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1.
Chemosphere ; 252: 126570, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32443266

RESUMO

Hydrotalcite precipitation is a promising technology for the on-site treatment of acid mine drainage (AMD). This technology is underpinned by the synthesis of hydrotalcite that can effectively remove various contaminants. However, hydrotalcite precipitation has only limited capacity to facilitate sulfate removal from AMD. Therefore, the feasibility of coupling biological sulfate reduction with the hydrotalcite precipitation to maximize sulfate removal was evaluated in this study. AMD emanating from a gold mine (pH 4.3, sulfate 2000 mg L-1, with various metals including Al, Cd, Co, Cu, Fe, Mn, Ni, Zn) was first treated using the hydrotalcite precipitation. Subsequently, biological treatment of the post-hydrotalcite precipitation effluent was conducted in an ethanol-fed fluidized bed reactor (FBR) at a hydraulic retention time (HRT) of 0.8-1.6 day. The hydrotalcite precipitation readily neutralized the acidity of AMD and removed 10% of sulfate and over 99% of Al, Cd, Co, Cu, Fe, Mn, Ni, Zn. The overall sulfate removal increased to 73% with subsequent FBR treatment. Based on 454 pyrosequencing of 16S rRNA genes, the identified genera of sulfate-reducing bacteria (SRB) included Desulfovibrio, Desulfomicrobium and Desulfococcus. This study showed that sulfate-rich AMD can be effectively treated by integrating hydrotalcite precipitation and a biological sulfate reducing FBR.


Assuntos
Hidróxido de Alumínio/química , Hidróxido de Magnésio/química , Eliminação de Resíduos/métodos , Sulfatos/química , Ácidos , Reatores Biológicos/microbiologia , Concentração de Íons de Hidrogênio , Metais , Mineração , Oxirredução , RNA Ribossômico 16S
2.
Chemosphere ; 255: 126937, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402882

RESUMO

Phosphate competes with arsenate for sorption sites on poorly crystalline iron and aluminum (hydr)oxides. The competition has implications e.g. for the management of arsenic-contaminated soil and water. Phosphate competition with arsenate on mixed phases containing both iron and aluminum (hydr)oxides has rarely been investigated. Here, the phosphate competition with arsenate on mixtures of poorly crystalline aluminum hydroxide (Alhox) and ferrihydrite (Fh), was investigated in batch experiments at pH 6.5. X-ray absorption spectroscopy (XAS) was performed on the phosphorus and arsenic K edges, which offered a unique insight in the partitioning of arsenate and phosphate on mixed Alhox-Fh sorbents. Under the studied conditions the sorption capacity of the mixed sorbents (per mol Al or Fe) increased at higher Alhox to Fh ratios. The XAS measurements provided direct evidence that phosphate competed more effectively with arsenate for sorption sites on Alhox than on Fh. For example, in a mixture with 50% of both sorbents and with similar additions of arsenate and phosphate, 71% of the oxyanions adsorbed on Fh and 46% on Alhox were arsenate. Consequently, phosphate may mobilize arsenate more easily from mixed iron-aluminum matrices that are rich in aluminum.


Assuntos
Hidróxido de Alumínio/química , Arseniatos/química , Fosfatos/química , Adsorção , Alumínio/química , Arsênico/química , Compostos Férricos , Ferro/química , Óxidos/química , Água
3.
World J Microbiol Biotechnol ; 36(3): 43, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32130537

RESUMO

Second generation ethanol has the prospect of becoming an important bioenergy alternative. The development of this technology is associated with the lignocellulosic materials' use, with emphasis on agricultural and agroindustrial by-products from which fermentable sugar can be produced. The acid hydrolysis depolymerizes the hemicellulose releasing mainly xylose. Subsequently, the cellulose can be converted into glucose by enzymatic hydrolysis. However, the acid hydrolysis produces toxic compounds, such as furan derivatives, phenolics, and organic acids, which are harmful to fermentative microorganisms. This study investigated different acid concentrations in the sulfuric acid hydrolysis of sugarcane bagasse (1- 5% m/v) and the use of adsorbents with the prerogative to improve the acid hydrolysate (AH) quality for microbial ethanolic fermentation. Cell growth and fermentative yield of Saccharomyces cerevisiae (PE-2) and Scheffersomyces stipitis (NRRL Y-7124) were evaluated. AH was used as a source of pentoses (17.7 g L-1) and molasses (ME) sugarcane as source of hexoses (47 g L-1). The following adsorbents were used: activated charcoal, clay, hydrotalcite and active and inactive cells of PE-2 and NRRL Y-7124, at concentrations ranging (1 - 8% m/v). Results of cell growth and chemical characterization allowed to select the most effective adsorbents with emphasis for active cells that removed 66% furfural and 51% 5-(hydroxymethyl) furfural) (5-HMF) and alcoholic productivity of 23.5 g L-1 in AH and ME substrates, in the presence of mixed culture. These results indicate the application of active yeast cells in the detoxification of acid hydrolysates of the sugarcane bagasse previously to the fermentation.


