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1.
Environ Res ; 261: 119655, 2024 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-39034022

RESUMEN

In the process of treating cerium fluorocarbon-cerium lanthanide mixed rare earth concentrates by sulfuric acid roasting method, a large amount of waste leach residue containing iron, rare earths and phosphorus produced by flood neutralization needs to be solved urgently. In this paper, sodium carbonate roasting decomposition was used to treat the water leach residue, in which iron and rare earths were transformed into oxides, and the phosphorus was transformed into sodium phosphate. The main reactions and thermodynamic mechanisms of the roasting decomposition process were investigated by thermogravimetric analysis, phase analysis and chemical analysis. When the mass ratio of sodium carbonate to water leach residue is 1.5:1, the roasting temperature is 700 °C, and the roasting time is 1.5 h, the leaching rate of phosphorus with the roasted product reaches more than 98%. Meanwhile, the phase of the roasted product after washing mainly consists of iron oxide and rare earth oxides. The combination of sodium carbonate roasting decomposition and water leaching is effective for the treatment of water leach residue, which provides an experimental and theoretical basis for solving the problem of environmental and resource waste caused by the accumulation of a large amount of water leach residue. In addition, because sodium carbonate can achieve the separation of iron and phosphorus, this method also has certain reference value for the recovery and utilization of iron phosphate in lithium iron phosphate battery waste.

2.
Iran J Pharm Res ; 23(1): e138677, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39005735

RESUMEN

Background: Batch cultures used for various purposes, such as expression screening and recombinant protein production in laboratories, usually have some drawbacks due to the bolus addition of carbon sources, such as glucose and buffers, that lead to overflow metabolism, decreased pH, high osmolality, low biomass yield, and low protein production. Objectives: This study aimed to overcome the problems of batch culture using the controlled release concept by a controlled porosity osmotic pump (CPOP) system. Methods: The CPOP was formulated with glucose as a carbon source feeding and sodium carbonate as a pH modifier in the core of the tablet that was coated with a semipermeable membrane containing cellulose acetate and polyethylene glycol (PEG) 400. The release rate was regulated with Eudragit L100 as a retardant agent in the core and PEG 400 as a pore-former agent in the coating membrane. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to elucidate compatibility between components and release mechanism, respectively. The in-vitro release of glucose and Na2CO3 studies were performed for 24 hours in a mineral culture medium (M9). Then, the effectiveness of CPOP in the growth of Escherichia coli (E. coli BL21) as a microorganism model was evaluated. Glucose consumption, changes in medium's pH, and acetate concentration as a by-product were also monitored during the bacterial growth. Results: Fourier-transform infrared spectroscopy confirmed the compatibility between the components in the osmotic pump, and SEM elucidated the release mechanism due to in-situ delivery pores created by dissolving soluble components (PEG 400) on the coated membrane upon contact with the dissolution medium. The in-vitro release studies indicated that the osmotic pump was able to deliver glucose and sodium carbonate in a zero-order manner. The use of CPOP in E. coli (BL21) cultivation resulted in a statistically significant improvement in biomass (over 80%), maintaining the pH of the medium (above 6.8) during the exponential phase, and reducing metabolic by-product formation (acetate), compared to bolus feeding (P < 0.05). Conclusions: The use of CPOP, which is capable of controlled release of glucose as a carbon source and sodium carbonate as a pH modifier, can overcome the drawbacks of bolus feeding, such as decreased pH, increased acetate concentration, and low productivity. It has a good potential for commercialization.

