查找使用阿拉丁产品的科研文献

Real-Time QCM-D Monitoring of the Adsorption–Desorption of Expansin on Lignin

Mei Cui,Yuhao Duan,Yuanyuan Ma,Khaled W.A. Al-Shwafy,Yudong Liu,Xudong Zhao,Renliang Huang,Wei Qi,Zhimin He,Rongxin Su

Expansin has nonhydrolytic disruptive activity and synergistically acts with cellulases to enhance the hydrolysis of cellulose. The adsorption–desorption of expansin on noncellulosic lignin can greatly affect the action of expansin on lignocellulose. In this study, three lignins with different sources (kraft lignin (KL), sodium lignin sulfonate (SLS), and enzymatic hydrolysis lignin (EHL)) were selected as the substrates. The real-time adsorption–desorption of Bacillus subtilis expansin (BsEXLX1) on lignins was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The effects of temperature and Tween 80 on the adsorption–desorption behaviors were also investigated. The results show that BsEXLX1 exhibited high binding ability on lignin and achieved maximum adsorption of 283.2, 273.8, and 266.9 ng cm–2 at 25 °C on KL, SLS, and EHL, respectively. The maximum adsorption decreased to 148.2–192.8 ng cm–2 when the temperature increased from 25 to 45 °C. Moreover, Tween 80 competitively bound to lignin and significantly prevented expansin adsorption. After irreversible adsorption of Tween 80, the maximum adsorption of BsEXLX1 greatly decreased to 33.3, 37.2, and 10.3 ng cm–2 at 25 °C on KL, SLS, and EHL, respectively. Finally, a kinetic model was developed to analyze the adsorption–desorption process of BsEXLX1. BsEXLX1 has a higher adsorption rate constant (kA) and a lower desorption rate constant (kD) on KL than on SLS and EHL. The findings of this study provide useful insights into the adsorption–desorption of expansin on lignin.

Bovine serum albumin bioconjugated graphene oxide: Red blood cell adhesion and hemolysis studied by QCM-D

Bing Cai,Kebang Hu,Chunming Li,Jing Jin,Yuexin Hu

Graphene oxide (GO) had great potential in various applications especial biomedical materials. In this study, we improved the hemocompatibility especial hemolysis properties of GO nanosheets by grafting bovine serum albumin (BSA). The hemocompatibility of GO-g-BSA was improved. The hemolysis ratio of GO-g-BSA was lower than 0.2% and no visible hemoglobin release was observed. In a flowed condition, the interaction between GO and RBC was monitored real time by quartz crystal microbalance with dissipation (QCM-D) and the hemolysis rates of eluted RBC solution was determined. The balance between the adsorption and degradation of RBC on the surface of GO was a linear process. The GO-g-BSA surface decreased the adhesion of RBC in a flowed condition, maintained the morphology of RBC and reduced the hemolysis rate in the most effective manner. The inert of BSA resisted GO interacting with the lipid bilayers of RBC and the negative charge on the surface of BSA repelled the approach of negative charged RBC. The excellent hemocompatibility of the BSA modified GO might confer its great potentials for various biomedical applications.

A wireless electrode-free QCM-D in a multi-resonance mode for volatile organic compounds discrimination

Xuefei Su,Daqi Chen,Nan Li,Adrian Carl Stevenson,Guang Li,Ruifen Hu

Wireless sensor technology is a facile way of realizing low cost and miniaturized device for the detection of the volatile organic compounds (VOCs). A wireless electrodeless quartz crystal microbalance with dissipation (WE-QCM-D) sensor array was developed by using a single sensor working in a multi-resonance mode, which obtained an acoustic spectra of the quartz crystal at four harmonics (6 MHz, 18 MHz, 30 MHz and 42 MHz). Multi-responses (frequency shift, and energy dissipation) of WE-QCM-D sensor array were obtained via a ring-down mode and employed as discrimination factors for VOCs. The gas discrimination capability of the WE-QCM-D sensor array has been tested by coating a 100 μ g polyvinylpyrrolidone film on the quartz disc and achieved an optimal recognition rate of 97.5 % with K nearest neighbor algorithm. The results indicate that the single element WE-QCM-D sensor array could be a promising way to realize compact and low-cost VOCs monitoring systems.