Assuntos
Celulose/análise , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomycetales/crescimento & desenvolvimento , Saccharum/microbiologia , Adsorção , Hidróxido de Alumínio/química , Carvão Vegetal/química , Fermentação , Hexoses/química , Hidróxido de Magnésio/química , Pentoses/química , Saccharum/química
4.
Int J Nanomedicine ; 15: 239-252, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32021177

RESUMO

Introduction: Aluminum salts, although they have been used as adjuvants in many vaccine formulations since 1926, exclusively induce a Th2-biased immune response, thereby limiting their use against intracellular pathogens like Mycobacterium tuberculosis. Methods and Results: Herein, we synthesized amorphous and crystalline forms of aluminum hydroxide nanoparticles (AH nps) of 150-200 nm size range. Using Bacillus anthracis protective antigen domain 4 (D4) as a model antigen, we demonstrated that both amorphous and crystalline forms of AH nps displayed enhanced antigen D4 uptake by THP1 cells as compared to commercial adjuvant aluminum hydroxide gel (AH gel). In a mouse model, both amorphous and crystalline AH nps triggered an enhanced D4-specific Th2- and Th1-type immune response and conferred superior protection against anthrax spore challenge as compared to AH gel. Physicochemical characterization of crystalline and amorphous AH nps revealed stronger antigen D4 binding and release than AH gel. Conclusion: These results demonstrate that size and crystallinity of AH nps play important roles in mediating enhanced antigen presenting cells (APCs) activation and potentiating a strong antigen-specific immune response, and are critical parameters for the rational design of alum-based Th1-type adjuvant to induce a more balanced antigen-specific immune response.


Assuntos
Adjuvantes Imunológicos/farmacologia , Hidróxido de Alumínio/química , Antraz/prevenção & controle , Antígenos de Bactérias/imunologia , Toxinas Bacterianas/imunologia , Nanopartículas Metálicas/química , Adjuvantes Imunológicos/química , Adjuvantes Imunológicos/farmacocinética , Hidróxido de Alumínio/imunologia , Hidróxido de Alumínio/farmacologia , Animais , Antraz/imunologia , Vacinas contra Antraz/química , Vacinas contra Antraz/imunologia , Vacinas contra Antraz/farmacologia , Linhagem Celular , Modelos Animais de Doenças , Difusão Dinâmica da Luz , Feminino , Humanos , Camundongos , Células RAW 264.7 , Espectroscopia de Infravermelho com Transformada de Fourier , Células Th1/imunologia
5.
Chemosphere ; 247: 125899, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31945718

RESUMO

In this work, we newly synthesized granular composite (GASA) via hydrothermal treatment of polyaluminum chloride (PAC) and subsequently granulation pelleting with starch gel as an organic binder. The resulting composite was characterized with analytic instruments, and the feasibility of utilizing GASA as adsorbent for the removal of fluoride (F-) was tested in the batch and column experiments. The characterization results revealed that GASA possessed a spherical/porous framework consisting of aluminosilicate (i.e., ordered albite, NaAlSiO3O8). The results of final pH effect experiments and XRD/XPS analyses showed the dominant adsorption mechanisms of F- on GASA were electrostatic attraction by protonated surface Al-OH, ligand exchange between surface hydroxyl groups and F ions, and surface precipitation (i.e., cryolite formation). Based on the results of adsorption kinetics and adsorption isotherm, granulation resulted in the relatively slow kinetics of F adsorption compared to the powder type, but was preferred to retain good adsorption capacity. The regeneration possibility of GASA was also proven with the adsorption/desorption cyclic test. In the column study, 15-cm length of the GASA layer and the flow rate less than 0.85 mL min-1 were proposed to keep the satisfactory level of F in water. The experimental results offer a potential of PAC sludge-derived composite as adsorbent for the removal of F from water.