3.
Anal Bioanal Chem ; 416(13): 3261-3269, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38573342

RESUMEN

At present, the National Metrology Institute of Japan provides six national primary pH buffers under the Japan Calibration Service System. Each batch of these buffers is certified by the primary pH method using a Harned cell. On the basis of these primary buffers, the designated laboratories supply the secondary and working pH standards using a high-precision pH meter. This paper provides an estimate of the batch-to-batch reproducibility of the primary pH standard production based on the history of the certification of primary carbonate buffers in NMIJ. This buffer, which was chosen as the subject of the study because of the relative difficulty of its measurements (and thus a greater dispersion of results), is nominally the 0.025 mol kg-1 equimolal solution of disodium carbonate and sodium hydrogen carbonate. As its pH value is significantly affected by the purity of the reagents used, the evaluation of their source materials is made by both pH measurements and acidimetric gravimetric back titrations. Considering the experimentally determined pH reproducibility of ca. 0.010, potential risks to the pH accuracy are discussed when using recipe-based carbonate pH standards.

4.
J Environ Sci (China) ; 142: 21-32, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-38527886

RESUMEN

In the context of carbon capture, utilization, and storage, the high-value utilization of carbon storage presents a significant challenge. To address this challenge, this study employed the bipolar membrane electrodialysis integrated with carbon utilization technology to prepare Na2CO3 products using simulated seawater concentrate, achieving simultaneous saline wastewater utilization, carbon storage and high-value production of Na2CO3. The effects of various factors, including concentration of simulated seawater concentrate, current density, CO2 aeration rate, and circulating flow rate of alkali chamber, on the quality of Na2CO3 product, carbon sequestration rate, and energy consumption were investigated. Under the optimal condition, the CO32- concentration in the alkaline chamber reached a maximum of 0.817 mol/L with 98 mol% purity. The resulting carbon fixation rate was 70.50%, with energy consumption for carbon sequestration and product production of 5.7 kWhr/m3 CO2 and 1237.8 kWhr/ton Na2CO3, respectively. This coupling design provides a triple-win outcome promoting waste reduction and efficient utilization of resources.


Asunto(s)
Dióxido de Carbono , Carbono , Carbonatos , Agua de Mar , Sodio
5.
Bioresour Technol ; 393: 130053, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-37993069

RESUMEN

Recent decarbonization efforts have led to interests in producing more bio-based chemicals. One attractive compound produced biochemically is the platform chemical known as 2,3-butanediol (2,3-BDO). In this work a mild alkaline pretreatment using sodium carbonate was performed on corn stover (CS) and switchgrass (SG) to generate hydrolysates for fermentation with the 2,3-BDO producer bacteria strain Paenibacillius polymyxa. Enzymatic hydrolysis performed on the pretreated CS and SG produced theoretical sugar yields of 80 % and 95 % for glucose and xylose, respectively. Fermentations with P. polymxya conducted in anaerobic bottles produced 2,3-BDO reaching concentrations ranging from 14 to 18 g/L with negligible conversion into acetoin. Bioreactor fermentations using the hydrolysate media generated up to 43 g/L and 34 g/L of 2,3-BDO from pretreated CS and SG, respectively, within 24 h of fermentation. However, 2,3-BDO product output was reduced by 40-50 % over the remainder of the fermentation due to conversion into acetoin caused by glucose depletion.


Asunto(s)
Paenibacillus polymyxa , Fermentación , Acetoína , Butileno Glicoles , Glucosa
6.
Bioengineering (Basel) ; 10(10)2023 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-37892926

RESUMEN

The prehydrolysate from dilute acid pretreatment of lignocellulosic feedstocks often contains inhibitory compounds that can seriously inhibit the subsequent enzymatic and fermentation processes. Acetic acid is one of the most representative toxic compounds. In this research, alkaline deacetylation of corn stover was carried out using sodium carbonate under mild conditions to selectively remove the acetyl groups of the biomass and reduce the toxicity of the prehydrolysate. The deacetylation process was optimized by adjusting factors such as temperature, treatment time, and sodium carbonate concentration. Sodium carbonate solutions (2~6 wt%) at 30~50 °C were used for the deacetylation step, followed by dilute acid pretreatment with 1.5% H2SO4 at 121 °C. Results showed that the acetyl content of the treated corn stover could be reduced up to 87%, while the hemicellulose loss remained low. The optimal deacetylation condition was found to be 40 °C, 6 h, and 4 wt% Na2CO3, resulting in a removal of 80.55% of the acetyl group in corn stover and a hemicellulose loss of 4.09%. The acetic acid concentration in the acid prehydrolysate decreased from 1.38 to 0.34 g/L. The enzymatic hydrolysis of solid corn stover and the whole slurry after pretreatment increased by 17% and 16%, respectively.

