Water Removal Technique Research Articles

Drying Controlled Synthesis of Catalytic Metal Nanocrystals Within 2D‐Material Nanoconfinements

AbstractThe synthesis of low‐dimensional metal nanocrystals with precise atom‐to‐nanoscale structure control is crucial for modulating their physicochemical properties. Traditional synthetic routes encounter challenges due to isotropic metallic bonding, which leads to limited control over metal nanostructures. Herein, a versatile approach is developed using various 2D material (2DM) nanoconfinements to produce a wide range of metal nanocrystals with controllable morphologies. Utilizing graphene oxide (GO) and Ti3C2Tx MXene nanosheets, thin multilayer films are assembled through vacuum filtration and are crosslinked with tetraammineplatinum(II) nitrate (TPtN), followed by in situ thermal reduction. By controlling the concentration of TPtN solution, precise loadings of platinum (Pt) are attained while preserving the nanoconfinement integrity. Two water removal techniques, air‐drying and freeze‐drying, are investigated to assess their impacts on resultant morphologies of Pt nanocrystals. Transmission electron microscopy and molecular dynamics simulations demonstrate high‐aspect‐ratio Pt nanosheets on MXene substrates and few‐atom Pt nanoclusters on GO substrates. A decrease in size distribution is observed upon the use of freeze‐drying. In the semihydrogenation reaction of phenylacetylene, freeze‐dried Pt–MXene heterostructures achieve a high turnover frequency of 2.93 s−1. This comprehensive study highlights the potential of utilizing 2DM nanoconfinement to synthesize metal nanostructures for catalysts and beyond.

Influence of Water Removal Techniques on the Main Characteristics of Nanofibrillated Cellulose Obtained from Different Lignocellulosic Materials

ABSTRACT Cellulose nanofibers are often available in aqueous suspensions (~90% water), and water removal becomes necessary to transportation, practical application, and characterization by specific instruments such as x-ray diffractometer or FTIR spectrometers. Since the water remotion interferes in some properties of nanocellulosic materials, the description of the applied technique is essential to the appropriate comparison and discussion of the published results. Aiming this issue at the present work, distinguished drying procedures were applied at eight different nanofibrils slurries. The products from the procedures were evaluated in terms of crystallinity degree, surface chemistry and morphology. The films or nanocellulosic paper obtained by casting were the result of a complex entangling of cellulose nanofibrils, and it resulted in a material with two specific properties: it could not be resuspended in water and had significantly lower crystallinity indexes (18.7–30.3%) in comparison to the powders obtained by atomization (26.6–43.3%) or the flakes by sublimation (29.5–45.2%). Even with the possibility of a resuspension, the thin and flow format of spray-dried powder lost its nanoscale after drying. The images obtained by scanning electron microscopy evidence the aggregation formed during the water removal. The results of the infrared diffractograms suggest that the drying procedure only affected the nanocellulose characteristics at the physical level.

Comparison of Water-Removal Efficiency of Molecular Sieves Vibrating by Rotary Shaking and Electromagnetic Stirring from Feedstock Oil for Biofuel Production

Adequate water-removal techniques are requisite to remain superior biofuel quality. The effects of vibrating types and operating time on the water-removal efficiency of molecular sieves were experimentally studied. Molecular sieves of 3 Å pore size own excellent hydrophilic characteristics and hardly absorb molecules other than water. Molecular sieves of 3 Å accompanied by two different vibrating types, rotary shaking and electromagnetic stirring, were used to remove initial water from the reactant mixture of feedstock oil in order to prevent excessive growth or breeding of microorganisms in the biofuel product. The physical structure of about 66% molecular sieves was significantly damaged due to shattered collision between the magnetic bar and molecular sieves during electromagnetic stirring for 1 h. The molecular sieves vibrated by the rotary shaker appeared to have relatively higher water-removal efficiency than those by the electromagnetic stirrer and by keeping the reactant mixture motionless by 6 and 5 wt.%, respectively. The structure of the molecular sieves vibrated by an electromagnetic stirrer and thereafter being dehydrated appeared much more irregular and damaged, and the weight loss accounted for as high as 19 wt.%. In contrast, the structure of the molecular sieves vibrated by a rotary shaker almost remained original ball-shaped, and the weight loss was much less after regenerative treatment for those molecular sieves. As a consequence, the water-removal process using molecular sieves vibrated by the rotary shaker is considered a competitive method during the biofuel production reaction to achieve a superior quality of biofuels.