Impacts of inorganic salts ions on the polar components desorption efficiency from tight sandstone: A molecular dynamics simulation and QCM-D study

Shun Wang,Jing Wang,Hui-Qing Liu,Hong-Quan Zhang,Fang-Na Liu,Ronald Omara Erik

Ions in brine significantly affect EOR. However, the mechanism of EOR with different brine is still controversial. By Combining Molecular Dynamics (MD) method and Quartz Crystal Microbalance with Dissipation (QCM-D) technology to analyze ions distribution and the mechanisms in detaching acidic components on the sandstone, an effective method to determine the detaching capacity was established. The results show that detaching capacity is related to ions distribution and hydration capacity. In the oil/brine/rock system, ions far from the rock are favorable for detaching, while ions near the rock are unfavorable for detaching due to ion bridging effect. The hydrogen bond between water and naphthenic acid is key to detaching. Cations strengthen the detaching by forming hydrated ions with water, and the detaching capacity is negatively correlated with hydrated ions radius and positively correlated with the water coordination number. The detaching determination coefficient was established by considering the ions distribution, ions types, and hydration strength, then verified by QCM-D. The brine detaching capacity with different Ca 2+ /Mg 2+ ratios was predicted based on MD and detaching determination coefficient, and verified by QCM-D. The optimal Ca 2+ /Mg 2+ ratio gave 7:3. This study provides theoretical guidance for targeted regulation of brine composition to improve the recovery of tight sandstone reservoir.

The Synergistic Effects of Al3+ and Chitosan on the Solid–Liquid Separation of Coal Wastewater and Their Mechanism of Action

Ming Chang,Xiaomin Ma,Xianshu Dong,Yuping Fan,Ruxia Chen

It is important to identify an environmentally friendly and efficient flocculant that can replace polyacrylamide for the solid–liquid separation of coal wastewater. In this study, to explore whether chitosan can be used as an environmentally friendly and efficient flocculant for the solid–liquid separation of coal wastewater, AlCl3–chitosan was used to conduct flocculation–sedimentation and dewatering tests under different chitosan dosages and shear-strength conditions for the prepared coal wastewater. Focused beam reflectance was measured to dynamically monitor the number of refractory fine particles, and the settled flocs were photographed and analyzed with microscopy to explore the effect of AlCl3–chitosan on the flocculation settlement effect and floc characteristics. The synergistic mechanisms of AlCl3and chitosan were investigated using quartz crystal dissipative microbalance and zeta potential measurement. The results showed that the addition of chitosan can significantly improve the flocculation–sedimentation and dewatering effects of coal wastewater. A reasonable dosage under a certain shear strength is conducive to the reduction of fine slime particles, which results in a compact floc structure, increases the floc size, and improves the settling effect. The synergistic effect of AlCl3–chitosan improved the electric neutralization and adsorption bridging abilities of the chitosan, and the mixed solution of AlCl3and chitosan had stronger adsorption on the carbon surface. This study provides a new approach to the selection of flocculants for coal wastewater treatment.Keywords:coal wastewater;chitosan;solid–liquid separation;FBRM;QCM−D

In situ kinetics and flocs conformation studies of kaolinite flocculated by Chi-g-CPAM

Xu Ruijing,Zou Wenjie,Rao Bo,Zhao Wei,Wang Ting,Zhang Zhijun

This study presents a comparative study of the flocculation behavior of kaolinite induced by chitosan-graft-poly(acrylamide-dimethyl diallyl ammonium chloride) (Chi-g-CPAM) and a commercial cationic polyacrylamide (CPAM). The flocculation behaviour was characterised in terms of both flocculation kinetics and the corresponding morphology changes during flocculation. Both Chi-g-CPAM and CPAM were grafted from silica wafers by means of atom transfer radical polymerization (ATRP). The quartz crystal microbalance with dissipation (QCM-D) tests were conducted. The equilibrium time flocculated by Chi-g-CPAM was found to be 0.46 times as that of CPAM, together with a larger total mass of kaolinite layer. The flocculation behaviour by Chi-g-CPAM can be well captured by a pseudo-first-order model. In contrast, the presence of CPAM leads to a more complex kinetics. A relatively larger fitting slope (0.4663) was obtained at the initial stage but the fitting slope droped to 0.2026 after 800 min, indicating a densification process caused by CPAM. The flocculation kinetics of CPAM can be captured by the Elovich model for the inital stage but the combination of pseudo-first-order and pseudo-second-order models for the latter stages, which can be attributed to the long chain of CPAM. With a dosage of 75 g/t, the settling test with Chi-g-CPAM exhibits the same turbidity in the supernatant but a smaller layer thickness of the settlement compared to CPAM. The study enables a better understanding of the flocculation behavior and contributes to the development of efficient flocculants in mineral processing and tailings treatment.

