Dynamic Adsorption Capacity Research Articles

An activated carbon from walnut shell for dynamic capture of high concentration gaseous iodine

In order to capture the high concentration gaseous iodine from off-gas streams under nuclear accident conditions, an advanced activated carbon was prepared by using walnut shell as a raw material and zinc chloride as an activator agent (named WS-ZnCl2). The pore structure and functional groups characteristics of the adsorbent were researched via three techniques including N2 adsorption–desorption isotherms, transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FTIR). The Brunauer-Emmett-Teller (BET) surface area, the total pore volume and the average pore size of the adsorbent were observed to be 1360 m2/g, 0.68 cm3/g and 2.00 nm, respectively. In addition, the adsorption capacities of the adsorbent to capture gaseous iodine were investigated with static and dynamic experimental adsorption methods. The results of the static experimental adsorption indicated that the gaseous iodine equilibrium adsorption capacity of the walnut shell before and after ZnCl2 activation increased from 606 mg/g to 2374 mg/g at condition of 80 °C and ambient pressure. The dynamic adsorption performance of the adsorbent for capture of gaseous iodine was studied by varying operating parameters, such as temperature, adsorption column height, and the flow rate. More significantly, the maximum dynamic adsorption capacity of the adsorbent for capture gaseous iodine reached a record of 1634 mg/g at 60 °C, 2.2 cm and 250 mL/min. Finally, the importance ranking of the influencing factors on the dynamic adsorption was analyzed by Grey relational analysis (GRA) method. The results showed that adsorption capacity was obviously affected by flow rate, whereas adsorption time was highly influenced by adsorption column height. The adsorbent researched in this paper has potential to capture high concentration gaseous iodine.

Comparative studies on the toluene sorption performance over silicalite-1 zeolites with different morphologies

The silicalite-1 zeolites with different morphologies (spherical-like, plate-like, and brick-like) were synthesized successfully to study the toluene sorption. The results demonstrate that morphology has a significant and different effect on toluene adsorption under dry or wet conditions. The dynamic adsorption capacities follow S–S (spherical-like silicalite-1) > P–S (plate-like silicalite-1) > B–S (brick-like silicalite-1) under the dry condition (303 K). For the wet condition (RH = 50%, 303 K), the order of the dynamic adsorption capacities is P–S > S–S > B–S. Silicalite-1 zeolites were tested for five adsorption-regeneration cycles to study the reusability and their performance remained stable above 85% after five cycles. The calculated rate constants of Yoon-Nelson model and Weber-Morris (W-M) intra-particle diffusion model reveal that there is less diffusion resistance in P–S. The findings may provide valuable information on zeolite-based adsorbents for adsorption removal or recovery of volatile organic compounds.

High efficient adsorption for thorium in aqueous solution using a novel tentacle-type chitosan-based aerogel: Adsorption behavior and mechanism

A novel tentacle-type chitosan-based aerogel with swelling resistance was prepared via sol-gel technology using resorcinol as enhancer and g-C3N4 as tentacle. The introduction of resorcinol and g-C3N4 could not only increase the stability of the chitosan-based aerogel but also reduce the inter-molecular and intra-molecular interactions in chitosan, thereby enhancing the response of active sites to thorium. The adsorption performance of the chitosan-based aerogel for thorium from solution was verified by static and dynamic adsorption experiments. The results showed that the chitosan-based aerogel possessed an outstanding adsorption property for thorium with a short equilibrium time (20 min), a fast adsorption rate (103.9 mg/(g·min)), a high removal efficiency at low concentration (99.4 %) and a large static saturated adsorption capacity (526.2 mg/g). The dynamic adsorption experiments showed that the maximum dynamic adsorption capacity of the chitosan-based aerogel reached about 499.7 mg/g, which was consistent with static adsorption, far exceeding the reported chitosan-based adsorption materials. The results indicated that the capture of thorium on the tentacle-type chitosan-based aerogel was controlled by various factors, such as electrostatic interactions, surface complexation and cation-π effect. In a word, the tentacle-type chitosan-based aerogel could be used as a promising adsorbent for the remediation of thorium-containing wastewater.