7.
Ecotoxicol Environ Saf ; 266: 115603, 2023 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-37856986

RESUMEN

Hydroxylamine is a highly reactive inorganic nitrogen compound that not only has a toxic effect on microorganisms, but also makes wastewater treatment more difficult, which in turn damages the environment and even endangers human health. This study reported a new method for converting of hydroxylamine by adding sodium carbonate or calcium bicarbonate to the hydroxylamine-polluted wastewater. The conversion efficiency of hydroxylamine was more than 99% in the presence of sodium carbonate or calcium bicarbonate under the reaction conditions of 25 °C, C/N ratio 15, and dissolved oxygen 7.4 mg/L. And its maximal conversion rate can reach 3.49 mg/L/h. This method overcomes various shortcomings of the reported hydroxylamine removal technologies that require a large material dosage and high cost. The technology in this report has many advantages: low cost, 'green' environmental protection, easy market promotion, and high economic benefits.


Asunto(s)
Hidroxilaminas , Aguas Residuales , Humanos , Hidroxilamina , Suplementos Dietéticos , Nitrógeno , Carbonato de Calcio
8.
J Texture Stud ; 54(6): 947-957, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37661756

RESUMEN

The impact of Na2 CO3 on the properties of doughs and noodles containing 70% Tartary buckwheat flour was investigated. Low-field 1 H nuclear magnetic resonance showed the mobility of water in the doughs significantly declined with the addition content of alkali from 0% to 0.9%. Na2 CO3 promoted the transformation from free sulfhydryl groups to disulfide bonds in doughs because the sulfhydryl groups in cysteine preferred to form thiolate anion and then oxidate under alkaline conditions. As for non-covalent chemical interactions, a significant increase of hydrogen bonds and a decrease of hydrophobic interactions were observed after Na2 CO3 addition. Quantitative analysis of microstructure showed that more uniform and denser gluten networks with higher branching rate and shorter average protein length and width formed in the doughs with 0.3%-0.6% of Na2 CO3 . The aggregated glutenin macropolymer and enhanced protein structure led to significantly stronger tensile of Tartary buckwheat dough sheets, which could meet the demand of continuous processing in the factory. Dough with alkali had higher swelling power and pasting viscosities, contributing to higher water absorption, and improved textural attributes of cooked noodles. This study demonstrated the possibility of adding Na2 CO3 at a moderate level for promoting the sheeting, cooking, and eating properties of high Tartary buckwheat flour composite noodles.


Asunto(s)
Fagopyrum , Harina , Harina/análisis , Fagopyrum/química , Álcalis , Agua
9.
Materials (Basel) ; 16(16)2023 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-37629914

RESUMEN

The effect of the addition of Fe0 and Fe3+ on the formation of expanded clay aggregates was studied using iron-free kaolin as an aluminosilicates source. Likewise, the incorporation of cork powder as a source of organic carbon and Na2CO3 as a flux in the mixtures was investigated in order to assess its effect in combination with the iron phases. An experimental protocol, statistically supported by a mixture experiments/design of experiments approach, was applied to model and optimize the bloating index, density, absorption capacity, and mechanical strength. The process of expansion and pore generation and the associated decrease in density required the addition of iron, such that the optimum mixtures of these properties presented between 25 and 40 wt.% of Fe0 or Fe3+, as well as the incorporation of 3.5-5 wt.% of organic carbon. The addition of Fe3+ produced a greater volumetric expansion (max. 53%) than Fe0 (max. 8%), suggesting that the formation of the FeO leading to this phenomenon would require reducing and oxidizing conditions in the former and the latter, respectively. The experimental and model-estimated results are in good agreement, especially in the aggregates containing Fe0. This reinforces the application of statistical methods for future investigations.