Kinetics and Thermodynamics of Hemicellulose Adsorption onto Nanofibril Cellulose Surfaces by QCM-D

Mingzhu Yao,Chen Liang,Shuangquan Yao,Yang Liu,Hui Zhao,Chenni Qin

The adsorption of hemicellulose derived from bagasse onto nanofibril cellulose has been studied in terms of kinetics and thermodynamics. In situ monitoring of bagasse hemicellulose with different molecular weights onto the nanofibril cellulose surfaces has been investigated using quartz crystal microbalance and dissipation. Then, the adsorption kinetics and thermodynamic properties were analyzed. Also, the sorption behavior and the adsorption layer properties were quantified in aqueous solutions. The maximum adsorption mass was 2.8314 mg/m2 at a concentration of 200 mg/L. Also, compared with that of the low-molecular-weight hemicellulose, the adsorption capacity of the high-molecular-weight hemicellulose was higher, and the adsorption rate changed faster and could reach an equilibrium in a shorter time. The intraparticle diffusion kinetic model represented the experimental data very well. Therefore, the kinetics of hemicellulose on the fiber adsorption was commonly described by a three-stage process: mass to transfer, diffusion, and equilibrium. The Gibbs energy change of the adsorption of hemicellulose was found to range from −20.04 to −49.75 kJ/mol at 25 °C. The entropy change was >0. It was found that the adsorption was spontaneous, and the adsorbed mass increased with the increase in temperature. This strengthened the conclusion that the adsorption process of the bagasse hemicellulose on the NFC was driven by the increase in entropy caused by the release of water molecules due to hydrophobic interaction or solvent reorganization.

A Hybrid Wireless Electrodeless QCM-D for the Discrimination of Volatile Organic Compounds

Ruifen Hu,Xuefei Su,Ye Wang,You Wang,Adrian Carl Stevenson,Guang Li

Probing the adsorption and interaction mechanisms of hydrophobically modified polyacrylamide P(AM-NaAA-C16DMAAC) on model coal surface: Impact of salinity

Wenjie Zou,Lu Gong,Jun Huang,Mingfei Pan,Zhenzhen Lu,Chunbao Sun,Hongbo Zeng

Selective flocculation is an efficient separation method for processing fine coal. In this work, one type of hydrophobically modified polyacrylamide, poly(AM-NaAA-C 16 DMAAC) (HMPAM), was synthesized and used as flocculants of coal. The adsorption and interaction of HMPAM on model coal surface under the influence of KCl concentration were compared with a commercial polyacrylamide (PAM) using quartz crystal microbalance with dissipation monitoring (QCM-D), multi-angle laser light scattering (MALLS) and atomic force microscope (AFM). The QCM-D results showed that the adsorption amounts of both PAM and HMPAM on model coal surface increased with increasing KCl concentration, and the amount of HMPAM was much higher than that of PAM in 100 mM KCl solution. This result could be due to the fact that the high salinity (e.g., 100 mM KCl) led to the compressed conformation of the polymers and significantly compressed electric double layer repulsion. The conformational changes were determined using MALLS. The AFM force measurement results showed that the adhesion between the polymers and model coal surface increased with increasing the KCl concentrations due to the compressed electric double layer, and the average adhesion of PAM was about one order of magnitude smaller than that of HMPAM. Such difference was mainly ascribed to the hydrophobic attraction between the hydrophobic chain of HMPAM and model coal surface. Meanwhile, the attractive hydrophobic interaction between the hydrophobic chains induced the formation of multiple layers of HMPAM, which was in consistence with the QCM-D results. The fundamental insights into the interaction mechanisms of HMPAM/PAM on model coal surface will benefit the rational development of effective polymer additives for fine coal preparation.

Deposition of polystyrene microplastics on bare or biofilm-coated silica analysed via QCM-D

Hui Tao,Lan Yang,Yiting Qi,Yiyang Chen,Duo Yu,Lingqin Zhou,Tao Lin,Hang Xu,Junlong Song

