Direct Addition Method Research Articles

Study on phase change materials integration in concrete: Form-stable PCM and direct addition

As the economy continues to develop, building energy consumption rises, necessitating sustainable solutions. Concrete, a pivotal building material, assumes a vital role in this context. To address the challenge of escalating energy consumption and environmental impact, this study studied the integration of phase change materials (PCMs) into concrete by two methods. Recycled aggregates serve as form-stable mediums for PCM absorption, while direct addition methods incorporate 7.5 % and 15 % free liquid PCM by volume of river sand. Six concrete mixtures underwent comprehensive evaluation encompassing workability, density, water absorption by immersion, compressive strength, flexural strength, chloride ion penetration, freeze-thaw cycling tests, and carbonation. The results reveal a decrease in concrete density and mechanical properties with increasing PCM content. Nevertheless, notable enhancements in chloride ion penetration resistance, reaching up to 18.5 % with free PCM incorporation, and zero carbonation depth were observed. These results underscore the potential of PCM-concrete composites in harmonizing energy efficiency and structural integrity, offering a sustainable alternative to fossil fuel-based air conditioning systems and with great potential from the point of view of the durability of the structures.

Immobilized lipase enzyme on green synthesized magnetic nanoparticles using Psidium guava leaves for dye degradation and antimicrobial activities.

Zinc ferrite nanoparticles (ZnF NPs) were synthesized by a green method using Psidium guava Leaves extract and characterized via structural and optical properties. The surface of ZnF NPs was stabilized with citric acid (CA) by a direct addition method to obtain (ZnF-CA NPs), and then lipase (LP) enzyme was immobilized on ZnF-CA NPs to obtain a modified ZnF-CA-LP nanocomposite (NCs). The prepared sample's photocatalytic activity against Methylene blue dye (MB) was determined. The antioxidant activity of ZnF-CA-LP NCs was measured using 1,1-diphenyl-2-picryl hydrazyl (DPPH) as a source of free radicals. In addition, the antibacterial and antibiofilm capabilities of these substances were investigated by testing them against gram-positive Staphylococcus aureus (S. aureus ATCC 25923) and gram-negative Escherichia coli (E. coli ATCC 25922) bacterial strains. The synthesized ZnF NPs were discovered to be situated at the core of the material, as determined by XRD, HRTEM, and SEM investigations, while the CA and lipase enzymes were coated in this core. The ZnF-CA-LP NCs crystallite size was around 35.0nm at the (311) plane. Results obtained suggested that 0.01g of ZnF-CA-LP NCs achieved 96.0% removal of 5.0ppm of MB at pH 9.0. In-vitro zone of inhibition (ZOI) and minimum inhibitory concentration (MIC) results verified that ZnF-CA-LP NCs exhibited its encouraged antimicrobial activity against S. aureus and E. coli (20.0 ± 0.512, and 27.0 ± 0.651mm ZOI, respectively) & (1.25, and 0.625μg/ml MIC, respectively). ZnF-CA-LP NPs showed antibiofilm percentage against S. aureus (88.4%) and E. coli (96.6%). Hence, ZnF-CA-LP NCs are promising for potential applications in environmental and biomedical uses.

Spectrophotometric Determination of Remdesivir Using the Ion Pair Complex Method Using through Alizarin Red S Dye

The research included the development of a simple and practical spectroscopic method for the estimation of remdesivir (RDV) by the ion-pair method, which is based on the interaction of RDV with Alizarin Red S (ARS) at laboratory temperature. Using water as a medium for the reaction, a product Red in color was formed, with a linear relation ranging from 1 to 25 ?g/ml. It gave the highest absorption at wavelength 524 nm, and the complex completed its reaction after an hour, as the value of the sample was a relative standard deviation of no more than 1%, the recovery rate is 100.2429%, and high sensitivity to low concentrations, where she was the values of limit of detection, limit of quantitation were 0.0198, 0.0602 ?g/ml, respectively, detection limit of 0.0139 ?g/mL, and a quantitation limit of 0.0422 ?g/mL. The molar absorptivity is 51340.668 L/mol/cm, and Sandell?s sensitivity value is 0.0117 ?g.cm-2. The recovery values ranged from 99.3088% to 100.5184%, with a relative standard deviation not exceeding 0.7886% for RDV. The method was successfully applied for the estimation of pharmaceutical preparations using both direct and standard addition methods.. KEYWORDS :Alizarin red S, Ion pair, Remdesivir, Spectrophotometric estimation.

