scholarly journals Fe3O4nanoparticles coated with a guanidinium-functionalized polyelectrolyte extend the pH range for phosphate binding

2017 ◽  
Vol 5 (35) ◽  
pp. 18476-18485 ◽  
Author(s):  
Laura Paltrinieri ◽  
Min Wang ◽  
Sumit Sachdeva ◽  
Nicolaas A. M. Besseling ◽  
Ernst J. R. Sudhölter ◽  
...  
Keyword(s):  
Phosphate Adsorption ◽  
Functional Coatings ◽  
Phosphate Binding ◽  
Alkaline Conditions ◽  
Ph Range

This work shows the enhanced effect of functional coatings on phosphate adsorption at alkaline conditions using Fe3O4NPs.

scholarly journals Adsorption of strontium on different sodium-enriched bentonites

2017 ◽  
Vol 82 (4) ◽  
pp. 449-463 ◽  
Author(s):  
Sanja Marinovic ◽  
Marija Ajdukovic ◽  
Natasa Jovic-Jovicic ◽  
Tihana Mudrinic ◽  
Bojana Nedic-Vasiljevic ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Adsorption Capacity ◽  
Textural Properties ◽  
X Ray Diffraction ◽  
Order Model ◽  
Surface Areas ◽  
Alkaline Conditions ◽  
Langmuir Isotherm Model ◽  
Pseudo Second Order ◽  
Ph Range

Bentonites from three different deposits (Wyoming, TX, USA and Bogovina, Serbia) with similar cation exchange capacities were sodium enriched and tested as adsorbents for Sr2+ in aqueous solutions. X-Ray diffraction analysis confirmed successful Na-exchange. The textural properties of the bentonite samples were determined using low-temperature the nitrogen physisorption method. Significant differences in the textural properties between the different sodium enriched bentonites were found. Adsorption was investigated with respect to adsorbent dosage, pH, contact time and the initial concentration of Sr2+. The adsorption capacity increased with pH. In the pH range from 4.0?8.5, the amount of adsorbed Sr2+ was almost constant but 2?3 times smaller than at pH ?11. Further experiments were performed at the unadjusted pH since extreme alkaline conditions are environmentally hostile and inapplicable in real systems. The adsorption capacity of all the investigated adsorbents toward Sr2+ was similar under the investigated conditions, regardless of significant differences in the specific surface areas. It was shown and confirmed by the Dubinin?Radushkevich model that the cation exchange mechanism was the dominant mechanism of Sr2+ adsorption. Their developed microporous structures contributed to the Sr2+ adsorption process. The adsorption kinetics obeyed the pseudo-second-order model. The isotherm data were best fitted with the Langmuir isotherm model.

scholarly journals Preliminary time-of-flight neutron diffraction studies ofEscherichia coliABC transport receptor phosphate-binding protein at the Protein Crystallography Station

2014 ◽  
Vol 70 (6) ◽  
pp. 819-822 ◽  
Author(s):  
K. H. Sippel ◽  
J. Bacik ◽  
F. A. Quiocho ◽  
S. Z. Fisher
Keyword(s):  
Neutron Diffraction ◽  
Binding Protein ◽  
Protein Crystallography ◽  
Phosphate Transport ◽  
Phosphate Binding ◽  
Science Center ◽  
Data Set ◽  
Acceptor Group ◽  
Phosphate Binding Protein ◽  
Ph Range

Inorganic phosphate is an essential molecule for all known life. Organisms have developed many mechanisms to ensure an adequate supply, even in low-phosphate conditions. In prokaryotes phosphate transport is instigated by the phosphate-binding protein (PBP), the initial receptor for the ATP-binding cassette (ABC) phosphate transporter. In the crystal structure of the PBP–phosphate complex, the phosphate is completely desolvated and sequestered in a deep cleft and is bound by 13 hydrogen bonds: 12 to protein NH and OH donor groups and one to a carboxylate acceptor group. The carboxylate plays a key recognition role by accepting a phosphate hydrogen. PBP phosphate affinity is relatively consistent across a broad pH range, indicating the capacity to bind monobasic (H2PO4−) and dibasic (HPO42−) phosphate; however, the mechanism by which it might accommodate the second hydrogen of monobasic phosphate is unclear. To answer this question, neutron diffraction studies were initiated. Large single crystals with a volume of 8 mm3were grown and subjected to hydrogen/deuterium exchange. A 2.5 Å resolution data set was collected on the Protein Crystallography Station at the Los Alamos Neutron Science Center. Initial refinement of the neutron data shows significant nuclear density, and refinement is ongoing. This is the first report of a neutron study from this superfamily.