The mobility of microplastics (MPs) in aqueous media is closely related to their environmental risk. The naturally occurring silica substrate surface in the aquatic environment is easily colonized by microorganisms and forms a biofilm, which may affect the migration and distribution of MPs. Herein, a typical MP, polystyrene (PS), and Pseudomonas fluorescens ( P. fluorescens ) biofilms were selected to study the deposition and release of pristine or ultraviolet (UV)-aged PS MPs on silica and biofilms under different ionic strengths using a quartz crystal microbalance dissipation (QCM-D) system. Statistical analyses of the deposition experiments revealed a significant impact of P. fluorescens biofilms on deposition ( p = 0.0042). The deposition rate of weathered MPs on the biofilms was 4.0 ± 0.1 to 16.3 ± 0.6 times that on silica. A release experiment revealed that the biofilm reduced the release fraction ( f r ) of weathered MPs by 34.5 ± 0.3 % compared to bare silica. In addition, the UV-ageing treatment reduced the deposition mass of MPs on the surface of silica by 27.6 ± 0.21 % compared to pristine microspheres. The analysis of the deposition mechanism revealed that the promotion and inhibition of biofilm or UV-ageing treatment on the deposition of microspheres could be attributed to the non-Derjaguin-Landau-Verwey-Overbeek (DLVO) force and the decreased electrostatic repulsion or the increased hydration repulsion, respectively.

Frequency-Amplitude Dual-Parameter-Modulated on a Single WE-QCM-D for VOCs Discrimination and Analysis

Changle Pei,Muhammad Hamza Nadeem,Nan Li,Jun Fu,Nan Xu,You Wang,Adrian Carl Stevenson,Guang Li,Ruifen Hu

The complexity of in situ volatile organic compounds (VOCs) detection demands high selectivity and anti-interference capability of electronic noses (E-noses). Multivariant virtual sensor array (VSA) is a new generation of E-noses under research to overcome the insufficient VOCs selectivity limitation of existing electronic noses and alleviate the issue of sensor drifts. In this paper, a frequency-amplitude dual-parameter modulation strategy is presented on a wireless electrodeless quartz crystal microbalance with dissipation (WE-QCM-D) to realize the recognition and analysis of VOC mixtures and complex real-world analytes with a single multivariant VSA E-nose, by probing the gas dynamic sorption in a sensitive film at various scales of oscillating shear displacements and obtaining multiple partially independent responses to VOCs. Ten VOC analytes from alcohols, esters, and aromatic hydrocarbons were classified with accuracies of above 95% for both interclass and intraclass discriminations. Additionally, a discriminating accuracy of 95% has been achieved on VOC mixtures, and their component concentrations were predicted with coefficients of determination above 0.9. For practical testing, the system was exposed to the headspace VOCs of banana, pineapple, and mango under different concentrations. It recognized different fruits and identified the ripen state of bananas based on the detection of their volatiles. The dual-parameter modulated WE-QCM-D paves a promising multivariant way to realize online real-time VOCs monitoring with high performance on selectivity and quantitative analysis.

Adsorption mechanisms of activated surface of quartz and feldspar with mixed NaOL/DDA

Lingfeng Shen,Ning Sun,Rui Xu,Wei Sun,Li Wang

In this paper, the flotation separation of quartz and feldspar was studied with CaCl 2 as activators and mixed sodium oleate/ dodecylamine (NaOL/DDA) collectors under alkaline condition, and the action mechanism of mixed NaOL/DDA collectors on the quartz and feldspar surfaces were systematically explored. The results of micro-flotation test showed that there were 90.98% quartz and 13.08% feldspar were floated with 0.5 mmol/L CaCl 2 and 2.8 mmol/L mixed NaOL/DDA collectors with molar ratio of 8/1 at pH 10.0. And the artificial mixed minerals flotation manifested these two minerals were able to efficient separation with CaCl 2 and mixed NaOL/DDA collectors at pH 10 ∼ 11. These outcomes indicated that DDA could increase recovery of quartz obviously and reduce about a half dosage of NaOL (from 0.5 mmol/L to 0.25 mmol/L) in flotation under alkaline condition; Meanwhile, mixed NaOL/DDA collectors were able to decreased the flotation separation pH from 12 to 10 on quartz and feldspar. Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results revealed that when NaOL collector was added alone, it could adsorb on activated quartz surface but hardly detected on feldspar surface at pH 10. However, they all were found on both quartz and felspar surface when mixed NaOL/DDA collectors were introduced as collectors. Quartz microcrystal balance with dissipation (QCM-D) experiment confirmed that mixed NaOL/DDA collectors showed a higher adsorption mass and more stable adsorption layer on quartz compared with NaOL was introduced as collector alone. In addition, whether CaCl 2 , NaOL or mixed NaOL/DDA, the adsorption mass on quartz sensor were larger than that on feldspar senor, which might cause difference of hydrophobicity on the surface of quartz and feldspar in flotation. The above experiments showed that the mixed NaOL/DDA collectors can significantly improve hydrophobic difference between quartz and feldspar after activating with CaCl 2 and expand the floated pH range of quartz compared with using NaOL as collector alone, which were efficient reagents to separate quartz and feldspar in flotation.