Saturated Adsorption Amount Research Articles

Adsorption of Cetylpyridinium Chloride at Silica Nanoparticle/Water Interfaces (I): Dependence of Adsorption Equilibrium on Particle Size.

In the current work, a size-effect model was developed to describe the particle size-dependence of adsorption at solid/liquid interfaces. A parameter, ΔQad, was introduced, defined as the change of the product of the solid/liquid interfacial tension and the molar volume of solid surface components caused by adsorption. The model predicts that with a decrease in particle radius (r), the saturation adsorption amount per unit area (Γm, mol/m2) decreases, while the change of the adsorption equilibrium constant (Kad) is determined by the ΔQad, namely, it decreases if ΔQad > 0 but increases if ΔQad < 0. There exists a critical r at which the saturation adsorption amount per unit mass (Γmg, mol/g) attains a maximum. In addition, the adsorption of cetylpyridinium chloride (CPyCl), a cationic surfactant, on silica nanoparticles with different r (ca. 6-61 nm) values was determined at 298 K and pH 9, showing an obvious size-dependence. With a decrease in r, Kad and Γm decrease, indicating a decrease in the affinity of silica particles toward CPyCl. The size-dependent adsorption data can be well described using our model. Adsorption can affect the molar volume of the solid surface phase, which plays an important role in the size-dependence of adsorption. This work provides a better understanding of the size-dependent adsorption phenomenon at solid/liquid interfaces.

Synthesis of PNIPAM/magnetite/multiamine-functionalized mesoporous silica composite and investigation of temperature of its aggregation and adsorption

A new adsorbent comprising of poly (N-isopropylacrylamide) (PNIPAM), magnetite, and multiamine-functionalized mesoporous silica (multiamine-PMMS) was synthesized in this study. The structure of the multiamine-PMMS sample was analyzed by X-ray diffraction (XRD), thermogravimetry (TG), and nitrogen adsorption measurements. It was found that the multiamine-PMMS sample contained magnetite (approximately 8.4 wt%) and PNIPAM (approximately 5 wt%). The multiamine-PMMS sample tended to aggregate above the lower critical solution temperature (LCST) of approximately 32 °C for PNIPAM; this aggregation caused the recovery ratio using a magnet at 45 °C to increase by approximately 30 wt% compared to that at room temperature (below the LCST). Five minutes after the precipitation test, the turbidity of the supernatant solution reached a range of 220–230 nephelometric turbidity units (NTU) at room temperature; however, it steeply decreased to approximately 60 NTU at 45 °C. Saturated adsorption amounts of methyl orange (MO) for the multiamine-PMMS samples calculated by the Langmuir adsorption model were 0.33, 0.53, and 0.71 mmol/g. In addition, the MO adsorption rate was considerably high, and equilibrium was reached in 10 min for all multiamine-PMMS samples.

Effects of Surface Heterogeneity of α-Quartz and α-Cristobalite on Adsorption of Crystal Violet

Silica minerals are a kind of important minerals and widespread on the earth’s surface. They play an irreplaceable role in the whole geochemistry and environment processes. The diversity in the crystal structure of SiO2 polymorphs might lead to the heterogeneity in their surface microstructures and properties. As two common SiO2 polymorph minerals in soil and sediments, α-quartz and α-cristobalite have been studied for the effects of their surface heterogeneity on adsorption behaviors toward crystal violet (CV) by batch adsorption experiments in different specific surface areas (SSAs) and at different pH values and temperatures, as well as by X-ray photoelectron spectroscopy (XPS) investigation. Owing to the larger surface site density, the saturated adsorption amount of α-quartz was larger than that of α-cristobalite. It was also indicated by the larger slope of adsorption lines as a function of SSA. The adsorption capacity of both increased with increasing pH and temperature. In the thermodynamic study, the negative ΔG indicated that the adsorption of CV on the surface was spontaneous and the positive ΔH suggested that the reaction was endothermic. The well-fitted Langmuir adsorption isotherms suggested that the CV adsorption was monolayer adsorption. The adsorption interaction force was mainly involved in electrostatic attraction force between the negatively charged surface reactive sites and positively charged N atoms in the dimethylamino groups of CV. The XPS spectra of N 1s showed that the stoichiometric ratio of Nlow/Nhigh changed from lower than 2:1 to about 2:1 as the adsorption changed from the unsaturated to saturated state. The change reflected that the spatial arrangement of adsorbed CV monomer on the mineral surface could be readjusted by lifting the average tilt angle between the average plane of the CV monomer and the sample surface during the adsorption process. Surface heterogeneity of α-quartz and α-cristobalite controlled the different distributions and postures of adsorbed CV monomers on the surface. The CV monomers adsorbed on α-quartz presented a larger average tilt angle because of its larger surface reactive site density, while α-cristobalite did conversely.

