Range Of Initial pH Values Research Articles

Visible light-mediated activation of periodate for bisphenol A degradation in the presence of Fe3+ and gallic acid at neutral pH

The current study demonstrates, for the first time, the effectiveness of an innovative visible light (VL) photo-Fenton like system using periodate (PI) mediated by Fe3+ and gallic acid (GA) for bisphenol A (BPA) elimination at neutral pH. The promotion of VL irradiation and GA on the Fe2+/Fe3+ cycle in the system allowed the VL/GA/Fe3+/PI system to exhibit excellent performance for BPA removal. Complete degradation of BPA was carried out in the VL/GA/Fe3+/PI process after 30 min reaction under the optimum conditions (0.10 mM Fe3+, 0.10 mM GA, 1 mM PI, and initial pH 7.0). Electron paramagnetic resonance analysis and quenching tests confirmed that the singlet oxygen, iodate radical, and hydroxyl radical were primarily involved in the elimination of BPA with minor contribution from superoxide anion radical and high-valent iron species (Fe4+ and Fe5+). BPA abatement was slightly inhibited by the addition of Cl−, NO3−, and SO42−, whereas the addition of HCO3− obviously hindered this process. Notably, Huimic acid dramatically expedited BPA decomposition. Besides, the VL/GA/Fe3+/PI process demonstrated remarkable removal efficiency over a broad range of initial pH values (3.01–8.97). Meanwhile, based on the eight identified intermediates, the possible degradation pathways of BPA were predicted. The phytotoxicity test concluded that a decrease in toxicity of the degraded intermediates to the growth of radish seed compared to BPA. In addition, the VL/GA/Fe3+/PI system demonstrated favorable potential for application in different actual water matrices. Moreover, efficient and simultaneous abatement of various organic contaminants by the GA/Fe3+/PI process was success accomplished under natural solar light or VL. Consequently, all results implied that the VL/GA/Fe3+/PI process might be a perspective technique for the treatment of organic contaminants.

Effect of different physical factors on the synthesis of spherical gold nanoparticles towards cost-effective biomedical applications.

Gold nanoparticles (AuNPs) have great potential to contribute to numerous application fields of biomedicine, which are highly dependent on their physicochemical properties, such as size and shape. Due to the final characteristics, nanoparticles (NPs) are primarily affected by different factors of reaction conditions; the present study aimed to evaluate the effects of manipulating the main physical parameters of the Turkevich method to optimise the fabrication of citrated capped AuNPs in a spherical shape, desirable final size, and efficiency. For this purpose, various experiments of citrate-capped spherical AuNPs synthesis were designed to study the roles of a wide range of initial pH values and temperature of reaction, Na3 Cit/HAuCl4 molar ratio, and two order reagent additions, method I and method II, in the final characterisations and reaction efficacy. Prepared NPs synthesised with different experiments were characterised by dynamic light scattering, UV-Visible, and fourier transform infrared spectroscopy. Furthermore, NPs obtained from optimised synthesis conditions were more detailed using UV-Visible, transmission electron microscopy, and XRD. The findings indicated that the final size and synthesis efficacy of citrated capped spherical AuNPs were significantly affected by all studied synthesis parameters and the order addition of reagents. The higher initial reaction temperature and Na3 Cit/HAuCl4 Molar ratio provided a smaller particle size with desirable synthesis efficacy. Besides, final optimised NPs were provided in cubic crystal structures, and each NP's single crystal was obtained. In sum, our findings indicated that optimising synthesis conditions could improve size distribution, morphology, crystallite size, and structures of final NPS, as well as efficiency, which is a principal factor associated with future cost-effective productions on large scales. Further studies are needed in this regard.

Effect of dielectric barrier discharge plasma on persulfate activation for rapid degradation of atrazine: Optimization, mechanism and energy consumption

Dielectric barrier discharge plasma (DBDP) is an emerging and promising advanced oxidation process (AOP) for wastewater treatment. After investigating the effect of input voltage, O3 (generated by dielectric barrier discharge), and peroxydisulfate (PDS) dosage, the DBDPO3/PDS system was established. With the assistance of PDS, the atrazine (ATZ) removal efficiency increased from 69.67% to 82.46% within 25 min. Synergistic effect calculation suggests that there were markedly synergies between DBDP, O3, and PDS. Under the effect of SO4−•, the total organic carbon (TOC) removal and dechlorination efficiency were significantly improved. In addition, the DBDPO3/PDS system maintained the ATZ removal efficiency at a high level over a wide range of initial pH values. According to quenching experiments and electron paramagnetic resonance (EPR) detection, the dominant radical for ATZ degradation in the DBDPO3/PDS system was HO•. A possible degradation pathway of ATZ was proposed based on density functional theory (DFT) analysis, quadrupole-time of flight-liquid chromatography/mass spectrometry (Q-TOF-LC/MS) results, and related literature. The acute toxicity to aquatic minnows and the developmental toxicity of intermediate products prediction confirmed that the DBDPO3/PDS system could effectively reduce ATZ toxicity. The electrical energy per order (EEO) was 7.10 kWh m−3 order−1 illustrating that the DBDPO3/PDS was a more energy-economic system than other energy-intensive processing technologies.

