A novel Cr(VI) ion imprinted polymer (IIP) was proposed for fast removal of Cr(VI) from aqueous solution. 4-Vinylpyridine and N,N-diethylaminoethyl methacrylate were used as functional monomers, and ethylene glycol dimethacrylate and 2,2-azoisobisbutyronitrile were used as cross-linker and initiator in the presence of a binary porogenic solvent. The prepared Cr(VI)-IIPs were characterized by the Fourier transform infrared spectroscopy and scanning electron microscopy. The effects of pH, initial concentration of Cr(VI) in aqueous solution, temperature, and operating time on adsorption were investigated. At the low pH range of 1.5–2.5, the adsorption capacities were high. The influence of temperature was slight. The adsorption equilibrium time was within 3 min. The adsorption process followed the pseudo-second-order equation and the Langmuir isotherm model. The maximum adsorption capacity was up to 286.56 mg/g, and the selectivity factors of Cr(VI)/Cu(II), Cr(VI)/Cd(II), and Cr(VI)/Cr(III) were up to 135.78, 145.44, and 69.91, respectively.

Due to the high energy consumption in CO2 capture by amine absorbents, CO2 phase change absorbent, CPCA, has attracted a great attention in research institutes recently. Two phases are formed after CO2 absorption with CPCA as the absorbent, and only the CO2-rich phase goes to the stripper, which could potentially reduce the energy consumption. In this work, the CPCAs composed of MEA/1-propanol/H2O were developed based on the principles of aqueous two-phase systems. The effects of temperature, amine concentration, and total CO2 loading on the phase separation of CPCAs were studied. CO2 loading and 1-propanol distributions in two phases under different experimental conditions were measured. The results indicated that the total CO2 loading is the key factor affecting the distribution of components in two phases. Moreover, in comparison to traditional 30 wt % MEA, the initial absorption rates of all CPCAs were higher than that of MEA, and its maximum value was 5 times higher. The cyclic capacity of the CPCA with 30% MEA + 30% 1-propanol + 40% H2O was 1.70 mol/kg, which was 52% increased comparing to traditional 30 wt % MEA.

•A better conversion enhancement obtained in a catalytically active membrane reactor.•A highly porous catalytic layer was prepared to decrease mass transfer resistance.•Membrane with low mass transfer resistance is key for better coupling performance.•A genuine in-situ water removal at molecular lever was realized.•Approximately 43% of conversion enhancement achieved when compared to equilibrium.A better conversion enhancement of esterification between acetic acid and n-butanol was achieved in a catalytically active membrane reactor (pCAMR) when compared to that in a traditional inert membrane reactor (IMR). This enhancement was attributed to a novel composite catalytically active membrane in which a highly porous catalytic layer was introduced. SEM images showed that the membrane consisted of three layers: the top layer was a highly porous catalytic layer with massive macrovoids and “sponge-like” pores, the middle layer was a dense polyvinyl alcohol selective layer, and the bottom layer was a porous polyethersulfone support layer. The preparation of a highly porous catalytic layer instead of a dense one in the composite membrane greatly decreased the overall mass transfer resistance of the reactor from 6.7 × 105 to 5.6 × 105 s/m, a value which is even comparable to that of IMR (5.1 × 105 s/m) where the additional catalytic layer was absent. The effects of operational parameters on the esterification-pervaporation coupling performance in pCAMR were systematically evaluated. Through a reasonable match between reaction rate and water removal rate, a genuine in-situ water removal at a molecular lever was realized. For comparison, coupling performances in an IMR and a catalytically active membrane reactor with a dense composite membrane (dCAMR) were also investigated. Results showed that the coupling performance in pCAMR outperformed both IMR and dCAMR due to a combination of much lower overall mass transfer resistance and higher mass transfer driving force for water removal in pCAMR. After 45 h at 85 °C, the acid conversion in pCAMR reached almost completion, an approximately 43% of conversion enhancement was achieved when compared to equilibrium conversion.

