scholarly journals Silica Pillared Montmorillonites as Possible Adsorbents of Antibiotics from Water Media

2018 ◽  
Vol 8 (8) ◽  
pp. 1403 ◽  
Author(s):  
Maria Roca Jalil ◽  
Florencia Toschi ◽  
Miria Baschini ◽  
Karim Sapag
Keyword(s):  
Complex Formation ◽  
Aqueous Media ◽  
Pillared Clays ◽  
Raw Material ◽  
Van Der Waals Interactions ◽  
Adsorption Mechanisms ◽  
Adsorption Sites ◽  
Adsorption Capacities ◽  
Inner Sphere ◽  
Sphere Complex

In this work, three silica pillared clays (Si-PILC) were synthetized, characterized, and evaluated as possible adsorbents of ciprofloxacin (CPX) and tetracycline (TC) form alkaline aqueous media. The pillared clays obtained showed significant increases in their specific surface areas (SBET) and micropore volumes (Vμp) regarding the raw material, resulting in microporosity percentages higher than 57% in all materials. The studies of CPX and TC removal using pillared clays were compared with the natural clay and showed that the Si-PILC adsorption capacities have a strong relationship with their porous structures. The highest adsorption capacities were obtained for CPX on Si-PILC due to the lower molecular size of CPX respect to the TC molecule, favoring the interaction between the CPX− and the pillars adsorption sites. Tetracycline adsorption on silica pillared clays evidenced that for this molecule the porous structure limits the interaction between the TCH− and the pillars, decreasing their adsorption capacities. However, the results obtained for both antibiotics suggested that their negative species interact with adsorption sites on the pillared structure by adsorption mechanisms that involve inner-sphere complex formation as well as van der Waals interactions. The adsorption mechanism proposed for the anionic species on Si-PILC could be considered mainly as negative cooperative phenomena where firstly there is a hydrophobic effect followed by other interactions, such as der Waals or inner-sphere complex formation.

Alternative treatments to improve the potential of rice husk as adsorbent for methylene blue

2016 ◽  
Vol 75 (2) ◽  
pp. 296-305 ◽  
Author(s):  
Dison S. P. Franco ◽  
Eduardo H. Tanabe ◽  
Daniel A. Bertuol ◽  
Glaydson S. dos Reis ◽  
Éder C. Lima ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Rice Husk ◽  
Aqueous Media ◽  
Surface Characteristics ◽  
Organic Fraction ◽  
Alternative Treatments ◽  
Adsorption Sites ◽  
Adsorption Capacities ◽  
Endothermic Process ◽  
Mb Adsorption

Alternative treatments, such as, NaOH, ultrasound assisted (UA) and supercritical CO2 (SCO2), were performed to improve the potential of rice husk as adsorbent to remove methylene blue (MB) from aqueous media. All the treatments improved the surface characteristics of rice husk, exposing its organic fraction and/or providing more adsorption sites. The Langmuir and Hill models were able to explain the MB adsorption for all adsorbents in all studied temperatures. The experimental and modeled parameters demonstrated that the MB adsorption was favored by the temperature increase and by the use of NaOH-rice husk. The maximum adsorption capacities for the MB solutions (ranging from 10 to 100 mg L−1), estimated from the Langmuir model at 328 K, were in the following order: NaOH rice-husk (65.0 mg g−1) > UA-rice husk (58.7 mg g−1) > SCO2-rice husk (56.4 mg g−1) > raw rice husk (52.2 mg g−1). The adsorption was a spontaneous, favorable and endothermic process. In general, this work demonstrated that NaOH, UA and SCO2 treatments are alternatives to improve the potential of rice husk as adsorbent.

Complex formation of beryllium sulfate in mixtures of water and dimethylformamide

1983 ◽  
Vol 36 (10) ◽  
pp. 1941 ◽  
Author(s):  
BI Gislason ◽  
H Strehlow
Keyword(s):  
Complex Formation ◽  
Sulfate Ion ◽  
Kinetic Measurements ◽  
Inner Sphere ◽  
Sphere Complex ◽  
Beryllium Sulfate ◽  
Rate Of Substitution

The complex formation of BeSO4 in mixtures of water and dimethylformamide (dmf) has been studied by using conductivity and kinetic measurements. In these solutions the complex Be(SO4)22- is shown to exist together with the outer- and inner-sphere complex of BeSO4. The rate of substitution depends on the composition of the solvatomer Be(H20)I(dmf)4-I2+ which reacts with the sulfate ion and on the kind of solvating molecule which is substituted by the ligand SO42-.