Osmotic dehydration of pineapple slices pre-treated by electroplasmolysis: Determination of color change kinetics

The pineapple (Ananas comosus (L.) Merrill) is a commercial tropical fruit belonging to the Bromeliaceae family. It is rich in organic acids (citric acid, malic acid), minerals (Fe, Mg, Ca, P, K, and Zn), and vitamins (A, B1, B2, B3, and B6). Osmotic dehydration is a water removal technique by immersing the fruit in a hypertonic solution to obtain minimally processed food with a longer shelf life and high nutritional value. It can also be considered as a pretreatment that reduces the required energy inputs for convective drying and freeze-drying. Electroplasmolysis is an electrical method that is based on the growth of pores in cell membranes. It has an important effect on the dehydration and extraction processes as it increases the cell permeability and mass transfer coefficients of plant tissues. In this study, it was aimed to determine the effect of electroplasmolysis pretreatment on color change kinetics in the osmotic dehydration of pineapple slices. Electroplasmolysis was applied by a drum‐type electroplasmolyzator with 80 V/cm voltage gradient for 60 s. The osmotic dehydration process was carried out with sucrose solutions of 40, 50 and 60 ◦Bx at 20 ◦C. The processing time was 6 h in all osmotic treatments. This time was determined in preliminary experiments. Osmotically dehydrated samples with elelctroplasmolysis pretreatment and the samples without electroplasmolysis application were compared via L, a, and b values during 8 hours. The results of the study showed that fresh pineapple samples had higher L, a, and b values than both electroplasmolysis treated and untreated samples. The color values of all the samples, with and without electroplasmolysis pretreatment, decreased parallel to time increase after the osmotic dehydration process. L, a, and b values of the samples which osmotically dehydrated at 60 ◦Bx solution were higher than the color values of the samples which were dehydrated at 40 and 50 ◦Bx solutions. Lightness and yellowness were found higher in the electroplasmolysis group than the other groups. The zero-order and first-order kinetic models were used to explain the color change kinetics and it was observed that L, a, and b were fitted to a first-order kinetic model.

Hydrogen production using thermochemical water-splitting Iodine–Sulfur process test facility made of industrial structural materials: Engineering solutions to prevent iodine precipitation

A thermochemical water-splitting iodine–sulfur process offers the potential for mass-producing hydrogen at high-efficiency levels, and it uses high-temperature heat sources, including high-temperature gas-cooled reactors, solar heat, and waste heat of industries. The raw material (H2O) is split into H2 and O2 by combining three chemical reactions using sulfur and iodine. Currently, R&D tasks are essential to confirm the integrity of the components that are made of practical structural materials and the stability of hydrogen production in harsh working conditions. A test facility for producing hydrogen was constructed from corrosion-resistant components that are developed using industrial materials. In addition, for stable hydrogen production, technical issues for instrumental improvements (i.e., stable pumping of the hydrogen iodide (HI)–I2–H2O solution without locking the shaft seal, prevention of leakage by improving the quality control of glass-lined steel, prevention of I2 precipitation using a water removal technique in a Bunsen reactor) were solved. The entire process was successfully operated for 150 h at the rate of ca. 30 L/h. The integrity of components made of practical structural materials and the operational stability of the hydrogen production facility in harsh working conditions were demonstrated.

Influence of water removal techniques on the composition and microstructure of hardened calcium sulfoaluminate cement pastes

Influence of different drying techniques, namely, vacuum drying, oven drying (40 °C) and D-drying on the composition and microstructure of the calcium sulfoaluminate (CSA) cement was investigated in this study. The vacuum drying and oven drying were performed after the samples were immersed in acetone or ethanol. The results show that D-drying decomposes ettringite (AFt) greatly. Following solvent replacement, oven drying slightly decomposes AFt when compared with the vacuum dried sample, possibly due to the carbonation of AFt in the oven drying process. The decomposition of AFt due to D-drying and oven drying affects both the compositional and microstructural analysis of CSA hydrates. In addition, the soaking time of the samples in the solvents has no effect on the thermogravic (TG) analysis of the hydration products of CSA cement, which indicates that the CSA cement hydrates have no interaction with the solvents.