scholarly journals Flotation Behavior of Diatomite and Albite Using Dodecylamine as a Collector

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 371 ◽  
Author(s):  
Ying Gao ◽  
Yuexin Han ◽  
Wenbo Li
Keyword(s):  
Unit Area ◽  
Alkaline Ph ◽  
Force Microscopy ◽  
Atomic Force ◽  
Mineral Flotation ◽  
Alkaline Conditions ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Ph Range ◽  
First Time

The flotation behaviors of diatomite and albite using dodecylamine (DDA) as a collector were investigated and compared. The pure mineral flotation results indicate that the flotability difference between albite and diatomite is above 87% at pH 5.5 to 10.5. The recovery of albite improves with increasing DDA dosage at pH 5.5 to 10.5. In the same pH range, diatomite has weaker flotability than albite, particularly in alkaline pH pulp. Zeta potential measurements indicate that diatomite has a higher negative surface charge than albite at pH 7 to 12, DDA interacts strongly with albite and weakly with diatomite. Thus, DDA preferentially absorbs on albite surface rather than diatomite under alkaline conditions. Fourier transform infrared spectra (FTIR) indicate that the amount of DDA adsorbed to albite is greater than that adsorbed to diatomite, under the same conditions. The adsorption of DDA on the surface of diatomite is investigated by using atomic force microscopy (AFM) for the first time. The adsorption of the collector DDA on the surface of albite per unit area is greater than that on diatomite. This accounts for the lower recovery of diatomite than that of albite.

scholarly journals Complexation of Th(IV) and Eu(III) by α-isosaccharinic acid under alkaline conditions

2001 ◽  
Vol 89 (6) ◽  
Author(s):  
K. Vercammen ◽  
M.A. Glaus ◽  
Luc R. Van Loon
Keyword(s):  
Stability Constants ◽  
Data Sets ◽  
Complexation Reaction ◽  
Sorption Data ◽  
Alkaline Conditions ◽  
The Stability ◽  
Ph Range ◽  
Complexation Reactions ◽  
Best Fit ◽  
Isosaccharinic Acid

The complexation of Th(IV) and Eu(III) by α-isosaccharinic acid (ISA) has been studied in the pH range from 10.7 to 13.3 by batch sorption experiments, and the influence of Ca on the complexation was investigated. Sixteen data sets – each determined at variable ISA concentrations – are used to determine the stoichiometry of the complexation reactions and the stability constants. Based on best-fit analysis of the sorption data, it is postulated that 1:1 Th:ISA complexes are formed in the absence of Ca according to the complexation reaction: Th+ISA↔(ThISA)

Phosphorus recovery as struvite from eutropic waters by XDA-7 resin

2012 ◽  
Vol 65 (12) ◽  
pp. 2091-2097 ◽  
Author(s):  
Huanwen Li ◽  
Zhiping Ye ◽  
Ying Lin ◽  
Fengying Wang
Keyword(s):  
Ammonium Phosphate ◽  
Phosphorus Recovery ◽  
Phosphate Adsorption ◽  
Nacl Solution ◽  
Acid Dissolution ◽  
Magnesium Ammonium Phosphate ◽  
Magnesium Ammonium ◽  
Struvite Precipitation ◽  
Ph Range ◽  
Removal And Recovery

Phosphorus releases into aquatic environment and its subsequent contribution to eutrophication have resulted in a widespread global pollution issue. However, phosphorus is a non-renewable source. The potential supplies of phosphorus are decreasing worldwide. Therefore, removal and recovery of phosphorus from the eutropic waters is important, emergent and necessary. In this research, experiments for recovering phosphate from eutropic waters by anion exchange combined with struvite precipitation were conducted. The results indicated that the prepared XDA-7 resin was an effective adsorbent for phosphate. The adsorption isotherm of XDA-7 resin was found to be a modified Freundlich type. The maximum phosphate adsorption (20.9 mg/g) occurred in the pH range of 6.0–8.0. Phosphate adsorbed on the XDA-7 resin was effectively desorbed with 8% NaCl solution, and the resin was able to be regenerated with 3% NaClO and 4% NaOH solutions. Phosphate desorbed from the resin was recovered as magnesium ammonium phosphate (struvite). The obtained struvite was analyzed by acid dissolution method, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The struvite precipitate was found to be 75.8% in purity, a high-value fertilizer.