Assuntos
Hidróxido de Alumínio/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Fluoretos , Concentração de Íons de Hidrogênio , Cinética , Esgotos , Fluoreto de Sódio , Água , Poluentes Químicos da Água/análise
6.
J Environ Sci (China) ; 89: 194-205, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31892391

RESUMO

A newly designed aluminum hydroxide gel-coated nanoscale zero-valent iron (AHG@NZVI) with enhanced activity and dispersibility of NZVI was successfully synthesized. The AHG@NZVI composite was synthesized via control of the surface AHG content. AHG@NZVI-1, AHG@NZVI-2 and AHG@NZVI-3 were prepared under centrifugal mixing speeds of 1000, 2000 and 4000 r/min, respectively. The activity of AHG@NZVI was evaluated by its tetracycline (TC) removal efficiency. The effects of AHG content, pH value, reaction temperature, and presence of competitive anions on TC removal were investigated. TC could be removed by both adsorption and chemical reduction on AHG@NZVI-2 (centrifugal speed 2000 r/min) in a short time with high removal efficiency (≥98.1%) at the optimal conditions. Such excellent performance can be attributed to a synergistic interaction between aluminum hydroxide gel and NZVI: (1) AHG could enhance the stability and dispersity of NZVI; (2) aluminum hydroxide gel could absorb a certain amount of TC and Fe2+/Fe3+, which facilitated the mass transfer of TC onto the NZVI surface, resulting in acceleration of the reduction rate of TC by the AHG@NZVI composite; and (3) AHG-Fe2+/Fe3+ could absorb a certain amount of TC by flocculation. The kinetics of TC removal by AHG@NZVI composite was found to follow a two-parameter pseudo-first-order model. The presence of competitive anions slightly inhibited the activity of AHG@NZVI systems for TC removal. Overall, this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.


Assuntos
Hidróxido de Alumínio/química , Tetraciclina/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Adsorção , Antibacterianos/química , Floculação , Ferro
7.
Int Arch Allergy Immunol ; 181(2): 94-102, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31865326

RESUMO

Only few data on safety during high-dose, accelerated escalation schedules during subcutaneous allergen immunotherapy (AIT) are available. The aim of this study was to assess the safety and tolerability of an accelerated dose escalation schedule of AIT in adult patients with moderate to severe seasonal rhinoconjunctivitis in a multicenter, open-label, randomized phase II trial. The dose escalation scheme for patients in Group I (1 strength) included 3 injections with 1 strength, B (10,000 TU/mL), whereas the dose escalation scheme for Group II (standard) included 7 injections with 2 strengths, A (1,000 TU/mL) and B (10,000 TU/mL), of an aluminum hydroxide-adsorbed allergoid grass pollen preparation. Overall, 72 of 87 randomized patients (83.7%) reported at least 1 treatment-emergent adverse event (TEAE; 82.2 [Group I] vs. 85.4% [Group II]); 58.8% of all reported TEAEs were assessed as being related to AIT (60.0 vs. 48.8%). The most frequently reported AIT-related TEAEs were swelling (46.7 vs. 34.1%), erythema (28.9 vs. 36.6%), and pruritus (31.1 vs. 17.1%) at the site of the injection. Systemic allergic reactions occurred in 5 (5.8%) patients overall, with more being reported in the 1-strength group (4 [8.9%] vs. 1 [2.4%]). All systemic allergic reactions were classified as World Allergy Organization (WAO) Grade 1 or Grade 2 reactions. Accelerated high-dose escalation with an aluminum hydroxide-adsorbed grass pollen allergoid can be initiated with a safety and tolerability profile comparable to the standard dose escalation schedule in patients with allergic rhinitis with or without asthma.


Assuntos
Alergoides/química , Alergoides/imunologia , Hidróxido de Alumínio/química , Poaceae/imunologia , Rinite Alérgica Sazonal/imunologia , Rinite Alérgica/imunologia , Adulto , Alérgenos/imunologia , Alergoides/administração & dosagem , Hidróxido de Alumínio/administração & dosagem , Hidróxido de Alumínio/imunologia , Antígenos de Plantas/imunologia , Asma/imunologia , Conjuntivite Alérgica/imunologia , Dessensibilização Imunológica/métodos , Feminino , Humanos , Masculino , Pólen/imunologia
8.
Chemosphere ; 239: 124738, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494316

