Concentration Of Iron Ions Research Articles

Combined conditioning of inorganic coagulant and polyamine to improve the dewaterability of municipal sludge, minimize dosage and reduce the influence of filtrate.

Efficient dewatering of sludge is necessary for its cost-effective transportation and final disposal. However, the common method of using polyferric sulfate (PFS) and polyacrylamide (PAM) requires a large amount of dosage and produces high iron ion content in the filtrate. This study examined a solution of applying polyamine (PA) coupled with inorganic coagulant PFS. The results demonstrated that using PFS + PA together could achieve the same or similar filtering rates as using PFS + PAM. The capillary suction time (CST) of PFS + PA (89.0 s) was equivalent to that of PFS (75.1 s) and better than that of PA (117.1 s) and raw sludge (RS, 403.8 s). Compared with PFS + PAM, the combination of PFS and PA efficiently removed Fe ions and chemical oxygen demand (COD) in sludge water content, with Fe ions in the sludge filtrate reduced by 97.8% and COD reduced by 78.9%, respectively. By analyzing the basic physicochemical properties of the sludge system, including the synergistic effect of coagulation and flocculation, sludge hydrolysis and flocculation, it indicated that PA + PFS could reduce bound water. These results demonstrated that combining PFS and PA to improve sludge dewatering performance is more beneficial than utilizing a coagulant or flocculant alone, even PFS + PAM.

An effective strategy to synthesize water-soluble iron heterocomplexes containing Dubb humic acid chelating agent as efficient micronutrients for iron-deficient soils of high pH levels

Humic acid (HA), the most known and popular water-soluble organic matter extracted from a variety of sources, has many applications in agriculture. Moreover, Fe-HA complexes are water-insoluble at high pH levels and thus they cannot be applied for iron-delivery to alkaline Fe-deficient soils. To solve this issue and to increase solubility and stability of Fe-HA complexes in alkaline soils (iron delivery to plants), herein, Dubb humic acid (DHA) extracted from lignite source was used and characterized by various techniques including X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) surface area, UV–Visible (UV–Vis) absorption and photoluminescence (PL) spectra, diffuse reflectance spectra (DRS), Fourier-transform infrared (FT-IR) spectra, gel permeation chromatography (GPC), and laser scattering particle size distribution analysis. To achieve iron complexes which were suitable for application in iron-deficient soils, firstly, some heterocomplexes containing non-DHA primary complexing agents were designed and synthesized using ammonium citrate (AC), ammonium sulfate (AS), and fulvic acid (FA) ligands. These complexes were water-soluble and could be easily used to synthesize final iron heterocomplexes with DHA coordinating agent, which were water-soluble in neutral and alkaline conditions. The desired heterocomplex structures with general formula of (A)n-(Metal)x-(B)m (A = DHA, Metal = Fe, B = AC, AS or FA) were synthesized through optimizing pH, DHA percentage, and initial iron ion concentration. Structural characterizations of the synthesized heterocomplexes were conducted by above-mentioned techniques. Elemental analysis of these heterocomplexes (particularly the AS containing sample) showed very much higher iron contents compared with commercial iron containing chelates. These results established that iron heterocomplexes designed in this study had an extraordinary potential for acting as valuable inorganic micronutrients for iron-deficient soils in alkaline conditions.

Molecular Regulatory Mechanism of the Iron-Ion-Promoted Asexual Sporulation of Antrodia cinnamomea in Submerged Fermentation Revealed by Comparative Transcriptomics.