Study on particle dispersion changes over time in aqueous Al2O3 slurries containing ammonium polyacrylate

In this study, we investigated the effects of additive amounts of polyelectrolyte and the amounts of unadsorbed polyelectrolyte on the long-term changes in the amount of polyelectrolyte adsorbed and the particle dispersion state of aqueous alumina slurries containing polyacrylic acid. Slurries were evaluated on the basis of viscosity, amount of adsorbed polymer, and elution amount of Mg and Al ions. At 80 days after the preparation of the sample slurry, the amounts of ammonium polycarboxylic acid adsorbed in the slurries had stabilized. The slurries were classified into two types: one in which particles agglomerate as the adsorption increases, and one in which dispersion occurs instead with increasing adsorption. In a slurry in which the amount of polymer electrolyte added is less than the saturated adsorption amount of the polymer electrolyte, polyvalent metal ions eluted from the powder bind the adsorption layers on the particle surface to each other, and the particles aggregate over time. In a slurry in which the amount of polymer electrolyte added is larger than the saturated adsorption amount of the polymer electrolyte, the eluted polyvalent metal ions bind to the unadsorbed polymer electrolyte; hence, the particles do not aggregate with each other and disperse with increase in the amount of polymer electrolyte adsorbed. Thus, when adding a polymer electrolyte to a slurry in which polyvalent metal ions are eluted, the amount of added polymer electrolyte should be greater than the amount of saturated polymer electrolyte adsorbed on the particles to maintain the dispersed state for a long period.

A novel low-density thermal insulation gypsum reinforced with superplasticizers

A novel low-density thermal insulation gypsum (TIG) containing 40 wt% vitrified microsphere (VM), 0–0.5 wt% sulfonated naphthalene formaldehyde (SNF) and polycarboxylate (PC) superplasticizers was produced. The physical and mechanical properties, hydration process, microstructure, and adsorption behavior of TIG were investigated. The results showed that both PC and SNF significantly improved the workability and contributed to 96.8% and 87.1% increases in the compressive strength at the optimum dosages of 0.2 wt% and 0.5 wt%, respectively, which are determined by the maximum water reduction rate of 28%. By comparing with SNF, PC had a better retardation effect in hydration rate, a lower saturated adsorption amount and gave a more compact microstructure with a low porosity, thus leading to higher strength in the hardened TIG. A recommendation of 0.2 wt% PC was proposed.

Adsorption and Decomposition of NOx on Heteropolyacids: An Evaluation of the Adsorption Performance

ABSTRACT In order to develop an efficient method by which to eliminate NOx pollution, several new catalyst systems including different heteropolyacids (HPAs) and supported phosphotungstic acids (HPWs) (HPW/SiO2, HPW/SnO2, HPW/USY and HPW/ZSM-5) for adsorption-decomposition of NOx were prepared and studied. The obtained catalysts were characterized using Brunauer-Emmett-Teller (BET) measurement and Fourier transform infrared (FT-IR) analysis. The results showed that W-containing HPAs were superior to Mo-containing HPAs. Among the selected catalysts, HPW/SnO2 with a 50% HPW loading had the highest NOx adsorption rate of 77.3%, for which the amount of saturated NOx adsorption (85.4 mg g–1) was much higher than that of HPW (50.5 mg g–1). The NOx adsorption performance of the catalyst was mainly determined by the interaction between the support and the HPW, which was also affected by the specific surface area of the catalyst. FTIR characterization revealed that the adsorbed NOx mainly existed in the HPW bulk phase in the form of NOH+. A gas chromatograph-mass spectrometer (GC-MS) was used to confirm the effectiveness of NOx decomposition into N2.

