Boric Acid Method Research Articles

Quorum quenching bacteria encapsulated in PAC-PVA beads for enhanced membrane antifouling properties

In order to improve the antifouling properties of quorum quenching (QQ) bacteria immobilized beads, the mechanical strength and permeability of QQ beads were modified by adding powdered activated carbon (PAC) based on traditional polyvinyl alcohol (PVA)-boric acid method. Optimal PAC concentration was investigated through measuring the mechanical strength, permeability and N-octanoyl-DLhomoserine lactone (C8-HSL) removal ratio of the PAC-PVA beads. Particularly, the enhanced antifouling effects of the optimal PAC-PVA beads were compared with those of original QQ beads through a membrane filtration experiment under constant pressure. The optimal concentration of PAC was 1% (w/v), under that PAC concentration, the mechanical strength, permeability and removal ratio of C8-HSL increased by 11.3%, 29.3% and 12.4% respectively. Synergistic effect between adsorption and biodegradation of 1% PAC-PVA beads was also observed. In membrane filtration experiment, membrane permeability with the 1% PAC-QQ beads decreased to 55.4% after 14 days, while the membrane permeability with 0% PAC-QQ beads decreased to 39.9%. The addition of PAC (1%) increased the antifouling efficiency of the QQ beads 15.5%. This paper demonstrated PAC-PVA bead as a QQ bacteria immobilized method had a great potential for biofouling control in membrane bioreactors (MBRs).

Adsorption and recovery of immobilized coffee ground beads for silver ions from industrial wastewater

Abstract To efficiently adsorb silver ions from industrial wastewater, powdered coffee grounds were immobilized as a bead form by modified polyvinyl alcohol and boric acid method. The beads with 2.0 mm of diameter have the 9.87 m2/g of surface area and were stable in the range of ∼45 °C and to all pH range in wastewater without untangling. In addition, the beads have excellent mechanical strength and low swelling ratio. The adsorption capacity of immobilized coffee ground beads for silver ion was achieved as about 36.3 mg/g at the pH 6.0 in wastewater solution when the beads containing 3.0 g of coffee grounds was used. The surface condition and the existence of silver ions onto the immobilized coffee ground beads were confirmed by the SEM image and EDX spectrum. The Langmuir isotherm model showed significant fit to the equilibrium adsorption data and maximum adsorption capacity of 39.583 mg/g of silver ions was achieved at the pH 6.0 of wastewater. The breakthrough point was appeared around 180 (1.0 mL/min) and 340 bed volumes (0.5 mL/min), respectively, and 6 bed volumes of 1.0 M HNO3 solution was required to get desorption efficiency of 95% in continuous process. And, the bed volumes can be still maintained as 310 even though secondary reused immobilized coffee ground beads were used.

Study on preparation and properties of PVA‐SA‐PHB‐AC composite carrier for microorganism immobilization

ABSTRACTPolyvinyl alcohol(PVA) bead crosslinked with boric acid has been widely utilized as a microorganism immobilization carrier. However, it has some disadvantages such as drastic cell viability loss, small adsorption capacity and mass transfer limitation. To improve upon these drawbacks, a new method to prepare PVA composite pieces with the addition of activated carbon (AC) and poly‐3‐hydroxybutyrate(PHB) was explored through a combination of freezing/thawing and the boric acid method and by using Tween‐80 to improve the mass transfer performance of hydrophobic organics. m‐Cresol and pyrene were used as representative compounds with benzene ring structures to model hydrophilic and hydrophobic organics in order to test the performance of PVA pieces. The results showed that, compared with the boric acid method alone, a combination of freezing/thawing and the boric acid method led to a decrease in total organic carbon(TOC) loss from 0.315 g g−1 to 0.033 g g−1 and increased the oxygen uptake rate(OUR) of microorganisms from 0.03 mg L−1·min−1 to 0.22 mg L−1 min−1. The m‐cresol equilibrium adsorption amount of the PVA‐SA(sodium alginate)‐PHB‐AC piece was 2.80 times that of the PVA‐SA piece. The diffusion coefficient of pyrene in the PVA‐SA‐PHB‐AC piece increased from 0.53×10−9 m2 min−1 to 2.30×10−9 m2 min−1 with increasing concentrations of Tween‐80 from 1000 mg L−1 to 5000 mg L−1. The PVA‐SA‐PHB‐AC composite carrier demonstrated great scope for immobilizing microorganisms for practical wastewater bio‐treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39837.