RESUMO

Stabilization/Solidification (S/S) has been widely used in soil remediation to both improve physical properties and immobilize extensive contaminants. GGBS (granulated ground blast furnace slag)-MgO-CaO (GMCs) was used to treat Pb/Zn contaminated soil. The physical and microstructural characteristics of stabilized/solidified contaminated soil were investigated in this study. Microstructural analysis showed that the main hydration products of GMC treated contaminated soil were C-S-H and hydrotalcite like gels (Ht), which dominated the physical strength of S/S soil. The unconfined compressive strength (UCS) and the leachability of GMC treated contaminated soil were improved with the increase in GMC proportion (5%-15%), curing time (7 days and 28 days) and temperature (5 °C, 21 °C and 45 °C) due to the enhanced hydration. The compressive strengths of the majority mixes met the US EPA criterion (0.35 MPa). The strength of S/S soils was less affected by the increase of curing temperature after a longer curing period (28 days). According to the XRD and SEM results, both Pb and Zn in S/S contaminated soil could be immobilized by the precipitation and the adsorption on the surface of calcium silicate hydrate (C-S-H). Zn can also be incorporated into the structure of C-S-H and Ht. The addition of Pb/Zn decreased the physical strength in the order of: Pb(5000 mg/kg)>Pb(10000 mg/kg)>Zn/Pb(5000 mg/kg)>Pb(20000 mg/kg).


Assuntos
Recuperação e Remediação Ambiental/métodos , Chumbo/química , Poluentes do Solo/química , Solo/química , Zinco/química , Hidróxido de Alumínio/química , Compostos de Cálcio/química , China , Hidróxido de Magnésio/química , Óxido de Magnésio/química , Microscopia Eletrônica de Varredura , Óxidos/química , Silicatos/química , Temperatura , Difração de Raios X
9.
J Environ Sci (China) ; 88: 1-11, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31862050

RESUMO

Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid (HA) to form composite contaminants. As an innovative recycled coagulant aid, Enteromorpha polysaccharides (Ep) were associated with polyaluminum chloride (PACl) (denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu2+ and HA in this study. The influence of different Al species coagulants (AlCl3, PAClb and PAClc) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail. Results showed that in the three PACl-Ep systems, PAClb-Ep gave the highest removal efficiencies for turbidity and Cu2+, and the best UV254 removal effect was reached by using PAClc-Ep. Higher contents of Alb and Alc contributed to great coagulation performance because of their stronger bridging and sweeping effects. For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions. Additionally, smaller and more agminated flocs with great recovery ability were formed by PAClb-Ep and PAClc-Ep systems (bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species). Similarly, due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.


Assuntos
Hidróxido de Alumínio/química , Cobre/química , Nanopartículas/química , Floculação , Concentração de Íons de Hidrogênio , Polissacarídeos/química , Purificação da Água
10.
J Food Sci ; 84(11): 3129-3139, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31599976

RESUMO

Although aluminum lakes are widely used in food industry for dyeing demands, there is still a dearth in the understanding of the colorant lake formation mechanism. In this study, indigo carmine (IC) lake (IC-aluminum hydroxide complex), a frequently used blue lake in the food industry, was investigated in terms of kinetics, isotherms, properties of colloidal particles, infrared (IR) spectra, and titration curves. Pseudo-second-order model presented the strongest correlation with the kinetic data at all pH levels (R2  ≥ 0.994). In pH range from 4 to 7, the colloidal particles of aluminum hydroxide were positively charged with zeta potential around 44 mV; a further pH increase induced to a decreased zeta potential, which reached negative levels at pH 10 and beyond. Diameter maximized at pH 10 (22.47 µm) and declined when the pH was reduced. Isotherm analysis showed that the adsorption followed monolayer adsorption patterns, as described by the Langmuir isotherm model. IR spectra indicated sulfonic acid groups participated in a chemical reaction during adsorption, and the titration assay further confirmed the formation of coordination bonds between sulfonic acid groups and aluminum atoms. This study profiled the reaction responsible for the formation of the blue lake and elucidated its reaction mechanism. Furthermore, the outcome could assist in improving the production efficiency of the lake through achieving higher reaction rate and adsorption capacity. PRACTICAL APPLICATION: The study elucidated the mechanism of indigo carmine (IC)-aluminum hydroxide lake formation, including profile of the adsorption process and molecular interaction between the blue dye and the hydroxide. The outcome of this study would help to improve the production efficiency of IC-aluminum hydroxide lakes, and to decrease the content of aluminum required in the lake by optimizing the production parameters to enhance the adsorption capacity of aluminum hydroxide, which would facilitate the alleviation of the potential health hazards caused by excessive intake of aluminum through foods.