Adsorption of Cationic and Anionic Dyes from Aqueous Solution Using Sunflower Husk

The current study deals with the removal of cationic dye (brilliant green) and anionic dye (methyl orange) from wastewater by using sunflower husk as an adsorbent. The operation takes place batch wise by applying several concentrations of the dye solution with various adsorbent amounts, at a range of initial PH values and particle sizes at varying contact time intervals. The percent of dye removed for two dyes increased with increasing time and adsorbent dose and decreased with increasing the dye concentration and particle size. The equilibrium time differed according to conditions used. The optimum removal for brilliant green dye was 98 %, which was achieved at 50 ppm dye concentration, 2 g\l adsorbent dose, 75 µm particles size and pH 7 at contact time of 1 h, compared with low removal for methyl orange that reached 54 % under optimum conditions (dye concentration 10 ppm, adsorbent dose 4 g/l, pH 3 at the same particles size and time). Kinetic studies were conducted and revealed that the adsorption was well defined by pseudo-second order model and could be described by the Langmuir isotherm.

Graphene oxide-induced formation of a boron-doped iron oxide shell on the surface of NZVI for enhancing nitrate removal

The surface products have a significant influence on the reactivity of zero-valent iron-based materials. Although the enhancing effect of graphene on the reactivity of nanoscale zero-valent iron (NZVI)/graphene composites have been confirmed, the effect of graphene on the formation of surface products of NZVI is not well understood. In order to assess the effect of graphene on the structural of the outer iron oxide layers of NZVI, the NZVI was pre-oxidized by graphene oxide (ONZVI-GO). Compared with the NZVI oxidized by O2 (ONZVI-O2), ONZVI-GO was shown to be effective at NO3− removal with a high efficiency over a wide range of initial pH values. The results from characterization showed that GO could induce the formation of a tight iron oxide shell with dense spinel structures. The boron introduced during the preparation of NZVI was doped into iron oxides on the surface of ONZVI-GO. The B–O in adsorbed borate was transformed to B–B/B–Fe in the lattice structure of iron oxides, causing the formation of highly electron-deficient Lewis acid sites on the surface of ONZVI-GO, which could effectively gather NO3− and OH−, leading to the higher efficiency removal of NO3− than ONZVI-O2 over a wide range of initial pH values. This study provides new insight into the interaction between graphene and the surface species of NZVI.

Potential Biological Deodorisation of Butyric Acid by Aerobic Bacterial Species of Bacillus Genus Under Different Ph Conditions

Waste volatile compounds, such as butyric acid, generated from pit latrines may cause discomfort to pit latrine users and they have undesirable impacts on sanitation promotion efforts and public health. The purpose of this work was to isolate and identify highly efficient deodorant butyric acid bacteria and investigate their feasibility of biologically removing butyric acid from enriched liquid medium under different pH conditions. The determination of the ability of these bacterial strains on removal of butyric acid was at the concentration of 1000 mgL-1 in MSM. The experiment was designed in a batch reactor under aerobic condition by shaking in a temperature controlled incubator at orbital shaking speed of 110 rpm and of 30 oC and initial pH was adjusted to 7.0. The results showed that these bacterial strains were identified as Bacillus cereus, Lysinibacillus fusiformis, Bacillus subtilis and Bacillus methylotrophicus. The bacterial strains were capable of growth and degrading butyric acid at a wide range of initial pH values but the optimal growth and butyric acid degradation was achieved at neutral pH. Complete butyric acid degradation was achieved within 20-24 h. The bacterial strains have proved to be potential candidates for the development of biodeodorization systems for pit latrines.