Antrodia cinnamomea is a precious edible and medicinal fungus with activities of antitumor, antivirus, and immunoregulation. Fe2+ was found to promote the asexual sporulation of A. cinnamomea markedly, but the molecular regulatory mechanism of the effect is unclear. In the present study, comparative transcriptomics analysis using RNA sequencing (RNA-seq) and real time quantitative PCR (RT-qPCR) were conducted on A. cinnamomea mycelia cultured in the presence or absence of Fe2+ to reveal the molecular regulatory mechanisms underlying iron-ion-promoted asexual sporulation. The obtained mechanism is as follows: A. cinnamomea acquires iron ions through reductive iron assimilation (RIA) and siderophore-mediated iron assimilation (SIA). In RIA, ferrous iron ions are directly transported into cells by the high-affinity protein complex formed by a ferroxidase (FetC) and an Fe transporter permease (FtrA). In SIA, siderophores are secreted externally to chelate the iron in the extracellular environment. Then, the chelates are transported into cells through the siderophore channels (Sit1/MirB) on the cell membrane and hydrolyzed by a hydrolase (EstB) in the cell to release iron ions. The O-methyltransferase TpcA and the regulatory protein URBS1 promote the synthesis of siderophores. HapX and SreA respond to and maintain the balance of the intercellular concentration of iron ions. Furthermore, HapX and SreA promote the expression of flbD and abaA, respectively. In addition, iron ions promote the expression of relevant genes in the cell wall integrity signaling pathway, thereby accelerating the cell wall synthesis and maturation of spores. This study contributes to the rational adjustment and control of the sporulation of A. cinnamomea and thereby improves the efficiency of the preparation of inoculum for submerged fermentation.

Development of resource treatment technology for fracturing backflow fluids of tight sandstone

Abstract Fracturing is an important means to realize the development value of tight sandstone unconventional reservoirs, which consumes serious water resources and generates high viscosity of backflow fluid with petroleum and suspended matter pollutants. Therefore, it is of great significance to recycle fracturing fluid from tight sandstone with low-carbon and environmental protection. In this study, the fracturing fluid of tight sandstone in a block of a certain oilfield was collected as the research object, and a comprehensive water quality analysis was carried out. The combined process technology for resource treatment of fracturing flowback fluid in tight sandstone were formed by studying on the influence factors of oxidation gel breaking, flocculation sedimentation, ion removal, filtration and process optimization. After treatment, the mass concentration of iron ion in fracturing flowback fluid was less than 5 mg/L, the mass concentration of suspended matter was less than 10 mg/L, and the mass concentration of oil was less than 5 mg/L, which could meet the water quality requirements of fluid distribution and reuse, and avoid the environmental pollution risk of flowback fluid effectively, while the consumption level of water resources in fracturing construction also was greatly reduced. This paper will have positive significance for the resource treatment technology and development of tight sandstone fracturing fluid.

Comparative Transcriptome Analysis Reveals Complex Physiological Response and Gene Regulation in Peanut Roots and Leaves under Manganese Toxicity Stress

Excess Manganese (Mn) is toxic to plants and reduces crop production. Although physiological and molecular pathways may drive plant responses to Mn toxicity, few studies have evaluated Mn tolerance capacity in roots and leaves. As a result, the processes behind Mn tolerance in various plant tissue or organ are unclear. The reactivity of peanut (Arachis hypogaea) to Mn toxicity stress was examined in this study. Mn oxidation spots developed on peanut leaves, and the root growth was inhibited under Mn toxicity stress. The physiological results revealed that under Mn toxicity stress, the activities of antioxidases and the content of proline in roots and leaves were greatly elevated, whereas the content of soluble protein decreased. In addition, manganese and iron ion content in roots and leaves increased significantly, but magnesium ion content decreased drastically. The differentially expressed genes (DEGs) in peanut roots and leaves in response to Mn toxicity were subsequently identified using genome-wide transcriptome analysis. Transcriptomic profiling results showed that 731 and 4589 DEGs were discovered individually in roots and leaves, respectively. Furthermore, only 310 DEGs were frequently adjusted and controlled in peanut roots and leaves, indicating peanut roots and leaves exhibited various toxicity responses to Mn. The results of qRT-PCR suggested that the gene expression of many DEGs in roots and leaves was inconsistent, indicating a more complex regulation of DEGs. Therefore, different regulatory mechanisms are present in peanut roots and leaves in response to Mn toxicity stress. The findings of this study can serve as a starting point for further research into the molecular mechanism of important functional genes in peanut roots and leaves that regulate peanut tolerance to Mn poisoning.