Assuntos
Hidróxido de Alumínio/química , Corantes de Alimentos/química , Indústria Alimentícia/métodos , Índigo Carmim/química , Adsorção , Coloides/química , Concentração de Íons de Hidrogênio , Cinética , Soluções/química , Espectrofotometria Infravermelho
11.
Mikrochim Acta ; 186(10): 678, 2019 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-31515633

RESUMO

Nanosheets of a porous layered double hydroxide were directionally arranged on boehmite nanowires and porous carbon and used as a coating for solid-phase microextraction (SPME) method. Porous carbon tubes were prepared from goat grass and then coated with layered double hydroxide nanosheets and boehmite nanowires. The nanomaterial was placed on a stainless-steel wire which then was used for the extraction of fifteen agrochemicals from aqueous sample solutions. The extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time were optimized. Following thermal desorption of the agrochemicals in the injector of the gas chromatograph, they were quantified by GC/MS. Under optimum conditions, the repeatability for one fiber, expressed as relative standard deviation, was between 2.9 and 11.1%. The detection limits for the agrochemicals are between 2-29 ng L-1. The method is simple, fast, and inexpensive (in terms of equipment). The fiber is thermally stable, and the relative recoveries from spiked samples are better compared to conventional methods of extraction. Graphical abstract Schematic illustration of the preparation of three-dimensional hierarchical boehmite/ layered double hydroxides/ porous carbon (Boeh/LDH/pC) SPME fibers and application for the extraction of fifteen agrochemicals from aqueous sample solutions following quantification by GC/MS.


Assuntos
Agroquímicos/química , Nanocompostos/química , Praguicidas/análise , Extratos Vegetais/análise , Microextração em Fase Sólida/instrumentação , Poluentes Químicos da Água/química , Hidróxido de Alumínio/química , Óxido de Alumínio/química , Carbono/química , Hidróxidos/química , Poaceae/química , Aço Inoxidável/química
12.
Int J Mol Sci ; 20(15)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374834

RESUMO

One of the current developments in drug research is the controlled release formulation of drugs, which can be released in a controlled manner at a specific target in the body. Due to the diverse physical and chemical properties of various drugs, a smart drug delivery system is highly sought after. The present study aimed to develop a novel drug delivery system using magnetite nanoparticles as the core and coated with polyvinyl alcohol (PVA), a drug 5-fluorouracil (5FU) and Mg-Al-layered double hydroxide (MLDH) for the formation of FPVA-FU-MLDH nanoparticles. The existence of the coated nanoparticles was supported by various physico-chemical analyses. In addition, the drug content, kinetics, and mechanism of drug release also were studied. 5-fluorouracil (5FU) was found to be released in a controlled manner from the nanoparticles at pH = 4.8 (representing the cancerous cellular environment) and pH = 7.4 (representing the blood environment), governed by pseudo-second-order kinetics. The cytotoxicity study revealed that the anticancer delivery system of FPVA-FU-MLDH nanoparticles showed much better anticancer activity than the free drug, 5FU, against liver cancer and HepG2 cells, and at the same time, it was found to be less toxic to the normal fibroblast 3T3 cells.


Assuntos
Hidróxido de Alumínio/química , Antimetabólitos Antineoplásicos/administração & dosagem , Preparações de Ação Retardada/química , Fluoruracila/administração & dosagem , Hidróxido de Magnésio/química , Nanopartículas de Magnetita/química , Álcool de Polivinil/química , Células 3T3 , Animais , Antimetabólitos Antineoplásicos/farmacologia , Combinação de Medicamentos , Sistemas de Liberação de Medicamentos , Fluoruracila/farmacologia , Células Hep G2 , Humanos , Camundongos , Neoplasias/tratamento farmacológico
13.
Artigo em Inglês | MEDLINE | ID: mdl-31390846