A Systematic Investigation of Factors Affecting the Formation of Zinc Sulfide (ZnS)

Summary Work was undertaken to systematically investigate the factors that affect the formation of zinc sulfide (ZnS) in an aqueous system. Experiments were performed at a series of temperatures from room temperature up to 90°C, at a range of initial pH values and in two brine systems. The effect of pH was examined further by changing the salt from Na2S·9H2O to NaSH·xH2O, therefore changing the initial sulfide source from S2– to HS–, as part of an ongoing method-development strategy. The formation of ZnS was achieved by the equivolume mixing of two preheated bottles, which contained aqueous “H2S” and zinc ions, respectively. Having pH adjusted the zinc brine to values calculated by an in-house thermodynamic model, the brines were preheated to the required temperature and mixed. Aliquots were removed at 2, 4, and 24 hours to perform elemental analysis by inductively coupled plasma optical emission spectrometry (ICP-OES), and pH measurements were performed on all samples after they had returned to room temperature. In addition, particle-size analysis and environmental scanning electron microscopy (ESEM) examination of the resulting precipitate were also performed for a subset of the samples prepared. The reaction between zinc ions and aqueous “H2S” was quantitative at all temperatures up to 90°C and in both brines. The final pH values of the supernatant were independent of the zinc brine pH, and instead were dependent on the molar ratio of zinc and sulfide ions. With a high pH, sulfide-dominated, and a low pH, zinc-dominated, plateau regions were seen with a sharp inflection between the two. As a consequence, reaching field-representative pH values was seen to be extremely difficult while retaining the ability to alter the relative concentrations of the reacting ions. Altering the sulfide source yielded the same trend, although with different absolute values. These observations have been rationalized with reference to the thermodynamic constants governing the reaction through scale-prediction modeling. The work presented here provides a greater understanding of the factors governing the formation of ZnS scale and the considerations required for more industrially relevant formation and inhibition experiments in the future.

Characteristics of hydrogen and bioflocculant production by a transposon-mutagenized strain of Pantoea agglomerans BH18

Based on the transposon-mutagenized library of Pantoea agglomerans BH18, the mutant strain 2-103 was obtained using mutant screens for high simultaneous production of hydrogen and bioflocculant. The mutant strain 2-103 was able to grow in medium with 50 μg/mL of kanamycin and could be amplified using Tn7-based transposon PCR amplification in cells from several passages, indicating that the mutant strain 2-103 transposon insertion was stable. The mutant strain 2-103 cell culture from batch experiments with varying initial pH values, glucose concentrations and NaCl concentrations was determined. The result indicated that the optimum initial pH for hydrogen production and bioflocculant activity was 7.0 and 8.0, respectively. The optimal glucose concentration for hydrogen and bioflocculant production was 20 g/L. In addition, the mutant strain 2-103 could produce hydrogen and bioflocculant under marine and fresh culture conditions. The mutant strain 2-103 had the highest production of hydrogen and bioflocculant with (1.55 ± 0.07) mol H2/mol glucose and (83.7 ± 5.89)% under marine culture conditions, which increased to (1.78 ± 0.08) mol H2/mol glucose and (93.5 ± 6.24)% under fresh culture conditions. This study found that the mutant strain 2-103 has the ability to produce hydrogen and bioflocculant within a range of initial pH values, glucose and NaCl concentrations, which is beneficial for the improvement of cost-effective bio-treatment processes.

Sorption of Synthetic Dyes Onto River Sediments: A Laboratory Study

Abstract This work deals with sorption of cationic synthetic dye thioflavine T (ThT) onto the river sediment obtained from the Váh River under conditions of batch and column system using spectrophotometric methods. We found that sorption of ThT onto river sediment was a rapid process with reaching of concentration equilibrium within 2 h of interaction. The values of distribution coefficient (DC) defined as concentration ratio [ThT]sediment : [ThT]solution were linearly increased with increasing concentration of river sediment in solution within the range Csediment 1.25 - 10.0 g/dm3 and minimally changed in the range of initial pH values 2 - 6. The increasing concentration of ThT in model solution caused exponentially decrease in the value of DC. The sorption processes characterized by dependence between equilibrium specific sorption Qeq and ThT concentration Ceq in solution were better described by adsorption isotherm according to Freundlich (R2 = 0.979) than according to Langmuir adsorption isotherm (R2 = 0.914). From evaluation of ThT sorption onto river sediment in column system containing of 5 cm sediment layer with 30 cm of water column on the basis of ThT concentration changes in infiltrated water we found that these processes were significantly dependent on the rate of infiltrated water flow through the sediment layer Riw as well as on qualitative and quantitative composition of water. The highest ThT desorption from the sediment layer was found in seepage of 50 % (v/v) ethanol (EtOH) solution through the sediment and efficiency of ThT desorption decreased in the order: 50 % (v/v) EtOH > 0.1 mol/dm3 HCl > deionized water. Obtained data from the point of view of physico-chemical characteristics of the river sediment, such as pH, pHzpc (potentiometric titration), cation-exchange capacity (CEC) and elemental composition (X-ray fluorescence spectrometry), was also discussed