The generalized E-DVA method: a new approach for multi-modal pushover analysis under multi-component earthquakes with local variables maximization

Pushover analysis is a common nonlinear static procedure, performed to evaluate seismic response of civil structures. This approach allows considering the structural nonlinear behavior under earthquake loading in a simplified yet effective way; however, in its classic formulation, it is limited by restrictive and unrealistic assumptions. Thus, the basic method is inadequate for the accurate analysis of buildings without a vertical plane of symmetry and/or for multi-component earthquakes, where torsion effects cannot be neglected. Furthermore, standard pushover analysis only comprises one dominant mode of vibration; higher modes, and therefore their effects, are not accounted for. For all these reasons, the standard technique is generally not considered suitable for the assessment of buildings at high risk of natural-technological (NaTech) events, such as nuclear facilities in areas of high seismic activity. To overcome these limitations, a multi-modal pushover analysis procedure is here tested and validated on the data from a non-symmetric structure (the SMART case study) under multi-component earthquakes. In detail, the procedure applies a linear combination of modal load patterns, defined according to the well-established Direct Vectorial Addition (DVA) method. With respect to other existing multi-modal pushover analysis techniques, elliptical response envelopes are employed to calculate the corresponding combination factors. Innovatively, the identification of the dominant modes for the load pattern is not limited to the classic maximization of the forces at the basis of a structure but rather generalized to shear and displacement maximization at different heights and locations throughout the whole structural frame.

The evolution characteristics of water absorption, hydration products and microstructure of supersulfated cement containing phosphogypsum by microbial induced carbonate precipitation

In this paper, microbial induced calcite precipitation (MICP) was adopted as a modifying technology for surface property enhancement of supersulfated cement (SSC) containing phosphogypsum (PG). A series of tests including waster absorption test, mercury intrusion porosimetry (MIP), X-ray diffractometry (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were conducted to investigate the modification mechanism of SSC containing PG. The results indicate that the enhancement of surface properties is highly dependent on the modification methods and conditions. The effect of surface treatments on the reduction of water absorption and the refine of pore structure is superior to that of the direct-addition method (DM). After surface treatment, the content of ettringite slightly drops, while the calcite content rises significantly. TM with the volume ratio of bacterial solution to cementation solution of 1:1 leads to the formation of more bio calcite with spherical or square particles, which can fill the inner pores and surface holes of the surface layer. The increase of treatment cycle has a limited effect on the increase of calcite content, while can refine the pore structure and reduce the absorption coefficient when the treatment cycle was 9. DM has a great influence on the alkalinity of SSC mortar, which can significantly reduce the content of ettringite and slightly increase the calcite content and it also changes the morphology of ettringite in matrix.

Spectrophotometric Determination of Diphenhydramine hydrochloride and Application to Pharmaceutical Preparations

The research involves the use of analytical method for determination of the diphenhydramine hydrochloride (DPH) drug in some pharmaceutical preparations using molecular absorption technique (UV-Vis.) in addition to the investigating of complexes obtained. The optimum analytical data obtained throughout of study could be summarized as follows: order of addition (DPH + 2% CS2 in CHCl3+Ag(I), pH(11),volume of ammonia solution (1ml), concentration of Ag(I) (8µg/ml), aqueous : organic phase ratio 1:1, reaction time (4 minutes), extraction time (8minutes), reaction temperature 25oC, one extraction process, extraction ratio (E%=99.82) chloroform proved to be the best solvent for extraction of DPH-Ag complex without interferences, λmax.=363nm. The analytical figures obtained were: linear dynamic range (0.25-80µg/ml)for DPH , RSD% (0.396), D.L (0.29µg/ml), Erel% (0.125), recovery (99.87%).This method was applied for determination of DPH in pharmaceutical preparation (syrup) using direct and standard addition methods, recovery's was found to be (97.8%, 98.2 %).

Highly Electrical Conductive PEDOT:PSS/SWCNT Flexible Thermoelectric Films Fabricated by a High-Velocity Non-solvent Turbulent Secondary Doping Approach.

