Ferron Method Research Articles

Profiles of and variations in aluminum species in PAC-MC used for the removal of blooming microalgae

Polyaluminum chloride modified clay (PAC-MC) is a safe and efficient red tide control agent that has been studied and applied worldwide. Although it is well known that the distribution of hydrolytic aluminum species in PAC affects its flocculation, little is known about the influence of particulars aluminum species on the microalgae removal efficiency of PAC-MC; this lack of knowledge creates a bottleneck in the development of more efficient MCs based on aluminum salts. The ferron method was used in this study to quantitatively analyze the distributions of and variations in different hydrolytic aluminum species during the process of microalgae removal by PAC-MC. The results showed that Ala, which made up 5%–20% of the total aluminum, and Alp, which made up 15%–55% of the total aluminum, significantly affected microalgae removal, with Pearson's correlation coefficients of 0.83 and 0.89, respectively. Most of the aluminum in the PAC-MC sank rapidly into the sediments, but the rate and velocity of settlement were affected by the dose of modified clay. The optimal dose of PAC-MC for precipitating microalgae was determined based on its aluminum profile. These results provide guidance for the precise application of PAC-MC in the control of harmful algal blooms.

Minimizing residual black particles in sand filtrate when applying super-fine powdered activated carbon: Coagulants and coagulation conditions

Because of the eminent adsorptive capacity and rate for dissolved organic molecules compared to conventionally-sized powdered activated carbon (PAC), super-fine powdered activated carbon (SPAC) is gathering momentum for use in not only the pretreatment for membrane filtration for drinking water purification but also the conventional water purification process consisting of coagulation-flocculation, sedimentation, and rapid sand-filtration (CSF). However, the probability of SPAC particles to leak through a sand bed is higher than that of PAC, and their strict leakage control is an issue to be challenged when applying SPAC to CSF. However, study focusing on very high particle removal, which yield residual concentrations down to around 100 particles/mL, has been very limited. A previous study mentioned that the tendency of SPAC leakage is related to its low destabilization. In response to this, the present study focused on the two key components of coagulation (mixing intensity and coagulants) and investigated how to effectively reduce the residual SPAC after CSF.Astonishingly, the flash mixing (the first process of CSF), especially its G (velocity gradient) value, played the most important role in determining the residual SPAC in the filtrate of sand filter (the fourth process). Even if the slow mixing time was short, a sufficiently large G value but short T (mixing time) value in flash mixing effectively reduced the residual SPAC. When the total GT value of flash and slow mixing was fixed at a constant, priority should be given to flash mixing to reduce the residual SPAC.Among 23 PACl (poly-aluminum chloride) coagulants, PACl with a high-basicity (basicity 70%) and with sulfate ion (0.14 of sulfate/aluminum in molar ratio), produced by Al(OH)3-dissolution, were the most effective to reduce the residual SPAC after CSF. PACls produced by base-titration, which have been intensively investigated in previous researches, were not effective due to lack of floc-formation ability. However, their Al species composition determined by the ferron method were almost the same as those of PACl by Al(OH)3-dissolution, and their charge-neutralization capacities were higher. PACls produced by Al(OH)3-dissolution possessed both charge-neutralization and floc-formation abilities, but the former ability was more important to minimize the residual of SPAC.

Optimized preparation of PPFAS and removal of heavy metals

The basification method was used for the optimized preparation of a new flocculant, poly‐ferric aluminum phosphate sulfate (PPFAS). The Ferron method was used to analyze the distributions of the Fe and Al forms in PPFAS. The conditions of the optimized preparation of PPFAS were as follows: the n(OH)/n(Fe) ratio of 0.6, the n(P)/n(Fe) ratio of 1/5, and the reaction temperature of 60°C. After each addition of NaOH and Na3PO4, the reaction was allowed to proceed for 10 min, and then, the reaction continued on the shaking table for 1 h; the aging process continued for 60 h at 25°C. Under these conditions, the content of the effective component, [Fe + Al]b, could reach up to 60%. The order of the removal rates of the mixed heavy metals by PPFAS is Cu(II)> Cr(III)> Pb(II)> Zn(II)> Cd(II). The order of the removal rates of the mixed complex heavy metals is EDTA‐Cd(II)> EDTA‐Zn(II)> EDTA‐Pb(II)> EDTA‐Cu(II)> EDTA‐Cr(III). © 2017 American Institute of Chemical Engineers Environ Prog, 37: 240–248, 2018

