Na2HPO4 Solution Research Articles

Evaluation of Antimicrobial Activity of Four Organic Acids Used in Chicks Feed to Control Salmonella typhimurium: Suggestion of Amendment in the Search Standard.

Today, the general public has become increasingly aware of salmonellosis problems. Organic acids are known by their antimicrobial potential and commonly used for improving the quality of poultry feed. In this context, the present work evaluated the inhibitory effect of four organic acids, namely, acetic acid, citric acid, lactic acid, and tartaric acid, at different levels of contamination by Salmonella typhimurium. The neutralization of these organic acids in vitro and in the presence of one-day-old chick's organs was also investigated during the search for Salmonella serovars in birds as described in the Moroccan standard “NM 08.0.550.” The effect of four organic acids on Salmonella typhimurium was tested in vitro and in the presence of chick's organs at different concentrations set of strain and organic acids tested. The MIC results demonstrated that tartaric acid, citric acid, and acetic acid inhibited Salmonella typhimurium at concentrations of 0.312%, 0.625%, and 0.512% for the three levels of strain: 10, 100, and 103 CFU/ml, respectively, while lactic acid and depending on the amount of the strain introduced acts differently: 0.078% for 10 CFU/ml and 0.156% for 100 and 103 CFU/ml. The concentration of 0.04M of Na2HPO4 solution has proved, in vitro, in caecums and organs of chicks (in presence of organic acids) that strain introduced, even at low concentrations, can be recovered. The use of additives has beneficial effects in Salmonella control program. However, the present results recommend the amendment of Salmonella research standard, taking into account the probable presence of organic acids in digestive content of one-day-old chicks.

Hemin-Modified SnO2/Metglas Electrodes for the Simultaneous Electrochemical and Magnetoelastic Sensing of H2O2

In this work, we present a simple and efficient method for the preparation of hemin-modified SnO2 films on Metglas ribbon substrates for the development of a sensitive magneto-electrochemical sensor for the determination of H2O2. The SnO2 films were prepared at low temperatures, using a simple hydrothermal method, compatible with the Metglas surface. The SnO2 film layer was fully characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), photoluminescence (PL) and Fourier Transform-Infrared spectroscopy (FT-IR). The properties of the films enable a high hemin loading to be achieved in a stable and functional way. The Hemin/SnO2-Metglas system was simultaneously used as a working electrode (WE) for cyclic voltammetry (CV) measurements and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The CV scans reveal direct reduction and oxidation of the immobilized hemin, as well as good electrocatalytic response for the reduction of H2O2. In addition, the magnetoelastic resonance (MR) technique allows the detection of any mass change during the electroreduction of H2O2 by the immobilized hemin on the Metglas surface. The experimental results revealed a mass increase on the sensor during the redox reaction, which was calculated to be 767 ng/μM. This behavior was not detected during the control experiment, where only the NaH2PO4 solution was present. The following results also showed a sensitive electrochemical sensor response linearly proportional to the concentration of H2O2 in the range 1 × 10−6–72 × 10−6 M, with a correlation coefficient of 0.987 and detection limit of 1.6 × 10−7 M. Moreover, the Hemin/SnO2-Metglas displayed a rapid response (30 s) to H2O2 and exhibits good stability, reproducibility and selectivity.

Scalable Room-Temperature Synthesis of Multi-shelled Na3(VOPO4)2F Microsphere Cathodes

Summary The large-scale application of rechargeable batteries in electric vehicles and energy-storage systems is still hindered by their high cost, particularly from the active materials. Here we proposed a concept of integration of extraction-separation and materials-preparation to further reduce the materials' cost. The power of this concept was demonstrated by the large-scale room-temperature synthesis (150 g per batch) of multi-shelled Na3(VOPO4)2F microspheres based on in situ generated bubbles as soft templates. The as-prepared Na3(VOPO4)2F shows superior rate capability with discharge capacity of 81 mAh g−1 at 15 C current rate and capacity retention of 70% after 3,000 cycles. Ex situ UV-vis was first employed to characterize the variation of oxidation state for vanadium during the charging and discharging process. This is the first report of a rapid and facile large-scale room-temperature controllable synthesis of Na3(VOPO4)2F microspheres, and this approach could be extended to synthesize other similar compounds.