Encapsulation of the peptide Ac–Glu–Thr–Lys–Thr–Tyr–Phe–Trp–Lys–NH2 into polyvinyl alcohol biodegradable formulations—Effect of calcium alginate

Abstract It has been recently reported that the peptide Ac–Glu–Thr–Lys–Thr–Tyr–Phe–Trp–Lys–NH 2 , analogue of the Glu1811–Lys1818 region of A3 light chain of blood coagulation factor VIII, presents in vitro significant anticoagulant activity. The encapsulation of this peptide into different polyvinyl alcohol formulations is examined here. The formulations were prepared using polyvinyl alcohol cross-linked with either boric acid or glutaraldehyde, giving a series of twelve different hydrogels. In case of PVA–boric acid method, a small percentage of sodium alginate was used in order to avoid bead's agglomeration. In that case, the most efficient encapsulation of the octapeptide (74%) was achieved with 0.2% (w/w) sodium alginate. It was also observed that the increase in sodium alginate percentage leads to beads with increased peptide release time, ranging from 60 to 90 min at 0.02% and 1% (w/w) sodium alginate respectively. The water holding of the PVA gels was estimated to be 27% regardless of the cross-linking reagent used, while it was increased with increasing sodium alginate concentration and reached about 60% for 1% sodium alginate. The longer octapeptide release, at 120 min, was observed with PVA–glutaraldehyde hydrogel, with encapsulation efficiency comparable to those obtained with boric acid, indicating that this hydrogel may be further used in drug delivery systems.

Understanding the sprayed boric acid method for bulk doping of silicon ribbons

The sprayed boric acid (SBA) method for bulk doping of silicon ribbons is investigated. Experimental procedures and main results are reviewed. Computational fluid dynamics and experimental tests using partial spraying suggest the role of gas transported evaporated boron oxide to explain the boron incorporation profiles along the sample. The industrial applicability of the SBA method is discussed.

Preparation and characterization of a novel macroporous immobilized micro-organism carrier

The traditional PVA–boric acid method was modified using calcium carbonate as a pore-forming agent to form the macroporous structure and formulated macroporous carrier (MPC) post-crosslinked with glutaraldehyde. The pore volumes, pore structure, porosity, and swelling behavior of MPCs were evaluated. The crosslinking density of MPCs with four different crosslinker dosages was calculated from their swelling properties using the modified Flory equation. MPCs demonstrated high swelling capacity, large specific surface area, high diffusion coefficient, as well as chemical and mechanical strength. The high crosslinking degree MPCs resulted in high biomass densities and low activity yield and vice versa. The characterizations of MPC suggest significant potential of its use for microbial immobilization and provide a scientific basis for immobilized carrier design and optimization.

Immobilization of Acidithiobacillus ferrooxidans by a PVA–boric acid method for ferrous sulphate oxidation

Acidithiobacillus ferrooxidans was immobilized in poly(vinyl alcohol) (PVA) by a PVA–boric acid method, and spherical beads of uniform size were produced. Biooxidation of ferrous iron by immobilized cells was investigated in repeated batch culture and continuous operation in a laboratory scale packed-bed bioreactor. During repeated batch culture, the cell-immobilized gels were stable and showed high constant iron-oxidizing activity. In continuous operation in a packed-bed bioreactor, biooxidation of ferrous iron fits a plug-flow reaction model well. A maximum Fe 2+ oxidation rate of 1.89 g l −1 h −1 was achieved at the dilution rate of 0.38 h −1 or higher, while no obvious precipitate was detected in the bioreactor.

Novel immobilization of alginic acid for heavy metal removal

To apply alginic acid efficiently to wastewater treatment system, it was immobilized by novel polyvinyl alcohol (PVA)–boric acid method using glutaraldehyde to reduce the hydration of the immobilized bead. Since the immobilized alginic acid bead did not swell and has enough mechanical strength, channeling of flow and the increase of pressure drop were not observed through the column operations. In addition, it was also stable under strong acidic (below pH 1.0) and high temperature (above 170 °C) conditions. The surface condition and existence of lead ions on the bead was confirmed by the SEM and (energy dispersive X-ray spectroscopy) EDX instrument analyses. The PVA–alginic acid bead showed that the breakthrough point emerged around 600 bed volumes and lead ions bound to the immobilized bead were readily desorbed by EDTA solution. Especially, the effect of alkaline metal ion (Ca 2+ and Mg 2+) on lead ion adsorption capacity was almost negligible.