•A catalytic layer with highly inter-connected sponge-like pores was prepared.•PVP was an optimal pore-forming additive to increase the membrane porosity.•Porosity of the membrane was as high as 81.6%.•Catalytic layer resistance decreased from 48.5% to 20.6% of overall resistances.•CAMR with pCAM showed a best reaction-pervaporation coupling performance.A composite catalytically active membrane was prepared focusing on the reduction of membrane mass transfer resistance to achieve a better esterification-pervaporation coupling performance. The effect of membrane preparation conditions on the membrane morphology was first evaluated. Under an optimized membrane preparation conditions, a “sandwich-like” composite membrane with a highly inter-connected sponge-like catalytic layer on a polyvinyl alcohol / polyethersulfone bilayer was obtained. The porosity of the membrane was found to be as high as 81.6%. A simple resistance-in-series model was developed to analyze the mass transfer resistance distribution in a traditional inert membrane reactor (IMR), a catalytically active membrane reactor (CAMR) with dense catalytic layer and a catalytically active membrane reactor with porous catalytic layer, respectively. Results showed that the preparation of a highly porous catalytic layer decreased the resistance of catalytic layer from 48.5% to 20.6% of overall resistances, leading to an enhanced water removal ability for the composite membrane. Finally, reaction-separation coupling experiments in IMR, CAMR with porous catalytic layer and CAMR with dense catalytic layer showed that, with a faster reaction kinetics and water removal rate, CAMR with porous catalytic layer exhibited a best coupling performance.

•VP-fermentation process is successfully applied to overcome ethanol inhibition.•Coupled with gas stripping, External VP exhibits the optimal performance.•An ethanol productivity of 3.33 g/(L·h) (increased by 56%) is achieved.Vapor permeation (VP) is applied to be integrated with ethanol fermentation as an in situ product recovery technique which could avoid the ethanol inhibition in this study. The polydimethylsiloxane o(PDMS) membrane is used in separating ethanol from model ethanol/water mixture and fermentation integrated processes. And the performance of VP-fermentation process is investigated and compared to that of Pervaporation (PV)-Fermentation and batch fermentation processes. Experimental results show that the ethanol removal is successfully achieved, while it still suffers low flux. Then, in order to reduce the mass transfer resistance in gas boundary layer and thus improving the ethanol removal rate, gas stripping is coupled with VP process to form a new configuration of VP process, i.e. external mode. Benefited from its high ethanol removal rate, the ethanol productivity of External VP-Fermentation process reaches 3.33 g/(L·h), much higher than 2.13 g/(L·h) in batch fermentation and 2.90 g/(L·h) in PV-Fermentation under its optimal condition, i.e. vapor cyclic flow of 1.3 L/min and module temperature of 35 ℃. In VP-fermentation process, membrane deterioration is also efficiently alleviated, which commonly occurs in PV-fermentation process. It makes the membrane process more feasible for industrial fermentation process.

In this study, a copolymerization modification method is used to modify the rigid structure of a high-flux poly(vinyltriethoxysilane) (PVTES) membrane, which was prepared from VTES monomers in our previous work, to further enhance its separation factor. A value of R/Si, which could characterize the density of organic groups and the chain flexibility in membrane materials, is introduced here to guide the selection of modification chemicals. Modifiers with different polymerization degree but the same flexible chain unit (DMDES, HSO and PDMS) are chosen to be copolymerized with PVTES. Analysis results show that the PVTES-HSO membrane possesses lower thickness, higher amount of hydrophobic groups, and an inner structure with greater chain flexibility and lower crystallinity, leading to the best pervaporation (PV) performance among these modified membranes, which is much better than the original PVTES membrane. Furthermore, PVTES-HSO membranes with different R/Si values are prepared to optimize their PV performance. And the optimal PVTES-HSO membrane (R/Si = 1.4) shows the best performance with the separation factor of 6.6 and flux up to 8160 g m−2 h−1 when separating 9 wt% ethanol aqueous solution at 35 °C.

Although the performance of membrane reactors (MR) is highly affected by the ratio of membrane area-to-reaction volume, there are few studies on this effect owing to the difficulties associated with reactor manufacture. In this study, an MR with high A/V ratio, a diameter of 35 m, and a height of 0.8 mm was fabricated. Separation performance of this MR was investigated in an n-butanol/water system. Esterification of acetic acid and n-butanol was used as the model reaction to investigate the performance of catalytically active membrane reactors (CAMR) with different A/V ratios. The reaction conversion was 38.59% in the CAMR with the high A/V ratio of 12,497/m, which was much higher than that in other CAMRs, for reaction time of 60 min and W/Vf ratio of 0.093 g/mL. Excellent catalytic stability of the CAMR was confirmed by performing long-term stability experiments.