Fabrication of apatite-coated gypsum granules and histological evaluation using rabbits

Calcium sulfate dihydrate (CSD) has been used as a material for bone augmentation for many years. However, rapid resorption of CSD sometimes results in insufficient formation of new bone. In the present study, the feasibility of fabricating apatite-coated CSD (Ap/CSD) was studied, with the hypothesis that the apatite coating would reduce the rate of CSD resorption and enhance the osteoconductivity. To prepare Ap/CSD granules, 300–400 µm CSD granules were immersed in Na2HPO4 solution at 20 °C or 60 °C, resulting in granules coated with apatitic precipitates. Granules were analyzed by microscopy and x-ray diffraction, and the dissolution rate into pH 7.5 Tris-HCl buffer solution was measured. Osteoconductivity was assessed by the release of calcium ions, and their ability to stimulate new bone formation was examined through reconstruction of rabbit distal femur bone defects. It was found that the apatite coating resulted in increased osteoconduction and a decreased dissolution rate compared with bare CSD granules. When rabbit distal femur bone defect was reconstructed with Ap/CSD, CSD and sintered hydroxyapatite (s-HAp), all samples demonstrated an excellent tissue response. Four weeks after surgery, a higher radio opacity was obtained for Ap/CSD when compared with CSD, indicating new bone formation. The s-HAp granules remained and thus, new bone formation was smallest even though s-HAp granules bonded with the bone. Ap/CSD that was fabricated at 60 °C induced greater bone formation than CSD. It is therefore concluded that Ap/CSD has good potential value as a bone augmentation material.

Setting time evaluation of injectable carbonate apatite cement using various sodium carboxymethylcellulose (Na CMC) concentration

Introduction: The injectable calcium phosphate cement has the advantage to be used in the bone defect with the limited access which supports a minimally invasive surgical technique. These Injectability properties of calcium phosphate cement can be modified by adding a sodium carboxymethylcellulose (Na CMC). The aim of this present study is to investigate the setting time of injectable bone cement based on CO3Ap using various Na CMC concentration. Methods: Vaterite (a polymorph of CaCO3) and Dicalcium Phosphate Anhydrous (DCPA) as powder phase mixed with 0.2 mol/L Na2HPO4 solution containing 1% polyethylene glycol (PEG) and various concentration of Na CMC as followed 0.5%, 1%, 1.5%, and 2%, respectively. Each concentration groups was consisting of 5 samples from total 20 samples. Powder and liquid phase was mixed with a spatula at a liquid to powder (L/P) ratio of 0.4. The setting time of CO3Ap cement was evaluated according to the modification method standardized by ISO 1566 for dental zinc phosphate cement using a custom fabricated Vicat needle apparatus. The cement was maintained at 37ºC and 100% relative humidity as a standard requirement. Results: The mean value of setting time cement was as followed 0.5% Na CMC 35:06 minutes, 1% Na CMC 38:48 minutes, 1.5% Na CMC 40:06 minutes, and 2% Na CMC 41:30 minutes. The result is statistically significant (p<0.05) with the group of 0.5% Na CMC compared to others group. Conclusion: Increasing the concentration of Na CMC could prolong the setting time of CO3Ap cement.