RESUMO

Climate change has often caused failure in water treatment operations. In this study, we report a real case study at a major surface water treatment plant in Alabama, USA. Following a severe winter storm, the effluent water turbidity surged to >15.00 Nephelometric Turbidity Units (NTU), far exceeding the 0.30 NTU standard. As a result, the plant operation had to be shut down for three days, causing millions of dollars of losses and affecting tens of thousands of people. Systematic jar tests were carried out with sediment samples from 22 upstream locations. The coagulation and settleability of sediment particles were tested under simulated storm weather conditions, i.e., low temperature (7 °C) and in the presence of various types and concentrations of natural organic matter (NOM) that was extracted from the local sediments. Experimental results proved that elevated NOM (6.14 mg·L-1 as Total Organic Carbon, TOC) in raw water was the root cause for the failure of the plant while the low temperature played a minor but significant role. Pre-oxidation with permanganate and/or elevated coagulant dosage were found effective to remove TOC in raw water and to prevent similar treatment failure. Moreover, we recommend that chemical dosages should be adjusted based on the TOC level in raw water, and a reference dosage of 0.29 kg-NaMnO4/kg-TOC and 19 kg- polyaluminum chloride (PACl) /kg-TOC would be appropriate to cope with future storm water impacts. To facilitate timely adjustment of the chemical dosages, the real time key water quality parameters should be monitored, such as turbidity, TOC, Ultraviolet (UV) absorbance, pH, and color. The findings can guide other treatment operators to deal with shock changes in the raw water quality resulting from severe weather or other operating conditions.


Assuntos
Hidróxido de Alumínio/química , Floculação , Compostos de Manganês/química , Óxidos/química , Purificação da Água/métodos , Tempo (Meteorologia) , Alabama , Sedimentos Geológicos/análise , Nefelometria e Turbidimetria , Oxirredução
14.
Mater Sci Eng C Mater Biol Appl ; 103: 109816, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31349466

RESUMO

Layered double hydroxide (LDH) nanoparticles (NPs) have potential applications for the loading and controlled release of drugs. This study investigated the synthesis of Zn/Al-LDH using the co-precipitation and ion-exchange methods, coating with SiO2 NPs and precise control of the release of vitamin C (VC). The results showed that more VC could be loaded by ion exchange. The surface of the VC-loaded LDH NPs was coated with SiO2 using the sol-gel and physical mixing methods. The structure, surface morphology, drug loading and thermostability were characterized and the drug release profile and release kinetics of the intercalated LDHs were studied. It was found that the SiO2 NPs more uniformly coated the LDH surfaces using the sol-gel process than the physical mixing method. The release behavior of VC from the intercalated nanohybrid is well described by the Avrami-Erofe'ev and Elovich models in the slow and fast stages. The sol-gel coated LDH@SiO2 nanohybrid system showed sustained drug delivery compared to the physical mixing method. The overall VC release from LDH increased more than 3-fold after coating with SiO2 NPs. Taken together, the Zn/Al-LDH@SiO2 coated by sol-gel should be considered as a potential sustained-release drug delivery system for VC.


Assuntos
Hidróxido de Alumínio/química , Ácido Ascórbico/farmacocinética , Sistemas de Liberação de Medicamentos/métodos , Hidróxidos/química , Nanopartículas/química , Dióxido de Silício/química , Compostos de Zinco/química , Liberação Controlada de Fármacos , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria , Difração de Raios X
15.
AAPS PharmSciTech ; 20(6): 248, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31286298

RESUMO

Anti-caries activity of fluoride ions is due to the protection against demineralization and the enhancement of remineralization of tooth enamel. Dentifrices available on the market contain sodium fluoride, sodium monofluorophosphate, stannous fluoride, and amine fluoride as source of these ions. A new compound working both as fluoride ion source and as abrasive was projected. Hybrids based on F- ions intercalated between the lamellae of hydrotalcite-like compounds (HTlc-F), namely MgAl-HTlc-F and ZnAl-HTlc-F, were prepared and characterized. Then, three different percentages (2, 3, and 4%) of both HTlc-F compounds were assayed. After the rheological characterization, the dentifrices containing 3 and 4% of MgAl-HTlc-F and ZnAl-HTlc-F, respectively, resulted to be the most suitable ones. Two novel in vitro methods, "rotary toothbrush method" and "manual brushing method," were developed and used in order to study the F- ions release from the prepared dentifrices. The obtained results showed that the dentifrice containing ZnAl-HTlc-F (4%) was the most effective in releasing fluoride ions. The "rotary toothbrush method" resulted to be the most suitable as the simulation of the brushing movements is standardizable and reproducible.


