CaCl2 Concentration Research Articles

Interfacial properties of cationic and anionic Gemini surfactant mixtures

AbstractThe possibility and the prospect of cationic/anionic (“catanionic”) surfactant mixtures based on sulfonate Gemini surfactant (SGS) and bisquaternary ammonium salt (BQAS) in the field of enhanced oil recovery was investigated. The critical micelle concentration (CMC) of SGS/BQAS surfactant mixtures was 5.0 × 10−6 mol/L, 1–2 orders of magnitude lower than neat BQAS or SGS. A solution of either neat SGS or BQAS, could not reach an ultra‐low interfacial tension (IFT); but 1:1 mol/mol mixtures of SGS/BQAS reduced the IFT to 1.0 × 10−3 mN/m at 100 mg/L. For the studied surfactant concentrations, all mixtures exhibited the lowest IFT when the molar fraction of SGS among the surfactant equaled 0.5, indicating optimal conditions for interfacial activity. The IFT between the 1:1 mol/mol SGS/BQAS mixtures and crude oil decreased and then increased with the NaCl and CaCl2 concentrations. When the total surfactant concentration was above 50 mg/L, the IFT of SGS/BQAS mixtures was below 0.01 mN/m at the studied NaCl concentrations. Adding inorganic salt reduced the charges of hydrophilic head groups, thereby making the interfacial arrangement more compact. At the NaCl concentration was above 40,000 mg/L, surfactant molecules moved from the liquid–liquid interface to the oil phase, thus resulting in low interfacial activity. In addition, inorganic salts decreased the attractive interactions of the SGS/BQAS micelles that form in water, decreasing the apparent hydrodynamic radius (DH, app) of surfactant aggregates. When the total concentration of surfactants was above 50 mg/L, the IFT between the SGS/BQAS mixtures and crude oil decreased first and then increased with time. At different surfactant concentrations, the IFT of the SGS/BQAS mixtures attained the lowest values at different times. A high surfactant concentration helped surfactant molecules diffuse from the water phase to the interfacial layer, rapidly reducing the IFT. In conclusion, the cationic‐anionic Gemini surfactant mixtures exhibit superior interfacial activity, which may promote the application of Gemini surfactant.

Effective Pb2+ adsorption by calcium alginate/modified cotton stalk biochar aerogel spheres: With application in actual wastewater

A spherical composite aerogel adsorbent (CA/KCB aerogel) with excellent Pb2+ adsorption performance was prepared by sol-gel method using calcium alginate (CA) and KMnO4 modified cotton stalk biochar (KCB). The preparation parameters of CA/KCB aerogel were optimized by response surface methodology. The physicochemical properties and Pb2+ adsorption characteristics of CA/KCB aerogel were systematically investigated. The CA/KCB aerogel before and after Pb2+ adsorption was characterized by SEM, EDS, FTIR and XRD, and the adsorption mechanism was discussed. The optimal preparation parameters of CA/KCB aerogel are: the dosage of KCB was 6 g/L, the mass concentration of sodium alginate and CaCl2 was 3% and 1% respectively. CA/KCB aerogel was rich in oxygen-containing functional groups, exchangeable cations and interconnected pores, and can exist stably in aqueous solutions with a wide pH range (2−12). The data of adsorption kinetics and adsorption isotherms can be well fitted by the pseudo-second-order model and Langmuir model, respectively. The maximum adsorption capacity of Pb2+ was 664.6 mg/g. The adsorption process was an endothermic reaction dominated by monolayer chemisorption. The binding of CA and KCB in aerogel can promote the adsorption of Pb2+ synergistically. Finally, CA/KCB aerogel was directly applied to the treatment of electroplating wastewater. The coexisting heavy metals (Pb, Cu and Zn) in the wastewater can be effectively removed when the adsorbent dose was 35 g/L. The conclusion is that CA/KCB aerogel has a promising application prospect as adsorbent for heavy metal removal.