A cost-effective route for the synthesis of hydroxylamine chloride (NH2OH·HCl) was proposed by combining ammoximation and oxime hydrolysis reactions (A–O–H route). This route is limited by low equilibrium conversion of oxime hydrolysis, which is a reversible reaction that produces ketone and NH2OH·HCl. A pervaporation membrane reactor (PVMR) was recommended in this route for improving butanoxime hydrolysis conversion by in situ removal of byproduct butanone. Using a PDMS membrane, the effects of feed composition, temperature, and reactant concentration on the PVMR performance were investigated. An enhancement of conversion from about 20% to 84% was achieved. When using a high reactant concentration, NH2OH·HCl can be crystallized in the PVMR. The longtime experiment demonstrated that the membrane was stable in acidic and ionic environments in the reaction mixture.

To achieve a fast adsorption rate and a high adsorption capacity in the selective adsorption of Cr(VI) from wastewater, a novel Cr(VI) ion imprinted polymer (Cr(VI)-IIP) was synthesized by bulk polymerization with ethylene glycol dimethacrylate as a crosslinking agent, azodiisobutyronitrile as an initiator, and acetone as a solvent. Eight functional monomers, including acidic, basic and neutral agents, were investigated in the synthesis of Cr(VI)-IIPs. The Cr(VI)-IIP prepared with 4-vinyl pyridine (4-VP) as a functional monomer provided the highest adsorption capacity, which was characterized by Fourier infrared spectroscopy, zeta potential, Brunauer, Emmett and Teller and scanning electron microscopy. The influences of functional monomer amount, crosslinking agent, initiator, solvent, pH in aqueous solution, initial Cr(VI) concentration, and so on, on adsorption performance were studied. The adsorption process of Cr(VI)-IIP followed a pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The electrostatic interactions between Cr(VI) anion and the protonated N atoms of the functional pyridine groups on prepared IIPs could enhance the adsorption capacity and adsorption rate. Under the optimal operating conditions, the maximum adsorption capacity of Cr(VI)-IIP prepared with 4-VP was up to 338.73 mg g−1, and the adsorption equilibrium was reached within 3 min. The Cr(VI)-IIPs also showed good selectivity, reusability and stability. The selectivity coefficient was up to 189.05 and 96.56 for Cr(VI)/Cu(II) and Cr(VI)/Cr(III), respectively.

A novel thin poly(vinyltriethoxysilane) membrane with hydrophobic Si–O–Si backbone and vinyl groups is proposed to recover ethanol by pervaporation. It exhibits high flux (>10000 g m−2 h−1), which is about ten times higher than that of PDMS, demonstrating that this membrane would facilitate the ethanol industrial production by pervaporation–fermentation process.

The relationship between the flow conditions and the mass transfer in a hollow-fiber membrane contactor was quantitatively correlated by coupling a residence time distribution (RTD) method with a multicontinuous stirred tank reactor model (mCSTR). A vibration technique was applied to manipulate and intensify the mass transfer performance of the hollow-fiber contactor (HFC). Absorption behaviors of CO2 in deionized water were investigated as a model system. The effects of liquid feeding velocity, vibration direction and frequency, operating modes, and packing density on the flow conditions and mass transfer performance were investigated and quantitatively examined by the RTD analysis. The results indicated that the flow conditions as well as the mass transfer performance can be greatly improved at a low liquid-phase velocity or a high packing density. Similarly, the mass transfer intensification was more remarkable, when the absorbent flowed through the shell side of HFC, or the vibration and flow directions were vertical. The mass transfer coefficients obtained from the RTD-mCSTR model showed good agreement with those obtained from the experiments. It appeared that the vibration technique was a powerful method to improve the flow conditions and greatly enhanced the mass transfer performance.