Effect of coagulant basicity on virus removal from water by polyferric chloride

We investigated the effect of coagulant basicity on bacteriophage removal from river water by polyferric chloride (PFC). PFC at three basicities (basicity 0.9–2.1) was prepared by means of base titration (NaOH was added to ferric chloride (FeCl3) solution) and the virus removal efficiencies of those PFCs were compared with that of FeCl3 (basicity 0). The virus removal efficiencies of the PFCs were equal to or less than that of FeCl3 at both pH 6 and pH 8. This suggests that, unlike aluminum-based coagulants, increasing the basicity of iron-based coagulants does not improve virus removal efficiency. Furthermore, the relative abundance of monomeric iron(III) species in the PFCs decreased, whereas that of precipitated iron(III) species increased with increasing basicity, as assessed with a ferron method. Colloid charge density also decreased with increasing basicity. Therefore, it is likely that the reduction in the abundance of monomeric iron(III) species led to the reduction in colloid charge density, which then reduced virus removal efficiency. Thus, the development of novel iron-based coagulants with increased virus removal efficiency may not be possible by simply increasing the basicity of the coagulant.

Study on the hydrolysis/precipitation behavior of Keggin Al 13 and Al 30 polymers in polyaluminum solutions

The hydrolysis/precipitation behaviors of Al 3+, Al 13 and Al 30 under conditions typical for flocculation in water treatment were investigated by studying the particulates' size development, charge characteristics, chemical species and speciation transformation of coagulant hydrolysis precipitates. The optimal pH conditions for hydrolysis precipitates formation for AlCl 3, PAC Al13 and PAC Al30 were 6.5–7.5, 8.5–9.5, and 7.5–9.5, respectively. The precipitates' formation rate increased with the increase in dosage, and the relative rates were AlCl 3 ≫ PAC Al30 > PAC Al13. The precipitates' size increased when the dosage increased from 50 μM to 200 μM, but it decreased when the dosage increased to 800 μM. The Zeta potential of coagulant hydrolysis precipitates decreased with the increase in pH for the three coagulants. The iso-electric points of the freshly formed precipitates for AlCl 3, PAC Al13 and PAC Al30 were 7.3, 9.6 and 9.2, respectively. The Zeta potentials of AlCl 3 hydrolysis precipitates were lower than those of PAC Al13 and PAC Al30 when pH > 5.0. The Zeta potential of PAC Al30 hydrolysis precipitates was higher than that of PAC Al13 at the acidic side, but lower at the alkaline side. The dosage had no obvious effect on the Zeta potential of hydrolysis precipitates under fixed pH conditions. The increase in Zeta potential with the increase in dosage under uncontrolled pH conditions was due to the pH depression caused by coagulant addition. Al–Ferron research indicated that the hydrolysis precipitates of AlCl 3 were composed of amorphous Al(OH) 3 precipitates, but those of PAC Al13 and PAC Al30 were composed of aggregates of Al 13 and Al 30, respectively. Al 3+ was the most un-stable species in coagulants, and its hydrolysis was remarkably influenced by solution pH. Al 13 and Al 30 species were very stable, and solution pH and aging had little effect on the chemical species of their hydrolysis products. The research method involving coagulant hydrolysis precipitates based on Al–Ferron reaction kinetics was studied in detail. The Al species classification based on complex reaction kinetic of hydrolysis precipitates and Ferron reagent was different from that measured in a conventional coagulant assay using the Al–Ferron method. The chemical composition of Al a, Al b and Al c depended on coagulant and solution pH. The Al b measured in the current case was different from Keggin Al 13, and the high Al b content in the AlCl 3 hydrolysis precipitates could not used as testimony that most of the Al 3+ was converted to highly charged Al 13 species during AlCl 3 coagulation.

