Rising pH Value Research Articles

Synthesis and Characterization of Iron Doped Titanium Dioxide (Fe: TiO2) Nanoprecipitate at Different pH Values for Applications of Self-Cleaning Materials

Fe:TiO2 nano particles were deposited through sol-gel techniques, and the influence of pH values on structural, morphological, optical, and photoluminescence spectral behaviors was studied. Iron doped titanium dioxide nanopowders were analyzed using XRD, SEM, UV–ViS, and PL. Nano crystallized samples of titanium dioxide (72 nm, 77 nm, 78 nm, and 83 nm) were gained from X-Ray diffraction data and showed that there was the creation of unalloyed anatase and ructile segment with tetragonal configuration. The average crystal size was 77.5 nm. pH values provide the alteration of segments from anatase to ructile. The crystal size of prepared iron doped titanium dioxide nanoparticles was greater than before as pH value rises from 2 to 6 while FWHM and scrap sizes declined. Homogeneously disseminated cylindrical forms of iron doped titanium dioxide nanoparticles were perceived from scanning electron microscope graphics and rises in size with growing pH values from 2 to 6 in an acidic medium. Extremely translucent nanopowders are witnessed in the observable region by visible and redshifts near advanced wavelengths with rising pH values because of an increase in the size of particles from XRD data and SEM micrographs. The band gap of energy produced by nano concentrates was reduced with growing pH values that resemble the redshift of optical absorption superiority. The structural behaviors of deposited nanoparticles were also analyzed by Raman spectra and disclosed the existence of tetragonal anatase and ructile segments. EDS results confirmed that the dopant of pH values of the solutions might affect the size distributions of the Fe: TiO2 nanoparticles. The general decrement intensity was witnessed from photoluminescence outcomes.

Degradation of Doxycycline, Enrofloxacin, and Sulfamethoxypyridazine under Simulated Sunlight at Different pH Values and Chemical Environments

In this work, the dissipation of the antibiotics doxycycline (DC) (from the group of tetracyclines), enrofloxacin (ENR) (a fluoroquinolone), and sulfamethoxypyridazine (SMP) (a sulfonamide) is investigated both under simulated sunlight and in the dark, at three different pH (4.0, 5.5, and 7.2), and in the presence of different salts and humic acids. The results indicate that all three antibiotics are very sensitive to photodegradation, and this sensitivity increased with rising pH values, from 4.0 to 7.2. The rise in pH also caused an increase in the degradation kinetic constants and a decrease in the half-lives of antibiotics. In general, the half-lives ranged from a few minutes to 6 h, depending on the pH conditions and the specific antibiotic, and followed the sequence DC > SMP > ENR, although at pH 5.5 the sequence changed to SMP > DC > ENR. After 24 h of simulated sunlight, mineralization was always lower than 10%, although the antibiotic was not quantifiable after the same time of exposure to light (24 h), which indicates that intermediate compounds were generated. The effect of the presence of salts on the dissipation of the three antibiotics was negligible for NaCl and NaNO3, while NaHCO3 did favor the dissipation of DC and ENR. The presence of humic acids showed no effect on the dissipation of SMP, and it only slightly increased the dissipation of DC and ENR. These results may be useful in the assessment of the persistence/degradation of the antibiotics studied when they reach different environmental compartments and may suffer exposure to light under different physicochemical conditions.

Effect of Fe3+ concentration and pH on arsenic removal, migration and speciation transformation in lab-scale wet flue gas desulfurization system

Wet flue gas desulfurization (WFGD) system of coal-fired power station can synergistically remove arsenic from flue gas. However, the detailed mechanism of arsenic removal by desulfurization slurry and its further migration and transformation from gas to desulfurization products still remains unclear. In this study, two important factors, the Fe3+ concentration and the pH value, were investigated for their effects on arsenic removal, redistribution and transformation in a lab-scale reactor. The results show low Fe3+ concentration (≤1 mg L-1) in slurry may lead to the decrease of particle size and the increase of Zeta potential of gypsum particles, thus promoting arsenic removal from flue gas, while more Fe3+ (10–500 mg L-1) could reduce its removal due to the increase of mass transfer resistance. Arsenic removal efficiency decreases with pH value rising. The slurry with Fe3+ is easier to remove As(III) from flue gas than As(V) due to the strong polarity of AsCl3(g). Either increasing Fe3+ concentration (pH = 5.5) or rising pH value (Fe3+ concentration = 50 mg L-1) can promote arsenic migration from desulfurization wastewater into gypsum. At any pH value, Fe-gypsum has a stronger ability to adsorb As(V) than As(III). Acid leaching model test indicates the arsenate incorporated into gypsum lattice can reach 12% without Fe3+, but the presence of Fe3+ hinders the arsenate doped into gypsum crystal, which is less than 1%. This raises the potential environmental risk of further utilization of gypsum due to the unstable arsenic speciation. The main arsenates substituting SO42- doped into gypsum lattice are HAsO42- and AsO43-.