Stability and mobility of zinc oxide nanoparticles in aquatic environment: Influence of extracellular polymeric substances from cyanobacteria and microalgae

The stability and mobility of engineered nanoparticles in the natural water environment are influenced by various environmental factors, such as electrolyte conditions and the presence of natural organic matters. Cyanobacterial and microalgal extracellular polymeric substances (EPSs) are complex organic mixtures ubiquitous in eutrophic waters. In this study, bound EPSs (B-EPSs) and dissolved EPSs (D-EPSs) of Microcystis sp. and Chlorella vulgaris were extracted as the representative natural organic matters in the aquatic environment. Time-resolved dynamic light scattering and quartz crystal microbalance with dissipation monitoring were applied to investigate the influence of the extracted EPSs on zinc oxide nanoparticle (ZnO NP) aggregation and deposition behaviors. Data showed that EPSs with higher protein fractions were more efficient in hindering the aggregation of ZnO NPs in NaCl solutions and low CaCl2 concentration solutions. In higher CaCl2 concentration solutions (>50 mM), the presence of D-EPSs promoted aggregation by forming intermolecular bridging. By accelerating the Brownian movement of NPs and providing electrostatic and hydrophilic attraction between NPs and silica surfaces, B-EPSs facilitated ZnO NP deposition. On the contrary, D-EPSs hindered the deposition through steric repulsion. Moreover, B-EPS-coated ZnO NPs formed a more rigid layer, while the D-EPS-coated ZnO NPs formed a softer layer.

Camel Milk Curd Properties: Application of a Kiwi Juice as a Coagulant

Background: The transformation of camel milk into cheese is an operation considered very delicate because of several difficulties encountered in achieving coagulation. The present study aims to improve coagulation abilities of camel milk using enzyme extracts from kiwi juice. Methods: The optimum characteristics of extract were determined (pH, temperature and CaCl2 concentration), a fresh cheese was manufactured and the physicochemical and organoleptic qualities were determined. Result: Our results concerning the characterization of the enzymatic extract showed an extraction yield as 63.97%±5.22. The optimum coagulation conditions were: pH=6.6, temperature= 40°C and a volume of used enzymatic extract as 1.5 ml. A fresh cheese was made from camel milk with a particular nutritional quality and consistency. The kiwi proteases displayed chymosin-like properties and thus hold the best potential for use as a milk coagulant in cheese production.

The influence of calcium chloride concentration on the mechanical and barrier properties of high amylose corn starch film

In this study, high amylose corn starch (HACS) films were prepared using CaCl2 as cosolvent. The interaction between CaCl2 and HACS during the preparation was investigated. Differences in physicochemical properties between HACS films with and without CaCl2 were characterized using wide-angle X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), water vapor permeability (WVP), thermogravimetric analysis (TG) and atomic force microscopy (AFM). The tensile strength and elongation at break increased to 27.01 ± 1.13 MPa and 17.4 ± 1.9%, respectively, CaCl2 had plasticizing effect and provided mechanical reinforcement to the formed HACS films. The reinforcement was mainly due to (ⅰ) CaCl2 increased the content of free amylose chains in the aqueous phase, and (ⅱ) chelation between Ca2+ and starch chains enhanced the entanglement between HACS chains. The results of XRD and FTIR indicated the crystalline region and shot-range orderliness of films decreased, CaCl2 significantly increased the dispersion of starch chains and made the HACS films more homogeneous. CaCl2 improved the barrier properties and surface morphology. The surface roughness of the HACS films decreased fromRa = 189 nm, Rq = 242 nm toRa = 103 nm, Rq = 152 nm as the concentration of CaCl2 increased. However, high concentration of CaCl2 destroyed the inner and surface structure of the film to some extent.

Inclusion of partly purified protease from Abrus precatorius Linn in Ca-alginate gel beads

Abrus precatorius is an edible endemic plant in Cameroon. In the northern regions of Cameroon, the leaves of this plant are used as traditional medications, for the liquefaction of wort obtained after mashing of sorghum or millets for processing the local fermented beer called bili-bili, and to sweeten gruels made from red millet. Abrus precatorius has also being explored as a potential source of proteolytic enzymes. In this work, a partially purified protease from the leaves and stems of the plant was immobilized in a calcium alginate gel beads and the protease activity (PA), investigated using a central composite design plan under the conditions: alginate content (1–5%) (w/v), enzyme/alginate ratio (10–30%) (v/v), and CaCl2 concentration (100–400 Mmol/L). Results showed that the optimum activity was obtained for an alginate content of 1% (p/v), an enzyme/alginate ratio of 10% (v/v) and a CaCl2 concentration of 400 mmol/L. At the optimum, kinetic parameters of the immobilized enzyme (KM: 6.83 mg mL−1; Vmax: 46.95 g.L−1. min−1) were comparable to those of free enzyme (KM: 1.26 mg mL−1; Vmax: 153.85 g.L−1. min−1). The beads have been preserved at room temperature and reused for four days before loosing 88% of its activity. This indicates that the protease activity of the leaves and stems of A. precatorius can be immobilized in calcium alginate beads and preserve four days at ambient temperature.