Materials based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) can be potentially employed as flexible thermoelectric generators (TEGs) to capture waste heat and generate electrical energy. Among various methods, secondary doping is an effective way to modulate its thermoelectric (TE) performance. Different from conventional measures such as dropping, soaking, and steam fumigation, strong shear is integrated with the doping process and termed high-velocity non-solvent turbulent secondary doping (HNTD). We systematically investigate the transformation of PEDOT:PSS during this procedure and the formation mechanism of its highly conductive pathway. It is illustrated that PEDOT:PSS experiences PSS swelling, the phase separation of PEDOT from PSS, the removal of isolated PSS, and the evolution of PEDOT to a linear conformation. These evolutions contribute to the substantial elevation of electrical conductivity (σ). Furthermore, by employing continuous single-walled carbon nanotube (SWCNT) networks as structural units, highly conductive flexible PEDOT:PSS/SWCNT TE thin films could be prepared without sacrificing the Seebeck coefficient (S). Additionally, the effect of HNTD and direct addition method on TE properties of composite films is also compared. Finally, the PEDOT:PSS composite film with 40 wt % SWCNTs by the HNTD method exhibits the maximized power factor (PF) of 501.31 ± 19.23 μW m-1 K-2 with σ of 4717.8 ± 41.51 S cm-1 and S of 32.6 ± 0.13 μV K-1 at room temperature. It is worth mentioning that the σ value 4717.8 ± 41.51 S cm-1 is the highest among the composites based on commercial carbon fillers and organic semiconductors. Finally, a 6-leg TEGs prototype is assembled and illustrates an output power of 4.416 μW under a temperature difference (ΔT) of 58 K. It is thought that such a strategy may provide some guidelines for manufacturing PEDOT:PSS-based functional materials.

Potentiometric Determination of Free Fluoride Content in Wines from Dalmatia Region (Croatia)—A Comparative Study of Direct Potentiometry and Standard Addition Method

The aim of this study was to investigate 30 different types of Dalmatian wines as a potential source of fluoride. A fluoride ion selective electrode was used to measure the fluoride concentration in each sample. The direct potentiometric method and the standard addition method were evaluated, the latter being suggested as more accurate and precise. Measurements were performed in two buffers, acetate buffer and total ionic strength adjustment buffer (TISAB), to compare their influence on fluoride determination. The obtained results show that TISAB is a better choice than acetate buffer as a medium for fluoride determination. According to the proposed method, mass concentrations of fluoride of 0.19 and 0.18 mg/L were found in the studied red and white wines, with standard deviations of 0.04 and 0.03 mg/L, respectively. All determined fluorine levels in the tested wines were within the recommended limits and do not pose a risk to human health. No significant difference was found between the fluorine content in white and red wines, but there was a difference depending on the place of origin of the wine. The measured pH values for all the wines studied (except one sample) are very similar and show no significant correlation with the fluoride content.

Differences in Oxidative Stability, Sensory Properties, and Volatile Compounds of Pepper Aromatized Sunflower Oils Prepared by Different Methods during Accelerated Storage

AbstractThe study aims to compare the differences in the oxidative stability, sensory properties, and volatile compounds during accelerated storage of pepper aromatized sunflower oil (PASO) samples prepared by maceration method (PASO‐M), co‐pressing method (PASO‐C), and direct addition method (PASO‐A), respectively. The results exhibit that their oxidative stability is in the relative order: PASO‐A > PASO‐C > PASO‐M. Meanwhile, the PASO‐A sample is the most preferable aromatized sunflower oil by consumers according to sensory analysis. In addition, a total of 83 volatile compounds are identified in the three PASO samples during the storage, and the principal component analysis (PCA) shows that their volatile compounds are quite different at the initial stage of the storage. Still, they are similar among each other from the middle of storage period. As consequence, the aromatized sunflower oil sample prepared by the direct‐addition method during the storage possesses better oxidative stability and sensory attributes, and there is not much difference among their volatile compounds, indicating that the aromatized sunflower oil prepared by direct‐addition method can be developed as promising aromatized sunflower oil.Practical applications: This study shows that aromatization increases oxidative stability and sensory properties of sunflower oil. By this way some sunflower oils with special sensory properties are obtained: special smell and taste, special color, etc. These peppers aromatized sunflower oils can be used to increase taste and smell in some dishes. For example, they can be used in some salads and some roast meats to give more taste and color.