Effect of ampholyte nature on current-voltage characteristic of anion-exchange membrane

Current-voltage characteristics (CVCs) of a Neosepta AMX membrane are studied in NaH2PO4 (pH = 4.7, C = 0.02 mol/L) and KC4H5O6 (pH = 3.6, C = 0.02 mol/L) solutions. It is shown that in the case of NaH2PO4 there are two plateaus in the CVC, which correspond to achievement of the first, ilimI, and second, ilimII, limiting currents. ilimI occurs when the NaH2PO4 salt diffusion to the membrane surface is saturated, ilimII refers to the saturation of the proton flux when the membrane is almost completely converted into the HPO42− form. In the case of potassium hydrotartrate, there is no state corresponding to ilimI. The difference in CVC for two ampholytes is due to the difference in the ratio between the dissociation constants related to the first (Ka1) and second (Ka2) steps of ampholyte dissociation. In the case of NaH2PO4, where pKa1 and pKa2 differ greatly, a solution of this salt contains nearly exclusively the singly charged phosphate form. However, a KC4H5O6 solution contains, together with the C4H5O6− anion, about 15% of the doubly charged tartrates, which take part in charge transfer. Approximate analytical expressions are obtained for ilimI and ilimII in the case of monosodium hydrophospate solution. Their application gives the ilimI and ilimII values, which are in good agreement with the experiment and with numerical calculations using a mathematical model based on the Nernst-Planck equation, the electroneutrality condition, and the local chemical equilibrium condition in the membrane and two adjacent diffusion boundary layers.

Feasibility evaluation of low-crystallinity β-tricalcium phosphate blocks as a bone substitute fabricated by a dissolution-precipitation reaction from α-tricalcium phosphate blocks.

Although sintered β-tricalcium phosphate blocks have been used clinically as artificial bone substitutes, the crystallinity of β-tricalcium phosphate, which might dominate biocompatibility, is extremely high. The objective of this study is to evaluate the feasibility of fabricating low-crystallinity β-tricalcium phosphate blocks, which are expected to exhibit good biocompatibility via a dissolution-precipitation reaction of α-tricalcium phosphate blocks as a precursor under hydrothermal conditions at 200°C for 24 h. Although β-tricalcium phosphate is a metastable phase, the presence of Mg2+ in the reaction solution inhibits the formation of its corresponding stable phase and induces β-tricalcium phosphate formation under acidic conditions. It was found that low-crystallinity β-tricalcium phosphate blocks could be fabricated from α-tricalcium phosphate blocks immersed in 1.0 mol/L MgCl2 + 0.1 mol/L NaH2PO4 solution while maintaining the shape of the α-tricalcium phosphate blocks. The crystallite size of the fabricated β-tricalcium phosphate blocks was 42 nm, which was substantially smaller than that of the sintered β-tricalcium phosphate blocks. When the fabricated β-tricalcium phosphate blocks were implanted into bone defects in rabbit femurs, they exhibited excellent tissue responses. In particular, the initial osteoconductivity (two and four weeks) was substantially greater than that of sintered β-tricalcium phosphate blocks.

Carbonate Apatite Containing Statin Enhances Bone Formation in Healing Incisal Extraction Sockets in Rats.

The purpose of this study was to evaluate the feasibility of using apatite blocks fabricated by a dissolution–precipitation reaction of preset gypsum, with or without statin, to enhance bone formation during socket healing after tooth extraction. Preset gypsum blocks were immersed in a Na3PO4 aqueous solution to make hydroxyapatite (HA) low crystalline and HA containing statin (HAFS), or in a mixed solution of Na2HPO4 and NaHCO3 to make carbonate apatite (CO) and CO containing statin (COFS). The right mandibular incisors of four-week-old male Wistar rats were extracted and the sockets were filled with one of the bone substitutes or left untreated as a control (C). The animals were sacrificed at two and four weeks. Areas in the healing socket were evaluated by micro-computed tomography (micro-CT) and histological analyses. The bone volume, trabecular thickness, and trabecular separation were greatest in the COFS group, followed by the CO, HAFS, HA, and C groups. The bone mineral density of the COFS group was greater than that of the other groups when evaluated in the vertical plane. The results of this study suggest that COFS not only allowed, but also promoted, bone healing in the socket. This finding could be applicable for alveolar bone preservation after tooth extraction.