Highly efficient synthesis of ZSM-5 zeolite by one-step microwave using desilication solution of coal gasification coarse slag and its application to VOCs adsorption

The increased production of coal gasification coarse slag (CGCS) has placed a significant environmental load on the environment. In this research, one-step microwave synthesis employing coal gasification coarse slag desilication solution as the major source of Si and Na increased the nucleation and crystallization rate of ZSM-5 zeolite. The optimum synthesis conditions were 180 °C, 4 h, Na2O/SiO2 molar ratio of 0.2, and SiO2/Al2O3 molar ratio of 200, which led to a relative crystallinity of ZSM-5 zeolite higher than 100 % and a specific surface area of 344.27 m2•g−1. The resulting high-purity ZSM-5 zeolite not only has high SiO2/Al2O3 molar ratio, good specific surface area, and regular hexagonal prism structure, but also has high crystallinity, smooth crystal surface and great grain homogeneity because of the microwave process. Its static adsorption capacities toward p-xylene and butyl acetate were 106.84 and 115.47 mg•g−1, respectively, and the dynamic adsorption capacities were 81.44 and 176.14 mg•g−1, respectively. The preparation method of ZSM-5 zeolite with high efficiency and low cost proposed in this paper not only contributes to the high-value utilization of CGCS, but also provides an effective method and practical guidance for the removal of volatile organic compounds (VOCs).

Cascaded membrane and chromatography technologies for fractionating and purifying of bovine milk oligosaccharides

We previously reported that major bovine milk oligosaccharides (BMO) can qualitatively and quantitatively analyzed using ultra high liquid chromatography on a high sensitivity fluorescence detection instrument; the method does not require the removal of lactose and uses small (only 100 μL) samples. In this study, we extended our strategy to fractionation and purification of BMO using membrane separation and chromatography techniques. The effects of membrane molecular weight cut-off (MWCO) and diafiltration the efficiency of the overall process were evaluated, with process optimization leading to suitable MWCOs for microfiltration (ceramic, 0.1 μm), ultrafiltration (spiral wound organic membrane, 30 kDa), and nanofiltration (spiral wound organic membrane, 500–700 Da). Total BMO recoveries of 97.36, 95.58, and 98.30% were observed for the microfiltration, ultrafiltration, and nanofiltration stages, respectively, with corresponding membrane fluxes of 75.74, 76.90, and 81.68 L/(m2·h), respectively. In addition, the crude BMOs were further purified using size-exclusion chromatography, activated charcoal, lactase digestion, dialysis, crystallization, and anion-exchange chromatography. Anion-exchange chromatography with Q Sepharose Fast Flow anion-exchange resin was found to be more suited to industrial BMO production than other methods; it not only effectively separates lactose and oligosaccharides, but also exhibits dynamic adsorption capacity of 1.20 mg BMOs/mL gel.

Nitrogen-rich triazine-based porous polymers for efficient removal of bisphenol micropollutants

Achieving both rapid adsorption rate and high adsorption capacity for bisphenol micropollutants from aquatic systems is critical for efficient adsorbents in water remediation. Here, we elaborately prepared three nitrogen-rich triazine-based porous polymers (NTPs) with similar geometric configurations and nitrogen contents (41.70–44.18 wt%) while tunable BET surface areas and micropore volumes in the range of 454.7–536.3 m2 g−1 and 0.20–0.84 cm3 g−1, respectively. It was systematically revealed that the synergy of hydrogen bonding, π−π electron-donor-acceptor interaction, and micropore preservation promoted the rapid (within 5 min) and high capacity adsorption of bisphenols by NTPs. Particularly, microporous-dominated NTPs-3 with the highest micro-pore volume (0.84 cm3 g−1) displays remarkable adsorption capacity towards bisphenol A as evidenced by the adsorption capacity of 182.23 mg g−1. A simple column filter constructed by NTPs-3 also expressed good dynamic adsorption and regeneration capacity. This work provided new insight into the rational design and engineering of nitrogen-rich porous polymers for the remediation of micropollutant wastewater.