Protonation effects on dynamic flux properties of aqueous metal complexes

2009 ◽  
Vol 74 (10) ◽  
pp. 1543-1557 ◽  
Author(s):  
Herman P. Van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Complex Formation ◽  
Metal Ion ◽  
Good Description ◽  
Minor Component ◽  
Outer Sphere ◽  
Metal Species ◽  
Central Metal ◽  
Inner Sphere ◽  
A Minor ◽  
Protonated Ligand

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

scholarly journals Mechanisms and adsorption capacities of biochar for the removal of organic and inorganic pollutants from industrial wastewater

2020 ◽  
Author(s):  
T. G. Ambaye ◽  
M. Vaccari ◽  
E. D. van Hullebusch ◽  
A. Amrane ◽  
S. Rtimi
Keyword(s):  
Organic Contaminants ◽  
Pyrolysis Temperature ◽  
Low Cost ◽  
Industrial Effluents ◽  
Economic Benefits ◽  
Inorganic Pollutants ◽  
Solution Ph ◽  
Adsorption Mechanisms ◽  
Adsorption Capacities ◽  
Temperature Solution

AbstractCurrently, due to the rapid growth of urbanization and industrialization in developing countries, a large volume of wastewater is produced from industries that contain chemicals generating high environmental risks affecting human health and the economy if not treated properly. Consequently, the development of a sustainable low-cost wastewater treatment approach has attracted more attention of policymakers and scientists. The present review highlights the recent applications of biochar in removing organic and inorganic pollutants present in industrial effluents. The recent modes of preparation, physicochemical properties and adsorption mechanisms of biochar in removing organic and inorganic industrial pollutants are also reviewed comprehensively. Biochar showed high adsorption of industrial dyes up to 80%. It also discusses the recent application and mechanism of biochar-supported photocatalytic materials for the degradation of organic contaminants in wastewater. We reviewed also the possible optimizations (such as the pyrolysis temperature, solution pH) allowing the increase of the adsorption capabilities of biochar leading to organic contaminants removal. Besides, increasing the pyrolysis temperature of the biochar was seen to lead to an increase in its surface area, while it decreases their amount of oxygen-containing functional groups, consequently leading to a decrease in the adsorption of metal (loid) ions present in the medium. Finally, the review suggests that more research should be carried out to optimize the main parameters involved in biochar production and its regeneration methods. Future efforts should be also carried out towards process engineering to improve its adsorption capacity to increase the economic benefits of its implementation.

scholarly journals “In Silico” Characterization of 3-Phytase A and 3-Phytase B from Aspergillus niger

2017 ◽  
Vol 2017 ◽  
pp. 1-23 ◽  
Author(s):  
Doris C. Niño-Gómez ◽  
Claudia M. Rivera-Hoyos ◽  
Edwin D. Morales-Álvarez ◽  
Edgar A. Reyes-Montaño ◽  
Nury E. Vargas-Alejo ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Phytic Acid ◽  
Aqueous Media ◽  
Alpha Helix ◽  
Proton Donor ◽  
Van Der Waals Interactions ◽  
Beta Sheet ◽  
Instability Index ◽  
Bioinformatic Tools ◽  
Helix 12

Phytases are used for feeding monogastric animals, because they hydrolyze phytic acid generating inorganic phosphate. Aspergillus niger 3-phytase A (PDB: 3K4Q) and 3-phytase B (PDB: 1QFX) were characterized using bioinformatic tools. Results showed that both enzymes have highly conserved catalytic pockets, supporting their classification as histidine acid phosphatases. 2D structures consist of 43% alpha-helix, 12% beta-sheet, and 45% others and 38% alpha-helix, 12% beta-sheet, and 50% others, respectively, and pI 4.94 and 4.60, aliphatic index 72.25 and 70.26 and average hydrophobicity of −0,304 and −0.330, respectively, suggesting aqueous media interaction. Glycosylation and glycation sites allowed detecting zones that can affect folding and biological activity, suggesting fragmentation. Docking showed that H59 and H63 act as nucleophiles and that D339 and D319 are proton donor residues. MW of 3K4Q (48.84 kDa) and 1QFX (50.78 kDa) is similar; 1QFX forms homodimers which will originate homotetramers with several catalytic center accessible to the ligand. 3K4Q is less stable (instability index 45.41) than 1QFX (instability index 33.66), but the estimated lifespan for 3K4Q is superior. Van der Waals interactions generate hydrogen bonds between the active center and O2 or H of the phytic acid phosphate groups, providing greater stability to these temporal molecular interactions.