Natural organic matter removal by adsorption onto magnetic permanently confined micelle arrays

To remove natural organic matter (NOM) from water, magnetic permanently confined micelle arrays (Mag-PCMAs) were synthesized by coating the surface of Fe 3O 4 particles with a silica/surfactant mesostructured hybrid layer. An environmental scanning electron microscope (ESEM) was used to characterize the particle size and surface morphology of the Mag-PCMAs. The zeta potential was used to assess the surface charge. Batch experiments were performed to investigate the adsorption of NOM by Mag-PCMAs. It was determined that NOM removal efficiency by Mag-PCMAs could be as high as 80% at a wide range of initial pH values (∼6.0–10.0). The adsorption isotherm was fitted well by a Langmuir model. Although Fe 3O 4 had a high positive charge and Mag-PCMAs a small negative charge, Mag-PCMAs had a higher removal efficiency of NOM than uncoated Fe 3O 4 particles (which are also magnetic), which indicated that the adsorption of NOM onto Mag-PCMAs was not dominated by electrostatic interactions. Possible mechanisms of the adsorption of NOM onto Mag-PCMAs were hydrophobic interactions and hydrogen bonding. It was feasible to reuse Mag-PCMAs after regeneration. These results indicate that Mag-PCMAs can be very attractive for the removal of NOM from aqueous matrices.

Effect of ultrasound on the physical and functional properties of reconstituted whey protein powders

Aqueous solutions of reconstituted whey protein- concentrate (WPC) & isolate (WPI) powders were sonicated at 20 kHz in a batch process for 1-60 min. Sonication at 20 kHz increased the clarity of WPC solutions largely due to the reduction in the size of the suspended insoluble aggregates. The gel strength of these solutions when heated at 80°C for 20 min also increased with sonication, while gelation time and gel syneresis were reduced. These improvements in gel strength were observed across a range of initial pH values, suggesting that the mechanism for gel promotion is different from the well known effects of pH. Examining the microstructure of the whey protein gels indicated a compact network of densely packed whey protein aggregates arising from ultrasound treatment. Comparable changes were not observed with whey protein isolate solutions, which may reflect the absence of larger aggregates in the initial solution or differences in composition.

Bioleaching of heavy metals from anaerobically digested sewage sludge

The effects of sulfur concentration, initial pH of the sludge and sludge solid content on metal bioleaching were examined using anaerobically digested sewage sludge procured from a typical sewage treatment plant in Delhi, the capital city of India. Experiments on effect of sulfur concentration were carried out using 0–4 g L−1 of elemental sulfur to optimize the concentration of elemental sulfur for efficient bioleaching. For the type of sludge (20 g L−1 solid content) used in the present study, 2 g L−1 of elemental sulfur was found sufficient in metal bioleaching in the following order: Zn 86%, Cu 71.5%, Mn 70%, Ni 58.3% and Cr 43.8%. Changes in pH, sulfate concentration and oxidation-reduction potential (ORP) as a function of time were experimentally monitored. A rapid change in the above parameters took place in 4–6 days followed by a slow change until the 10th day. The change in pH with time was observed to vary at different initial pH values (pH 7 to pH 3) of the sludge; however, there was not much difference in the final pH achieved and final metal solubilization which ranged from: Cu 83.6–94.2%, Ni 27.7–29.8%, Zn 89–94.8%, Mn 67.5-79% and Cr 34.1–44.1% The results of the present studies strongly indicate that using 2 g L−1 elemental sulfur, indigenous sulfur oxidizing microorganisms can bring down pH to a value needed for significant metal solubilization. Also, bioleaching can be carried out successfully over a wide range of initial pH values of the sludge. Further, at higher sludge solid concentration than 20 g L−1, lower metal solubilization was achieved due to the buffering capacity of the sludge.