Development of Nanoemulsions for Wound Dressings Containing Cassia alata L. Leaf Extraction.

Natural polymer-based hydrogel films possess considerable potential for use in biomedical applications and are excellent for wound healing. The purpose of this research was to use ionic crosslinking to improve the mechanical characteristics, absorption of fluid in the wound, and drug release behavior of Cassia alata L. (CA) extract loaded niosomes (CANs) that were incorporated in an alginate-pectin film (A/P). Then, chemically crosslinked A/P hydrogels were obtained by immersing them in different concentrations of calcium chloride (CaCl2) (0.5–1% w/v) for 15–120 s. The degree of crosslinking was controlled by both contact time and CaCl2 concentration. The optimal crosslinking conditions were 1% CaCl2 for 15 seconds. In this study, the following features of the hydrogel films were investigated: physical properties, morphological characteristics, drug loading, in vitro drug release, antibacterial activity, wound healing activity, cytocompatibility profiles, and hemocompatibility. The crosslinked hydrogel films maintained their physical integrity during use, with the 1% film attaining the best results in the shortest period (15 sec). Then, in vitro drug release from the films was examined. Crosslinking was observed to prolong the release of the CA extract from the hydrogel film. Finally, a cell viability experiment was conducted to evaluate the cytotoxicity profile. The A/P composite film exhibited excellent wound dressing qualities and good mechanical properties in preformulation testing. The in vitro drug release profile indicated that the A/P created a regulated drug release profile, and the cell viability experiment revealed that the film was nontoxic and hemocompatible. A/P composite films can be produced using CAN extract as a possible wound dressing. However, further studies in animals and humans are required to determine both safety and effectiveness.

Influence of pre-harvest calcium applications on table olive characteristics during Spanish-style elaboration process

Calcium is largely used in the agri-food industry thanks to its positive effects, such as its preserving activity or its protection against pathogens. Post-harvest spraying of calcium chloride (CaCl2) solutions has demonstrated an increase in firmness and phenolic content. The aim of this research was to investigate the effects of pre-harvest applications of two CaCl2 concentrations (Ca 0.5% and Ca 1.0%) during the Spanish-style elaboration process at the beginning, middle, and end of the fermentation process. The analysis focussed on the Ca concentration in the whole fruit and in the different tissues (pulp, pit, and seed), as well as on the firmness, phenolic content, and antioxidant activity in the ‘Ascolana tenera’ table olive. An increased Ca concentration in the pulp (20.2 and 55.1%) and seed (13.4 and 36.5%) was observed during a monitoring period in which 0.5% and 1.0% CaCl2 concentrations, respectively, were compared with Ca 0% (water). No significant Ca increase was found in the pit. The fruit firmness was higher following the Ca treatments (22.8% and 68.3%, respectively), and a decrease in the contents of hydroxytyrosol, tyrosol, and verbascoside was observed during the elaboration process. The highest content of these phenols was found on the first date of monitoring for a 1.0% CaCl2 concentration. Hydroxytyrosol, oleuropein, and PB1 showed a significant difference on different monitoring dates. The antioxidant activity during the fermentation period rose between 63.3 and 87.2% compared with the Control (Ca 0%). A similar increasing trend was registered for the phenolic compounds. Our results are useful for the table olive sector to improve the handling in post-harvest processing and to increase the final quality of the olives.

(Invited) Electrochemical Stability of Prussian Blue Analogs and Implications for Energy Storage and Water Desalination Applications