Impact of pH on the Corrosion of Novel Metal-Metal Glassy Alloys in Artificial Seawater: An Electrochemical and Morphology Study

Two novel Fe78Co9Cr10Mo2Al1 and Fe49Co49V2 (at.%) metal-metal glassy alloys were studied in artificial seawater at 27 °C with pH values in the 7.5-8.5 range. The corrosion behavior of both alloys was investigated by using electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic polarization (CP) measurements as well as physical techniques such as x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Good agreement between the resistance of both alloys with rising pH values was observed. The high corrosion rate for the VX50 alloy is related to the absence of passivation behavior on the alloy surface. The VX9 alloy shows a low corrosion current density and a low corrosion rate due to the alloying element such as Cr, which enables the formation of a protective film.

Impact of hexamine addition to a nitrite-based additive on fermentation quality, Clostridia and Saccharomyces cerevisiae in a white lupin-wheat silage.

Nitrite and hexamine are used as silage additives because of their adverse effects on Clostridia and Clostridia spores. The effect of sodium nitrite and sodium nitrite/hexamine mixtures on silage quality was investigated. A white lupin-wheat mixture was treated with sodium nitrite (NaHe0) (900 g t-1 forage), or mixtures of sodium nitrite (900 g t-1 ) and hexamine. The application rate of hexamine was 300 g t-1 (NaHe300) or 600 g t-1 (NaHe600). Additional treatments were the untreated control (Con), and formic acid (FA) applied at a rate of 4 L t-1 (1000 g kg-1 ). Additives improved silage quality noticeably only by reducing silage ammonia content compared with the control. The addition of hexamine to a sodium nitrite solution did not improve silage quality compared with the solution containing sodium nitrite alone. The increasing addition of hexamine resulted in linearly rising pH values (P < 0.001) and decreasing amounts of lactic acid (P < 0.01). Sodium nitrite based additives were more effective than formic acid in preventing butyric acid formation. Additives did not restrict the growth of Saccharomyces cerevisiae compared to the control. The addition of hexamine did not improve silage quality compared with a solution of sodium nitrite. © 2018 Society of Chemical Industry.

Effect of pH on the selective separation of metals from acidic wastewater by controlling potential

Abstract In the face of difficulties in separating similar metals from acidic wastewater, a new process is proposed to selectively separate metals from acidic wastewater by controlling potential. In this paper, the effect of pH value on precipitation ratio and separation efficiency is investigated. Through thermodynamic calculations, a 3D E -pH diagram of the Me-S-H 2 O system was plotted. The results reveal that rising pH value is helpful for metal precipitation, but high pH value may cause co-precipitation of metals impurity. The crystallinity and size of precipitates are obviously affected by pH value. Co can be effectively separated from Zn by xanthate precipitation under controlling potential, and the xanthate dosage is dependent on pH value. Mn-inclusions appear in Zn-precipitate due to high Mn 2+ concentration. The optimal pH value for Cu 2+ , Co 2+ , and Zn 2+ precipitation were 1, 2, and 2, respectively. Mn 2+ could be recovered by carbonate precipitation from the solution after Zn removal. Cu 2+ , Co 2+ , Zn 2+ , and Mn 2+ precipitation ratios reached to 99%.

Polyvinyl alcohol-based nanocomposite hydrogels containing magnetic laponite RD to remove cadmium.

In this study, magnetic nanocomposite hydrogels based on polyvinyl alcohol were synthesized. Magnetic polyvinyl alcohol/laponite RD (PVA-mLap) nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results indicated that PVA-mLap had desirable magnetic-sorption properties and magnetic-laponite nanoparticles were successfully synthesized and added to polyvinyl alcohol. The present nanocomposites were applied to remove Cd2+ from aqueous solution. The influence of initial Cd2+ concentration, magnetic-laponite concentration, pH, and ionic strength on adsorption isotherm was investigated. Heterogeneity of adsorption sites was intensified by increasing magnetic concentration of adsorbents and by rising pH value. Results of ionic strength studies indicated that by increasing ionic strength more than four times, the adsorption of Cd2+ has only decreased around 15%. According to the results, the dominant mechanism of Cd2+ sorption by the present adsorbents was determined chemical and specific sorption. Therefore, the use of the present nanocomposites as a powerful adsorbent of Cd2+ in the wastewater treatment is suggested. Isotherm data were described by using Freundlich and Langmuir models, and better fitting was introduced Langmuir model.