scholarly journals Efficient encapsulation of proteins with random copolymers

2018 ◽  
Vol 115 (26) ◽  
pp. 6578-6583 ◽  
Author(s):  
Trung Dac Nguyen ◽  
Baofu Qiao ◽  
Monica Olvera de la Cruz
Keyword(s):  
Enzymatic Activity ◽  
Average Distance ◽  
Aqueous Media ◽  
Adsorbed Layer ◽  
Computational Design ◽  
Polymer Chains ◽  
Disordered Proteins ◽  
Random Copolymers ◽  
Adsorption Sites

Membraneless organelles are aggregates of disordered proteins that form spontaneously to promote specific cellular functions in vivo. The possibility of synthesizing membraneless organelles out of cells will therefore enable fabrication of protein-based materials with functions inherent to biological matter. Since random copolymers contain various compositions and sequences of solvophobic and solvophilic groups, they are expected to function in nonbiological media similarly to a set of disordered proteins in membraneless organelles. Interestingly, the internal environment of these organelles has been noted to behave more like an organic solvent than like water. Therefore, an adsorbed layer of random copolymers that mimics the function of disordered proteins could, in principle, protect and enhance the proteins’ enzymatic activity even in organic solvents, which are ideal when the products and/or the reactants have limited solubility in aqueous media. Here, we demonstrate via multiscale simulations that random copolymers efficiently incorporate proteins into different solvents with the potential to optimize their enzymatic activity. We investigate the key factors that govern the ability of random copolymers to encapsulate proteins, including the adsorption energy, copolymer average composition, and solvent selectivity. The adsorbed polymer chains have remarkably similar sequences, indicating that the proteins are able to select certain sequences that best reduce their exposure to the solvent. We also find that the protein surface coverage decreases when the fluctuation in the average distance between the protein adsorption sites increases. The results herein set the stage for computational design of random copolymers for stabilizing and delivering proteins across multiple media.

scholarly journals Uptake of Methylene Blue from Aqueous Solution by Pectin–Chitosan Binary Composites

2020 ◽  
Vol 4 (3) ◽  
pp. 95
Author(s):  
Dexu Kong ◽  
Lee D. Wilson
Keyword(s):  
Methylene Blue ◽  
Aqueous Media ◽  
Dye Adsorption ◽  
Adsorption Properties ◽  
Point Of Zero Charge ◽  
Cross Linking ◽  
Gravimetric Analysis ◽  
Adsorption Sites ◽  
Biopolymer Composites

To address the need to develop improved hybrid biopolymer composites, we report on the preparation of composites that contain chitosan and pectin biopolymers with tunable adsorption properties. Binary biopolymer composites were prepared at variable pectin–chitosan composition in a solvent directed synthesis, dimethyl sulfoxide (DMSO) versus water. The materials were characterized using complementary methods (infrared spectroscopy, thermal gravimetric analysis, pH at the point-of-zero charge, and dye-based adsorption isotherms). Pectin and chitosan composites prepared in DMSO yielded a covalent biopolymer framework (CBF), whereas a polyelectrolyte complex (PEC) was formed in water. The materials characterization provided support that cross-linking occurs between amine groups of chitosan and the –COOH groups of pectin. CBF-based composites had a greater uptake of methylene blue (MB) dye over the PEC-based composites. Composites prepared in DMSO were inferred to have secondary adsorption sites for enhanced MB uptake, as evidenced by a monolayer uptake capacity that exceeded the pectin–chitosan PECs by 1.5-fold. This work provides insight on the role of solvent-dependent cross-linking of pectin and chitosan biopolymers. Sonication-assisted reactions in DMSO favor CBFs, while cross-linking in water yields PECs. Herein, composites with tunable structures and variable physicochemical properties are demonstrated by their unique dye adsorption properties in aqueous media.

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