The increasing share of renewables in our electricity grid requires affordable and scalable battery technology that uses sustainable materials and has long lifetime. At the same time, growing water scarcity necessitates new desalination technologies with a similar requirement for sustainability and lifetime. Prussian blue analogs (PBAs), e.g., manganese hexacyanoferrate, MnFe(CN)6, or nickel hexacyanoferrate, NiFe(CN)6, are promising intercalation materials for secondary batteries.1–4 Recently, this material class has been shown to be suitable for a novel energy-efficient water desalination approach, based on sodium intercalation into PBAs, sometimes referred to as battery desalination.5–8 Hence, PBAs are potentially suitable electrode materials for, both, energy storage and water desalination, but it is important to investigate the materials’ stability to processing conditions and repeated ion intercalation. Prussian blue analogs like NaxMnFe(CN)6, 0<x<2, show high sensitivity towards moisture, which results in structural change and loss of sodium from the structure.9,10 Different approaches can be utilized to mitigate this issue, such as surface coating or handling of the material under strictly inert conditions, starting from the storage of powder to slurry preparation and electrode processing.9,11 In this study, we investigated the changes in surface chemistry during ambient storage, water exposure and subsequent heating of stored PBAs. Infrared spectroscopy (ATR-FTIR) and thermal analysis (TGA-MS) of materials stored for different times ranging from one hour to one week show a sharp increase in the moisture content of the active material. X-ray diffraction of exposed materials shows a clear trend between hydration state and crystal structure. Furthermore, surface hydroxides and carbonates are found by ATR-FTIR. A reheating step at relatively low temperature shows the release of adsorbed and interstitial water, but hydroxides and carbonates remain on the surface of the active material.The moisture stability of PBAs has important implications for aqueous electrode processing in energy storage applications and water-based device operation in desalination applications. We demonstrate effective drying strategies of electrodes made with aqueous slurries and appropriate binders. The as-prepared water-based electrodes show similar cycling stability as their non-aqueous counterparts. In the desalination context, exposure of the active material to water is unavoidable and may reduce performance and lifetime since the material remains hydrated during operation. We quantify performance and lifetime metrics of the novel battery desalination cells that employ NiFe(CN)6 electrodes at opposite state-of-charge separated by an anion exchange membrane.12 Using objective metrics like retention of specific capacity (mAh/g), energy consumption (Wh/l) and productivity (l/h/m2) we show that these cells achieve vastly different performance for removal of monovalent and divalent ions. Stable charge/discharge cycling can be achieved for over 500 cycles with NaCl feed water, but rapid aging is observed with CaCl2 feeds. Synchrotron-based characterization of NiFe(CN)6 electrodes from the battery desalination cells is used to elucidate the reason for capacity fade (see Figure 1). X-ray absorption spectroscopy and X-ray fluorescence spectroscopy reveal Fe dissolution from the NiFe(CN)6 active material as a primary aging mode with CaCl2 water feeds. Based on the performance of Prussian blue analogs in, both, energy storage and water desalination, we will discuss potential synergies between these fields and strategies for efficient device design.13 References C. D. Wessells, S. V. Peddada, R. A. Huggins, and Y. Cui, Nano Lett., 11, 5421–5425 (2011).C. D. Wessells et al., ACS Nano, 6, 1688–1694 (2012).M. Pasta et al., Nat. Commun., 5, 1–9 (2014).A. Firouzi et al., Nat. Commun., 9 (2018).M. Pasta, C. D. Wessells, Y. Cui, and F. La Mantia, Nano Lett., 12, 839–843 (2012).J. Lee, S. Kim, and J. Yoon, ACS Omega, 2, 1653–1659 (2017).T. Kim, C. A. Gorski, and B. E. Logan, Environ. Sci. Technol. Lett., 4, 444–449 (2017).S. Porada, A. Shrivastava, P. Bukowska, P. M. Biesheuvel, and K. C. Smith, Electrochim. Acta, 255, 369–378 (2017).D. O. Ojwang et al., ACS Appl. Mater. Interfaces, 13, 10054–10063 (2021).J. Song et al., J. Am. Chem. Soc., 137, 2658–2664 (2015).L. Yang et al., J. Power Sources, 448, 227421 (2020).M. M. Besli et al., Desalination, 517, 115218 (2021).M. Metzger et al., Energy Environ. Sci., 13, 1544–1560 (2020). Figure 1. (a) Three-electrode cells for evaluation of electrochemical stability of NiFe(CN)6 towards mono- and divalent ion intercalation. (b) Specific capacity versus cycle number for 1C cycling with high and low concentrations of NaCl or CaCl2. (c) Visual inspection of electrolyte, revealing strong discoloration and brown precipitate after 300 cycles with 1 M CaCl2, and no discoloration after 400 cycles with 1 M NaCl. Figure 1

Intelligent-Responsive Enrofloxacin-Loaded Chitosan Oligosaccharide–Sodium Alginate Composite Core-Shell Nanogels for On-Demand Release in the Intestine