10.
Ecotoxicol Environ Saf ; 262: 115187, 2023 Jun 27.
Artículo en Inglés | MEDLINE | ID: mdl-37385019

RESUMEN

Once established within a water resource, harmful algal blooms (HABs) can occur seasonally with an intense and rapid onset, giving water resource managers limited time to respond to lessen risks. An attractive strategy to decrease human, ecological, and economic risks from HABs is to implement proactive algaecide treatments applied to overwintering cyanobacteria (i.e., akinetes and quiescent vegetative cells) in sediments prior to the formation of a HAB; however, this approach is novel and very limited efficacy data exist. Therefore, the specific objectives of this research were to 1) evaluate copper- and peroxide-based algaecides, applied as single and repeat treatments at the bench scale, to identify effective proactive treatments, and 2) compare correlations between cell density and other response measurements (i.e., in vivo chlorophyll a and phycocyanin concentrations and percent benthic coverage), to identify informative metrics to assess overwintering cyanobacteria responses. Twelve treatment scenarios using copper- and peroxide-based algaecides were applied to sediments containing overwintering cyanobacteria prior to a 14 d incubation under favorable growth conditions. Responses of cyanobacteria in the planktonic (i.e., cell density, in vivo chlorophyll a and phycocyanin concentrations) and benthic (percent coverage) phases after a 14 d incubation were evaluated in treatments and controls. The HAB-forming cyanobacteria present after a 14 d incubation were: Aphanizomenon, Dolichospermum, Microcystis, Nostoc, and Planktonthrix. Successive treatments of copper sulfate (CuSulfate) followed by sodium carbonate peroxyhydrate (PeroxiSolid) (second algaecide applied after 24 h) as well as repeat applications of a single algaecide, PeroxiSolid (second treatment applied after 24 h) resulted in statistically significant (p ≤ 0.05; α = 0.05) declines in cell density relative to untreated controls. Planktonic cyanobacteria responses measured in terms of phycocyanin concentrations were strongly correlated with cyanobacteria density measurements (Pearson's correlation coefficient (r) = 0.89). Chlorophyll a concentrations and percent benthic coverage did not correlate with planktonic cyanobacteria density measurements (r = 0.37 and -0.49, respectively) and therefore, were unreliable metrics for cyanobacterial responses in this study. These data provide initial evidence of the efficacy of algaecides for treating overwintering cells in sediments and contribute to our overarching hypothesis that proactive treatments may delay the onset and intensity of HABs in impacted waterbodies.

11.
Sci Total Environ ; 883: 163822, 2023 Jul 20.
Artículo en Inglés | MEDLINE | ID: mdl-37121321

RESUMEN

Coal combustion provides plenty of energy, along with enormous coal fly ash (CFA) and CO2 emission. CFA could be recycled for mesoporous silica synthesis, but expensive templates are usually needed. In this work, we proposed a multi-win strategy using CO2 as the precipitator and template. Mesoporous silica powders, with a maximum specific surface area of 355.45 m2/g, a pore volume of 0.73 cm3/g, and an average pore size of around 7.67 nm, were synthesized. The influences of silicon concentration, CO2 flow rate, and ultrasound were investigated. In addition, the Na2CO3 by-product was produced with a purity of over 92 %. By averagely calculating, 1 ton CFA could generate 285 kg mesoporous silica and 1.02 t crude Na2CO3. Around 433 kg of CO2 could be absorbed. Therefore, multi-goals of CFA disposal, CO2 storage, and valuable silica materials production were realized, and the study could pave the way for large-scale industrial applications.

