueous solution. These 100-cm-long NaA zeolite membranes with low cost and high performance demonstrated a promising industrial application prospects for PV dehydration of DMM/H2O mixtures and other organic water mixtures.
V. Fuentes, JessicaZamora, Edgar B.Chakraborty, AnirbanZavala, Gerardo...
16页
查看更多>>摘要：A novel kind of random acrylic terpolymers based on butyl acrylate (B), 2-(dimethylamino)ethyl acrylate (Ae), and 2-carboxyethyl acrylate (Ce) monomers was obtained by emulsion polymerization. Monomers' weight ratios were varied, keeping in all cases a higher content of butyl acrylate (60, 70, 80, and 90 wt%) and controlling the number average molecular mass ((M) over bar (n)) during polymerization. The random acrylic terpolymers were characterized by spectroscopic techniques; subsequently evaluated as demulsifier agents in three aged heavy crude oils of 7.55, 6.11, and 3.33 degrees API (apparent gravities), which form very stable water-in-oil (W/O) emulsions. The best performance for removing the emulsified water at 80 degrees C was obtained with terpolymers containing 90-80 wt% of the hydrophobic monomer B and small amounts of the hydrophilic monomers Ae and Ce (BAeCe-9551 and BAeCe-8111), being more efficient than two commercial demulsifiers (FDH-1 and F-46 TRETOLITE (TM)). Moreover, the BAeCe-9551 terpolymer was evaluated in a fresh heavy crude oil of 20.2 degrees API at 60 degrees C - temperature of separation tanks -, showing better performance as breaker, coalescer, and clarifier than FDH-1. Finally, a quantitative structure-activity relationship (QSAR) analysis was carried out employing terpolymers' molecular parameters and crude oils' physicochemical parameters. Only one equation fulfilled all thresholds for Q(F1)(2), Q(F2)(2), Q(F3)(2), and r(m)(2), parameters, proving to be the most accurate to predict the water removal efficiency (WRE) of BAeCe-1 and BAeCe-2 series terpolymers when added to heavy crude oils. This correlation will allow selecting the best terpolymer for demulsifying a petroleum stream as a function of its physicochemical characteristics.
查看更多>>摘要：It is significant to develop an effective adsorbent for the separation of Mo(VI) and Re(VII) owing to congenital isomorphism. Herein, gallic acid-functionalized microcrystalline cellulose microspheres (MCGA) were synthesized via radiation technology. Batch and column experiments were systematically performed to evaluate the separation behaviors for Mo(VI) and Re(VII). It was discovered that MCGA showed higher adsorption capacity and stronger affinity for Mo(VI) than Re(VII) under the tested condition. The separation of Mo(VI) and Re(VII) could be easily achieved by MCGA, exhibiting a separation factor (beta(Mo/Re)) in the range of 5.23-735.53. Significantly, the dynamic column experiment revealed that the MCGA could selectively recover Mo(VI) from a simulated leaching solution of molybdenite. In addition, different eluents can achieve the stepwise elution of Mo(VI) and Re(VII). With increasing temperature, Mo(VI) and Re(VII) could be more easily separation from the solution. Ultimately, the capture of Mo(VI) by MCGA was attributed to the formation of hydrogen bond and complexes between the adjacent phenolic hydroxyl group and metal ions, while Re(VII) was mainly associated with MCGA by hydrogen bond. Moreover, the excellent adsorption properties indicated that MCGA is a candidate for separation of Mo(VI) and Re(VII) from Mo-Re bearing solution.
查看更多>>摘要：Heavy metals such as mercury and arsenic in water resources have become a global concern due to their toxic, persistent, bio-accumulative, and carcinogenic characteristics. To address health-related issues as well as environmental concerns, it is important to eliminate mercury and arsenic contaminants from water streams. In this study, mercury and arsenic ions were removed from aqueous solutions through micellar-enhanced ultrafiltration (MEUF) using sodium dodecyl sulfate (SDS) and cetylpyridinium chloride (CPC) as chelating agents, respectively. Response surface methodology (RSM), based on the full factorial design (FFD) method, was applied to optimize the process parameters. The relationship between the removal of targeted heavy metals and process variables, including pressure, metal concentration, pH, and molar ratio of surfactant to metal defined by the proposed quadratic models. The models were statistically significant, as shown by analysis of variance. Experimental results presented the optimum operating parameters for > 95% mercury removal were: 2.5 bar pressure, 10 ppm mercury concentration, SDS to mercury MR of 12:1, and pH 8.0. In the case of arsenic, >90% removal was achieved with pressure at 2.5 bar, 15 ppm arsenic concentration, and CPC to arsenic MR at 8:1, and pH 8.0. Statistical validation of RSM models using predicted and experimental results indicated that the proposed model effectively provided a relationship between targeted heavy metal removal and process variables. Additionally, the MEUF performance for mercury and arsenic removal from an aqueous solution was predicted using a gene expression programming model that presented a good fit with the experimental results.
查看更多>>摘要：Membrane technology can minimize spread of viruses in the environment during pandemics, however, its efficiency is highly limited by biofouling. In the current study, a composite membrane composed of commercial membrane material, poly(vinylidene fluoride) (PVDF), and thermo-responsive attapulgite (t-ATP) was developed. The t-ATP was synthesized by surface modification of attapulgite (ATP) nanofiber with poly(N-isopropylacrylamide) (PNIPAM). t-ATP acted as a nucleating seed to expedite crystallization of PVDF and as a hydrophilic modifier to enhance the wetting performance of membrane. The tensile strength, elongation, and permeance of membrane increased with increase in t-ATP content without compromising pore structure. PNIPAM chains in t-ATP were swollen or shrunken with the change in temperature, thus releasing adhesion between membrane and biofoulants. The modified membrane exhibited superior biofouling resistance performance compared with the pristine PVDF membrane owing to the hydrophilic property of t-ATP and the stretchable chains on its surface. Notably, 89% of biofouling on membrane surface was easily removed through a simple temperature-change coupling ultrasonic cleaning process. High performance of the PVDF/t-ATP membrane indicates its potential application for high-efficient biological wastewater treatment.
查看更多>>摘要：In recent years, activation of persulfate via Mn-based composites has gained interest due to extraordinary kinetics and performance for the degradation of organic contaminants. However, the potential of pristine manganese oxides (Mn3O4) in removing organic compounds and its mechanism has not been comprehensively explored yet. This study systemically investigated the Mn3O4 based peroxymonsulfate (PMS) activation to effectively mitigate bisphenol A (BPA) in different real water matrixes. Substantial mineralization (75.9%) with efficient removal of BPA (96.7%) has been achieved at optimum conditions in 60 min. A long-term performance, eight cycles of reusability, has shown merely an 11% reduction in BPA removal, highlighted the higher stability of Mn3O4. The oxidizing contributions of reactive oxygen species (ROS) were in the order of O-1(2) > O-2(center dot-) > SO4 center dot- > (OH)-O-center dot. The different water matrixes have influenced BPA degradation by<10%. Linear changes in BPA aromatic contents were recorded using log-transformed ultraviolet (UV) spectra and fluorescence excitation-emission matrix (EEM). Total 17 transformation products (TPs) were detected in Mn3O4/PMS/BPA system, with 13 decreasing concentrations and 4 TPs in increasing concentration with the beta-scission reaction as the main pathway for the degradation of BPA. The toxicity of BPA after degradation was also significantly suppressed measured by the activated sludge inhibition method.
NSTL
Elsevier