Simple SummaryNovel pharmaceutical formulations are attracting interest in their potential to overcome the poor palatability and strong gastric irritation of enrofloxacin. To overcome the difficulty of treating intestinal Escherichia coli infections, an oral intelligent-responsive chitosan-oligosaccharide (COS)–sodium alginate (SA) composite core-shell nanogel loaded with enrofloxacin was designed and systematically evaluated. Scanning electron microscopy images revealed that enrofloxacin nanogels were incorporated into the nano-sized cross-linked networks. The physical state and molecular interaction among the components of the nanogel and the enrofloxacin were evaluated by Fourier transform infrared spectroscopy. Furthermore, their biocompatible structure, high drug loading efficacy, ideal stability, “on-demand” release at the target site, and antibacterial activity were confirmed. Thus, the present study may serve as a fruitful platform to explore nanogel to resolve the challenge of enrofloxacin formulation development and the fight against intestinal bacterial infections.Enrofloxacin has a poor palatability and causes strong gastric irritation; the oral formulation of enrofloxacin is unavailable, which limits the treatment of Escherichia coli (E. coli) infections via oral administration. To overcome the difficulty in treating intestinal E. coli infections, an oral intelligent-responsive chitosan-oligosaccharide (COS)–sodium alginate (SA) composite core-shell nanogel loaded with enrofloxacin was explored. The formulation screening, characteristics, pH-responsive performance in gastric juice and the intestinal tract, antibacterial effects, therapeutic effects, and biosafety level of the enrofloxacin composite nanogels were investigated. The optimized concentrations of COS, SA, CaCl2, and enrofloxacin were 8, 8, 0.2, and 5 mg/mL, respectively. The encapsulation efficiency, size, loading capacity, zeta potential, and polydispersity index of the optimized formulation were 72.4 ± 0.8%, 143.5 ± 2.6 nm, 26.6 ± 0.5%, −37.5 ± 1.5 mV, and 0.12 ± 0.07, respectively. Scanning electron microscopy images revealed that enrofloxacin-loaded nanogels were incorporated into the nano-sized cross-linked networks. Fourier transform infrared spectroscopy showed that the nanogels were prepared by the electrostatic interaction of the differently charged groups (positive amino groups (-NH3+) of COS and the negative phenolic hydroxyl groups (-COO−) of SA). In vitro, pH-responsive release performances revealed effective pH-responsive performances, which can help facilitate targeted “on-demand” release at the target site and ensure that the enrofloxacin has an ideal stability in the stomach and a responsive release in the intestinal tract. The antibacterial activity study demonstrated that more effective bactericidal activity against E. coli could have a better treatment effect than the enrofloxacin solution. Furthermore, the enrofloxacin composite nanogels had great biocompatibility. Thus, the enrofloxacin composite core-shell nanogels might be an oral intelligent-responsive preparation to overcome the difficulty in treating intestinal bacterial infections.

Calcium decreases cell wall swelling in sweet cherry fruit

Swelling of epidermal cell walls decreases cell-to-cell adhesion and increases cracking susceptibility in sweet cherry. Ca is suggested to decrease cracking susceptibility by crosslinking of cell wall components and, possibly, by decreasing swelling. The objective is to test this hypothesis. The effect of Ca on swelling of anticlinal epidermal cell walls was quantified microscopically in vivo using excised skin sections and in vitro using extracted cell walls. After removal of turgor, cell wall thickness increased. Incubation in CaCl2 decreased cell wall thickness up to 3 mM CaCl2. At higher concentrations thickness remained constant. Decreased cell wall swelling in vivo also occurred with other salts of divalent and trivalent cations, but not with those of monovalent cations. Decreased swelling was due to the Ca cation, the anions had no effect. Ca also decreased swelling of cell walls that were already swollen. CaCl2 also decreased swelling of extracted cell walls in vitro. There was no effect on swelling pressure. The effect on swelling increased as the CaCl2 concentration increased. Chlorides of divalent and trivalent cations, but not those of monovalent cations decreased swelling in vitro. The decrease in swelling among the divalent cations was linearly related to the radius of the cation. The results indicate that Ca decreases cracking susceptibility by decreasing swelling.

Response of Freesia (freesia Refrecta L.) Plant to Different Growth Media, Calcium Chloride And Gibberellic Acid