Factors affecting germination of horseweed (Conyza canadensis)

Weed Science ◽  
2006 ◽  
Vol 54 (5) ◽  
pp. 898-902 ◽  
Author(s):  
Vijay K. Nandula ◽  
Thomas W. Eubank ◽  
Daniel H. Poston ◽  
Clifford H. Koger ◽  
Krishna N. Reddy
Keyword(s):  
Seedling Emergence ◽  
Soil Surface ◽  
Conyza Canadensis ◽  
Light Conditions ◽  
Complete Darkness ◽  
Continuous Darkness ◽  
Factors Affecting ◽  
Nacl Concentration ◽  
Alkaline Conditions ◽  
Ph Range

The influence of environmental factors on germination and emergence of horseweed was examined in growth chamber experiments. Germination was highest (61%) under 24/20 C day/night temperature under light. Horseweed seed germination was observed under both light (13 h photoperiod) and complete darkness (24 h), but germination under continuous darkness was only 0 to 15% compared with 0 to 61% under light. All other experiments were conducted under 24/20 C and 13-h light conditions. Germination was 19 to 36% over a pH range from 4 to 10, with a trend toward higher germination under neutral-to-alkaline conditions. Horseweed germination was > 20% at < 40 mM NaCl concentration and lowest (4%) at 160 mM NaCl. These data suggest that even at high soil salinity conditions, horseweed can germinate. Germination of horseweed decreased from 25% to 2% as osmotic potential increased from 0 (distilled water) to −0.8 MPa, indicating that germination can still occur under moderate water stress conditions. Horseweed seedling emergence was at its maximum on the soil surface, and no seedlings emerged from seeds placed at a depth of 0.5 cm or higher.

Adsorption of Methylene Blue and Congo Red on Bentonite Modified with CaCO3

2017 ◽  
Vol 727 ◽  
pp. 853-858 ◽  
Author(s):  
Han Bing Zhang ◽  
Ning Hua Chen ◽  
Zhang Fa Tong ◽  
Qi Feng Liu ◽  
Yan Kui Tang ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Adsorption Isotherms ◽  
Adsorption Kinetics ◽  
Congo Red ◽  
Phosphate Adsorption ◽  
Adsorption Effect ◽  
Adsorption Performance ◽  
Initial Ph ◽  
Removal Efficiencies ◽  
Ph Range

Both bentonite and CaCO3 are cheap and abundant superior regional non-metal ores in Guangxi province, so it is very meaningful to jointly exploit bentonite and CaCO3 for real applications. In this study, bentonite modified with CaCO3 (CCB) was prepared and its adsorption performance of Congo Red (CR) and Methylene Blue (MB) was evaluated by investigating the adsorption influencing effects of initial pH, SDBS and phosphate. Adsorption isotherms and adsorption kinetics models were also fitted to analysis the corresponding kinetic characteristics of CCB. The results show that CCB exhibited superior adsorption performance with the respective > 90% MB and CR removal within the initial pH range 2 ~ 10. To a certain extent, MB removal efficiencies by CCB can be increased with the addition of SDBS. On the other hand, CR adsorption on CCB was inhibited slightly in presence of SDBS. But as a whole, removal efficiencies of MB and CR by CCB were kept constant when SDBS co-existed. MB and CR adsorption on CCB decreased to some extent because of competitive adsorption effect when phosphate co-existed. It also demonstrated that CCB can remove phosphate at the same time with dyes. Adsorption models including adsorption isotherms adsorption kinetics indicated that MB and CR adsorption on CCB was a monolayer process, and the adsorption rate depended on both adsorbent and adsorbate. In summary, CCB is a promising adsorbent for dyes removal with many advantages such as simple preparation technology, excellent adsorption performance for anionic and cationic dyes, broad fitting pH range and SDBS resistance. Besides, it can remove dyes together with phosphate at the same time. Therefore, this study is very useful for the dyeing wastewater treatment and exploiting the resources of bentonite and CaCO3.

2´-carboxy-3-keto-D-arabinitol 1,5-bisphosphate, the six-carbon intermediate of the ribulose bisphosphate carboxylase reaction

1986 ◽  
Vol 313 (1162) ◽  
pp. 397-407 ◽  
Keyword(s):  
Metal Ion ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Divalent Metal Ion ◽  
Ph Range ◽  
Short Time ◽  
Hydrolysis Of