Assuntos
Hidróxido de Alumínio/química , Dentifrícios/química , Fluoretos/química , Hidróxido de Magnésio/química , Fosfatos/química , Remineralização Dentária , Esmalte Dentário , Técnicas In Vitro
16.
Chemosphere ; 236: 124369, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31323555

RESUMO

Chlorinated hydrocarbons (CHCs) are recalcitrant compounds frequently found as contaminants in groundwater. Hydrotalcites (HT) have emerged as promising sorbents due to their tunable properties and anion exchange capacity. Here, two types of organo-HT were synthesized, via coprecipitation, by intercalation of two different anionic surfactants, sodium dodecyl sulfate and sodium 1-dodecane sulfonate. These compounds were first characterized by a suite of techniques to quantify surfactant intercalation and to evaluate their physico-chemical properties. Next, the sorption affinity of these organo-HT towards a suite of CHCs was tested under various conditions, including interlayer surfactant type, single and multiple CHCs systems, and different water chemistry (pH, ionic composition). Sorption coefficients (Kd) and organic-matter-normalized partition coefficient (Kom) derived from linear sorption isotherms for individual CHC were inversely correlated to their hydrophobicity in the order of: tetrachloroethylene > tetrachloromethane > trichloroethylene> 1,1,2-trichloroethane > trichloromethane. Kom values were further affected by the organo-HT drying process. In contrast, varying water chemistry and pH, and the co-existence of multiple CHCs had little effect on Kom values, indicating that competition between CHCs and ionic strength have a marginal effect on the sorption affinity. The inverse linear relationship between CHC hydrophobicity and Kom is shown to be a suitable tool to predict organo-HT's sorption efficiency in complex CHCs contaminated groundwaters. Overall, organo-HT's might be used as potential sorbents for ex situ treatment of CHCs in groundwater.


Assuntos
Hidróxido de Alumínio/química , Água Subterrânea/química , Hidrocarbonetos Clorados/química , Hidróxido de Magnésio/química , Nanopartículas/química , Água/química
17.
Environ Sci Pollut Res Int ; 26(27): 27854-27861, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31342349

RESUMO

In this paper, a flexible and efficient nano-reinforced polymer inclusion membrane (PIM) was fabricated and used for cyanide (CN-) extraction from water samples. Aliquat 336 (a liquid anion exchanger) was embedded in poly(vinyl chloride) (PVC) support as the extractant. Mg-Al-CO3 layered double hydroxide (LDH) with high surface area and anion exchange ability was applied to promote the extraction efficiency of PIM. A PIM comprising 56% PVC, 40% Aliquat 336, and 4% Mg-Al-CO3 LDH showed the best extraction efficiency. A single beam ultraviolet-visible spectrophotometer was used for the detection of cyanide. Surface morphology of the PIM was studied by field emission scanning electron microscopy. The experimental parameters influencing the extraction process were investigated and optimized. The intra- and inter-day relative standard deviations at two different concentrations were in the range of 2.8-7.6%. The dynamic range of the method was in the range of 5-500 µg L-1, and the detection limit was 1.4 µg L-1. The LDH reinforced PIM showed proper characteristics for the extraction of cyanide from real water and wastewater samples with recoveries between 82 and 115%.


Assuntos
Hidróxido de Alumínio/análise , Cianetos/análise , Hidróxidos/análise , Magnésio/análise , Hidróxido de Alumínio/química , Cianetos/química , Hidróxidos/química , Limite de Detecção , Magnésio/química , Microscopia Eletrônica de Varredura , Polímeros , Águas Residuárias , Água
18.
Inorg Chem ; 58(13): 8369-8378, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31247863

RESUMO

This article reports the effect of Gd(III) doping on the structure, microstructure, and optical properties of boehmite nanoparticles. The bright-blue fluorescence along with a long lifetime makes our material an efficient candidate for optical applications. Our material particularly targets and eliminates hexavalent chromium ions (Cr(VI)) from aqueous media, which turns it into a multifunctional fluorescent nanosensor (MFNS). The development of an efficient hexavalent chromium ion (Cr(VI)) sensor to detect and quantify Cr(VI) ions is still a serious issue worldwide. Thus, this work will be very beneficial for various environmental applications. No such work has been reported so far which includes cost-effective and biocompatible boehmite nanoparticles in this field. Detailed synthesis and characterization procedures for the MFNS have been incorporated here. The biocompatibility of the MFNS has also been studied rigorously by performing cell survivability assay (MTT) and cellular morphology assessments. Our extensive research confirmed that the "turn-off" sensing mechanism of this sensor material is based on a collisional quenching model which initiates the photoinduced electron transfer (PET) process. High selectivity and sensitivity (∼1.05 × 10-5 M) of the MFNS toward hexavalent chromium ions even in real life wastewater samples have been confirmed, which makes this fluorescent probe a potential candidate for new age imaging and sensing technologies.