Extraction of iron (III) ions by core-shell microgel for in situ formation of iron nanoparticles to reduce harmful pollutants from water

Since the most transition metal ions and organic dyes are hazardous, it is crucial to remove them from water. For this purpose, various systems are reported for removal of only transition metal ions or organic dyes. I have introduced a new system which is suitable for removal of both metal ions and organic dyes. The free radical precipitation polymerization method was used to create the spherical system of silica surrounded by poly(N-vinylcaprolactam-acrylic acid) S@P(NVCP-AA) core shell microgels and then characterized by using FTIR, DLS, XRD, and STEM. The S@P(NVCP-AA) microgel system was applied as adsorbent to extract iron (III) ions from water under various concentrations of S@P(NVCP-AA), iron (III) ions content, pH, and agitation time. The adsorption process of iron (III) ions on S@P(NVCP-AA) microgels was investigated by different adsorption isotherms. The kinetics of adsorption of iron (III) ions on S@P(NVCP-AA) microgel system was also examined by intra-particle diffusion model (InPDM), pseudo-1st order (P1O), pseudo-2nd order (P2O) and Elovich model (EM). Iron nanoparticles were formed by in-situ reduction of iron (III) ions that had been adsorbed in the P(NVCP-AA) shell region of the S@P(NVCP-AA) microgel. The organic pollutants and toxic transition metal ions like 4-nitrophenol (4NiP), methyl red (MeR), methylene blue (MeB) and chromium (VI) ions (CMI) were reduced from an aqueous medium by using the iron nanoparticles loaded in S@P(NVCP-AA) microgels. The pseudo 1st order rate constant values for the catalytic reduction of 4NiP, MeR, MeB and CMI were found to be 0.778 min−1, 0.928 min−1, 0.943 min−1 and 0.142 min−1 respectively. The resulting S@Fe-P(NVCP-AA) system can act as an efficient catalyst for a wide range of additional organic transformations.

Chemical adsorption of iron ions from drinking water using Jordanian zeolitic tuff

Jordanian natural zeolitic tuff is distributed in the northeast, central and southern parts of Jordan. Zeolitic tuff used in this work was brought from Al Hala Volcano piles located in the southern part of Jordan to investigate its capability to remove iron ions from drinking water. The main zeolitic minerals identified in Al Hala are phillipsite and chabazite. The effects of iron concentration, pH values, contact time, zeolite grain size and amounts of used zeolitic tuff were examined in the removal process using batch experiments. Two zeolitic tuff grain sizes with two different amounts were used and designated as HZ1 and HZ2, two iron concentrations from two different water wells were investigated and designated as W1 and W2 were examined for different contact time periods. Batch tests were performed to determine the ability of zeolite to remove Fe3+ (iron III) from drinking water. In static regime experiments, the use of the HZ2 type shows a higher percentage of Fe3+ removal as compared to the HZ1 type for the same time and concentration. The results indicate that iron ions can be removed from drinking water with approximately 100% efficiency at the beginning of the contact time regardless the concentration of iron ions in the water. Al Hala zeolitic tuff used in iron removal showed a high capability with complete Fe3+ removal from drinking water. The HZ2 is more efficient in iron ions removal than HZ1, the pH value is not significantly affected.

Fluorapatite nanorod arrays with enamel-like bundle structure regulated by iron ions.

Pigmented rodent tooth enamel is mainly composed of parallel hydroxyapatite nanorods and a small amount of organic matrix. These hydroxyapatite nanorods tend to be carbonated and contain traces of iron, fluorine, and magnesium. The pigmented rodent tooth enamel which contains trace iron is stronger and more resistant to acid corrosion than unpigmented rodent enamel, which could provide inspiration for the preparation and synthesis of high performance and corrosion resistant artificial materials. However, the regulatory role and mechanical enhancement of iron ions in enamel growth are unclear. Here, we synthesized enamel-like fluorapatite nanorod arrays in vitro using a mineralization technique at room-temperature. To investigate the regulatory effect of iron ions on the fluorapatite nanorod arrays (FAP-Fe), the phosphate solution is slowly transfused dropwise in the calcium ion solution, and different concentrations of iron ions are added to the calcium ion solution in advance. We demonstrated that fluorapatite nanorod arrays (FAP) can be epitaxially grown from amorphous calcium phosphate nanoparticles and iron ions can improve the microstructure of FAP nanorod arrays and obtain the same enamel bundle structure as the natural enamel. Moreover, high concentration of iron ions can inhibit the crystallization of fluorapatite. The FAP-Fe nanorod arrays controlled by 0.02 mM Fe3+ have good mechanical properties. Their hardness is 1.34 ± 0.02 GPa and Young's modulus is 65.3 ± 0.4 GPa, respectively. This work is helpful to understand the role of trace elements in natural enamel in the regulation of enamel formation and to provide a theoretical foundation for the preparation of high strength artificial composites, which can play a greater role in the fields of biological alternative materials, anti-oil coating, oil/water separation, anti-bioadhesion and so on.