A pot experiment has been conducted in a plastic house at the Department of Protected Cultivation, Technical Institute of Zakho, Duhok Polytechnic University during the fall season of 2021–2022 to investigate the effects of three growth media (peat moss, loam + peat moss (1:1) and clay + peat moss (1:1)), foliar spraying of calcium chloride (CaCl2) at three concentrations (0, 500 and 1000 mg. L-1) and Gibberellic acid (GA3) at three concentrations (0, 200 and 400 mg. L-1) on vegetative growth, flowering and corm yield of freesia (Freesia refrecta L.) plant. The experiment was laid out in a Randomized Complete Block Design (RCBD) of three factors with three replicates. The obtained results displayed that the peat moss medium surpassed other media in giving the highest vegetative growth traits (plant height, leaf area, and number of leaves per plant) as well as enhancing flowering traits (number of florets/spike, and vase life of cut flower) and corm yield traits (number of produced corm/plant, and corm volume). The same significant impact was exhibited by CaCl2 at concentrations of 500 and 1000 mg. L-1. Whereas GA3 at concentrations of 200 and 400 mg. L-1 improved most studied traits except number of florets per plant and vase life of cut flowers. The maximum vegetative, flowering, and corm harvest traits were obtained from grown plants in peat moss medium and by spraying them with increased concentrations of CaCl2 and GA3. Therefore, the peat moss medium in combination with increased concentrations of GA3 and CaCl2 is recommended for the improvement of freesia production quality and vase life

Calcium Chloride Toxicology for Food Safety Assessment Using Zebrafish (Danio rerio) Embryos.

The salt calcium chloride (CaCl₂) is widely used in industry as a food additive; levels for human consumption are regulated by international or governmental agencies. Generally, the food industry relies on toxicity studies conducted in mammals such as mice, rats, and rabbits for determining food safety. However, testing in mammals is time-consuming and expensive. Zebrafish have been used in a range of toxicological analyses and offer advantages with regard to sensitivity, time, and cost. However, information in not available with regard to whether the sensitivity of zebrafish to CaCl₂ is comparable to the concentrations of CaCl₂ used as food additives. The aim of this study was to compare the CaCl₂ tolerance of zebrafish embryos and larvae with concentrations currently approved as food additives. Acute toxicity, embryotoxicity, cardiotoxicity, and neurotoxicity assays were used to determine the threshold toxic concentration of CaCl₂ in zebrafish embryos and larvae. The data showed that doses above 0.4% had toxic effects on development and on the activity of the cardiac and neuronal systems. Furthermore, all embryos exposed to 0.8 and 1.6% of CaCl₂ died after 24 hpf. These findings are consistent with the limits of CaCl₂ concentrations approved by Codex Alimentarius. Therefore, zebrafish embryos could be suitable for screening food additives.

Effects of CaCl2 on concentration and speciation of soil Cd around a Pb-Zn mine

Remediation of Cd contaminated soil around mines is still the current academic focus. In order to discuss the activation and extraction effects of CaCl2 on concentration and speciation of soil Cd around a Pb-Zn mine, field investigation and soil sample collection were conducted. Batch experiment was used to study the influence of concentration and time on Cd activation and extraction. Cd contents were analysed. And Cd species were extracted by sequential extraction procedures. Results show that there are obvious concentration effect and time effect for Cd extraction by CaCl2. The best choice of CaCl2 concentration is 0.1 mol/L. And the best extraction time is 4h. Results also show that the percentage and content of exchangeable Cd is the lowest with the value of 9.1% and 0.16 mg/kg when the CaCl2 content is 0.1 mol/L. And the percentage and content of exchangeable Cd is the lowest with the value of 10.5% and 0.18 mg/kg when the extraction time is 4h. It is found that transformation of Cd species such as exchangeable, carbonates bound and Fe-Mn oxides bound should be the main reasons of concentration effect and time effect. And the extraction of soil Cd around a Pb-Zn mine by CaCl2 is a complex coupling process of dissolution, ion exchange, desorption, acidolysis, oxidation-reduction and complexation, etc. All of these above will aid to provide a basis for the research, development and application of remediation technology for Cd contaminated soil around this and other Pb-Zn mines.

MOTILIDADE E MIGRAÇÃO DE NEMATOIDES EM AMBIENTES SALINOS

ABSTRACT Plant parasitic nematodes cause severe agricultural damage in Northeast Brazil. Additionally, soil salinization, especially in the semiarid region of the Northeast, is another factor that limits crop yield. The study evaluated the motility of Meloidogyne enterolobii and Pratylenchus coffeae, and the vertical migration of P. coffeae under saline conditions. Motility was assessed by submitting juveniles of the second stage of M. enterolobii and juveniles and adults of P. coffeae to saline solutions of NaCl, CaCl2, and MgCl2 at concentrations of 0.00, 0.25, 0.50, 0.75, and 1.00 M, and in a mixed solution (combination of the three salts in a 7:2:1 ratio) at 2, 4, 6, and 8 days of exposure. The migration of P. coffeae was studied in segmented columns of 10 cm in length and 4.40 cm in internal diameter, filled with saline soil (mixture of NaCl, CaCl2, and MgCl2) and non-saline, whose evaluations were carried out at 2, 4, and 6 days after soil infestation. The motility and number of active juveniles of both nematodes reduced with increasing saline concentration. From 0.50 M, M. enterolobii activity was not observed in any of the exposure periods to NaCl and CaCl2. The increase in the concentrations of NaCl, CaCl2, and MgCl2 exponentially reduced the number of active P. coffeae, decreasing its activity from 0.75 M. The vertical migration of P. coffeae in the soil was negatively affected by salinity, presenting a more uniform distribution in the non-saline soil.