Load of Ag3PO4 Particles on Sulfonated Polyphenylene Sulfide Superfine Fibre with High Visible-light Photocatalytic Activity

Ag3PO4 was loaded on sulfonated polyphenylene sulfide (SPPS) superfine fibre by a facile precipitation method. Both the structure and properties of the as-synthesized Ag3PO4/SPPS composites were characterized via XRD, SEM, EDS, XPS, FTIR, and UV-vis. The photocatalytic performance of Ag3PO4/SPPS composites was investigated via degradation of Methylene blue(MB) solution under visible light irradiation. The degradation results revealed that the photocatalytic activity of Ag3PO4/SPPS composites was greatly enhanced by the incorporation of Ag3PO4 with SPPS superfine fibre. For concentrations of AgNO3 and Na2HPO4 solutions of 0.3 M and 0.06 M in the preparation process, the Ag3PO4/SPPS composite showed higher photocatalytic activity under visible light irradiation.

An electrooxidative technique to fast fabricate copper phosphate electrodes capable of integrating high performance liquid chromatography for the label-free detection of fish freshness

A simple and fast one-step electrooxidative method has been developed to monolithically produce a copper phosphate (Cu3(PO4)2) compound on a disposable copper tape, which can be integrated with high performance liquid chromatography (HPLC) for the estimation of fish freshness. The Cu3(PO4)2 compound of flake-like nanostructures was formed by applying a first anodic peak potential at the copper tape for 10 min in a 1 M sodium dihydrogen phosphate (NaH2PO4) (pH 5.0) solution. The Cu3(PO4)2 electrodes can detect the oxidative reaction of histidine and histamine in 20 mM NaH2PO4 solutions with pH 5.0–8.5. When integrating the electrodes with a flow injection system, the linear range and the calculated detection limit of histamine were respectively 2.5–250 ppm and 0.15 ppm. The electrodes integrated to HPLC can specifically detect the histamine concentrations in fish samples in the pH 7.5 NaH2PO4 solution, achieving an accuracy rate of 95.3% and a recovery rate of 101.1%.

Aqueous solutions of NMA, Na2HPO4, and NaH2PO4 as models for interaction studies in phosphate–protein systems

Phosphate buffers are essential for many areas of studies. However, their influence on buffered systems is often ignored. The phosphate salts can interact with biologically important macromolecules (e.g. proteins) and stabilize or destabilize them. With our research, we want to answer question what kind of interactions, if any, occur between phosphate ions and a protein backbone model — N-methylacetamide (NMA). ATR-FTIR spectroscopy in the amide I range and in the regions characteristic for PO vibrations provides information on direct and indirect (water-mediated) interactions. The analysis is supported by chemometric, DFT, and QTAIM calculations. Our results indicate that direct NMA–phosphate ion interactions are quite rare and indirect. Water molecules seem to play an important role in such systems. The model studies indicate that no preferential interactions between NMA and phosphate ions in solutions are formed, and may imply that such interactions are also unfavorable in protein-based systems.

Simultaneous Determination of All Species Concentrations in Multiequilibria for Aqueous Solutions of Dihydrogen Phosphate Considering Debye–Hückel Theory

Solutions of citric acid and Na2HPO4 were studied with the dynamical approach to multiequilibria systems. This widely employed buffer has a well-defined pH profile and allows for the study of the distribution of phosphate species over a wide pH range. The dynamical approach is a flexible and accurate method for the calculation of all species concentrations in multiequilibria considering ionic strength (I) via Debye–Hückel theory. The agreement between the computed pH profiles and experiment is excellent. The equilibrium concentrations of the non-hydrogen species are reported for over 30 buffer mixtures across the entire pH range. These new concentration data enable researchers to lookup the equilibrium distribution of species at any pH. The data highlight the dramatic effects of ionic strength, and for example, the position of maximal H2PO4– concentration is shifted by almost an entire pH unit! From a more general perspective, the study allows for a discussion of the dependence of concentration quotients Qxy on ionic strength, pQxy = f(I), and for the numerical demonstration that the thermodynamic equilibrium constants Kxy,act(I) = Kxy. The analysis emphasizes the need for measurements of the concentrations of several species in complex multiequilibria systems over a broad pH range to advance multiequilibria simulations.