Constructing AgY@Cu-BTC hybrid composite for enhanced sulfides capture and moisture resistance

Metal-modified zeolites and function-matched metal organic frameworks (MOFs) have been adapted to different scenarios of sulfides capture in order to meet increasingly stringent quality requirements and environmental regulations. However, achieving enhanced performances of both adsorption capacity and moisture resistance is still challenging. In this study, we provided an approach to the synthesis of [email protected] hybrid composite for enhanced sulfides capture and moisture resistance. Multiple characterizations confirmed the hybrid structure of [email protected] Additionally, computational simulation and dynamic adsorption measurement were combined to evaluate the adsorption of several typical sulfides on synthesized adsorbents, and reveal the competitive adsorption mechanism. Both Ag species and ethanol solvent lead to the partial reduction of Cu(II) to Cu(I) within the [email protected] framework. The dynamic adsorption capacity of the [email protected] is 1.54 times and 1.38 times higher than those of the parent AgY and Cu-BTC, respectively. Moreover, the [email protected] retains much more adsorption capability for sulfides than the AgY sample with the same water content. Present study highlights the competitive adsorption of various sulfides on the hybrid structures as well as the influences of pre-adsorbed water on sulfide adsorption, and provides insights into the function-oriented development of adsorption materials.

Mussel inspired surface functionalization of polyamide membranes for the removal and adsorption of crystal violet dye

In this work, we report the adsorptive membrane technology with remarkable dynamic adsorption capacity (DAC) and selectivity towards crystal violet dye synthesized by mussel inspired co-deposition of dopamine (DP) and polyethyleneimine (PEI) on to the polyamide thin film composite (TFC) membrane. The dopamine coated TiO2 (TiO2-DP) acts as filler in which polydopamine (PDA) formation via the oxidative self-polymerization of dopamine facilitates high adhesion with the substrate. On the other hand, PEI offers abundant of amino groups that have separative and adsorption ability along with having both Schiff base reaction and Michael addition with dopamine to prompt covalent based interaction for greater stability. The invention of such structural design offers eminent dynamic adsorption capacity (up till 200 mg g−1) along with excellent selectivity (96%) towards crystal violet dye. Not only has the membrane offered high selectivity and dynamic adsorption capacity. More importantly, the membranes exhibits high chlorine resistivity and antifouling property. The data depicted in paper not solely facilitates novel approach to fabricated nanofiltration membranes, but also offers mussel inspired layer by layer strategical design composed of advanced material mainly for environmental based application.

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Study of the reversible/irreversible character of the deactivation of CuO/SBA–15 SOx adsorbents in wet conditions under SO2 adsorption/regeneration cycling experiments

The effect of water vapor on the DeSOx performance of regenerable CuO/SBA-15 adsorbent was investigated for different temperatures of adsorption/regeneration cycles and CuO loadings. At 400 °C a significant decrease of both dynamic and total SO2 adsorption capacity compared to the ones measured without water was observed. This decrease could be related to a faster migration and aggregation of the CuO active phase, an adsorption competition between water and SO2 molecules on the active sites and/or the formation of copper based sulfate/oxysulfate/hydroxy-oxysulfate species difficult to decompose during the reductive regeneration step. On the other hand, at 450 °C water vapor leads to an increase of the total SO2 adsorption capacity by more than 20%, which might be due to an acceleration of the oxidation of SO2, a faster chemisorption of the sulfur species on the active sites and a more efficient regeneration step with regard to 400 °C. The decrease of the CuO loading from 15 to 7 wt% leads to a lower deactivation (i.e loss of SO2 adsorption capacity) at the breakthrough of the adsorbent under wet conditions. Whatever the temperature and the CuO loading, once the water vapor is removed from the gas stream, the dynamic SO2 adsorption capacities are totally or partially recovered. This behavior shows that the deactivation of the CuO/SBA–15 adsorbent induced by water vapor is a reversible or partially reversible phenomenon. It appears that during the DeSOx process a migration towards the pore mouth and an aggregation of the CuO active phase occur faster under water vapor conditions with the formation of large particles of CuO.