Evaluating the accumulated dose distribution of organs at risk in combined radiotherapy for cervical carcinoma based on deformable image registration

ObjectiveTo evaluate the feasibility and value of deformable image registration (DIR) in calculating the cumulative doses of organs at risk (OARs) in the combined radiotherapy of cervical cancer. Patients and methodsThirty cervical cancer patients treated with external beam radiotherapy (EBRT) combined with intracavitary brachytherapy (ICBT) were reviewed. The simulation CT images of EBRT and ICBT were imported into Varian Velocity 4.1 for the DIR-based dose accumulation. Cumulative dose-volume parameters of D2cc for rectum and bladder were compared between the direct addition (DA) and DIR methods. The quantitative parameters were measured to evaluate the accuracy of DIR. ResultsThe three-dimensional cumulative dose distribution of the tumor and OARs were graphically well illustrated by composite isodose lines. In combined EBRT and ICBT, the mean cumulative bladder D2cc calculated by DIR and DA was 86.13 Gy and 86.27 Gy, respectively. The mean cumulative rectal D2cc calculated by DIR and DA was 72.97 Gy and 73.90 Gy, respectively. No significant differences were noted between these two methods (p > 0.05). As to the parameters used to evaluate the DIR accuracy, the mean DSC, Jacobian, MDA (mm) and Hausdorff distance (mm) were 0.79, 1.0, 3.84, and 22.01 respectively for the bladder and 0.53, 1.2, 7.31, and 29.58 respectively for the rectum. In this study, the DSC seemed to be slightly lower compared with previous studies. ConclusionDose accumulation based on DIR might be an alternative method to illustrate and evaluate the cumulative doses of the OARs in combined radiotherapy for cervical cancer. However, DIR should be used with caution before overcoming the relevant limitations.

Modification of hydroxyapatite coating in the presence of adipic acid for Mg-based implant application

This study investigated the role of adipic acid (AA) in improving the anti-corrosion performance and in-vitro bioactivity of hydroxyapatite coating applied on AZ31 Mg alloy. Firstly, hydroxyapatite (HA) coating was applied on the AZ31 Mg alloy. In the next step, the optimized hydroxyapatite-based coating, modified with adipic acid by direct addition and post-treatment methods. Corrosion behavior of uncoated sample and different coated samples were studied by Electrochemical Impedance Spectroscopy (EIS) and Direct Current (DC) Polarization techniques. Surface characterization was examined by Field Emission Scanning Electron Microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD) and contact angle measurements. According to the contact angle results, all coated samples reveal high hydrophilic behavior. Additionally, the XRD analysis confirms the formation of hydroxyapatite crystals in all coated samples and the presence of the AA in HA + AA and HA − AA coatings does not change the crystal structure of the hydroxyapatite. Electrochemical studies display that the Rp value of HA coating is increased from 3630 Ω.cm2 to 10784 Ω.cm2 by the direct addition method also by the post-treatment method the polarization resistance reached 10294 Ω.cm2. In addition, an in-vitro bioactivity assessment was performed in a simulated body fluid (SBF). Based on FE-SEM studies, a protective layer of AA is formed on HA coating by the post-treatment method which improves the anti-corrosion behavior efficiently. The results showed that the adipic acid-modified hydroxyapatite coatings by direct addition and post-treating methods display better anti-corrosion properties and bioactivity compared to the optimal hydroxyapatite coating.

Controlled release of corrosion inhibitor from microwave-responsive capsules and anti-corrosion performance of steel bars

A novel type of microwave-responsive, actively controlling capsule (ActiveCaps) is designed and prepared. In this study, ActiveCaps are used to carry corrosion inhibitors, and their controlled release behaviour is studied using ethylenediamine tetra-acetic acid (EDTA) titration in a simulated concrete pore solution. Electrochemical measurements were then performed to investigate the influence of controlled release on the anti-corrosion performance of the steel bars. The results show that ActiveCaps have a slow and sustained release behaviour, following the Peppas–Sahlin release model. Compared with the traditional direct addition method, the controlled release of the inhibitor Na2PO3F through ActiveCaps can form a thicker passive film on steel bars, and the inhibition efficiency is increased by 28.73% at 28 d, indicating a higher anti-corrosion performance in the long term. This is due to the formation of Ca5(PO4)3F, which serves as a protective layer covering the surface of the steel bars, precipitated by the reaction between the sustained-released Na2PO3F and Ca2+ in solution. Thus, the utilisation efficiency of Na2PO3F is improved. The proposed novel, actively controlling technology provides a promising alternative for enhancing the durability of reinforced concrete structures using corrosion inhibitors effectively.