Effects of common cooking heat treatments on selenium content and speciation in garlic

The effect of traditional thermal treatments, normally applied during cooking practices, on the stability of Se-amino acids and Se-proteins present in Se-enriched garlic was studied. Five heat treatments including, convection oven (180 °C, 10 min), boiling (100 °C, 10 min), microwave oven (800 W, 3 min), steaming (10 min) and stir-frying (180 °C, 3 min) were assayed. Modifications on the molecular weight fractions profiles of protein extracts were evaluated by size exclusion chromatography with UV–visible and inductively coupled plasma mass spectrometry (ICP-MS) detection using a 0.05 M Tris(hidroxymethyl)aminomethane solution at pH 7.3 as the mobile phase. Possible modifications of Se-amino acids were evaluated by anion exchange chromatography (AEC), with a 30 mM Na2HPO4 solution (pH 6) as the mobile phase, coupled to ICP-MS after enzymatic hydrolysis. SEC chromatograms showed the incorporation of Se to high (7 kDa) and low molecular weight fractions (2–4 kDa) while AEC chromatograms showed mostly the presence of Se-methylselenocysteine. However, it could be observed that heat treatments significantly affect this important Se-amino acid.

Surfactant-Enhanced Electroosmotic Flushing in a Trichlorobenzene Contaminated Clayey Soil.

Remediation of the sites contaminated with organic contaminants, such as chlorobenzenes, remains a challenging issue. Electroosmotic flushing can be a promising approach which is based on mechanism of electrokinetic remediation for removal of organic contaminants from fluids in low-permeability soil. To select an optimum surfactant that can effectively enhance electroosmotic flushing, three common surfactants, Triton X-100 (EK2), Tween 80 (EK3), and a mixture of sodium dodecyl sulfate and Triton X-100 (EK4) buffered with Na2 HPO4 /NaH2 PO4 solution, were tested. The efficiency of each kind of surfactant was evaluated using a three-dimensional box filled with a clayey soil spiked with 1,2,4-trichlorobenzene, and compared with a test (EK1) without surfactant. The results demonstrated that the buffer solutions efficiently neutralized H+ and OH- produced by electrolysis. EK3 with Tween 80 added in the flushing solution reached the highest electroosmotic permeability of 10-4 cm2 /v/s and achieved a notably high cumulative electroosmotic flow (EOF) of 5067 mL within 6d, which was 6.3, 3.4, and 4.2 times higher than that in EK1, EK2, and EK4, respectively. There were 420 mL more cumulative EOF obtained after 50 h of electrical application in EK4 than in EK2. The introduction of nonreactive ions can increase the current, thereby benefiting the EOF. Both the higher pH caused by the buffer and the application of nonionic surfactants can make the zeta potential more negative, thereby increasing the EOF. Tween 80 can be recommended as the best flushing solution for removing organic contaminants from sites when electrokinetic remediation is applied.

Effect of Protolysis Reactions on the Shape of Chronopotentiograms of a Homogeneous Anion-Exchange Membrane in NaH2PO4 Solution

Single-pulse and double-pulse chronopotentiograms of a homogeneous anion-exchange membrane AX in 0.02 M solutions of NaCl (system 1) or NaH2PO4 (system 2) have been recorded in underlimiting and overlimiting current modes. It has been found that in the case of exceeding the limiting current (i > i lim Lev ) calculated using the convection–diffusion model, the time required to establish a steady state in system 2 increases by more than an order of magnitude compared to system 1. The slow growth of the potential drop is due to a gradual transition of the membrane from the form in which the main counterion is H2PO 4 – to the HPO 4 2– form. This transition is due to the deprotonation of a part of H2PO 4 – ions forming HPO 4 2– and protons as they enter the membrane. The participation of H+ in charge transfer in the depleted diffusion layer at a given current density causes a lower value of the potential drop than in system 1 for the same i/i lim Lev ratio. In intense current regimes, chronopotentiograms of system 2 exhibit two inflection points. The first point corresponds to the classical Sand transition time and is due to reaching the limiting current of H2PO 4 – ions (the main charge carrier for i < i lim Lev ) in the depleted diffusion layer. The second point is associated with a critical current that can be called the second limiting current in the system with NaH2PO4 and has no analogue in the system with NaCl. This current, which is approximately 2i lim Lev , corresponds to the state when the membrane is completely transformed into the HPO 4 2– form. Meanwhile, the source of protons due to the transformation of H2PO 4 – into HPO 4 2– ions as they enter the membrane is exhausted. After reaching this critical value of the potential drop, either the HPO 4 2– deprotonation reaction to give triply charged PO 4 3– ions in the membrane or the water splitting on fixed groups located at the membrane/solution interface may occur.