•The effect of module scale on the mass transfer of hollow fiber renewal liquid membrane.•Mass transfer performance of HFRLM is directly proportional to the Peclet number on the shell side.•A new mass transfer correlation including the effect of non-ideal flowing is proposed.The effect of hollow fiber module scale on the mass transfer performance of hollow fiber renewal liquid membrane technique is studied experimentally and theoretically. Five scales of polypropylene hollow fiber membrane modules with same packing density and effective length are used for experiments. CuSO4 aqueous solution is used as feed phase, the organic solution of LIX984N in kerosene is used as liquid membrane phase, and H2SO4 is used as the stripping phase. The non-ideal flow status on the shell-side of the hollow fiber module is described by residence time distribution curves and quantitatively characterized by the Peclet number. Peclet number increases with the increase of L/d in hollow fiber module, and reaches its maximum value when L/d is 20, then decreases. The overall mass transfer coefficient is directly proportional to the Peclet number on the shell side in single-pass, recycling and cascade operation modes in the hollow fiber renewal liquid membrane process. A new mass transfer correlation is proposed to quantitatively describe the non-ideal flow on the shell-side of the hollow fiber module with Peclet number. Then, the corresponding mathematical model for hollow fiber renewal liquid membrane process is developed and the calculated results show good agreement with the experimental data.

Membrane gas absorption technique is one of the most attractive alternatives for CO2 capture. In this paper, a mathematical model for membrane gas absorption process has been developed to describe the solute concentration profile and the mass transfer behavior near the membrane surface, which are important factors for the process. The finite volume method is used to solve the model. The modeling results show that the different solute diffusing distances in the vertical and parallel directions near the membrane surface result in varied concentration profiles. For the membrane with small pore size, the solute concentration profile near the membrane surface can reach uniform distribution instantly, and the membrane porosity has little effect on mass transfer. Contrarily, for the membrane with large pore size, especially at higher absorbent pH value or liquid velocity, the solute concentration distribution is comparatively non-uniform. The mass transfer is significantly affected by membrane porosity. That is the mass transfer coefficients are varied at different membrane porosities. Experiments are conducted to verify the model for CO2 removal using flat sheet membrane contactor with de-ionized water or NaOH solution as absorbents. The comparison between the experimental results and the prediction results shows that the model is validated.

Extraction separation of Cu(II) and Co(II) from sulfuric wastewater is studied with hollow fiber renewal liquid membrane (HFRLM) technique. The organic solution of LIX 984N in kerosene is used as the liquid membrane phase to selectively separate and concentrate Cu(II) from aqueous solution; and the extractant of CYANEX 272 is used as carrier to remove and concentrate Co(II) from aqueous solution. In the selective separation process, LIX 984N has good selectivity on Cu(II); the interactions among metal ions can be negligible; the pH in the feed aqueous solution has significant influence, while the influence of hydrogen ion concentration in the stripping phase is slight. The removal efficiency of Cu(II) increases with the increasing flow rate on lumen side, while decreases with the increasing flow rate on shell side. The results of lab-scale cascade experiments show that the HFRLM technique is a promising treatment method for simulated sulfuric wastewater containing copper and cobalt with separation factor higher than 100. The Cu(II) and Co(II) concentrations in the raffinate are lower than 0.50 mg L−1 and 1.0 mg L−1, respectively, which are both below the standard of wastewater discharge in China. Based on the surface renewal theory, resistance-in-series model and mass balance law, a corresponding mass transfer mathematical model is developed; and the calculated results are in good agreement with experimental data.Research highlights▶ Multicomponent wastewater treatment by a new liquid membrane technique. ▶ Selective extraction characteristics of hollow fiber renewal liquid membrane. ▶ Two extractant for selective extraction of copper and cobalt. ▶ Mathematical mass transfer model based on the surface renewal theory.