Assuntos
Hidróxido de Alumínio/química , Óxido de Alumínio/química , Cromo/análise , Corantes Fluorescentes/química , Nanopartículas/química , Águas Residuárias/análise , Adsorção , Hidróxido de Alumínio/síntese química , Óxido de Alumínio/síntese química , Linhagem Celular Tumoral , Fluorescência , Corantes Fluorescentes/síntese química , Gadolínio/química , Humanos , Limite de Detecção , Microscopia de Fluorescência/métodos , Porosidade , Espectrometria de Fluorescência/métodos
19.
Carbohydr Res ; 481: 52-59, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31247450

RESUMO

High efficiency conversion of cellulose to 5-hydroxymethylfurfural (HMF) remains a challenge today. A simple solid acid catalyst Boehmite (γ-AlOOH) with high hydrothermal stability was prepared and used as sole catalyst for the direct conversion of cellulose into HMF in mixed reaction solvents of ionic liquid 1-buthyl-3-methylimidazolium chloride (BmimCl) and dimethyl sulfoxide (DMSO). This was aimed at developing an efficient and inexpensive catalyst for the production of HMF. The effects of factors such as water, solvent, catalyst load, temperature and reaction duration were investigated. An impressive HMF yield of 58.4% with 97.2% cellulose conversion was obtained at 160 °C after 2 h. More importantly, the catalyst γ-AlOOH was reused several times without loss of its catalytic properties. After five reaction runs, an HMF yield of 47.8% with 91.0% conversion was also obtained. In addition, the catalyst γ-AlOOH displayed excellent catalytic effects on the degradation of other carbohydrates. High yields of HMF from other carbohydrates such as glucose (61.2%), starch (62.7%) and inulin (70.5%) were achieved using γ-AlOOH as the catalyst. The proposed catalytic method shows a promising potential for HMF preparation, especially for industrial-scale HMF production from renewable bioresources.


Assuntos
Hidróxido de Alumínio/química , Óxido de Alumínio/química , Celulose/química , Custos e Análise de Custo , Furaldeído/análogos & derivados , Catálise , Furaldeído/química , Glucose/química , Solventes/química , Temperatura , Água/química
20.
J Oleo Sci ; 68(7): 679-687, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31178468

RESUMO

Hydrotalcite or Mg-Al LDHs were synthesized by co-precipitation method. The Mg-Al mixed oxide was then derived by calcination of hydrotalcite at 450°C. The metal modified catalysts (Mo/Mg-Al and V/Mg-Al) were prepared by incipient wetness impregnation method. The obtained catalysts were characterized by several useful techniques and tested the reactivity for dehydrogenation and oxidative dehydrogenation of ethanol (gas-phase) to produce acetaldehyde. The catalytic reactions were performed at temperature range from 200 to 400°C for both non-oxidative and oxidative atmospheres. The results showed that the vanadium-modified hydrotalcite (V/Mg-Al) exhibited the highest ethanol conversion (34.3%) and acetaldehyde yield (15.5%) at 400℃ in the non-oxidative atmosphere. For the oxidative dehydrogenation of ethanol, the V/Mg-Al catalyst showed the highest activity at 400°C giving the ethanol conversion and acetaldehyde yield of 73.7% and 29.5%, respectively. This result probably related to the highest base density of V/Mg-Al catalyst (6.13 µmol CO2/m2) measured by CO2-TPD. The catalytic activity of Mg-Al catalyst and metal modified catalyst slightly decreased upon time-on-stream test for 10 h on oxidative dehydrogenation of ethanol due to carbon deposition.


Assuntos
Compostos de Alumínio/química , Hidróxido de Alumínio/química , Etanol/química , Compostos de Magnésio/química , Hidróxido de Magnésio/química , Molibdênio/química , Vanádio/química , Compostos de Alumínio/síntese química , Hidróxido de Alumínio/síntese química , Carbono , Catálise , Precipitação Química , Temperatura Alta , Hidrogenação , Compostos de Magnésio/síntese química , Hidróxido de Magnésio/síntese química , Oxirredução
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