Synthesis and characterization of thiol-polystyrene microsphere and its adsorption properties of thallium

Thallium (Tl) is highly toxic in the environment. In order to solve the harm of Tl pollution to the environment, thiol-polystyrene microsphere (TPM) with good adsorption properties for Tl were prepared in this paper. The GAUSSIAN software was used to calculate the adsorption performance of the TPM on Tl+, and the adsorption mechanism was discussed. The thermogravimetric analysis show that the TPM prepared with chloromethyl polystyrene microspheres (CPM) and thiourea as the main raw materials has good chemical thermal stability. In the Tl+ solution of 1mg/L, the adsorption and removal rate of the TPMs in was 99%, with a significant adsorption of Tl+ properties. When the dosage of TPM is 0.4L/g, pH is 6-10, temperature is 5-20 °C, and adsorption time reaches 640min, thallium-containing water with Tl+ concentration of 5mg/L can be treated to within the national discharge standard (5μg/L). The analytical effect of 0.5mol/L dilute sulfuric acid on TPM can reach 99.96%, and the adsorption capacity of TPM on Tl+ is reduced by only 0.1% after repeated use 4 times, which has good regeneration performance. The modified polystyrene microspheres were characterized by EDS, FT-IR, Raman spectra and XPS, and it was proved that the TPM were ligated with Tl+ through the grafted mercapto group, so as to adsorb and remove Tl+ from the solution. According to the isotherm and kinetic model of TPM adsorption Tl+, the maximum saturated adsorption amount of TPM to Tl+ can reach 3.47mg/g, mainly chemical adsorption, and the membrane diffusion stage is the main control step of TPM adsorption Tl+. The results showed that the TPM could be a promising adsorbent with good adsorption capacity and reusability for Tl+ removal from wastewater

Effects of Residual Silanol on Solid Phase Extraction of Organic Compounds to Octadecylsilyl Silica.

Batchwise equilibrium study was carried out on the retention of nonpolar and polar organic compounds to octadecylsilyl (ODS) silicas of different properties at atmospheric pressure. While nonpolar compounds were retained only by distribution on the ODS phase, polar compounds were retained by both distribution and Langmuir-type adsorption on residual silanol. Retention on ODS silica with more silanol proceeded at a higher rate than retention on ODS silica with less silanol and was reversible on this solid phase extraction time-scale. An increase in surface density of ODS decreased the distribution constant, due to a decrease in fraction of ODS functioning as an extracting medium and also decreased the saturated adsorption amount, due to reductions of the residual silanol and the functioning ODS. The ODS silica with the lowest ODS density showed a distribution constant 31 times higher and a saturated adsorption amount 27 times higher than the ODS silica with the highest ODS density. On the other hand, because the interaction between the organic part and the ODS group introduced at higher density is strengthened, the adsorption constant is increased by about 5 times compared to the low density ODS silica. The electronic effects of substituents to nitrogen- and oxygen-containing compounds on retention were discussed. In conclusion, ODS silica with an appreciable amount of residual silanol is superior for solid phase extraction.

Numerical study of mass transfer and desorption behaviors in deformable porous media using a coupling lattice Boltzmann model.