12.
J Funct Biomater ; 14(4)2023 Apr 18.
Artículo en Inglés | MEDLINE | ID: mdl-37103320

RESUMEN

A push for environmentally friendly approaches to biomaterials fabrication has emerged from growing conservational concerns in recent years. Different stages in silk fibroin scaffold production, including sodium carbonate (Na2CO3)-based degumming and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)-based fabrication, have drawn attention for their associated environmental concerns. Environmentally friendly alternatives have been proposed for each processing stage; however, an integrated green fibroin scaffold approach has not been characterized or used for soft tissue applications. Here, we show that the combination of sodium hydroxide (NaOH) as a substitute degumming agent with the popular "aqueous-based" alternative silk fibroin gelation method yields fibroin scaffolds with comparable properties to traditional Na2CO3-degummed aqueous-based scaffolds. The more environmentally friendly scaffolds were found to have comparable protein structure, morphology, compressive modulus, and degradation kinetics, with increased porosity and cell seeding density relative to traditional scaffolds. Human adipose-derived stem cells showed high viability after three days of culture while seeded in each scaffold type, with uniform cell attachment to pore walls. Adipocytes from human whole adipose tissue seeded into scaffolds were found to have similar levels of lipolytic and metabolic function between conditions, in addition to a healthy unilocular morphology. Results indicate that our more environmentally friendly methodology for silk scaffold production is a viable alternative and well suited to soft tissue applications.

13.
Carbohydr Polym ; 299: 120146, 2023 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-36876775

RESUMEN

A new micellization method was applied to produce the nano octenyl succinic anhydride (OSA) modified starch micelles with controllable size. The underlying mechanism was explored by using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), zeta-potential, surface tension, fluorescence spectra and transmission electron microscope (TEM). Due to the new starch modification method, the electrostatic repulsion between the deprotonation carboxyl groups prevented the aggregation of starch chains. With the progress of protonation, the weaken electrostatic repulsion and enhanced hydrophobic interaction driven the self-assembly of micelles. The size of micelles increased gradually with the increase of the protonation degree (PD) and concentration of OSA starch. However, a V-shaped trends were observed in the size as the increase of substitution of degree (DS). Curcuma loading test indicated that micelles had good encapsulated capability and the maximum value was 52.2 µg/mg. The understanding of the self-assembly behavior of OSA starch micelles can facilitate and improve the starch-based carrier designs used to synthesis complex and smart micelle delivery system with good biocompatibility.

14.
Food Chem X ; 17: 100577, 2023 Mar 30.
Artículo en Inglés | MEDLINE | ID: mdl-36845496

RESUMEN

Studies are being carried out on achieving the maximum quality of garlic through various approaches. In Bangladesh, new garlic varieties (BARI 1-4, BAU-1, BAU-2, BAU-5) have been recently developed by artificial selection to enhance their quality. The present study aimed to evaluate their potency in terms of bioactive properties and organosulfur compounds content using different bioassay and GC-MS techniques while comparing them with other accessible varieties (Chinese, Indian, Local). The new variety, BARI-3 showed the highest antioxidant activity and total phenolic content. It was also found with the highest level of a potent blood pressure-lowering agent, 2-vinyl-4H-1,3-dithiine (78.15 %), which is never reported in any garlic at this percentage. However, the local variety exhibited greater inhibitory properties against the tested organisms including multidrug-resistant pathogens compared to other varieties. This study primarily shows the potential of these two kinds of garlic for their further utilization and development.

15.
Astrobiology ; 23(3): 269-279, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36689196

RESUMEN

The plume of Enceladus is thought to originate from the dispersion of a liquid source beneath the icy crust. Cryovolcanic activity on Enceladus may present a direct way of accessing material originating from the potentially habitable subsurface ocean. One way to test the hypothesis of whether life is present within the ocean of Enceladus would be to investigate the plume material for the presence of microbial life. In this study, we investigated the entrainment of Bacillus subtilis within Enceladus-like fluids under boiling conditions caused by exposure of the fluids to low pressure. We show that boiling, associated with exposure of a fluid to low pressure, works as a mechanism for dispersing bacteria in Enceladus plume-like environments. Exposure of Enceladus-type fluids (0.01-0.1 molal Na2CO3 and 0.05-0.2 molal NaCl) to low pressure (5 mbar) results in the dispersion of bacteria in droplets that evaporate to produce particles of salt. We find that, for particles with radius (r) ≤ 10 µm, the number of dispersed particles containing cells was between 7.7% and 10.9%. However, for larger particles 10 < r ≤ 50 µm, 64.4% and 56.4% contained cells for lower and upper end-member solutions, respectively. Our results suggest that the gravity-induced size sorting of plume particles will result in plume deposits closer to the vent source containing a larger volume of biological material than within the plume. If life is present in the ocean of Enceladus, we would expect that it would be effectively entrained and deposited on the surface; therefore, it would be accessible with a surface-lander-based instrument.