Mechanical Strength Properties of Injectable Carbonate Apatite Cement with Various Concentration of Sodium Carboxymethyl Cellulose

Mechanical strength is one of the key factors for clinical application of injectable carbonate apatite (CO3Ap) cement. Incorporation of polymeric additives into the mixing liquid of injectable bone cement has been known to improve cement injectability. The aim of this study is to determine whether incorporation of sodium carboxymethyl cellulose (Na CMC) into the mixing liquid would affect the diametral tensile strength (DTS) of injectable CO3Ap cement. In the present study, Na CMC, a polymeric additive and a cellulose derivative, was used to promote the injectability of CO3Ap cement. Three groups of CO3Ap cement samples consist of CaCO3 and CaHPO4 powder in each group were mixed with 0.5 %, 1%, and 2% Na CMC solution incorporated to 0.2 mol/L Na2HPO4 solution. As a control, powder mixed with 0.2 mol/L Na2HPO4 solution was used. Samples were kept in an incubator (37°C, 100% relative humidity, 24 hours). The mechanical strength properties were evaluated by diametral tensile strength (DTS). The average DTS of samples containing 0.5%, 1%, and 2% Na CMC were 3.19 MPa, 3.57 MPa, and 3.06 MPa, respectively. While the average DTS of the control group was 3.29 MPa. The groups containing Na CMC in all concentrations showed no statistical difference (p&gt;0.05) on DTS compared to the control group. The injectability improved as the concentration of Na CMC increased. In conclusion, revealed that Na CMC does not affect the mechanical strength of CO3Ap cement. Therefore, it may be considered as an effective material to promote cement injectability. Further study of additives that can be used to promote the injectability of CO3Ap cement and enhance the mechanical strength awaits based on this initial finding.

Thermal analysis of phosphorus-modified boehmite nanosheets and isoelectric points (IEP) of the corresponding γ-alumina

Phosphorus-modified boehmite nanosheets were synthesized through equivalent-volume impregnation with Na2HPO4 solutions, which was further calcined to form γ-alumina. The XRD and HR-TEM analyses indicated that the phosphorus modification had no significant effects on the framework of the boehmite nanosheets. The FTIR spectra suggested that the phosphorus groups replaced some –OH groups and formed P–O–Al bonds with the boehmite. The modified boehmite nanosheets impregnated at the P/Al molar ratio of 1% showed a α-phase transition temperature at 1298.3 °C, much higher than that of boehmite (1189.1 °C). The IEP of the phosphorus-modified γ-alumina prepared by 2 h calcination of phosphorus-modified boehmite (P/Al = 5%) at 600 °C was as low as 7.1.