Difference among the quality indices, chemical composition and frying performance of galangal flavored sunflower oil prepared by three methods

Flavored vegetable oils have attracted more and more attentions from consumers and researchers due to their high oxidative stability and sensory quality. In the present study, the quality indices, chemical composition and frying performance of galangal flavored sunflower oil prepared by infusion method (GFSO-I), combination pressing method (GFSO-C) and direct addition method (GFSO-A) were investigated. The results displayed that the preparation time, the levels for the acid value (AV), peroxide value (PV), p -anisidine value (AnV), total oxidation value (TOTOX), and the values for total polar compounds (TPC), thiobarbituric acid (TBA), K 232 and K 268 of GFSO-C were prominently low ( P < 0.05), compared with that of GFSO-I and GFSO-A, while the fatty acid composition of them were similar. In the frying of Chinese Maye (tradional Chinese food, fried dough stick) at 180 °C for 30 h, the values for TPC, TBA, K 232 and K 268 , polymer, viscosity and b * of GFSO-C were obviously low ( P < 0.05), while the value for L * was obviously high ( P < 0.05), compared with that of GFSO-I and GFSO-A. In the sensory evaluation, the flavor, taste, crispness and overall acceptance of Chinese Maye fried by GFSO-C were better than that of Chinese Maye fried by GFSO-I and GFSO-A. Consequently, GFSO-C is more suitable for cooking, and the combination pressing method is optimal for industrial production of GFSO. • The galangal flavored sunflower oil was defined as GFSO. • The quality indices of GFSO prepared by combination method were better. • The chemical composition of GFSO prepared by three methods was similar. • The frying performance of GFSO prepared by combination method was better. • GFSO prepared by combination method could be developed as flavored vegetable oil.

Antimicrobial synergism and antibiofilm activity of amoxicillin loaded citric acid-magnesium ferrite nanocomposite: Effect of UV-illumination, and membrane leakage reaction mechanism

Magnesium ferrite nanoparticles (Mg Fe2O4 NPs) was synthesized by a chemical co-precipitation method and characterized via structural and optical properties. The surface of Mg Fe2O4 NPs was stabilized with citric acid (CA) by a direct addition method (CA-Mg Fe2O4 NPs), then Amoxicillin (AX) was loaded with CA-Mg Fe2O4 nanocomposites. Furthermore, their antimicrobial, and antibiofilm activities, growth curve, and effect of UV-illumination methods were examined against different pathogenic microbes. Based on XRD, HRTEM and SEM analyses, it is found that Mg Fe2O4 NPs are located at the core, while the CA and AX are coated this core. In-vitro zone of inhibition (ZOI) and minimum inhibitory concentration (MIC) results verified that AX-loaded CA-Mg Fe2O4 nanocomposites exhibited its encouraged antimicrobial activity against S. aureus, E. coli, and C. albicans (32.2, 22.0, and 19.0 mm ZOI, respectively) & (0.312, 0.625, and 1.25 μg/ml MIC, respectively). AX-CA-Mg Fe2O4 nanocomposites are showed antibiofilm percentage against S. aureus (95.34%), E. coli (93.93%), and C. albicans (76.23%). AX-CA-MgFe2O4 nanocomposites are an excellent disinfectant agents once they are excited by UV light. Membrane leakage assay explains the formation of holes on the surface of bacteria, and confirms SEM reaction mechanism. AX-loaded CA-Mg Fe2O4 NPs are promising for potential applications in biomedical uses.

Development of Chromium(III) Selective Potentiometric Sensors for Its Determination in Petroleum Water Samples Using Synthesized Nano Schiff Base Complex as an Ionophore.