Asunto(s)
Exobiología , Sodio , Exobiología/métodos , Cloruro de Sodio , Bacterias
16.
Food Chem ; 398: 133853, 2023 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-35988412

RESUMEN

Plant-based phenolic extracts have gained significant attention in the food industry due to their antimicrobial and health-promoting effects. However, their usage is limited because of poor water solubility and instability during processing. Therefore, encapsulation of phenolics with a suitable carrier system is essential for overcoming these problems and increasing their application in food products. In this study, encapsulated phenolic extracts were used for the first time in vacuum impregnation (VI). For this purpose, different phenolic extracts (cinnamon, turmeric, pomegranate peel) were obtained from the plant source. PPE was selected because it has the highest total phenolic content, antioxidant capacity, and antimicrobial activity against Botrytis cinerea. Then, PPE was encapsulated with different emulsifiers (T80, GMO, IN, WPI, and LEC). After the characterization and stability studies were performed, PPE encapsulated with T80 was used to produce a functional strawberry snack by VI technology. The results showed that the diffusion rate of EPPE was significantly increased compared to the control and PPE-VI group. EPPE-enriched strawberries were the preferred snack with high-quality characteristics.


Asunto(s)
Fragaria , Antioxidantes , Fenoles/análisis , Extractos Vegetales , Tecnología , Vacio
17.
Membranes (Basel) ; 12(12)2022 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-36557139

RESUMEN

One option for new nitrogen sources is industrial liquid side streams containing ammonium nitrogen (NH4-N). Unfortunately, NH4-N often exists in low concentrations in large water volumes. In order to achieve a highly concentrated NH4-Nsolution, scalant removal is needed. In this study, scalant removal by precipitation was investigated. At alkali pH, sodium carbonate (Na2CO3) was used as a precipitation chemical while at acidic pH, the chemical used was oxalic acid (C2H2O4). At alkali pH, high Na2CO3 dose was needed to achieve low content of calcium, which, with sulphate, formed the main scalant in the studied mine water. NH4-N at alkali pH was in the form of gaseous ammonia but it stayed well in the solution during pre-treatment for nanofiltration (NF) and reverse osmosis (RO). However, it was not rejected sufficiently, even via LG SW seawater RO membrane. At acidic pH with CaC2O4 precipitation, NF90 was able to be used for NH4-N concentration up to the volume reduction factor of 25. Then, NH4-N concentration increased from 0.17 g/L to 3 g/L. NF270 produced the best fluxes for acid pre-treated mine water, but NH4-N rejection was not adequate. NF90 membrane with mine water pre-treated using acid was successfully verified on a larger scale using the NF90-2540 spiral wound element.

18.
Carbohydr Polym ; 298: 120068, 2022 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-36241267

RESUMEN

High strength and excellent selectivity are two important aspects of porous cellulose microspheres as adsorbents for protein separation. For this purpose, self-reinforced all-cellulose microspheres (SCMs) with high strength were fabricated using natural cellulose nanofibers (CNFs) as fillers and then immobilized via 3-aminophenylboronic acids as affinity ligands for selective enrichment of glycoproteins. In particular, the inherent stiffness of entrapped CNFs endowed SCMs with more inflexibility, because the stress can be efficiently transferred from the network of SCMs to the stiff CNFs during the separation process. Besides, SCMs, as an all-cellulose material with homogenous surface chemistry and pore structure characteristics, are more suitable as supports for adsorbents. Finally, the SCMs were immobilized with 3-aminophenylboronic acids (BA/EPI-SCMs) and tested their performance in affinity adsorption of glycoproteins. BA/EPI-SCMs showed fast separation, high adsorption amount, and excellent selectivity toward glycoproteins.