Changes of Soil Phosphorus Fractionation According to pH in Red Soils of China: An Incubation Experiment

ABSTRACTPhosphorus (P) deficiency is one of the main problems limiting crop growth in red soils of southern China. The primary objective of this study was to examine P availability as a function of soil acidity. Soils were sampled from a long-term fertilization experiment and are referred as low-P (No P fertilization) and high-P (120 kg P2O5 ha–1). Both low-P and high-P treatments were incubated adjusting soil pH to seven levels from 3.0 to 6.5 for 10, 20, 30 and 45 days. The pH, DIP, and Olsen-P were determined after each incubation period, and inorganic P fractions were measured at the end of incubation. For both low-P and high-P treatments, DIP decreased with rising pH value and increased with decreasing soil pH. Olsen-P, Ca-P (Ca2-P, Ca8-P, and Ca10-P) and Al-P increased significantly with soil pH in low-P treatment. In high-P, Olsen-P increased with pH between 3.4 and 5.0 and was stable at higher pH. Moreover, Ca-P and Al-P increased significantly but Fe-P decreased with soil pH increase. The redundancy analysis showed that Ca-P, Al-P, and pH had positive effects on Olsen-P, but Occluded-P showed a negative correlation with Olsen-P in both soils. Our results confirmed that soil P availability was influenced by pH and that the changes in DIP and Olsen-P were linked to changes of inorganic fractions from occluded to Ca- and Al-bound forms. Managing soil acidity is a key issue regarding the availability of P in red soils of China and our results suggest that at least a pH of 5.0 should be targeted.

Degradation kinetic of dibutyl phthalate (DBP) by sulfate radical- and hydroxyl radical-based advanced oxidation process in UV/persulfate system

Abstract The ultraviolet/persulfate (UV/PS) process was used to degrade dibutyl phthalate (DBP) at different reaction conditions and a steady-state kinetic model was established based on the elementary reactions involved as well. UV/PS process, which can generate both sulfate radical (SO4− ) and hydroxyl radical (HO ) proved by the evidence that methanol had a larger inhibition impact on the degradation than tert-butyl, could effectively degrade DBP. The second-order rate constant of (1.2 ± 0.1) × 108 M−1 s−1 between DBP and SO4− and the second-order rate constant of (6.3 ± 0.1) × 109 M−1 s−1 between DBP and HO were determined by competition kinetics. The degradation efficiency of DBP was affected by PS dosage, initial DBP concentration, solution pH value, natural organic matter (NOM) and inorganic anions. Increasing PS dosage could enhance the degradation of DBP before PS dosage reaching 1.6 mM. However, the pseudo-first-order rate constants (ko) decreased as initial DBP concentration increased probably owing to the radical scavenging effect of DBP. Generally, the ko value decreased slightly at pH values ranged from 4.0 to 6.0 while decreased significantly as pH increased from 6.0 to 8.0, which might be due to the scavenging effect on SO4− and HO by OH− and increasing concentration of HPO 4 2 - (with higher scavenging capacity than H 2 PO 4 - ) from the phosphate buffer with rising pH value. NOM and HCO 3 - showed an inhibition effect on the degradation of DBP through quenching SO4− and HO . However, Cl− had a dual role on the degradation of DBP in the UV/PS system, which enhanced the degradation at lower concentration (0–1 mM) and suppressed as Cl− concentration further increased to 2 mM. Additionally, a simple steady-state kinetic model involving SO4− and HO was developed to simulate the ko values and the radical contributions in this reaction system. Generally, HO had a higher contribution to DBP degradation than SO4− . The total cost including the electrical energy per order and oxidant cost was increased with increasing PS dosage and the oxidant cost was the major one. The results in this study can serve as a guide and indicate that UV/PS process is feasible for the treatment of water contaminated with DBP.