Comparison of coagulation behavior and floc structure characteristic of different polyferric-cationic polymer dual-coagulants in humic acid solution

Three polyferric-cationic polymer dual-coagulants were comparatively evaluated in terms of coagulation behavior and floc structure characteristic in the coagulation of humic acid (HA) solution. The first dual-coagulant, PFC–PDADMAC, was prepared by premixing of polyferric chloride (PFC) and polydiallyldimethylammonium (PDADMAC) before dosing. The other two were achieved by dosing PFC and PDADMAC in different order. For the given neutral condition, all three dual-coagulants gave similar HA removal before reaching optimal dosage. The strongest charge neutralization and narrowest effective coagulation dosage range were obtained when PFC was dosed firstly. While the weakest charge neutralization and the broadest effective coagulation dosage were obtained when PDADMAC was used as the primary coagulant. The HA removal of all three dual-coagulants was slightly pH dependent for optimum coagulant doses. Fe(III) hydrolysis species distributions of the dual-coagulants in coagulation process were measured by ferron method. PFC–PDADMAC gave the highest content of active Fe(III) coagulating species which is responsible for the coagulation performance of ferric coagulant. The evolution of floc size and floc fractal dimension ( D f) in coagulation process was measured under optimum dose and neutral condition by laser diffraction instrument and small-angle laser light scattering (SALLS), respectively. All three dual-coagulants gave similar final floc size but different floc growth rate and floc structure. Both the growth rate and D f were in the same order: PFC dosed firstly > PDADMAC dosed firstly > PFC–PDADMAC.

Rhizotoxicity of aluminate and polycationic aluminium at high pH

Although monomeric Al species are often toxic in acidic soils, the effects of the aluminate ion (Al(OH) 4 − ) on roots grown in alkaline media are still unclear. Dilute, alkaline (pH 9.5) nutrient solutions were used to investigate the effects of Al(OH) 4 − on root growth of mungbean (Vigna radiata L.). Root growth was reduced by 13% after 3 d growth in solutions with an Al(OH) 4 − activity of 16 µM and no detectable polycationic Al (Al13). This decrease in root growth was associated with the formation of lesions on the root tips (due to the rupturing of the epidermal and outer cortical cells) and a slight limitation to root hair growth (particularly on the lateral roots). When roots displaying these symptoms were transferred to fresh Al(OH) 4 − solutions for a further 12 h, no root tip lesions were observed and root hair growth on the lateral roots improved. The symptoms were similar to those induced by Al13 at concentrations as low as 0.50 µM Al which are below the detection limit of the ferron method. Thus, Al(OH) 4 − is considered to be non-toxic, with the observed reduction in root growth in solutions containing Al(OH) 4 − due to the gradual formation of toxic Al13 in the bulk nutrient solution resulting from the acidification of the alkaline nutrient solution by the plant roots.

Speciation stability of inorganic polymer flocculant–PACl

The speciation distribution, physico-chemical properties of coagulants, and principles for their further species transformation under various water and wastewater treatment conditions are of paramount importance in coagulation processes. In this paper, the effect of various factors on the speciation transformation of typical inorganic polymer flocculants (IPFs)–polyaluminum chloride (PACl) was investigated by ferron assay. Dilution and co-existing electrolyte exhibit little effect on the speciation distribution of PACl after dosing. Solution pH has significant effect on the species transformation, depending mainly on OH/Al ratio (denoted as B value). The lower the B value, the more significant the effect pH exhibits. A large amount of Al b, i.e. rapid reactive species by ferron assay, could form for alum and PACl 0 in the weak acidic pH range, which transforms quickly into Al c after aging. PACl, at high B values, maintains high speciation stability under the various conditions investigated. The ferron method provides a measure to explain the reactivity of different species with ferron. The classification of three kinds of aluminum hydrolysis species based on kinetic differences needs further modification.

The electrochemical production of highly effective polyaluminum chloride

This paper presents a new electrolytic method for the synthesis of PAC (polyaluminum chloride). The ECR (electrochemical reactor) used aluminum sheets as anode and AlCl 3 aqueous solution as electrolyte. This method adopted low voltage and high electric current intensity during electrolysis. Some factors of the electrochemistry and the chemistry of the aqueous solution, affecting the formation of the most effective species of PAC, were also studied. The liquid product of PAC, in which the most effective species, Alb (The polymeric Al component estimated by the ferron method), was above 70% by weight of the total aluminum with a basicity, B (OH/Al molar ratios)=2.4, was successfully generated. The results measured by the ferron method and 27Al NMR method showed that the Alb or Al 13 content of the E-PAC (PAC prepared by electrolysis) were obviously higher than that of the general PAC and other coagulants.