Estimation of area- and mass-based leaf nitrogen contents of wheat and rice crops from water-removed spectra using continuous wavelet analysis

BackgroundThe visible and near infrared region has been widely used to estimate the leaf nitrogen (N) content based on the correlation of N with chlorophyll and deep absorption valleys of chlorophyll in this region. However, most absorption features related to N are located in the shortwave infrared (SWIR) region and the physical mechanism of leaf N estimation from fresh leaf reflectance spectra remains unclear. The use of SWIR region may help us reveal the underlying mechanism of casual relationships and better understand the spectral responses to N variation from fresh leaf reflectance spectra. This study combined continuous wavelet analysis (CWA) and water removal technique to improve the estimation of N content and leaf mass per area (LMA) by reducing the effect of water absorption and enhancing absorption signals in the SWIR region. The performance of the wavelet-based method was evaluated for estimating leaf N content and LMA of rice and wheat crops from fresh leaf reflectance spectra collected over a 2-year field experiment and compared with normalization difference (ND)-based spectral indices.ResultsThe LMA and area-based N content (Narea) exhibited better correlations with the determined wavelet features derived from the water-removed (WR) spectra (LMA: R2 = 0.71, Narea: R2 = 0.77) than those from the measured reflectance (MR) spectra (LMA: R2 = 0.62, Narea: R2 = 0.64). The wavelet features performed remarkably better than the optimized ND indices for the estimations of LMA and Narea with MR spectra or WR spectra. Based on the best estimations of LMA and Narea with wavelet features from WR spectra, the mass-based N content (Nmass) could be retrieved with a high accuracy (R2 = 0.82, RMSE = 0.32%) in the indirect way. This accuracy was higher than that for Nmass obtained in the direct use of a single wavelet feature (R2 = 0.68, RMSE = 0.42%).ConclusionsThe enhancement of absorption features in the SWIR region through the CWA applied to water-removed (WR) spectra was able to improve the spectroscopic estimation of leaf N content and LMA as compared to that obtained with the reflectance spectra of fresh leaves. The success in estimating LMA and N with this method would advance the spectroscopic estimations of grain quality parameters for staple crops and individual dry matter constituents for various vegetation types.

Tooling for Production of the Green Fiber Bottle

Ever since the invention of plastics, packaging has become extremely cheap and efficient. In recent times, the demand for more ecological packaging is increasing leading back to the roots of using naturally available resources, which are biodegradable. The manufacturing process of the Green Fiber Bottle (GFB) is based on moulding of wood fibers. The process is still at the research stage and not commercialized. Tooling is the most critical element in moulding and should be adapted to quick water removal techniques, such as Impulse Drying Technology. In this work, functional requirements for the development of a robust tooling solution are identified. Tooling alternatives are investigated and compared with the capacity to enable water removal. Characterization and assessment of porous tool materials using computed tomography are also outlined and discussed.

Harvesting and lipids extraction of Pavlova Lutheri

The use of microalgal lipids for liquid fuels production is an emerging alternative. Before extracting lipids from microalgae, some important stages are necessary such as: microalgae dewatering and lipids extraction. The cultivation of microalgae is made in a great amount of water, then it is necessary the use of water removal techniques before the lipids extraction. Furthermore, lipids extraction techniques must be tuned up in order to achieve a better separation depending on the type of technique and the solvent. The purpose of the present study is to compare two different microalgae harvesting techniques and two methods for the total lipids extraction of Pavlova–Lutheri microalgae. The studied harvesting techniques for microalgae recovery were: flocculation–coagulation (99.8% efficiency) and electrocoagulation (97.4% efficiency). Two extraction methods were also studied with different solvents: Soxhlet and ultrasound. It was observed that, the use of ultrasound irradiation for lipids extraction improves the extraction efficiency. In ultrasound extraction, the highest percentage (47.20%) was reached with a mixture of chloroform and methanol 1:2 as extraction solvent. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1842–1847, 2016