The aim of this paper is to investigate the pore-scale mass transfer and desorption behaviors in deformable porous media using a coupling immersed boundary method (IBM)-lattice Boltzmann (LB) scheme. In this numerical model, a three-dimensional multiple-relaxation-time LB model is used to simulate fluid flow in porous media consisting of movable rigid adsorbent particles. To consider the effect of dynamic deformation of a porous structure, an improved immersed boundary method scheme is introduced to describe the fluid-structure interaction at the interface between the carrier gas and moving absorbent particles. Moreover, a LB model for the convection diffusion equation is adopted to consider the mass transfer of adsorbate into the macropores and micropores of the porous adsorbent. This coupled IBM-LB model is used to illustrate the mass transfer and desorption processes in shrinkage deformation of the porous structure caused by the movement of rigid adsorbent particles along different directions. At the initial time, these adsorbent particles have a saturation adsorption amount, and the adsorbate in the macropores has the uniform concentration distribution. The numerical results show that the time history curve of the adsorbate concentration in the macropores can be divided into an upturn period and a downturn period during the dynamic desorption process. In the concentration upturn period governed by Langmuir adsorption kinetics, the shrinkage deformation of the porous structure along different directions has no remarkable effect on the mass transfer and desorption behaviors. However, during the concentration downturn period governed by the mass transfer rate of the adsorbate, the shrinkage deformation of the porous structure obviously decreases the efficiency of the desorption process. In addition, the roles of the deformation direction and morphology of the porous media in the desorption process are illustrated in this work.

A Nanosensor for Naked-Eye Identification and Adsorption of Cadmium Ion Based on Core-Shell Magnetic Nanospheres.

Fe3O4@SiO2 nanospheres with a core–shell structure were synthesized and functionalized with bis(2-pyridylmethyl)amine (BPMA). The photoresponses of the as-obtained Fe3O4@SiO2-BPMA for Cr3+, Cd2+, Hg2+ and Pb2+ ions were evaluated through irradiation with a 352 nm ultraviolet lamp, and Fe3O4@SiO2-BPMA exhibited remarkable fluorescence enhancement toward the Cd2+ ion. The adsorption experiments revealed that Fe3O4@SiO2-BPMA had rapid and effective adsorption toward the Cd2+ ion. The adsorption reaction was mostly complete within 30 min, the adsorption efficiency reached 99.3%, and the saturated adsorption amount was 342.5 mg/g based on Langmuir linear fitting. Moreover, Fe3O4@SiO2-BPMA displayed superparamagnetic properties with the saturated magnetization of 20.1 emu/g, and its strong magnetic sensitivity made separation simple and feasible. Our efforts in this work provide a potential magnetic functionalized nanosensor for naked-eye identification and adsorption toward the Cd2+ ion.

Sorption Behaviors of Copper Ions and Tetracycline on Microplastics in Aqueous Solution

The interaction between microplastics, heavy metals, and antibiotics can lead to combined pollution, which could result in greater environmental damage. The pathway and mechanism of the interaction between microplastics, heavy metals, and antibiotics are the preconditions for evaluating the associated environmental risk; however, these are not well understood. As probe sorbates, the sorption behaviors of copper ions (Cu2+) and tetracycline (TC) on two microplastics [high density polyethylene (HPDE) and general-purpose polystyrene (GPPS)] in aqueous solution were investigated and the welding theory with relevant experimental results were discussed. The adsorption capacity of HDPE was greater than that of GPPS in a single Cu solution, whereas the reverse situation occurred in a single TC solution. Moreover, the adsorption capacity of the microplastics in a Cu2+-TC binary solution was larger than that in the single solutions. The pseudo-second-order kinetic models to describe the adsorption process were reasonable and the entire process could be divided into two phases:surface adsorption and internal diffusion. The Langmuir model provided a better fit of the data than did the Freundlich model. In the single solutions, the saturated adsorption amounts of Cu2+ and TC were 0.178 μmol·g-1 and 0.257 μmol·g-1, respectively, for GPPS, and 0.334 μmol·g-1 and 0.194 μmol·g-1, respectively, for HDPE. In the binary solution, the corresponding numerical values were 0.529 μmol·g-1 and 0.411 μmol·g-1, respectively, for GPPS and 0.471 μmol·g-1 and 0.341 μmol·g-1, respectively, for HDPE. The variations in the surface morphological characteristics and chemical functional groups were the main reasons for the difference in the adsorption behavior of microplastics. The variation of the pH of the adsorption system could change the existing forms and surface electrical properties of microplastics and adsorbed objects, and subsequently affected the equilibrium adsorption capacity. When the ambient temperature was in the range of 15 to 35℃, increasing the temperature was unfavorable for the adsorption process. Cu2+ and TC could produce a synergistic effect under the conditions of coexistence. The formation of complexes and bridging make Cu2+ and TC more easily adsorbed by microplastics.