The effects of organic solutions on the stability and extraction equilibrium of penicillin G were investigated. N-Butyl acetate, methyl isobutyl ketone, 2-ethyl hexanol, kerosene, and n-heptane were used for physical extraction; di-N-octylamine, tri-N-octylamine, N235 (a mixture of tertiary amines), tributyl phosphate, and di-(2-ethylhexyl)phosphoric acid were used as the extractants, with N-butyl acetate, kerosene, and n-heptane as diluents for reactive extraction. The degradation efficiency of penicillin G increases with increasing temperature. The stability of penicillin G was better in the presence of an amine-based extractant, while it was worse in the presence of a phosphorus acid extractant. The effect of neutral extractant on the stability of penicillin G was mainly dependent on the temperature. The degradation of penicillin G in alkali solution was governed by pH. The efficiency of physical extraction of penicillin G increased with decreasing pH in the aqueous solution. The efficiency of reactive extraction with an amine-based extractant was highest under the range studied. The extractant of phosphorus acid was better than neutral phosphorus extractant for the extraction of penicillin G. The distribution coefficient decreases with increasing pH, temperature, and initial penicillin G concentration in the aqueous solution under the studied conditions. The mechanism of degradation and extraction was also discussed.

As an energy-efficient alternative to distillation, pervaporation has been widely combined with fermentation to remove organic compounds from their dilute solutions in a fermentation broth. In this work, the organic permselective composite membrane is prepared by coating polydimethylsiloxane (PDMS) cross-linked with n-heptane on the substrate of polytetrafluoroethylene(PTFE) membrane. The separation behavior is studied in different dilute organic solutions, which include acetone dilute solution, butanone dilute solution, cyclohexanone dilute solution, ethanol dilute solution, isopropanol dilute solution, n-butyl alcohol dilute solution, acetic acid dilute solution, and ethyl acetate dilute solution. Most of these solutions are main reaction products or by-products from fermentation process. The effects of solubility of organics in the membrane, molecular weight, and polarity of the organics on the pervaporation performance are investigated. The effects of operating temperature and organic concentration in the feed solutions on the performance of composite membrane are studied as well. The experimental results show that molecular volume has less influence than solubility and molecular polarity for these organic solvent. The selectivity of PDMS membrane to ethyl acetate is relative high due to good solubility and diffusion of ethyl acetate molecules in polymer.

The synthesis of butyl oleate was studied in this paper with immobilized lipase. Five types of membrane were used as support to immobilize Rhizopus arrhizus lipase by following a procedure combining filtration and protein cross-linking. Results showed that hydrophobic polytetrafluoroethene membrane with nonwoven fabric (HO-PTFE-NF) was the favorite choice in terms of higher protein loading, activity, and specific activity of immobilized lipase. The factors including solvent polarity, lipase dosage, concentration, and molar ratio of substrate and temperature were found to have significant influence on conversion. Results showed that hexane (logP = 3.53) was a favorable solvent for the biosynthesis of butyl oleate in our studies. The optimal conditions were experimentally determined of 50 U immobilized lipase, molar ratio of oleic acid to butanol of 1.0, substrate concentration of 0.12 mol/L, temperature of 37 °C, and reaction time of 2 h. The conversion was beyond 91% and decreased slightly after 18 cycles. Lipase immobilization can improve the conversion and the repeated use of immobilized lipase relative to free lipase.

A method of improving the absorption performance in hollow fiber contactor by adding a third solid phase into the shell side absorbent is proposed. Powdered kieselgur, graphite, and BaSO4 are chosen as the additives to intensify the absorption process of the CO2/NaOH(aq) system. Ultrasound is used in this work as an approach to make the solid particles suspend in the liquid absorbent. The mass-transfer rate is enhanced about 40% by adding solid particles into the absorbent liquid in the presence of ultrasound. As for different types of particles, the smaller the density difference between the absorbent and the solid, the higher enhancement factor obtained. The enhancement factor is a function of the solids loading as well as the liquid velocity in the shell side of the module. The mass-transfer coefficient and enhancement factor remain almost the same with increasing pH from 7 to 11; as pH further increases, both the mass-transfer coefficient and the enhancement factor are increasing dramatically. The results also indicate that the enhancement factors increase with an increase of the packing density. The residence time distribution (RTD) curves are measured to observe the flow status in the shell side; the results demonstrate that addition of solid particles can improve the flow conditions in the shell side. A mathematical model for the intensification process based on surface renewal theory is developed; the calculated results have a good agreement with the experimental results under the present experimental conditions.