Nano‑calcium phosphate bone cement based on Si-stabilized α-tricalcium phosphate with improved mechanical properties

This study aimed to develop nano‑calcium phosphate cement (nCPC) and evaluate the effect of nanosized precursors on mechanical, physical and handling properties (injectability and setting time) as well as conversion rate of nano-reactants into nano-hydroxyapatite (nHA). In this study, while alpha tricalcium phosphate (α-TCP, 98wt%) and HA (2wt%) were applied as the powder phase, 2.5wt% NaH2PO4 solution was used as liquid phase of cement. Before nano-CPC preparation, Si-stabilized α-TCP nanopowder with particle size of 10±3.6nm was firstly synthesized in a two-step process of sol-gel followed by mechanical alloying. Moreover, HA nanopowder with particle size of 32±3.6nm was synthesized using sol-gel process. Our results revealed that after 3days of immersion in ringer's solution, reactants almost completely converted to nHA. Moreover, the initial and final setting time of nano-CPC was obtained 6.3±2.1min and 14.3±4.0min, respectively. Furthermore, injectability of this formulation was reached 87.90±2.60%. In addition, our results confirmed that the compressive strength and modulus of nano-CPC enhanced with increasing immersion time in ringer's solution from 9.50±1.27MPa and 0.38±0.07GPa (at 1day) to 18.70±2.23MPa and 0.57±0.15GPa (at 5days), respectively. Finally, in order to evaluate cellular responses to nano-CPC, MG63 cells were cultured on it and cell morphology and cytotoxicity were evaluated. Results revealed that nano-CPC enhanced proliferation and spreading of osteoblast like cells compared to control (tissue culture plate) which could be due to both appropriate physical and chemical properties of nano-CPC which stimulate cell proliferation. Our findings suggest the formation of an injectable nano-CPC with appropriate mechanical, physical and degradation rate which can potentially utilized for filling bone defects.

Electroflotation of precipitated phosphate from synthetic solution

ABSTRACT The phosphate recovery from a 20 mg L-1 Na2HPO4 solution through precipitation with Ca(OH)2 followed by electroflotation was evaluated. X-ray diffraction and particle size measurements indicated that the precipitates were a mixture of hydroxyapatite and calcium-deficient hydroxyapatite, with size ranging from 3 to 10 μm. Electroflotation with Na-oleate as surfactant was used to recover the precipitates. The surfactant adsorption was evaluated through zeta potential measurements. The influence of Na-oleate concentration, pH and bubble size on phosphate recovery was investigated. In the absence of Na-oleate, a phosphate recovery of 50% was achieved, while in the presence of 20 mg L-1 of Na-oleate it was increased to 90%, at pH 11. The phosphate recovery also increased with Ca(OH)2 concentration increase and bubble size decrease, reaching 100% at 300 mg L-1 Ca(OH)2 and bubble size around 39 µm.

Comparative study on phosphate adsorption by inorganic and organic adsorbents from a diluted solution

Technology of phosphate adsorption from a diluted solution is important in the field of water supply or waste water treatment. Although a number of adsorbent for phosphate is developed up to date, there have been little studies on the survey of their phosphate uptakes in the same criteria. Such approach enables us to clarify the factors that improve the phosphate selectivity.Phosphate uptakes from a diluted NaH2PO4 solution (CP=3 mg-P/L) were studied using 63 kinds of inorganic and organic adsorbents. Schwertmannite type hydrous iron oxide (Sch-1), Mg-Al type layered double hydroxide (MgAl-1), activated magnesium oxide (aMgO), Fe-Al type double hydroxide (FeAl-2), Ce2(CO3)3·8H2O, and La(OH)3 showed large phosphate uptakes above 20 mg-P/g. Sch-1 and MgAl-1 had high adsorption rates and large phosphate uptakes of 15 and 9 mg-P/g, respectively, even at CP=0.01 mg-P/L. The influence of excess bicarbonate ion (2mM NaHCO3) in the solution was small for the iron-containing adsorbents, while was marked for the other adsorbents. This difference could be partly explained by the difference in adsorption mechanism: ion exchange or dissolution-precipitation. The phosphate uptakes by different kinds of hydrous iron oxide showed that schwertmannite types had good phosphate adsorptivity independent of preparation method. Control of the state of sulfate ions in the adsorbent may be important for improving the phosphate adsorptivity by SO42−/phophate ion exchange. A future subject is to improve the reusability of adsorbent, since the 2nd adsorptions after phosphate desorption did not show satisfactory phosphate uptakes.