Influence of “tentacle structure” on the properties of jellyfish-like 3D dispersants based on tannic acid for preparing high-concentrated coal–water slurry

Three kinds of jellyfish-like three-dimensional dispersants with different “tentacle structures” were designed and synthesized via polymerization reaction of tannic acid (TA) with starch, allyl polyoxyethylene ether 1200 (APEG1200), and acrylic acid (AA), respectively. These dispersants were employed for preparing high-concentrated coal–water slurry (CWS). Their structures and surfactivity were characterized using FTIR, 1H NMR and surface tension. The effects of the TA-based dispersants on the performance of CWS were fundamentally investigated. The TA-based dispersant with starch as the “tentacle structure” (TA-St) exhibited the better viscosity-reducing and stabilizing capability for CWS than those with APEG1200 (TA-APEG) or AA (TAA). The apparent viscosity reduced to 317 mPa·s at 0.5 wt% TA-St, and the maximum coal content exceeded 71 wt%. Rheological experiments showed that the CWS prepared with the three TA-based dispersants behaved as pseudoplastic fluids, and the CWS with TA-St presented the smallest yield stress. After 3.5 days of storage, the separated water ratio of CWS with TA-St reached 4.15 wt%. Meanwhile, the TA-St dispersant showed a better effect in increasing the adsorption capacity and adsorption film thickness, wettability, and absolute value of zeta potential of the coal surface compared with TAA and TA-APEG. The saturated adsorption quantity of TA-St on the coal surface was 1.77 mg/g. The excellent performances of TA-St in dispersing and stabilizing coal particles in CWS were due to the great steric hindrance and electrostatic repulsion effect derived from the starch “tentacle structure”, which effectively reduced the aggregation among coal particles.

Alkyl polyglucosides for potential application in oil recovery process: Adsorption behavior in sandstones under high temperature and salinity

This study is primarily focusing on the adsorption behavior of alkyl polyglucosides (APG) in sandstones under high temperature and salinity, which is rarely reported before. The results indicate that the adsorption quantity of APG on the sandstone surface is concentration dependent and the adsorption process is spontaneous in terms of Gibbs free energy change (ΔGo), and the adsorption behavior can be exactly fitted by the Langmuir/Freundlich isotherm models. Under the high temperature, APG adsorption at the sandstone is proven to be an entropy-driven spontaneous process. It is also found that, with increasing of solution salinity, the adsorption quantity on sandstone surface increases sharply. The dynamic adsorption behavior of APG suggests that the saturated adsorption quantity is detected at 0.14–0.31 mg/g in porous media, which is much smaller than that under the static condition. Ultimately, the investigation verifies that APG has certain competitive advantages in terms of IFT reduction, wettability alteration, dynamic adsorption loss, pro-environment and cost, causing a great potential for application in enhanced oil recovery.

Dephosphorization using ceramsites modified by coprecipitation with FeSo4 and KMnO4 and high-temperature combustion

Water eutrophication can be controlled through phosphorus adsorption. Herein, ceramsites were used as carriers and FeSo4 and KMnO4 as modifiers to create superior adsorbents for phosphorus. After coprecipitation with the modifiers, various types of adsorbents were prepared by high-temperature combustion. The modification process increased the Langmuir specific surface areas of the ceramsites, which correlated well with the theoretical maximum saturation adsorption amount (R2= 0.9275). Phosphorus adsorption by the modified ceramsites was consistent with the Langmuir isothermal adsorption model. The FeSo4-, KMnO4-, and FeSo4+KMnO4—modified ceramsites exhibited maximum saturation adsorption capacities of 2.444, 1.538, and 2.751 mg/g, respectively, while that of the untreated ceramsites was 1.182 mg/g. The results show that dense nanoparticles of Fe2O3 and (Fe0.67Mn0.33)OOH formed on the FeSo4+KMnO4-modified ceramsites. The main phosphorus absorption mechanism was the replacement of hydroxyl groups by phosphate on the Fe-Mn oxide surfaces to form a monodentate and bidentate complex.The modified ceramsites had lower phosphorus desorption rates, which increased as the initial phosphorus concentration increased. The pseudo-second-order kinetic model was capable of accurately describing the phosphorus adsorption kinetics of the modified ceramsites. At higher reaction temperatures, the initial adsorption rates (IARs) of various types of ceramsites were increased. Additionally, the modified ceramsites had larger IARs than the untreated ceramsite under similar temperature conditions. An analysis of the adsorption thermodynamics showed that phosphorus adsorption via ceramsites was a spontaneous and endothermic process.