Effect of pH on Poly(acrylic acid) Solution Polymerization

The free-radical redox-initiated aqueous solution polymerization of fully and partially neutralized acrylic acid was carried out at room temperature under full exposure to air. The effect of neutralization degree on the polymerization rate and product properties was studied. Increasing neutralization of the reaction mixture with sodium hydroxide resulted in greater conversion of acrylic acid to sodium acrylate. The rate of polymerization, determined from a gravimetric off-line water removal technique, was shown to decrease significantly with decreasing degree of neutralization. Molecular weight also decreased with decreasing degree of neutralization. The glass transition temperature and hydrophilicity of the polymer product decreased with increasing degree of neutralization. In-line infrared monitoring was also used to monitor the reaction progress and was shown to be an effective tool for this purpose.

Optimization of enhanced coal-bed methane recovery using numerical simulation

Although the enhanced coal-bed methane (ECBM) recovery process is one of the potential coal bed methane production enhancement techniques, the effectiveness of the process is greatly dependent on the seam and the injecting gas properties. This study has therefore aimed to obtain a comprehensive knowledge of all possible major ECBM process-enhancing techniques by developing a novel 3D numerical model by considering a typical coal seam using the COMET 3 reservoir simulator. Interestingly, according to the results of the model, the generally accepted concept that there is greater CBM (coal-bed methane) production enhancement from CO2 injection, compared to the traditional water removal technique, is true only for high CO2 injection pressures. Generally, the ECBM process can be accelerated by using increased CO2 injection pressures and reduced temperatures, which are mainly related to the coal seam pore space expansion and reduced CO2 adsorption capacity, respectively. The model shows the negative influences of increased coal seam depth and moisture content on ECBM process optimization due to the reduced pore space under these conditions. However, the injection pressure plays a dominant role in the process optimization. Although the addition of a small amount of N2 into the injecting CO2 can greatly enhance the methane production process, the safe N2 percentage in the injection gas should be carefully predetermined as it causes early breakthroughs in CO2 and N2 in the methane production well. An increased number of production wells may not have a significant influence on long-term CH4 production (50 years for the selected coal seam), although it significantly enhances short-term CH4 production (10 years for the selected coal seam). Interestingly, increasing the number of injection and production wells may have a negative influence on CBM production due to the coincidence of pressure contours created by each well and the mixing of injected CO2 with CH4.

Efficient direct ester condensation between equimolar amounts of carboxylic acids and alcohols catalyzed by trifluoromethanesulfonic acid (TfOH) in Solkane365mfc

A simple, practical, and environmentally benign esterification protocol has been devised on the basis of TfOH as the catalyst and Solkane365mfc as the reaction medium. The direct condensation of equimolar amounts of various carboxylic acids and alcohols was conveniently carried out without recourse to any additional water removal technique, giving the desired carboxylic esters in excellent yields.

Water-removed spectra increase the retrieval accuracy when estimating savanna grass nitrogen and phosphorus concentrations

Information about the distribution of grass foliar nitrogen (N) and phosphorus (P) is important for understanding rangeland vitality and for facilitating the effective management of wildlife and livestock. Water absorption effects in the near-infrared (NIR) and shortwave-infrared (SWIR) regions pose a challenge for nutrient estimation using remote sensing. The aim of this study was to test the utility of water-removed (WR) spectra in combination with partial least-squares regression (PLSR) and stepwise multiple linear regression (SMLR) to estimate foliar N and P, compared to spectral transformation techniques such as first derivative, continuum removal and log-transformed (Log( 1 / R )) spectra. The study was based on a greenhouse experiment with a savanna grass species ( Digitaria eriantha). Spectral measurements were made using a spectrometer. The D. eriantha was cut, dried and chemically analyzed for foliar N and P concentrations. WR spectra were determined by calculating the residual from the modelled leaf water spectra using a nonlinear spectral matching technique and observed leaf spectra. Results indicated that the WR spectra yielded a higher N retrieval accuracy than a traditional first derivative transformation ( R 2 = 0.84 , RMSE = 0.28) compared to R 2 = 0.59 , RMSE = 0.45 for PLSR. Similar trends were observed for SMLR. The highest P retrieval accuracy was derived from WR spectra using SMLR ( R 2 = 0.64 , RMSE = 0.067), while the traditional first derivative and continuum removal resulted in lower accuracy. Only when using PLSR did the first derivative result in a higher P retrieval accuracy ( R 2 = 0.47 , RMSE = 0.07) than the WR spectra ( R 2 = 0.43 , RMSE = 0.070). It was concluded that the water removal technique is a promising technique to minimize the perturbing effect of foliar water content when estimating grass nutrient concentrations.