Many analytical techniques, such as X-ray fluorescence spectrometry, inductively coupled plasma-atomic emission spectrometry, and even traditional spectroscopic and fluorimetric methods, are used for the measurement of Cr(III) ions. These methods are sophisticated and very expensive, so thecheapest and low-cost ion selective electrodes were used. The quantification of Cr(III) ions in various samples of petroleum water using ion selective electrodes was suggested. Nano chromium modified carbon paste sensor (MCPE) and nano chromium modified screen printed sensor (MSPE) based on Schiff base Cr(III) complex are developed. The developed nano Cr(III) Schiff base chelate was characterized using elemental, spectroscopic, and thermal analysis techniques. The proposed nano Cr(III) has good properties for antibacterial and antifungal activity. The modified carbon paste and screen-printed sensors were fabricated for determination of Cr(III) ion. The proposed MCPE (sensor I) and MSPE (sensor II) obeys Nernstian equation upon incorporating nano Cr(III) ionophore in the paste at 25°C with a trivalent cationic slope of 18.8 ± 0.2 and 20.0 ± 0.4 mV/decade. They have showed fast response time around 8 and 5 s, and they may be used for at least 98 and 240 days without significant changes in MCPE and MSPE potential, respectively. The sensors I and II showed good selectivity for Cr(III) ion toward a wide variety of metal ions or anions as confirmed by potentiometric selectivity coefficients values. The detection and quantification limits were defined alongside the other process validation parameters. The results have been compared well to those obtained by atomic absorption spectrometry (AAS), and the data of F- and t-test indicated no significant difference between the proposed and AAS methods. These sensors have been used to determine Cr(III) ions in genuine spiked different petroleum well water samples with satisfactory percentage recoveries, low standard, and relative standard deviation values using direct potentiometric and standard addition methods. The proposed method of producing nano Cr(III) complex as a sensor material possesses the distinct advantages of being simple, easily reproducible, appropriate for operation, and highly selective and sensitive. Modified carbon paste and screen-printed electrodes were fabricated based on nano Cr(III) complex as ionophore. The electrodes follow Nernstian behavior, and they optimized according to IUPAC recommendation. They showed a high selectivity for Cr(III) ion over many bi- or trivalent metal ions and anions. The results obtained compared well with those obtained using AAS. They successfully applied for determination of Cr(III) in petroleum water samples.

Chronic Alcohol Exposure of Cells Using Controlled Alcohol-Releasing Capillaries.

Alcohol is one of the main causes of liver diseases such as fatty liver, alcoholic hepatitis, and chronic hepatitis with liver fibrosis or cirrhosis. To reproduce the conditions of alcohol-induced liver diseases and to identify the disease-causing mechanisms at the cellular level, several methods have been used to expose the cells to ethanol. As ethanol evaporates easily, it is difficult to mimic chronic alcohol exposure conditions at the cellular level. In this study, we developed a glass capillary system containing ethanol, which could steadily release ethanol from the polyethylene tubing and hydrogel portion at both sides of the capillary. The ethanol-containing capillary could release ethanol in the cell culture medium for up to 144 h, and the concentration of ethanol in the cell culture medium could be adjusted by controlling the number of capillaries. A long-term exposure to ethanol by the capillary system led to an increased toxicity of cells and altered the cellular physiologies, such as increasing the lipid accumulation and hepatic transaminase release in cells, as compared to the traditional direct ethanol addition method. Ethanol capillaries showed different gene expression patterns of lipid accumulation- or chronic alcoholism-related genes. Our results suggest that our ethanol-containing capillary system can be used as a valuable tool for studying the mechanism of chronic alcohol-mediated hepatic diseases at the cellular level.

Extraction efficiency of alcohols from activated carbon and silica gel sampling agents in the low concentration region

Activated carbon and silica gel adsorbents are commonly used as sampling agents in small glass tube products for work environment measurements of organic solvent vapor in air. In the measurements, extraction efficiency of organic solvent components from sampling agents is very important for accuracy of the determination. We have investigated the effect of two representative efficiency determination methods as established by the Industrial Safety and Health Act in Japan: the direct addition and phase equilibrium methods, using both of these adsorbent materials found in typical recent sampling tube products in Japan and four types of alcohol. The results indicate that the phase equilibrium method has a tendency to show slightly higher values compared with the direct addition method for each adsorbent. In addition, compared with silica gel, petroleum-based activated carbon can be a preferable sampling agent of alcohols in the extremely low concentration region, below approximately 10 ppm.