Hollow fiber renewal liquid membrane (HFRLM) technique for simultaneous separation and concentration of Cr(VI) from acidic dilute solution has been studied using tri-n-butyl phosphate as mobile carrier. The influences of the mobile carrier concentration, pH of the feed phase, the initial Cr(VI) concentration, and the stripping concentration on the mass transfer rate are investigated. The transport rate of Cr(VI) increases with increasing the carrier concentration and the stripping concentration, then reaches a “plateau”. The concentration factor as high as 25∼30 has been achieved easily. A mathematical model is proposed to explain the transport mechanism. The validity of this model is evaluated and good agreement between predicted results and experiment data are obtained. Results suggest that the HFRLM technique provides a promising alternative to treat industrial wastewater at low Cr(VI) concentration.

The facilitated transport of penicillin G from aqueous solutions to the stripping phase through bulk liquid membrane (BLM) containing TBP in 3% iso-octanol and n-butyl acetate was studied. Na2CO3 solution was used as the stripping phase. Experiments were performed as a function of stirring rate, TBP concentration and type of diluent in the liquid membrane phase, pH, and initial penicillin G concentration in the feed phase, Na2CO3 concentration in the stripping phase, etc. The results showed that the BLM process could carry out the simultaneous separation and concentration of penicillin G from dilute aqueous solutions, and arise “up-hill” effect due to the characteristic of non-equilibrium mass transfer. The diffusion of penicillin G complex in the liquid membrane phase played an important role in BLM process. The mass transfer mechanism of BLM for this system was also discussed.

In this paper, the effects of pH on the mass transfer of copper extraction with hollow fiber renewal liquid membrane (HFRLM), which is a new type of liquid membrane system based on the surface renewal theory, were investigated. The system of CuSO4 in acetate buffer solution + D2EHPA in kerosene + acidic aqueous solutions was used to study the effects of pH and acetate ion concentration in the feed phase and type and acidity of the stripping phase on the mass transfer performance of the HFRLM process. Results showed that the mass transfer flux and removal efficiency of copper increase with increasing pH in the feed phase, reach a maximum value at pH of 4.44, and then decrease; an addition of acetate buffer solution at a low acetate ion concentration in the feed phase is enough for maintaining the higher mass transfer flux and removal efficiency in the HFRLM process. The influence of the stripping phase on the mass transfer performance of the HFRLM process is weak in our ranges studied. The stripping phase at a low hydrogen concentration is enough for the extraction of copper by HFRLM. The mass transfer fluxes of copper ions from feed solutions with different stripping acids followed the order: Cl− > PO43− > SO42− > NO3−. And, a detailed mathematical model was developed based on the surface renewal theory. The calculated results have good agreement with experimental results.

With micron talcum particles and nano-CaCO3 powder as test dust, a series of experiments have been carried out to systematically study the gas filtration and regeneration behavior of polytetrafluoroethylene membrane, and some comparisons were made with common filter media. The experimental results showed that the PTFE membrane had a filtration efficiency of above 99.99% for micron particles, and excellent regeneration behavior was obtained, though a much higher initial pressure drop existed. Based on the results, it was concluded that the PTFE membrane is an excellent surface-filtration media for micron particles. Effects of operation parameters, including airflow velocity, particle concentration and particle characteristics were also investigated. To better understand the evolution of pressure drop during the filtration process, a mathematical model with operation parameters and characteristics of particles was derived from the gas-solid two-phase flow theories. A novel method on the determination of regeneration period of the filter media was put forward based on the analysis of the pressure drop according to this model.

Eight kinds of flat membranes with different micro-structures were chosen to carry out the membrane absorption experiments with CO2 and de-ionized water or 0.1 mol·L−1 NaOH solution as the experimental system. According to experimental results, the membrane pores shape (stretched pore and cylinder pore) and membrane thickness do not affect the membrane absorption process, and the membrane porosity has only little influence on membrane absorption process for slow mass transfer system. However, the influence of porosity on the membrane absorption process became visible for fast mass transfer system. Moreover, the mass transfer behavior near the membrane surface on liquid side was studied. The results show that the influence of membrane porosity on mass transfer relates to flow condition, absorption system and distance between micro-pores, etc.