Optimal pore size design guided by GCMC molecular simulation for VOCs adsorption

Adsorption has been proved to be an effective control method of Volatile organic compounds (VOCs). However, the design of porous carbon materials with a high VOCs adsorption performance is still a challenging topic. Herein, we proposed a novel material preparation path, namely, the synthesis of porous carbon materials guided by molecular simulation. Firstly, the optimal adsorption pore size of VOCs was calculated by grand canonical Monte Carlo (GCMC) simulation, and then cork based porous carbon with the optimal pore size controlled by urea and KOH was prepared. The sample treated at 900 °C had a specific surface area of 1940 m2/g, a total pore volume of 1.27 cm3/g, a micropore volume of 0.71 cm3/g, which showed an excellent VOCs adsorption performance at 25 °C. Specifically, the dynamic adsorption capacity of acetone and toluene were 6.1 mmol/g and 5.4 mmol/g, and the static adsorption capacity of acetone and toluene were 17.5 mmol/g (18 kPa) and 9.5 mmol/g (3 kPa), respectively. In terms of the pore size distribution, the contribution of the optimal pore sizes to the adsorption process was estimated to be about 69% for acetone and 59% for toluene. Besides, the relationship between the optimal pore size and its adsorption capacity was explored by mathematical methods, which showed a highly linear one. This study provides a novel idea for the design and optimization of excellent adsorbent materials.

Removing Calcium Ions from Remelt Syrup with Rosin-Based Macroporous Cationic Resin.

Mineral ions (mainly calcium ions) from sugarcane juice can be trapped inside the heating tubes of evaporators and vacuum boiling pans, and calcium ions are precipitated. Consequently, sugar productivity and yield are negatively affected. Calcium ions can be removed from sugarcane juice using adsorption. This paper described the experimental condition for the batch adsorption performance of rosin-based macroporous cationic resins (RMCRs) for calcium ions. The kinetics of adsorption was defined by the pseudo-first-order model, and the isotherms of calcium ions followed the Freundlich isotherm model. The maximal monolayer adsorption capacity of calcium ions was 37.05 mg·g−1 at a resin dosage of 4 g·L−1, pH of 7.0, temperature of 75 °C, and contact time of 10 h. It appeared that the adsorption was spontaneous and endothermic based on the thermodynamic parameters. The removal rate of calcium ions in remelt syrup by RMCRs was 90.71%. Calcium ions were effectively removed from loaded RMCRs by 0.1 mol·L−1 of HCl, and the RMCRs could be recycled. The dynamic saturated adsorption capacity of RMCRs for calcium ions in remelt syrup was 37.90 mg·g−1. These results suggest that RMCRs are inexpensive and efficient adsorbents and have potential applications for removing calcium ions in remelt syrup.

Montmorillonite-reduced graphene oxide composite aerogel (M−rGO): A green adsorbent for the dynamic removal of cadmium and methylene blue from wastewater