Study on the Action Process and Mechanism of Fluorine between Reservoir Water and Bottom Sediments

The surface sediments in the control of pollutants in surface water fluoride fate plays a key role and effectiveness, to reveal the process and mechanism of action, the dynamic test and the adsorption and desorption experiment, combining with the pseudo two order kinetics equation, isothermal adsorption equation, simulation of reaction process between three springs reservoir sediment and reservoir water fluoride. The results showed that: (1) by fluorine ion dynamics in the process of chemical reaction control in surface sediments, can be described by the pseudo two order kinetics equation, the fitting equation is t/qt= 0.7401t + 0.1266, the correlation coefficient R2 = 0.9985; (2) the linear adsorption isotherm of F-in surface sediments, the regression equation is Qe=0.0047Ce+0.0115 that decision coefficient of R2 reached 0.99, the saturated adsorption amount of F-in the sediments of 30.56 mg/g.

An in situ displacement method to evaluate demulsification performance of demulsifiers

Chemical demulsification is the most effective, common and the cheapest method to break crude oil emulsion during oil extraction. The chemical demulsification process is related with the natural emulsifier displacement by demulsifier. In this article, a single droplet in situ displacement method was employed to evaluate demulsifier displace capacity and the experimental device was built. This device determines the displacement capacity of demulsifier by measuring the oil-water interfacial tension, demulsifier concentration and saturated adsorption amount of demulsifier. Displacement capacities of four commercially available polyether demulsifiers and the relationship between demulsifier displacement capacity and demulsification performance were investigated. The results showed that the demulsifier displacement capacity was not affected by natural emulsifier type (asphaltene, resin, or mixture of asphaltene) and was related to the demulsifier type, concentration, and temperature. Demulsifier displacement capacity increased with demulsifier concentration and temperature. However, only when the asphaltene concentration of was over 6.78 wt%, the demulsification increased with demulsifier displacement capacity.

Synthesis of ZIF-8/Fly Ash Composite for Adsorption of Cu2+, Zn2+ and Ni2+ from Aqueous Solutions.

In this study, fly ash (FA) coated with ZIF-8 (ZIF-8/FA) nanocomposite was first synthesized by taking 2-methylimidazole and zinc nitrate hexahydrate as reactants and then used as an adsorbent for adsorption of copper, zinc, and nickel ions from aqueous solution. The characteristic of FA and ZIF-8/FA samples were analyzed based on the data from scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, grain size analyzer and N2 adsorption-desorption isotherm. The results showed that ZIF-8 deposited on the FA evenly. The average crystallite size of ZIF-8 on the surface of FA is 15.85 nm. The specific surface area of FA was increased from 1.8 to 249.5 m2/g. The adsorption efficiency of the ZIF-8/FA nanocomposite for the removal of heavy metal ions from aqueous solution was optimized in terms of different parameters such as pH, adsorbent dosage, and contact time. It was shown that the saturated adsorption amounts of the obtained composite for adsorption of Cu2+, Zn2+, and Ni2+ are 335, 197, and 93 mg·g−1. ZIF-8/FA had better stability and more mesoporous volume than that of ZIF-8 and exhibited higher rate for adsorption of heavy metal ions from aqueous solution than FA and ZIF-8, suggesting an adsorption synergy between ZIF-8 and FA. The adsorption mechanism of heavy metal ions by ZIF-8/FA includes surface adsorption, pore adsorption, and ion exchange. The obtained ZIF-8/FA nanocomposite can solve the encountered problems of FA for low adsorption and the difficult recycling of ZIF-8 for their small size, high cost, and poor stability.