The influence of water removal techniques on the composition and microstructure of hardened cement pastes

The removal of water from hardened cement paste for analysis or to arrest ongoing hydration has been reported to affect the composition of hydrated phases and microstructure. The effect that arresting the hydration of hardened cement paste by replacing the pore water with acetone before drying, and by removing the water by freeze, vacuum and oven drying has on the hardened cement paste has been investigated. Two pastes were studied, a cemented iron hydroxide floc where a high proportion of ordinary Portland cement (OPC) had been replaced by pulverised fuel ash, and a pure hydrated OPC. The results showed that none of the water removal techniques caused any major deterioration in the composition and microstructure of the hardened cement pastes studied, but the pores appeared better preserved after arresting hydration using acetone quenching. Freeze drying appeared to cause more cracking of the microstructure than the other water removal techniques.

Efficient condensation of carboxylic acids with alcohols catalyzed by fluorous ammonium triflates

The use of fluorous ammonium salts as metal-free catalysts for the direct condensation of equimolar amounts of carboxylic acids and aliphatic alcohols has been investigated. Esterification reactions were thus conveniently carried out under mild fluorous biphasic conditions, in the presence of 1 mol % of fluorous ammonium triflate and without recourse to any additional water removal technique. Good to excellent ester yields were obtained in the case of primary and secondary aliphatic alcohols. The fluorous salt was easily recovered by simple phase separation and reused at least three times without considerable loss of activity.

Experimental diagnostics of PEM fuel cells

In this study, water removal techniques were experimentally developed as a diagnostic tool for the investigation of polymer electrolyte membrane (PEM) fuel cell performance in order to achieve consistent, reliable and repeatable performance. The three water removal methods developed include cell orientation, cell shaking and hydraulic permeation, and instantaneous improvement in the fuel cell performance had been observed when these methods were employed. All the experiments were carried out with a single PEMFC with the active surface area of 50 cm2. Pure hydrogen was used as fuel and air was used as oxidant. It was found that operating the fuel cell at an orientation of 45 degrees towards gas outlet ports helped removing trapped liquid water from the cathode side; when cell assembly was shaken during the fuel cell operation, liquid water was observed to be removed from the cell structure and cell performance was improved. Water removal by hydraulic permeation was achieved by maintaining the pressure of hydrogen stream 10 kPa lower than that of air stream, which helped water removal by the anode gas stream. It was observed that the simultaneous application of these water removal methods allowed the test results obtained to be consistent, reliable and repeatable, and in general it increased the performance by 25% in ohmic polarization region and 30% in mass transport dominant region. Then these methods were applied to investigate the effects of the various operating conditions on the performance of the PEM fuel cell, including the effect of reactants temperature, pressure, stoichiometry, humidification and cell aging.

Magnesium Perchlorate as an Alternative Water Trap in AMS Graphite Sample Preparation: A Report On Sample Preparation at Kccams at the University of California, Irvine

We present a brief discussion of sample preparation procedures at the Keck Carbon Cycle Accelerator Mass Spectrometer (KCCAMS), University of California, Irvine, and a systematic investigation of the use of Mg(ClO4)2 as an absorptive water trap, replacing the standard dry ice/ethanol cold finger in graphite sample preparation. We compare high-precision AMS measurement results from oxalic acid I and USGS coal samples using Mg(ClO4)2 under different conditions. The results obtained were also compared with those achieved using the conventional water removal technique. Final results demonstrate that the use of Mg(ClO4)2 as an alternative water trap seems very convenient and reliable, provided the Mg(ClO4)2 is replaced frequently.