Asunto(s)
Celulosa , Nanofibras , Adsorción , Celulosa/química , Glicoproteínas , Concentración de Iones de Hidrógeno , Ligandos , Microesferas , Nanofibras/química
19.
Materials (Basel) ; 15(15)2022 Aug 04.
Artículo en Inglés | MEDLINE | ID: mdl-35955310

RESUMEN

Sodium carbonate (Na2CO3), an environmentally friendly activator, has been shown to have vast potential for the development of sustainable alkali-activated slag mortars. However, Na2CO3-activated slag mortars exhibit a delayed reaction process and limited early-age strength development, restricting their wider application. In this work, the recycled concrete fines were calcined at a temperature of 800 °C for 1 h and then used as an auxiliary activator to improve the reaction kinetics of Na2CO3-activated slag mortars. The impact of the calcined recycled concrete fines (CRCF) dosage and Na2CO3 concentration on the compressive strength, hydration kinetics, and phase assemblage of mortars was evaluated. The results show that CRCF can react directly with Na2CO3 in the early stages, swiftly removing the CO32- in aqueous solution and providing an alkaline environment suitable for the dissolution of slag. This promotes the development of C-(A)-S-H, hydrotalcite, hemicarbonate, and monocarbonate. The hydration process and strength-giving phase of mortars can be improved further, as an increase in Na2CO3 concentration increases the initial alkaline content. Additionally, the most remarkable compressive strength value of 39.2 MPa was observed at 28 days in the mortar with 6% sodium oxide equivalent (Na2O-E) of Na2CO3 and 15% CRCF because of the synergistic effect of CRCF and Na2CO3.

20.
Gels ; 8(8)2022 Aug 06.
Artículo en Inglés | MEDLINE | ID: mdl-36005090

RESUMEN

Laboratories and industries that handle chemicals are ubiquitously prone to leakages. These may occur in storage rooms, cabinets or even in temporary locations, such as workbenches and shelves. A relevant number of these chemicals are corrosive, thus commercial products already exist to prevent material damage and injuries. One strategy consists of the use of absorbing mats, where few display neutralizing properties, and even less a controlled neutralization. Nevertheless, to the authors' knowledge, the commercially available neutralizing mats are solely dedicated to neutralizing acid or alkali solutions, never both. Therefore, this work describes the development and proof of a completely novel concept, where a dual component active mat (DCAM) is able to perform a controlled simultaneous neutralization of acid and alkali leakages by using microencapsulated active components. Moreover, its active components comprise food-grade ingredients, embedded in nonwoven polypropylene. The acid neutralizing mats contain sodium carbonate (Na2CO3) encapsulated in sodium alginate microcapsules (MC-ASC). Alkali neutralizing mats possess commercial encapsulated citric acid in hydrogenated palm oil (MIRCAP CT 85-H). A DCAM encompasses both MC-ASC and MIRCAP CT 85-H and was able to neutralize solutions up to 10% (v/v) of hydrochloric acid (HCl) and sodium hydroxide (NaOH). The efficacy of the neutralization was assessed by direct titration and using pH strip measurement tests to simulate the leakages. Due to the complexity of neutralization efficacy evaluation based solely on pH value, a thorough conductivity study was performed. DCAM reduced the conductivity of HCl and NaOH (1% and 2% (v/v)) in over 70%. The composites were characterized by scanning electron microscopy (SEM), differential calorimetry (DSC) and thermogravimetric analysis (TGA). The size of MC-ASC microcapsules ranged from 2 µm to 8 µm. Finally, all mat components displayed thermal stability above 150 °C.

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