Design of hybrid Chitosan-Montmorillonite materials for water treatment: Study of the performance and stability

Using hybrid chitosan-montmorillonite materials as environmentally-friendly alternatives to metallic salts in water treatment, and especially for drinking water production, is a new challenge. However, the coagulation-flocculation process requires minimization of polymer release and reactivity optimization to guarantee low Dissolved Organic Carbon content of the treated waters. To meet these requirements, hybrid materials were designed in this study to combine structural stability and good sorption efficiency, even in hard waters. The influence of preparation parameters (polymer molecular weight, polymer to clay mass ratio, addition method and post-preparation treatment) was evaluated and the obtained composites were fully characterized by X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Jar-Test experiments were carried out to assess the performance of the hybrids toward MethylOrange, a model molecule for the hardly removable hydrophilic compounds. The best results were obtained by drying the hybrids prepared at a 0.5:1 polymer to clay mass ratio by the direct addition method. Structural analysis revealed that the polymer chains of the dried-hybrid were more strongly bound to the Montmorillonite particles while remaining accessible to the organic molecules. This structure prevented its destabilization in the presence of high ionic strength. Under these conditions, all chitosan based materials exhibited some reactivity loss. However, the dissolved chitosan release was reduced to 13% of the initial dosage for the optimized dried hybrid compared to 47% for the undried version. To conclude, the optimized hybrids still outperformed pristine chitosan, Montmorillonite and FeCl3 for the removal of MethylOrange, thus highlighting their potential for future use.

Co-fermentation of municipal waste streams: Effects of pretreatment methods on volatile fatty acids production

The effects of direct enzyme cocktail addition and other pretreatment methods on VFA production through co-fermentation of primary sludge and external organic waste were studied under initial alkaline (pH 10) and acidic (pH 5) conditions. Besides the direct enzymes addition, 24-h enzymatic, ultrasonic, ultrasonic+24-h enzymatic and thermal were the other pretreatment methods employed. Under the alkaline condition, direct addition of enzymes enhanced VFA production by 29–39%, attaining VFA yields of 364–633 mg COD g−1 VS throughout the experimental period, whereas there was 37–43% increase in VFA production under the acidic condition only at retention days 1 and 2, achieving VFA yield of 207 and 215 mg COD g−1 VS, respectively. VFA composition was dominated by acetic acid (54–67%) and propionic acid (31–46%) under alkaline and acidic conditions, respectively. Direct enzyme addition increased the percentage of caproic acid from 8-9% to 16–17%, under the acidic condition. While 24-h enzymatic pretreatment didn't show any improvement on VFA production, thermal, ultrasonic+24-h enzymatic and ultrasonic pretreatment methods increased VFA production by only 18, 14 and 4%, reaching maximum VFA yields of 512, 486 and 445 mg COD g−1 VS, respectively. On the other hand, these pretreatment methods significantly increased biogas production. Experiment without pretreatment achieved maximum biogas production of 392 NmL CH4 at day 9 while experiments with pretreatments achieved a maximum of 679–954 NmL CH4 in the order of no pretreatment < ultrasonic < thermal < 24-h enzymatic < ultrasonic+24-h enzymatic. The study gives insight into how pretreatment strategy can influence VFA production and composition.

Speciation Analysis of Cr(VI) and Cr(III) in Water with Surface-Enhanced Raman Spectroscopy.

Identifying and quantifying chromium in water are important for the protection of precious water resources from chromium pollution. Standard methods however are unable to easily distinguish toxic hexavalent chromium, Cr(VI), from innocuous trivalent chromium, Cr(III), are time-consuming, or require large sample quantity. We show in this report that Cr(VI) and Cr(III) in water can be differentiated based on their distinct spectral features of surface-enhanced Raman scattering (SERS). Their SERS signals exhibit different pH dependences: the SERS features of Cr(VI) and Cr(III) are most prominent at pH values of 10 and 5.5, respectively. The obtained limit of detection of Cr(VI) in water is below 0.1 mg/L. Both concentration curves of their SERS signals show Langmuir sorption isotherm behavior. A procedure was developed to quantify Cr(VI) concentration based on the direct retrieval or addition method with an error of 10%. Finally, the SERS detection of Cr(VI) is shown to be insensitive to co-present Cr(III). The developed SERS procedure offers potential to monitor toxic chromium in fields.