Suppressing Heavy Metal Leaching through Ball Milling of Fly Ash

Ball milling is investigated as a method of reducing the leaching concentration (often termed stablilization) of heavy metals in municipal solid waste incineration (MSWI) fly ash. Three heavy metals (Cu, Cr, Pb) loose much of their solubility in leachate by treating fly ash in a planetary ball mill, in which collisions between balls and fly ash drive various physical processes, as well as chemical reactions. The efficiency of stabilization is evaluated by analysing heavy metals in the leachable fraction from treated fly ash. Ball milling reduces the leaching concentration of Cu, Cr, and Pb, and water washing effectively promotes stabilization efficiency by removing soluble salts. Size distribution and morphology of particles were analysed by laser particle diameter analysis and scanning electron microscopy. X-ray diffraction analysis reveals significant reduction of the crystallinity of fly ash by milling. Fly ash particles can be activated through this ball milling, leading to a significant decrease in particle size, a rise in its BET-surface, and turning basic crystals therein into amorphous structures. The dissolution rate of acid buffering materials present in activated particles is enhanced, resulting in a rising pH value of the leachate, reducing the leaching out of some heavy metals.

Preparation and characterization of dual-responsive spiropyran-based random copolymer brushes via surface-initiated atom transfer radical polymerization

Silica nanoparticles (SiO2) were grafted with the precursor random copolymer of 1′-(2-acryloxyethyl)-3′,3′-dimethyl-6-nitrospiro-(2H-1-benzopyran-2,2′-indoline) (SPMA) and tert-butyl methacrylate (tBMA) by surface-initiated atom transfer radical polymerization (SI-ATRP), and SiO2-g-P(SPMA-co-methacrylic acid (MAA)) was obtained via chemical hydrolysis of the resulting precursor random copolymer in acidic conditions. From transmission electron microscopy, we observed the spherical morphology of monodispersed silica nanoparticles and core-shell structure of SiO2-g-P(SPMA-co-MAA). Energy dispersive spectroscopy, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and the thermogravimetric analysis indicated that the polymer had been successfully grafted onto the surface of silica nanoparticles. The dual-responsive properties were characterized by means of ultraviolet-visible spectrophotometer and dynamic light scattering. The average hydrodynamic diameter of SiO2-g-P(SPMA-co-MAA) increased from 185.7 to 212.7 nm under ultraviolet light irradiation for 5 min. Also, the particle size of SiO2-g-P(SPMA-co-MAA) increased with the rising pH value of surrounding condition.

Kinetic and Thermodynamic Studies of the Biosorption of Ni(II) by Modified Rape Straw

Biosorption equilibrium, kinetics and thermodynamics of Ni(II) onto the modified rape straw (MRS) by ZnCl2 were studied in a batch system with respect to pH, temperature and initial metal ion concentration. The Ni(II) removal rate increased with rising pH values, reaching about 99.7% at pH 6.5. The biosorption efficiency of Ni(II) to the biomass decreased as the initial concentration of metal ions was increased. But it is less likely to be affected by temperature from 303K to 323K. The adsorption data fit Langmuir adsorption isotherm at 303K and 313K. According to Langmuir isotherm, the theoretical maximum adsorption capacity of MRS was 9.17mg·g-1 and 10.45mg·g-1 at 303K, 313K, respectively. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data for initial Ni(II). The pseudo-second-order kinetic model provided the best correlation of the used experimental data. Thermodynamic parameters can be calculated by Gibbs equation, ΔG is negative, but ΔH is positive, it can be concluded that the process of removing Ni(II) by MRS are spontaneous and endothermic. The XPS spectrum of nickel-treated biosorbent reveals that Ni(II) is really sorbed onto biosorbent.

PH-Responsive and Self-Healing Hydrogels Fabricated with Guar Gum and Reactive Microgels

Hydrogels (MR gels) with pH-responsive and self-healing properties were prepared via guar gum solutions and reactive microgel. The reactive microgel was characterized through scanning electron microscope (SEM), laser particle-size analysis measurements, and FTIR. Compared with general hydrogels cross-linked by borax (B gels), the MR gels exhibit superior properties on the aspects of viscosity, viscoelasticies, and temperature resistance. Furthermore, the viscosities of MR gels increase with the rising pH value, and it can dynamically reconstruct after being destructed by external force. In addition, the microstructure of the MR gel was characterized by SEM, which confirms that the reactive microgel indeed as cross-linker and each microgel can cross-link several chains as if the chains were grafting from the microgels. These features show that the addition of reactive microgels can enhance the strength of MR gels significantly and indicate that the MR gels have a great potential application in hydraulic fracturing, especially in high-temperature oil fields.