Adsorption of Humic Acid onto Nanoscale Zerovalent Iron and Its Effect on Arsenic Removal

Batch experiments were performed to investigate the feasibility of humic acid (HA) removal by synthetic nanoscale zerovalent iron (NZVI) and its interaction with As(III) and As(V), the most poisonous and abundant of groundwater pollutants. High-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) were used to characterize the particle size, surface morphology of the pristine NZVI and HA-treated NZVI (NZVI-HA), and the zero valence state of the pristine NZVI. It was determined that HA was completely removed by NZVI (0.3 g/L) within a few minutes, at a wide range of initial pH values (approximately 3.0-12.0). Fourier transform infrared (FTIR) and laser light scattering (zeta potential measurement) studies confirmed that NZVI-HA forms inner-sphere surface complexation at different initial pH conditions. The effects of competing anions showed that there was complete removal of HA in the presence of 10 mM NO(-3) and SO4(2-) whereas HA removal was observed 0%, 18% and 22% in presence of 10 mM H2PO4(2-), HCO(3-) and H4SiO4(0), respectively. However, the presence of 2 mM CA2+ and Mg2+ enhanced HA removal from 17 mg g(-1) to 76 mg g(-1) and 55 mg g(-1), respectively. Long-term time-resolved studies of XRD and field emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray (EDX) revealed the formation of various types of new iron oxides (magnetite, maghemite, and lepidocrocites) during the continuous reaction of HA in the presence of water and NZVI at 1, 30, 60, and 90 days. In addition, the surface-area-normalized rate constant (ksa) of adsorption of As(III) and As(V) onto NZVI was reduced in the presence of HA (20 mg L(-1)), from 100% to 43% and 68%, respectively. Our results show the potential use of NZVI in removing HA and its possible effects on arsenic removal during the application of NZVI in groundwater remediation.

Agar plate growth studies of Rhizopus oligosporus and Aspergillus oryzae to determine their suitability for solid-state fermentation

Colony radial growth rates of Rhizopus oligosporus and Aspergillus oryzae were compared under various conditions on agar plates containing cassava starch. Both organisms grew well on cassava starch as their sole source of carbon and energy, although growth was stimulated by the addition of yeast extract and peptone. Neither organism utilized ungelatinized starch effectively. The optimum initial pH for R. oligosporus was 7, although good growth was obtained at pH 5 when ammonium sulfate was partially replaced by urea. A. oryzae grew well over a range of initial pH values from 5 to 8. Growth of R. oligosporus was inhibited by NaCl concentrations above 0.5% (w/v) while A. oryzae was unaffected up to 4% NaCl. The best colony radial growth rate obtained for R. oligosporus was 1.01 mm/h, which was far superior to that obtained for A. oryzae (0.29 mm/h). R. oligosporus was chosen as the more suitable organism for future studies of the protein enrichment of cassava by solid-state fermentation.

Modulation of competence for genetic transformation in Streptococcus pneumoniae.

The spontaneous development of competence by cultures of Streptococcus pneumoniae in casein hydrolysate medium was strongly dependent on the initial pH of the culture medium. Cells growing in cultures beginning with a wide range of initial pH values (6.8 to 8.0) all developed competence, as measured by [3H]DNA uptake, [3H]DNA degradation and genetic transformation; but the initial pH of the medium affected both the timing of the occurrence of competence and the number of times the culture became competent. In cultures grown in media of lower initial pH, competence occurred only once, at high population densities, while in more alkaline media a succession of competence cycles occurred, beginning at lower cell densities. The critical population density required for the initiation of competence varied tenfold over the pH range studied. Successive competence cycles in an alkaline medium were not equivalent: while the percentage of competent cells in the first competence cycle was high (approximately 80%), that in the second competence cycle was lower (approximately 12%). Correspondingly, competence-specific proteins were less prominent in the labelled-protein pattern of the second competence cycle than in that of the first. These features of the physiology of competence control make it possible to adjust the expression of competence to suit various experimental requirements.

The nutrition of Phytophthora fragariae

An investigation was made into the nutritional requirements of three physiologic races of Phytophthora fragariae using homogenized mycelium as inoculum. The optimal calcium concentrations for growth on a complex amino-acid medium were between 20 and 50 p.p.m. No growth occurred in the absence of Ca ions. Strontium could partially replace Ca for two of the isolates but Ba was wholly ineffective. The Ca requirements of the fungi were independent of the nature of the C or N sources used. Glucose, maltose, sucrose and dextrin were good C sources for the fungi. Fructose, mannose and raffinose were utilized to a limited extent. Organic acids and amino acids were not used as C sources by P. fragariae 11. The fungi did not use nitrate or ammonium N, even in the presence of organic acids and over a fairly wide range of initial pH values. Of 18 amino acids tested, singly, for ability to support growth, DL -alanine, L -proline, L -asparagine, DL -serine, DL -valine and DL -aspartic acid proved to be good sources of N. Ammonium ions inhibited the growth of P. fragariae 11 in a medium containing DL -alanine as the N source.