Characterization of Amorphous Aluminum Hydroxide by the Ferron Method

Characterization by the ferron method of the solid formed during hydrolysis of aqueous aluminum(III), under conditions of water and wastewater treatment, is the focus of the present study. It has been found that the rate of reaction (later referred to as aluminum reactivity) between freshly precipitated amorphous aluminum hydroxide and the reagent containing a reduced form of ferron may be used to characterize the precipitate. With increasing age between 1 min and 45 d, the reactivity of aluminum in the precipitate was found to steadily decrease. For example, a t 50 value (indicating the time for 50% recovery of the added aluminum) for a 1-min aged aluminum hydroxide was found to be near 10 min, while for the 10 000-min aged sample the t 50 value was near 100 min

On the Phytotoxicity of Polynuclear Hydroxy‐Aluminum Complexes

AbstractIn a previous study we demonstrated the phytotoxicity of polynuclear hydroxy‐Al, a finding that disagrees with a number of existing reports. The objectives of this study were to examine how toxicity of polynuclear Al might vary with experimental conditions or with choice of test plants, and to identify and characterize the toxic polynuclear species. Wheat (Triticum aestivum L. cv. Tyler or Seneca) or soybean (Glycine max (L.) Merr. cv. Stafford) seedlings were cultured for 2 d in dilute CaCl2 solutions containing 15 µM total Al at a basicity (initial molar OH/Al ratio) of 2.0. Increasing rate of base addition, solution age, or levels of added phosphate decreased the fraction of reactive polymers (Alb) and increased that of precipitated Al (Alc) as determined by the ferron method. Mononuclear Al was consistently ≤3 µM and did not contribute to toxicity. Inhibition of root growth was well correlated with [Alb] for both plant species. That only 3 to 4 µM [Alb] was required to fully inhibit wheat root growth suggested that detection of toxic polynuclear Al may at times be difficult in chemically complex media. All plants tested were considerably more tolerant of Al3+ than of Alb, suggesting fundamental physiological differences in the toxicity of the two types of Al. This conclusion was further supported by the finding that the two wheat cultivars exhibited differential tolerance to Al3+, but not to Alb. Several analyses suggested that Alb was composed primarily of the so‐called Al13 polymer, which may form as a consequence of synthesis conditions. Given uncertainties in the occurrence of this polymeric species, both in the laboratory and in nature, several lines of future investigation are suggested.

ChemInform Abstract: Characterization of Non‐Framework Aluminum in Zeolites Y by the Ferron Method.

AbstractThe non‐framework aluminum occurring in dealuminated zeolites Y is shown to be nonuniform in nature.

ESTIMATION OF PHYTOTOXIC ALUMINUM IN SOIL SOLUTION USING THREE SPECTROPHOTOMETRIC METHODS

In the current investigation three spectrophotometric techniques -8-hydroxyquinoline, aluminon, and ferron- were compared for their ability to estimate phytotoxic Al in soil solution. Soil solution Al reacting with 8-hydroxyquinoline in 15 s, ferron in 30 s, and aluminon in 30 min were related to root and shoot growth of subterranean clover (Trifolium subterraneum L. cv. Mt. Barket) and switchgrass (Panicum virgatum L. cv. Cave-in-Rock) in limed and unlimed treatments of 10 acidic subsoil horizons. Across all 10 soils the amount of Al reacting with 8-hydroxyquinoline was generally the lowest, and that reacting with ferron the highest, although overlap among methods did occur. Manganese interference in several of the soil solutions limited the utility of the ferron method. The amounts of Al reacting with 8-hydroxyquinoline and aluminon were significantly related (P < 0.05) to root and shoot growth limitations exhibited by subterranean clover and switch-grass. Activities of Al/sup 3 +/ (a/sub Al/sup 3 +//) calculated from the GEOCHEM program using the Al reacting with 8-hydroxyquinoline and aluminon as the Al inputs were generally the best predictors of root and shoot growth.