Influence of calcium chloride in coal on guar-based foam fracturing fluid rheological property: An experimental study

To investigate the influence of calcium chloride (CaCl2) in coal seams on the rheological property of a foam fracturing fluid, the guar powder was used as a foam stabilizer, and the anionic and cationic surfactants were used as foaming agents. The impact of CaCl2 concentrations on the foaming volume, half-life, viscosity, and surface tension of foam was investigated. The results show that CaCl2 has a more significant effect on the foaming amount and foam stability of the anionic surfactant-prepared foam. When the concentration of CaCl2 exceeds 0.25%, the viscosity of the base fluid shows a downward trend and gradually tends to a stable level below 10 mPa s. The foam half-life increases as the shape parameter an in the gamma function increases and decreases as the scale parameter b increases. The effect of CaCl2 on the bubble size of the anionic surfactant foam fracturing fluid is significantly greater than that of the cationic surfactant foam fracturing fluid. For coal reservoir foam fracturing, a foaming agent with better CaCl2 compatibility should be employed to reduce the influence of CaCl2 in the formation water on fracturing performance.

PREPARATION AND IN-VITRO CHARACTERIZATION OF FLOATING-PULSATILE HOLLOWBEADS CONTAINING INDOMETHACIN

Objective: Objective: Designing matrix structured controlled release systems using polymers or waxy lipids is a popular option today. Hollowbeads are formulations characterized by the formation of an air-filled cavity inside. In our study, indomethacin was chosen as a model drug. Cetyl alcohol was selected to create the hollowbeads structure, and NaCMC was chosen to achieve long-term release. Kollicoat® MAE100P was used to reduce and/or prevent ulcer formation and control release.Material and Method: The formulations were prepared using a new “wax removal” technique. Different concentrations of ZnCl2 and CaCl2 were used as crosslinkers. In the preformulation studies, 24 different formulations were prepared by changing the amount of NaCMC, the amount of crosslinker, and the crosslinking time. The structure, size, encapsulation efficiency, yield, hollow structure, and long-term release capacity were investigated in the formulations. These parameters were statistically evaluated depending on the amount of NaCMC, the type of crosslinker, the amount of crosslinker, and contact times with the crosslinker.Result and Discussion: Hollowbeads were characterized by SEM and FT-IR. In vitro release studies, release kinetics, and release mechanisms were performed in pH 1.2 HCl and pH 6.8 phosphate buffer media. Swelling, and buoyancy studies were performed. The long-term stability, encapsulation efficiencies, drug loading efficiencies, and yields of the formulations were also evaluated. Two promising formulations (F2 and F19) were found to be able to release indomethacin in both the stomach and intestinal media for 24 hours.

Incorporation of Mixing Microbial Induced Calcite Precipitation (MICP) with Pretreatment Procedure for Road Soil Subgrade Stabilization.

Microbial induced carbonate precipitation (MICP) provides an alternative method to stabilize the soil. To further improve the reinforcement effect, this study aims to propose a strategy by incorporating the mixing MICP method with pretreatment procedure. A series of laboratory tests were performed to investigate the preparation parameters (including the moisture content and dry density of the soil, the concentration of urea and CaCl2 in cementation solution), the engineering properties, the CaCO3 distribution as well as the mineralogical and micro structural characteristics of pretreatment-mixing MICP reinforced soil (PMMRS). Based on the orthogonal experiment results, the optimum preparation parameters for PMMRS were determined. The UCS of PMMRS was more strongly dependent on the moisture content and concentration of CaCl2 than the concentration ratio of CaCl2 to urea. Moreover, it was testified that incorporation of pretreatment procedure improved the stabilization effect of traditional mixing MICP method on the clayed sand (CLS). The UCS of PMMRS specimen was increased by 198% and 78% for the pure CLS and the simple mixing MICP reinforced soil, respectively. Furthermore, the CaCO3 products generated consisted of the aragonite, calcite and vaterite, which distributed unevenly inside the specimen no matter the lateral or vertical direction. The reason for the uneven distribution might be that oxygen content varied with the regions in different directions, and hence affected the mineralization reaction. In addition, the mineralization reaction would affect the pore structure of the soil, which was highly related to the stabilization effect of MICP reinforced soil.