Loss of thermodynamic spontaneity in methanogenic consortium with ammonia contents

Over 60% of the primary and secondary sludge produced in the UK is now processed by mesophilic anaerobic digestion in order to “stabilise” and extract bio-energy from the organic material. However inhibition and destruction of microorganisms is frequently reported and related to elevated ammonia concentrations. Ammonia is released from proteinaceous material in the wastewater and concentrated in the sludge. Empirically observed inhibition or loss of bio-kinetic rate is seldom attributed to specific underlying causes such as loss of enzyme activity or loss of thermodynamic driving force. This work takes a theoretical electrochemical modelling approach to investigate thermodynamic limitations by free energy, enthalpy and entropy analysis. From the Gibb’s free energy results, there is no evidence for thermodynamic limitation arising from even very high concentrations of ammonium ion. However entropy analysis shows a sudden loss of spontaneity when the initial ratio of ammonia to the other solutes, R, exceeds a, concentration dependent, threshold value. The loss of spontaneity is not directly related to the rising pH value which is indicative of the addition of ammonium ions. The loss is however attributable to the depletion of carbonates occurring in anaerobic ammonium oxidation. These results suggest that empirically observed ammoniacal inhibition in anaerobic digestion arises from reduced activity of hydrogenophilic methanogens which are dependent on the simultaneous availability of hydrogen and bi-carbonate ion.

Study of hybrid immobilized biomass of Pleurotus sajor-caju and Jasmine sambac for sorption of heavy metals

The current study deals with evaluation of biosorption feasibility for removal of Cu(II) and Zn(II) by hybrid immobilized biosorbent of Pleurotus sajor-caju and Jasmine sambac. Batch adsorption experiments were carried out to assess the effect of pH, initial metal concentration, biomass dose, temperature and time. The biosorption efficiency of Cu(II) and Zn(II) ions for hybrid immobilized biosorbent increases with rising pH values. The hybrid immobilized biosorbent illustrated the highest biosorption capability at pH 5 for Cu(II), 6 for Zn(II), at 0.05 g/100 mL dose and 100 mg/L initial metal concentration of both ions. Uptake kinetics followed the pseudo-second-order model and equilibrium was described by Langmuir and Freundlich isotherms. Adsorption ratios of Cu(II) and Zn(II) were best fitted to Langmuir isotherm. The best temperature for ion uptake was found to be 30 °C.

Global synchrony in biospheric variations and influence on soil pH

Data collected from 1968 through 1997 showed a globally synchronous annual increase in soil acidity during the period June through August which was highly correlated with progressively decreasing geomagnetic field strength despite periodic local alterations in electromagnetic activity at the planetary boundary layer. Monthly determinations of soil pH for periods of one or more years at sites in Australia, South America, North America, Scotland, and Germany showed pH values to be consistently and significantly correlated with the monthly average geomagnetic field strength and the auroral electrojet values recorded during the time period covered by the data. Unweighed simple and multiple least squares linear regressions of soil pH on geomagnetic D, H, and Z, and the auroral electrojet gave r2 and p values as high as r2 = 0.9997, p = 0.0000. These relationships were subject to modifications in soil pH by telluric currents and electromagnetic events, such as thunderstorms and accompanying acid rain, occurring at the planetary boundary layer. Short-term variations in electrical conductivity of soil, in situ plant-available soil moisture, availability of soil mineral nutrient elements for plant uptake, soil pH, and the pH of fresh and stored samples of soil diluted 1:5 in water, rainwater, and other solutions, and Rn levels in soil and air were highly correlated with ambient telluric currents and with atmospheric electrical discharges. Decreasing soil pH values were consistently associated with decreased availability of soil mineral nutrients for plant uptake, lower foliar mineral element content in growing plants, and reduced health status, fertility, and productivity of herbivores. Rising pH values were accompanied by increases in available soil mineral nutrient elements and improvements in plant and animal health and productivity.

Preparation of redox fibers containing hydroxy-alkyl amino groups and their adsorptive properties toward Au(III)