The six-carbon intermediate of the ribulose 1,5-bisphosphate (RuBP) carboxylase reaction, 2'-carboxy-3-keto-D-arabinitol 1,5-bisphosphate (CKABP), was prepared enzymatically by quenching the reaction with acid after a short time ( ca 12 ms). Over a wide pH range (4-11), GKABP undergoes a slow ( t 1/2 = 1 h), pH-independent decarboxylation. No detectable decomposition of CKABP occurs over a six-week period at — 80 °C. The decarboxylation of CKABP is acid-catalysed and is also catalysed by deactivated enzyme lacking the activator carbamate-divalent metal ion complex. Decarboxylation is accompanied by β-elimination of the C-1 phosphate from the 2,3-enediolate. Under alkaline conditions (pH >11) CKABP undergoes hydrolysis. Non-enzymatic hydrolysis of the intermediate is also accompanied by β-elimination of the C-1 phosphate (presumably from the aci-acid of the upper glycerate 3-phosphate) and the formation of pyruvate. Fully activated enzyme catalyses the complete hydrolysis of CKABP to glycerate 3-phosphate, although enzymic hydrolysis of CKABP is limited by an event not on the direct path of carboxylation. Carbon-13 NMR analysis of [2',3- 13 C]CKABP indicates that it exists in solution predominantly (> 85%) as the C-3 ketone. In contrast, borohydride trapping of CKABP formed from [3- 18 O]RuBP indicates that the intermediate exists on the enzyme predominantly (> 94%) as the hydrated C-3 gem-diol. In solution, the hydration of the C-3 ketone of CKABP proceeds slowly ( k = 2.5 x 10 -3 s -1 ). The enzymatic hydration of CKABP must proceed at least as fast as k cat ( ca. 5 s -1 ) or at least 2000 times faster than the hydration of CKABP in solution.

scholarly journals Rational Design of Aptamer Switches with Programmable pH Response

2020 ◽  
Author(s):  
Ian A.P. Thompson ◽  
Liwei Zheng ◽  
Michael Eisenstein ◽  
H. Tom Soh
Keyword(s):  
Rational Design ◽  
Molecular Devices ◽  
Design Strategies ◽  
Ph Response ◽  
Dna Motif ◽  
Alkaline Conditions ◽  
Previous Design ◽  
Ph Conditions ◽  
Target Binding ◽  
Ph Range

AbstractAptamer switches that respond sensitively to local variations in pH could enable the development of molecular devices that greatly enhance diagnostic accuracy and therapeutic efficacy. Previous design strategies relied on inserting a known pH-sensitive DNA motif into the aptamer structure. Unfortunately, their performance was ultimately governed by the intrinsic pH-response of the inserted motif and could not be readily tuned to operate across arbitrary pH ranges. In this work, we present a general methodology for converting virtually any aptamer into a pH-responsive switch that can be modulated to undergo a strong change in affinity - in acidic, neutral, or alkaline conditions. This was achieved by inserting two orthogonal motifs that can be manipulated in parallel to tune sensitivity to different pH conditions without altering the core sequence of the aptamer itself. Using a single ATP aptamer, we achieve pH-dependent target binding and release under diverse pH conditions, producing as much as 1,000-fold pH-induced change in affinity. Importantly, we also demonstrate the novel capability to predictably engineer aptamer switches that only exhibit strong target affinity within a narrowly defined pH range. Our approach should offer a highly generalizable strategy for integrating pH-responsiveness into molecular devices.

scholarly journals Phosphate adsorption onto bagasse iron oxide biochar: Parameter optimization, kinetic analysis, and study of mechanism

BioResources ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. 1335-1357
Author(s):  
Qing Zhang ◽  
Yan-mei Ding ◽  
Lin Lu ◽  
Jing-xi Li ◽  
Mei-na Liang ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Photoelectron Spectroscopy ◽  
Phosphate Adsorption ◽  
Phosphorus Concentration ◽  
X Ray Diffraction ◽  
Phosphorus Adsorption ◽  
X Ray ◽  
Bet Specific Surface Area ◽  
Ph Range

This study combined chemical ultrasonic modifications and microwave oven heating to prepare a novel adsorbent, bagasse iron oxide biochar, (BIBC) to remove phosphate from aqueous solutions. The characterization of BIBC was made by energy dispersive spectrometry (EDS), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses, and the mechanism of phosphorus adsorption on BIBC was researched by adsorption batch experiments with emphasis on pH, dosages of BIBC, initial phosphorus concentration, and adsorption time. The BIBC’s BET specific surface area and pore volumes were 81.94 m2 g−1 and 26.74 cm3 g−1, respectively. The pH for the optimal phosphorus adsorption by BIBC ranged from 5.0 to 7.0. The maximum adsorption capacities of phosphorus (according to the Langmuir model) were 3.62, 4.06, and 4.32 mg g-1 at temperatures of 25, 35, and 45 °C, respectively. Electrostatic interaction, surface adsorption of phosphorus on BIBC, and ion exchange were the main mechanisms of phosphorus adsorption. According to XPS results, Fe2p was involved in the adsorption reaction. The adsorption of phosphorus by BIBC is considered to be mainly chemical adsorption. The BIBC was stable under a pH range from 4.0 to 10.0 and secondary pollution did not result.

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