In this study, a type of montmorillonite-reduced graphene oxide aerogel (M−rGO) was successfully prepared by the sol–gel method and used for the effective removal of heavy metals (cadmium, Cd) and cationic dyes (methylene blue, MB) in wastewater. The chemical composition and micromorphology of the resulting M−rGO were characterized utilizing scanning electron microscopy and energy dispersive spectrometry, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction. Furthermore, the effects of the initial concentration, adsorption time, and temperature on the static adsorption process were systematically studied. Equally important, the effects of the concentration, pH, ionic strength (IS), and pumping flow rate of contaminated solution on the dynamic removal of Cd and MB by M−rGO were investigated by a fixed-bed column experiment. The kinetics, isothermals, and thermodynamic adsorption experiment results showed that the Langmuir and pseudosecond-order models best suited the adsorption process in which physical adsorption and chemical adsorption act together. Functional groups containing O and C were involved in the adsorption of Cd and MB, and the hydrogen bonds, π-π, n-π interaction, and hydrophobic interaction between M−rGO and MB made important contributions to adsorption. The lower initial concentration, higher pH value, and slower pumping flow rate of the contaminated solution can effectively increase the dynamic adsorption capacity of Cd and MB on M−rGO. Contrary to that of Cd, the adsorption capacity of MB on M−rGO increased with IS. Both static adsorption and dynamic column experiments confirmed that the presence of Cd promoted the adsorption of MB, and MB inhibited the adsorption of Cd by M−rGO. In addition, the Cd/MB combined pollution wastewater experiment and the regeneration study showed that M−rGO could be a cost-effective and promising sorbent for Cd and MB wastewater treatment due to its high efficiency and excellent reusability.

High mechanical performance submicron-sized Cu2O-derived necklace-shaped PAN nanofiber composite membrane towards adsorption desulfurization application

The selective adsorption desulfurization technology is considered to be of energy conservation and environment-friendly operation. However, the ongoing development of adsorption desulfurization is greatly restricted by the adsorbents with preferable mechanical properties and sustainable separation efficiency. In this paper, a submicron-sized Cu2O necklace-shaped polyacrylonitrile (PAN) nanofiber composite membrane (Cu2O/PAN NFM) was prepared by electrospinning technology. The structure and mechanical properties of NFM were determined by a series of characterizations. The results showed that the resulting Cu2O/PAN-NFM has a larger total pore volume (0.0802 mL/g), higher tensile strength (5.65 MPa) and lower friction coefficient (0.2571) than those of PAN nanofiber membrane (PAN NFM). The static and dynamic adsorption performances of the Cu2O/PAN NFM were investigated with thiophene(TH) simulated oil. The results showed that the static and dynamic saturated adsorption capacities of the Cu2O/PAN NFM were up to 32.91 mg/g and 4.57 mg/g at 500 mg/L initial concentration, respectively. Besides, the adsorption kinetics and isotherms of TH on the Cu2O/PAN NFM indicated that the TH adsorption data are fitting to Avrami model and Liu isotherm. In addition, the exclusive notable merits of the Cu2O/PAN NFM expressed at the robust mechanical properties and outstanding separation efficiency while keeping the sustainable adsorption capacity after the repeated recycling, which exhibited a promising application towards adsorption desulfurization.

A hyper-cross-linked polymer derived from pitch as an efficient adsorbent for VOCs

Hyper-cross-linked polymers (HCPs) have been attracted widespread attention as adsorbents in recent years. A series of HCPs (HCP-1, HCP-2 and HCP-3) were synthesized via a Friedel-Crafts reaction using low-cross-linked pitch as precursor and dichloromethane (DCM) as cross-linking reagent and solvent. The prepared HCPs were characterized by N2 adsorption, Fourier transform infrared (FI-IR), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and static water contact angle. The resultant HCPs possess micro/meso pore structures and a high stability. The Brunauer-Emmett-Teller (BET) surface areas of HCP-1, HCP-2 and HCP-3 are 152 m2·g−1, 467 m2·g−1 and 447 m2·g−1, respectively. Their total pore volumes vary from 0.207 cm·g−1 to 0.545 cm3·g−1 and following the sequence of HCP-1<HCP-3<HCP-2. The FTIR spectra of HCPs suggests the DCM is successfully grafted onto the skeleton structure. Dynamic adsorption capacities of the prepared HCP-1, HCP-2 and HCP-3 were examined and the results show the adsorption properties of o-xylene on HCP-2 are significantly higher than that of the other HCPs. The adsorption amount of o-xylene on HCP-2 is 198.18 mg·g−1, which is higher than that of benzene, suggesting a strong adsorption selectivity for o-xylene over benzene. In addition, the effect of water vapor on the adsorption of o-xylene onto HCP-2 was investigated. The dynamic adsorption amount of o-xylene on HCP-2 decreases by 76.47% under the relative humidity (RH) of 30%, implying that the HCP-2 has poor hydrophobicity. The equilibrium adsorption capacity of o-xylene on HCP-2 shows a slight decline after five adsorption cycles. [Formula: see text]