Three kinds of redox fibers (fibers II, III, and IV) are prepared by amination of the reactive chloromethylated poly(vinyl acetate) grafting polystyrene-divinylbenzene fiber (fiber I) with diethanolamine, ethanolamine, or triethanolamine. The N-content of the fibers is 2.26, 2.71, and 1.86 mmol g−1, respectively. Results of static adsorption experiments show that the adsorption amount of fibers II, III, and IV toward Au(III) reaches 550 mg g−1, 620 mg g−1, and 409 mg g−1, respectively, between pH 2.0 and pH 3.0. Some adsorbed Au(III) can be reduced to Au(0). The reduction percentage of Au(III) adsorbed by fiber II increases with rising pH value of the solution and can be as high as 87% at pH 5.0. The amount of Au(III) adsorbed by fiber II increases with solution temperature, but decreases with ionic strength of the solution. The adsorption amount of fibers II and III toward Au(III) is less in ethanol or in acetacetate medium than in water. Kinetic adsorption data indicates that 50 min is needed for fiber II to adsorb half of its saturate adsorption amount of Au(III). It was proved by elemental analysis, infrared spectroscopy, nuclear magnetic resonance, and electron spectroscopy for chemical analysis determinations that the carbon atoms connecting with the hydroxy groups near the nitrogen atoms were easily oxidized into carbonyl ones during redox adsorption reaction of fibers II, III, and IV with Au(III). Some grains of gold adsorbed on fiber II were discovered under scanning electron microscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 47–54, 1999

Effects of pH on rhodopsin photointermediates from lumirhodopsin to metarhodopsin II.

Time-resolved absorption difference spectra of membrane suspensions of bovine rhodopsin at pH 5, 6, 7, 8, 9, and 10 were collected in the time range from 1 micro s to 200 ms after laser photolysis with 7-ns pulses of 477-nm light. The data were analyzed using singular value decomposition (SVD) and global exponential fitting. At pH 7 the data agree well with previously obtained data (Thorgeirsson et al. (1993) Biochemistry 32, 13861-13872) with fits improved at all pH's by inclusion of a small component due to an absorbance change caused by rotational diffusion which is detectable even at magic angle polarization. A "square scheme" suggested to best explain the previous data, which involves two branches following decay of the lumi intermediate with pathways (1) lumi --> MI480 right harpoon over left harpoon MII and (2) lumi right harpoon over left harpoon MI380 --> MII, could be confirmed throughout the entire pH range. However, to account for the increased rate of the MII --> MI480 reaction in path 1 for rising pH values, we propose that the MII in the square scheme consists of deprotonated MII and protonated MIIH+ forms in rapid equilibrium with each other, resulting in an extended square scheme and increasing the number of 380-nm products from two to three. In addition to the kinetic processes described by the extended square scheme, above pH 8 fast ( approximately 10 micro s) and slow ( approximately 50 ms) components were found. The fast component was assigned to the decay of a blue-shifted lumi intermediate, and the slow component, resolvable only at pH 10, was assigned to formation of a 450 nm absorbing photoproduct.

Crystallisation of gelatinous aluminium hydroxide

AbstractThe gelatinous precipitates from aqueous aluminium chloride solution on the addition of alkalies at various pH have been aged in the mother liquors for a given period of time. The resulting materials have been examined by X‐ray diffraction studies. In addition, the changes in the pH value of the mother liquor and the amount of aluminium dissolved in the mother liquor during ageing have been checked under various conditions. As a result, it is found that the freshly precipitated gelatinous aluminium hydroxide exists in an amorphous type independently of the pH value and goes to pseudoboehmite by ageing, but the amount of aluminium dissolved in the mother liquor increases with rising pH value. By further ageing, however, hydrargillite is produced in contact with the aqueous medium at low pH, and bayerite at higher pH.It is concluded that the crystallisation of gelatinous aluminium hydroxide precipitates aged with an aqueous medium occurs in the process magnified image and the presence of alkali plays an important role in promoting these transformations.

Water quality criteria for European freshwater fish: Report on ammonia and inland fisheries

In establishing water quality criteria for European inland fisheries, the effect of ammonia is an important factor to be considered. Sewage effluent, effluents from certain industries and from agriculture are common sources of ammonia in water.The harmful effects of ammonia on fish are related to the pH value and the temperature of the water due to the fact that only the un-ionized fraction of ammonia is poisonous. The un-ionized fraction increases with rising pH value, and with rising temperature.Fish differ slightly in their tolerance to ammonia depending on species. The difference in tolerance being more significant for short periods of exposure. The difference in tolerance is, however, not great enough to justify different criteria for different species.The lowest toxic concentration found for salmonids is 0·2 mg NH3 1−1 (un-ionized), but other adverse effects caused by prolonged exposure are only absent at concentrations lower than 0·025 mg NH3 1−1 (un-ionized). Concentrations of total ammonia which contain this amount of un-ionized ammonia vary from 19·6 mg 1−1 (pH 7·0, 5°C) to 0·12 mg 1−1 (pH 8·5, 30°C).The criterion should not be applied to temperatures below 5°C or to pH values above 8·5 when other factors have to be taken into consideration.