Filtration is one of the most effective methods to remove suspended fine particles from air. In filtration processes, pressure drop of compact dust cake causes problems in efficiency and economy, which has received increasing attention and still remains challenging. In this study, we developed a novel technique to intensify the filtration of fine particles with efficient humidification. Two strategies for humidification, including ultrasonic atomization and steam humidification (controlling of ambient humidity), were employed and proved to be both effective. The regeneration frequency of the filter could be reduced by 55% with ultrasonic atomization, while steam humidification could lead to a 78% reduction in regeneration frequency. The effect of operating conditions on pressure drop and the mass loading during filtration were investigated. The dust cake showed a loose and porous structure with an optimized droplet-to-particle ratio. With the ratio of 1.53 and 0.0282, the maximum mass loading was 552 g·m− 2 upon the ultrasonic atomization and 720 g·m− 2 upon the steam humidification. The results show that humidification could slow down the increase of pressure drop during filtration and improve the efficiency of process.Download full-size image

The extraction ability of organophosphorus extractant D2EHPA (di-2-ethylhexyl phosphoric acid) and hydroximic extractant Lix984N are investigated by the extraction equilibrium experiments. Effects of carrier concentration and organic/aqueous volume ratio on the mass transfer of hollow fiber renewal liquid membrane (HFRLM) are studied. Results show that, in the extracting process, kerosene and n-heptane are more suitable than methyl-isobutyl ketone, butylacetate and benzene as the diluents of D2EHPA or Lix984N. The favorable feed pH is 4.4 for D2EHPA and 2.6 for Lix984N. The mass transfer flux of HFRLM increases with carrier concentration and finally reaches a plateau. The mass transfer flux and the overall transfer coefficient increase with the organic/aqueous volume ratio, reach the maximum and then decrease.

•An approach to develop CO2 phase change absorbent (CPCA) was proposed.•The novel MEA-based CPCAs composed of MEA/alcohol/H2O were developed.•Species distributions in two phases were characterized.•The optimal CO2 cyclic capacity of CPCA was 62% higher than that of 30 wt% MEA/H2O.By using the salting-out phenomenon to induce phase separation, the novel CO2 phase change absorbents (CPCAs) composed of MEA/water-miscible alcohol/H2O were developed. The absorbents using 1-propanol, 2-propanol and tertiary butanol as the diluent were selected as CPCAs. The CPCAs composed of MEA/1-propanol/H2O were further examined include the species distributions in the two phases, physical properties, cyclic capacity and absorbent regenerability. In comparison to 30 wt% MEA/H2O, the optimal CO2 cycle capacity of CPCA is 2.59 mol CO2/kg which increase 62% and the volume of CPCA sent to the stripper decreased over 67%. The developed CPCAs would benefit to reduce energy consumption of CO2 capture.Download high-res image (67KB)Download full-size image

To achieve a fast adsorption rate and a high adsorption capacity in the selective adsorption of Cr(VI) from wastewater, a novel Cr(VI) ion imprinted polymer (Cr(VI)-IIP) was synthesized by bulk polymerization with ethylene glycol dimethacrylate as a crosslinking agent, azodiisobutyronitrile as an initiator, and acetone as a solvent. Eight functional monomers, including acidic, basic and neutral agents, were investigated in the synthesis of Cr(VI)-IIPs. The Cr(VI)-IIP prepared with 4-vinyl pyridine (4-VP) as a functional monomer provided the highest adsorption capacity, which was characterized by Fourier infrared spectroscopy, zeta potential, Brunauer, Emmett and Teller and scanning electron microscopy. The influences of functional monomer amount, crosslinking agent, initiator, solvent, pH in aqueous solution, initial Cr(VI) concentration, and so on, on adsorption performance were studied. The adsorption process of Cr(VI)-IIP followed a pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The electrostatic interactions between Cr(VI) anion and the protonated N atoms of the functional pyridine groups on prepared IIPs could enhance the adsorption capacity and adsorption rate. Under the optimal operating conditions, the maximum adsorption capacity of Cr(VI)-IIP prepared with 4-VP was up to 338.73 mg g−1, and the adsorption equilibrium was reached within 3 min. The Cr(VI)-IIPs also showed good selectivity, reusability and stability. The selectivity coefficient was up to 189.05 and 96.56 for Cr(VI)/Cu(II) and Cr(VI)/Cr(III), respectively.