Atomic layer deposited Pt/TiO2-SiO2 and Pt/ZrO2-SiO2 for sequential adsorption and oxidation of VOCs

In this work, Pt nanoparticles were loaded on SiO2, TiO2-thin-film-modified SiO2 (TiO2-SiO2), or ZrO2-thin-film-modified SiO2 (ZrO2-SiO2) particles and the composites were investigated for sequential adsorption and desorption/catalytic oxidation of benzene. The SiO2 was prepared via sol–gel method, while TiO2-SiO2 and ZrO2-SiO2 were synthesized via atomic layer deposition (ALD) thin film coating of TiO2 or ZrO2 on SiO2 particles substrate. In the sequential capture-reaction tests, the materials were first exposed to ca. 500 ppmv benzene gas at 25 °C and 1 atm until 5% breakthrough was attained, followed by tandem desorption and catalytic oxidation while raising bed temperature to 200 °C. The benzene vapor adsorption isotherms followed type-IV isotherm classification, revealing a combination of monolayer, multilayer and capillary condensation adsorption mechanisms in sequence. The xPt/ZrO2-SiO2 materials exhibited superior capture-conversion capabilities relative to their xPt/TiO2-SiO2. In particular, 3Pt/ZrO2-SiO2, prepared with 3 cycles of Pt ALD, exhibited the maximum in-situ conversion at ∼ 100% and turnover frequency of 17.1 mmolC6H6/molPt/s with a dynamic adsorption capacity of 0.45 mmol/g, indicating synergistic effects of Pt nanoparticles and ZrO2 in the ALD-based dual-function materials.

Rapid removal of PFOA and PFOS via modified industrial solid waste: Mechanisms and influences of water matrices.

Emerging perfluoroalkyl and polyfluoroalkyl substances contaminate waters at trace concentrations, thus rapid and selective adsorbents are pivotal to mitigate the consequent energy-intensive and time-consuming issues in remediation. In this study, coal combustion residuals-fly ash was modified (FA-SCA) to overcome the universal trade-off between high adsorption capacity and fast kinetics. FA-SCA presented rapid adsorption (teq = 2 min) of PFOX (perfluorooctanoic acid and perfluorooctanesulfonic acid, collectively), where the dynamic adsorption capacity (qdyn = qm/teq) was 2-3 orders of magnitude higher than that of benchmark activated carbons and anion-exchange resins. Investigated by advanced characterization and kinetic models, the fast kinetics and superior qdyn are attributed to (1) elevated external diffusion driven by the submicron particle size; (2) enhanced intraparticle diffusion caused by the developed mesoporous structure (Vmeso/Vmicro = 8.1); (3) numerous quaternary ammonium anion-exchange sites (840 μmol/g), and (4) appropriate adsorption affinity (0.031 L/μmol for PFOS, and 0.023 L/μmol for PFOA). Since the adsorption was proven to be a synergistic process of electrostatic and hydrophobic interactions, effective adsorption ([PFOX]ini = 1.21 μM, concentration levels of highly-contaminant-sites) was obtained at conventional natural water chemistries. High selectivity (>85.4% removal) was also achieved with organic/inorganic competitors, especially compounds with partly similar molecular structures to PFOX. In addition, >90% PFOX was removed consistently during five cycles in mild regeneration conditions (pH 12 and 50 °C). Overall, FA-SCA showed no leaching issues of toxic metals and exhibits great potential in both single-adsorption processes and treatment train systems.