High Toxicity of Hydroxy-Aluminum Polymer Ions to Plant Roots

Investigations on the differential toxicity among Al ion species were carried out. The results are summarized as follows. 1) In the Al solutions containing similar concentrations of total ionic Al, polymer-Al ions predominated at pH 4.7 whereas monomer-Al ions predominated below pH 4.7. 2) At pH 4.7, the Al content of excised roots was maximum, while the K content was minimum. 3) At extremely low pH below ca. 4.5, the greater loss of K from roots associated with the low pH was prevented when Al was present in the solution. 4) The toxicity of Al ion species to the root growth and to the K retention in roots was in the order of polymer-Al ions > monomer-Al ions>AlSO4 +. 5) The increase of the basicity of Al solutions increased the concentration of the polymer-Al ions in the solution while the retardation of root elongation and the loss of K from roots were enhanced. 6) The modified ferron method was suitable for the identification of Al ion species, but the aluminon method enabled to determine the amount of precipitated Al. In conclusion, polymer-Al ions appear to be preferentially absorbed by roots, they destroy the plasmalemma of root cells, and finally inhibit considerably root elongation.

Speciation of Hydroxy‐Aluminum Solutions by Wet Chemical and Aluminum‐27 NMR Methods

AbstractPartially neutralized Al solutions with OH/Al molar (ñ) ratios ranging from 0.25 to 2.5 were studied employing 27Al nuclear magnetic resonance spectroscopy and the ferron‐timed colorimetric assay. The monomeric Al concentrations (Ala) estimated by the ferron assay were consistently higher than the actual concentration determined by NMR spectroscopy. The differences between the methods indicate the presence of a small polymer which reacts rapidly with ferron and is erroneously assigned to the monomeric Al fraction. The polymeric Al component (Alb) estimated by the ferron method could be partitioned into a more rapidly reacting fraction (≤1 h) and a slowly reacting fraction (&gt;1 h). The amount of Al associated with the rapidly reacting polymeric fraction corresponded to the amount of [AlO4 Al12(OH)24(H2O)12]7+ polymer directly determined by NMR spectroscopy. The slower reacting component of the Alb fraction is believed to be a polymer of the hexameric ring morphology. Direct NMR measurements provided evidence for specific adsorption of Al13 to a cation exchange resin and differential precipitation kinetics of this polymer with added sulfate. These data indicate that characterizing hydroxy Al solutions without direct measurements can lead to erroneous interpretations concerning the distribution between monomeric and polymeric Al and the nature and types of polymeric Al present.

Aluminium speciation: comparison of two spectrophotometric analytical methods and observed concentrations in some acidic aquatic systems in Southern Norway

The toxicity of A1 to aquatic biota varies with speciation. Driscoll (1980) has developed a scheme for determining three A1 fractions using the ferron method (Smith, 1971) to detect Al. We have compared the results obtained with Driscoll's method with those obtained when pyrocatechol violet is the complexing agent. The agreement is generally satisfactory. The latter method is more sensitive and less influenced by interferences. Results for water samples, mainly from two streams in southern Norway, are discussed. For most samples the labile monomeric Al-fraction dominates, the major species being either A13+ or AIF2+. Possible equilibria between A13+ and some minerals and the temperature changes in these equilibria, are discussed.

Comparison of atomic absorption spectrometric, spectrophotometric, and fluorimetric methods for determination of aluminum in water

Three methods for quantifying aluminum in water samples are compared. An electrothermal atomic absorption method is assumed to be free of interferences and has an applicable range of 10 to above 1000 μg Al l -1. The colorimetric ferron method has multiple interferences and is useful in the 50–1500 μg Al l -1 range. The fluorimetric method based on lumogallion has few important interferences and is useful to below 1 μg Al l -1.

Spectrophotometric determination of aluminium with ferron and a quaternary ammonium salt

The reproducibility of the ferron method for aluminium has been greatly improved by the addition of cetyltrimethylammonium chloride (CTMAC). The improvement is attributed to reduction of the reagent blank and increased stability of Al(ferron) 3− 3. The aluminium—ferron complex formed in the presence of CTMAC has an absorption peak at 385 nm. The interference from iron can be eliminated by application of a correction based on measurement at two wavelengths.