Recovery of non-ferrous metals from sulfide ores by the method of heap bioleaching on the example of Allarechensk technogenic deposit

On the example of the Allarechensk technogenic deposit ore, the heap bioleaching method feasibility for the copper-nickel ores processing and non-ferrous metals recovery was considered. The content of metals in the initial ore sample was following: nickel – 2.42 %, copper – 0.75 %. The ore grinded to a size of -5+3 mm was irrigated with a solution containing a strain of Acidithiobacillus ferrivorans. The S:L ratio was 4:1, the flow rate was 0.1 mL/min. In pregnant solutions, the pH and ORP values were controlled, and the concentrations of ferrous and ferric iron, copper, and nickel ions were also measured. The experiment duration was 330 days, 8.9 % nickel and 6.1 % copper were recovered. The pathways for the metals extraction from pregnant solutions, as well as the utilization of bioleaching residue were considered.

Study of the spatiotemporal variation of iron and manganese ions content in the Oued Moulouya water (North-East of Morocco)

Oued Moulouya is one of the most important water resources, not only for water supply, but also for the agro-industrial development of the North-East region of Morocco. However, the remarkable modification in terms of physico-chemical quality of this water resource which is constantly expressed by high concentrations of various mineralogical and organic components. This calls for the necessary measures to be taken to remedy this pollution. To understand the contribution of each source of this imbalance, whether geological and/or anthropogenic, we conducted a study to monitor, during the both wet and dry periods, the spatiotemporal variations of iron and manganese ions at eight stations along the Oued Moulouya. The water samples collected were therefore analysed to determine their pH (in situ) and their contents in these two ions following the method of Inductive Coupled Plasma spectrometry. The results obtained showed disparities in the concentrations of various components between the two periods of the year: wet and dry periods. Thus, the two elements monitored (Fe and Mn), expressed their maximum levels during the dry period, with values of 21.75 mg/l and 4.9 mg/l. These values were recorded at the station near the city of Guercif. While the minimum concentrations of these elements were recorded upstream of the Oued during the rainy months with values of 0.047 mg/l for iron and 0.016 mg/l for manganese. Hence, it is concluded, that the variation of the content of these two elements Fe and Mn is influenced by the geochemical contribution, which occurs during the dry periods and decreases by the physical dilution during the rainy periods.

Iron Oxides Nanoparticles as Components of Ferroptosis-Inducing Systems: Screening of Potential Candidates

This study presents an analysis of a set of iron oxides nanoparticles (NPs) (γ-Fe2O3, α-FeOOH, δ-FeOOH, 5Fe2O3·9H2O, and Fe3O4) as potential candidates for ferroptosis therapy in terms of a phase state, magnetic characteristics, and the release of Fe2+/Fe3+ as ROS mediators. Due to the values of saturation magnetization for Fe3O4 (31.6 emu/g) and γ-Fe2O3 (33.8 emu/g), as well as the surface area of these particles (130 and 123 m2/g), it is possible to consider them as promising magnetically controlled carriers that can function with various ligands. The evaluation of the release of Fe2+/Fe3+ ions as catalysts for the Fenton reaction showed that the concentration of the released ions increases within first 3 h after suspension and decreases within 24 h, which probably indicates desorption and adsorption of ions from/onto the surface of nanoparticles regardless their nature. The concentration of ions released by all nanoparticles, except α-FeOOH-Fe2+, reached 9.1 mg/L for Fe3+ to 1.7 mg/L for Fe2+, which makes them preferable for controlling the catalysis of the Fenton reaction. In contrast, a high concentration of iron ions to 90 mg/L for Fe3+ and 316 mg/L for Fe2+ released from compound α-FeOOH-Fe2+ allows us to utilize this oxide as an aid therapy agent. Results obtained on iron oxide nanoparticles will provide data for the most prospective candidates that are used in ferroptosis-inducing systems.