A new nitrogen-enriched biochar modified by ZIF-8 grafting and annealing for enhancing CO2 adsorption

To increase the CO2 adsorption capacity of biochar, a facile modification method of biochar is proposed. Through in-situ synthesis and annealing (< 500 °C), ZIF-8 (zeolitic imidazolate frameworks) was successfully grafted onto biochar to form nitrogen-enriched modified biochar. The results show that the in-situ synthesis method improves the dispersion of ZIF-8 nanoparticles and the modified biochar inherits the parental characteristics of high nitrogen content of ZIF-8 (>10 at.%). Compared with raw biochar, the pore structure of modified biochar was significantly improved: the maximum surface area was increased from 10 to 882 m2/g. The biochar modified by ZIF-8 grafting and annealing of 400 °C (MNBC3–400) shows the highest CO2 dynamic adsorption capacity of 1.8 mmol/g at 30 °C and 1 bar and it is regenerable and stable during 10 cycles of CO2 adsorption-desorption. Moreover, MNBC3–400 also exhibits the maximum CO2 uptake of nearly 2 mmol/g from CO2 adsorption isotherms and the highest CO2/N2 selectivity of 16.0 at 25 °C and 1 bar. The density functional theory (DFT) results show that the modified biochar has a higher CO2 adsorption energy than the parent materials and the van der Waals effect is dominant in the CO2 adsorption system.

Mechanistic Study on the Decrease in Injectivity during Salt-Resistant Polymer Flooding.

According to numerous laboratory experiments and field applications, polymer flooding can effectively modify the liquid absorption profile and increase the sweep efficiency, thereby enhancing the oil recovery. However, long-term injection of polymers decreases the effective permeability of the reservoir and plugs the formation pores, resulting in irreversible reservoir damage. In the development process, polymer types and concentrations must be selected according to the reservoir to avoid problems such as plugging of the formation pores. This study was aimed at clarifying the degree of plugging and the injection limit of the reservoir when a salt-resistant polymer (SRP) is used in production processes of the Daqing Oilfield. To this end, oil displacement experiments, dynamic and static adsorption experiments, and SEM observations were performed using representative reservoir fluid and core samples. The static adsorption of “medium-molecular” SRP reached equilibrium after 36 h, and the saturated adsorption capacity was 3.56 mg/g, which was approximately 2–5 times the dynamic adsorption capacity. For medium-molecular SRP, with a molecular mass of 7 million, the lower limit of the core permeability was 20–40 mD. When the permeability was less than 100 mD, the SRP concentration injected into the core could not exceed 900 mg/L. The oil displacement capacity of SRP decreased owing to the macromolecular hydration radius and the strong aggregation effect of SRP. Polymer adsorption and the retention of sand-carrying critically decreased water permeability. This study provides insights into SRP flooding under different geological conditions in the Daqing Oilfield and can help clarify the molecular mass and concentration of polymers with changes in the reservoir conditions.

Nitrogen-doped porous carbons from polyacrylonitrile fiber as effective CO2 adsorbents

In this report, nitrogen-doped porous carbons were synthesized from polyacrylonitrile fiber by a facile two-step synthesis process i.e. carbonization followed by KOH activation. Activation temperature and KOH/carbon ratio are two parameters to tune the porosity and surface chemical properties of sorbents. The as-obtained sorbents were carefully characterized. Special attention was paid concerning the change of sorbents’ morphology with respect to synthesis conditions. Under the activation temperatures of this study, the sorbents can still retain their fibrous structure when the KOH/carbon mass ratio is 1. Further increasing the KOH amount will destroy the original morphology of polyacrylonitrile fiber. CO2 adsorption performance tests show that a sorbent retaining the fibrous shape possesses the highest CO2 uptake of 3.95 mmol/g at 25°C and 1 bar. Comprehensive investigation found that the mutual effect of narrow microporosity and doped N content govern the CO2 adsorption capacity of these adsorbents. Furthermore, these polyacrylonitrile fiber-derived carbons present multiple outstanding CO2 capture properties such as excellent recyclability, high CO2/N2 selectivity, fast adsorption kinetics, suitable heat of adsorption, and good dynamic adsorption capacity. Hence, nitrogen-doped porous carbons with fibrous structure are promising in CO2 capture.