Preparation of supramolecular viscoelastic polymers with shear, temperature, and salt resistance/sensitivity by amphiphilic functional monomer modification

To develop high-salinity, high-temperature reservoirs, a novel supramolecular viscoelastic polymer-based fracturing fluid modified with an amphiphilic functional monomer was developed. Investigation of the thickening ability, solubility, and rheology revealed that the as-developed gel system with a rigid hydrophobically associating space network structure and linear entanglement can improve the thickening ability, solubility, temperature adaptation range, and chemical environment resistance sensitivity of supramolecular polymers. The surface/interfacial tension test revealed that the modified polymers exhibit surface and interface activity. At an MHAP-15 concentration of 1500 mg/L, the surface tension was 39.29 Nm/m. At an MHAP-15 concentration of 800 mg/L, a minimum interfacial tension of 0.86 Nm/m was observed. The shear sensitivity test revealed that the copolymer fluid exhibits a high creep recovery performance and elastic response as well as a 100% viscosity recovery rate. In addition, the viscoelasticity and thixotropy of the copolymer solution were investigated. The results revealed that the higher the number of the oxyethylene groups in amphiphilic functional monomers, the higher the increase in the viscous modulus of the copolymer solution. In the modified polymer, the highest energy was required for the destruction of the MHAP-15 solution, reaching 66.5 Pa; this result confirmed the best synergistic effect of hydrophobic association and linear entanglement of the MHAP-15 solution molecules, as well as the best temperature and salt resistance. The viscosity of 0.6 wt% MHAP-15 was 120 mPa s after shearing for 50 min at 120 °C and at 170 s−1. At 160 °C and 100 s−1, the viscosity of the 0.8 wt% MHAP-15 polymer solution reached 153 mPa s after shearing for 50 min. At a NaCl concentration of 25 × 104 mg/L, the viscosities of the 0.6 wt% and 0.8 wt% MHAP-15 solutions were 203 and 245 mPa s, respectively, indicative of the stimulation response of salt thickening. At a CaCl2 concentration of 2 × 104 mg/L, the viscosity of 0.6 wt% MHAP-15 was 87 mPa s, and the viscosity retention rate was 47.9%. Finally, by X-ray diffraction, the particle size test in solution, and scanning electron microscopy, the higher the number of oxyethylene groups in the amphiphilic functional monomers, the higher the mixing entropy of copolymers, and the particle size in solution and multi-peak distribution were higher, as well as more clear linear entanglement between copolymers; all of these factors were conducive to the formation of large-scale supramolecular structures of super-bridged copolymers.

Optimization of agarose–alginate hydrogel bead components for encapsulation and transportation of stem cells

Hydrogels have potential uses in various biological applications because of their unique characteristics. Fine-tuning of agarose–alginate (Ag–Al) hydrogel components improves the mechanical characteristics of the final construct for cell encapsulation and transportation. Formulation of suitable dissolving agents may enable the release of encapsulated cells for further applications in laboratory or clinical settings. ObjectivesThis study aimed at optimizing the composition of Ag–Al hydrogel beads and their dissolving agents for potential use in the transportation of stem cells. MethodsVarious agarose, alginate, and CaCl2 concentrations were tested to construct hydrogel beads. The degradation rate and swelling ratio of each hydrogel sample were recorded. The optimized Ag–Al hydrogels were used for encapsulation of stem cells from human exfoliated deciduous teeth (SHED). Optimization of dissolving agents was performed and tested with the hydrogel-encapsulated cells. Data were statistically analyzed in SPSS. ResultsThe selected concentration of Ag–Al hydrogels components was successfully demonstrated to encapsulate SHED, which remained viable until day 10. An average of 2 min was required for degradation of the hydrogel with encapsulated SHED by a dissolving agent consisting of 100 mM sodium citrate and 100 mM EDTA. The cell viability of SHED released after day 10 of encapsulation was 29.1%. ConclusionAlteration of Ag-Al components has considerable influence on the mechanical properties of the constructed hydrogel. The feasibility of performing the optimized cell encapsulation protocol, as well as the dissolving step, may provide a useful guide for the transportation of viable cells between countries, for medical research.