The inappropriate application of the regression Langmuir Qm for adsorption capacity comparison

The Langmuir equation, the best known adsorption model in the past century, was extensively applied to describe adsorption isotherms. The saturated adsorption amount (Qm) obtained from the Langmuir model is an essential index to evaluate the maximum adsorption capacity of the adsorbent, which was assumed to be irrelevant to the aqueous concentration of the adsorbate. Adsorption isotherms of cadmium onto soil and biochar were performed in the current study, and the regression Langmuir Qm was demonstrated to be highly dependent on the aqueous concentration. The regression Qm increased from 0.066 to 2.17 mg·g−1 (by ~3-fold) for the selected soil, and from 2.12 to 48.4 mg·g−1 (by ~23-fold) for the chosen biochar when the highest initial aqueous concentration increased from 2.34 to 887 mg·L−1. One inappropriate application for comparison of the regression Langmuir Qm as the adsorption capacity is found, i.e., it is difficult to directly compare the regression Qm without neither a saturated isotherm nor considering the experimental conditions. It is also very hard to accurately predict adsorption behavior by the regressed Langmuir model obtained from a partial adsorption isotherm. It is suggested to pay more attention to the difference between the saturated adsorption capacity and the regression Qm value derived from one unsaturated isotherm.

Property evaluation of synthesized anionic-nonionic gemini surfactants for chemical enhanced oil recovery

Gemini surfactant has a good application prospect in the field of enhanced oil recovery (EOR) due to the advantages of high interfacial activity, low critical micelle concentration (CMC) and good wettability alteration. In this paper, ethylenediamine, sodium 2-bromoethanesulphonate and fatty alcohol polyoxyethylene ether are used as raw materials to synthesize a new kind of anionic-nonionic gemini surfactant which hydrophilic group consists of two parts nonionic and anionic groups through a mild reaction of amination. The surface tension, interfacial tension, wettability and oil displacement of the synthesized anionic-nonionic gemini surfactants were evaluated. Parameters of surfactant the saturated adsorption amount Γmax and the minimum molecular occupied area Amin were calculated. The structures of the optimal product were characterized by IR and 1H-NMR. The results showed that the critical surface tension of the synthesized anionic-nonionic gemini surfactant was as low as 28.94 mN/m, and the critical micelle concentration was 4.9 × 10−5 mol/L. An interfacial tension between the aqueous solution of 600 mg/L optimal surfactant and Dagang crude oil was 0.0804 mN/m. 1500 mg/L aqueous solution can reduce the surface contact angle of lipophilic low permeability core from 144.5° to 71.5°. The anionic-nonionic gemini surfactant (1000 mg/L; 0.4 PV) can improve oil displacement efficiency by 7.03%. The current study opens a new pathway for designing enhancing oil recovery applicable gemini surfactants with excellent performance, wide source of raw materials and low dosage.

Dye adsorption by self-recoverable, adjustable amphiphilic graphene aerogel

A type of self-recoverable, adjustable amphiphilic graphene aerogel (GA) was prepared and applied to the dye adsorption. The GA with polyvinyl alcohol (PVA) as its cross-linking agent has the characteristics of adjustable amphiphilicity. By adjusting the PVA content in GA, the later can be used to adsorb dyes with different hydrophobic and hydrophilic properties. Four kinds of dyes (Malachite green, Rhodamine B, Methylene blue and Methyl orange) were applied as targets and the saturated adsorption amounts were calculated. The Langmuir adsorption model and the Lagrange pseudo-second-order equation mathematical model were used to study the behavior of dye adsorption by GA, and the experimental data was in full compliance with the mathematical models. The excellent mechanical properties (compressibility and recoverability) make the GA suitable for dye adsorption. A computational simulation was also performed to verify the adsorption energy of GA to dyes. The GA was able to retain 89.5% of its initial removal efficiency (for malachite green) after 10 cycles of application.