Rapid and sensitive determination of catecholamines and the metabolite 3-methoxy-4-hydroxyphen-ethyleneglycol using HPLC following novel extraction procedures

In the present study assays were improved for the determination of free catecholamines and 3-methoxy-4-hydroxyphenethyleneglycol (MHPG), the major metabolite of peripheral and central noradrenaline. The compounds were extracted by a fluid phase extraction: a diphenyl boric acid method for the purification of catecholamines and an ethyl acetate extraction for MHPG were used, respectively. High-performance liquid chromatography with electrochemical detection was employed for quantitative analysis. In previous studies, significant differences between plasma concentrations of these substances in normal volunteers and hospital patients were demonstrated. Therefore, we established valid reference values for a hospital population. Blood and urine samples of 59 patients without disorders and medication affecting catecholamine synthesis and metabolism or the activity of the sympatho-adrenal system were collected and analyzed for free and total (free plus conjugated) MHPG, noradrenaline (NA), adrenaline (A) and dopamine (DA); total MHPG was assayed after enzymatic hydrolysis of conjugates. Our data clearly demonstrate that these methods are sensitive, specific, rapid, and can easily be standardized. The intra- and inter-assay precision were high (CV 2.6–5.3% and 4.3–6.9% for plasma, CV 3.8–4.9% and 5.1–8.2% for urine, respectively). For plasma, the mean concentrations ± SD were determined to be 20.82 ± 4.70 pmol/ml for free MHPG, 68.43 ± 16.21 pmol/ml for total MHPG, 2.11 ± 0.24 pmol/ml for NA and 0.31 ± 0.08 pmol/ml for A. For 24h-urine the mean concentrations ± SD were determined to be 0.44 ± 0.13 mol/24h for free MHPG, 8.79 +- 2.13 mmol/24h for total MHPG, 169.8 ± 58.25 nmol/24h for NA, 62.19 ± 21.79 nmol/24h for A and 757.2 ± 382.6 nmol/24h for DA. In summary, these novel and rapid methods can clearly be employed in a routine clinical setting.

Protection of methanogenic bacteria from low pH and toxic materials by immobilization using polyvinyl alcohol

The applicability of cell immobilization to the anaerobic treatment process using the polyvinyl alcohol (PVA)-boric acid method was investigated. The acetate-utilizing methanogens were cultivated, concentrated and immobilized. The beads formed were stable for one year maintaining methanogenic activity. The possible advantage of immobilized cells over non-immobilized cells for low pH shock and for the presence of toxic substances was examined. The immobilized cells recovered their methanogenic activity faster than the non-immobilized cells from the inhibition caused by transient low pH (5.0) for 12–48 h in a continuously fed reactor. Formation of a pH gradient within the bead due to the consumption of acetic acid inside the bead is a possible mechanism of relief of the inhibitory effect. Batch experiments showed that the inhibitory effect of phenol, oleic acid, nickel, sulfide and propionic acid on the methanogenic bacteria was also reduced by immobilizing the bacteria. Formation of a pH gradient or the adsorption of toxic materials by PVA are likely mechanisms of this relief of inhibition.

Immobilization of activated sludge by PVA–boric acid method

A new method (polyvinyl alcohol-boric acid method) for an inexpensive and effective immobilization of activated sludge was developed. Using activated sludge immobilized by this PVA-boric acid method, synthetic waste-water was treated at a high loading rate of 0.5-2.35 kg TOC/m(3) day. Total organic carbon and total nitrogen were removed at efficiencies of 93 and 30-40%, respectively. The kinetic constants Y and b for this immobilized activated-sludge process were determined to be 0.594g mixed liquor suspended solids (MLSS)/g TOC and 0.0219 day(-1), respectively. The cost calculation of chemicals required for the immobilization of activated sludge by this PVA-boric acid method was proved to be extremely inexpensive for the immobilization of activated sludge.

Analysis of Ozone in Aqueous Solutions Using A Modified Iodometric Technique with as (III)

Abstract A modified iodometric procedure using an absorbing solution of 2% NBKI with a known amount of As(III) is described for 10 ml aqueous samples. Ozone contents from 0.5 to 65 mg O3/I were determined. High ozone concentrations can also be measured for generator calibration. This method gives results which are not significantly different than a boric acid method but are for a modified standard methods procedure. Volatility of iodine has been completely eliminated. Stabilized samples do not make the time between sampling and final titration critical.

Revised Kjeldahl Total Nitrogen Method for Feeds and Premixes

Abstract A Kjeldahl method for equivalent crude protein in feeds was modified by using a smaller sample (0.25 g) and smaller amounts of reagents in order to reduce analysis time and cut costs. A 6% CuSO4 catalyst was used for the complete digestion of refractory material. Winkler’s boric acid method was modified by including a 90% pretitration to insure complete retention of ammonia so that only one standardized reagent is needed.