Chemical Damage Constitutive Model Establishment and the Energy Analysis of Rocks under Water–Rock Interaction

The physical and mechanical properties of rocks can be reduced significantly by an acidic environment, resulting in engineering weaknesses, such as building foundation instability, landslides, etc. In order to investigate the mechanical properties of rocks after hydrochemical erosion, a chemical damage constitutive model was established and used to analyze chemical damage variables and energy transformation. It is assumed that the strength of the rock elements obeyed Weibull distribution, considering the nonuniformity of rock. The chemical damage variable was proposed according to the load-bearing volume changes in the rock under water–rock chemical interactions. The chemical damage constitutive model was derived from coupling the mechanical damage under the external load and the chemical damage under hydrochemical erosion. In order to verify the accuracy of the model, semi-immersion experiments and uniaxial compression experiments of black sandy dolomite were carried out with different iron ion concentrations. Compared with the experimental data, the chemical damage constitutive model proposed could predict the stress–strain relationship reasonably well after water–rock interaction. The effects of water–rock interaction on the rock were a decrease in peak stress and an increase in peak strain. The peak strain increased by 4.96–29.58%, and the deterioration rate of peak strength was 0.19–4.18%. The energy transformation of the deterioration process was analyzed, and the results showed that the decrease in releasable elastic energy, Ue, is converted into dissipated energy, Ud, after hydrochemical erosion.

Research on the manipulation of iron ions and alkalis in Chlorella vulgaris culture

• The experimental results shown that the variant concentration of iron ions in the medium and the variant pH of the initial algal fluid did different effects on the growth of Chlorella vulgaris . The Chlorella vulgaris can thrive better in the culture fluid with iron ions raising. The initial pH of the algae fluid affects its growth mainly in 1–3 days. Meanwhile, in a weak alkaline environment, such as pH 8.27 is beneficial to the growth of Chlorella vulgaris during the initial developing period. Also we find out in a certain range of alkaline environments such as pH 8 to 9 is the more conducive to its growth. By concluding the results of the research, we can obtain the optimal chlorella aquaculture production cultivation conditions with economic benefits. The use of microalgae as raw materials to produce various new biomass energy in the aquaculture industry has become a key issue in building a friendly ecology. However, maximizing algal growth and profit by regulating iron ion concentration (Fe 3+ ) and acid-base value (pH) remains a major challenge. Therefore, this study utilized Chlorella vulgaris to explore the influence of Fe 3+ concentration and initial pH value on algal growth to obtain optimum economic benefits and chemical culture conditions. Using an air-lift columnar photobioreactor for cultivation and a fluorescent lamp as a light source, the experiments were conducted at a light intensity of 3537 Lux at approximately 24 °C. To achieve economically optimal culture conditions, the daily OD 660 value of the Chlorella vulgaris cultures was used to explore the effects of different iron ion concentrations and initial pH values on algae growth and biomass accumulation. Our results demonstrated that different iron ion concentrations and pH conditions of the algal culture rendered different effects on Chlorella vulgaris growth. Overall, the enriched iron-containing medium was more favorable for algae growth. Over time, the medium with higher iron concentration (1.0 g/L) achieved higher OD faster and its accumulated chlorophyll was higher. Moreover, the initial pH of the algae culture medium affected its growth mainly within the first three days. Particularly, a weak alkaline environment (e.g., pH 8.27) benefited Chlorella vulgaris growth during the initial growth period. With the results of this study, our research determined the optimal Chlorella production conditions that maximize economic benefits.

Removal of artificial iron ions using activated carbon from sago pith waste

In the present day, the industry is growing rapidly. Every process in the industries brings out pollution. Heavy metals, especially iron ions have contaminated water resources due to industrial activity. The high concentration of iron ions is dangerous for human life. To solve this issue an activated carbon from sago pith waste was developed to remove iron ions from industrial wastewater represented by artificial iron solution. The objective of this research is to measure the adsorption capacity of sago pith waste activated carbon (SPWAC) for treating artificial iron solution. The adsorbent was carbonized at 300 °C and 80 min. Further, it was activated by citric acid 0.1 M. The treated iron solution was analyzed by condutometer to examine the iron content. Subsequently, the functional groups of SPWAC were tested via Fourier Transform Infra-Red (FTIR). The result indicates that the SPWAC can reject iron ions of more than 80 % with an iron ions concentration of 1.81 mg/L at 60 min and 300 rpm. While, FTIR analysis show alkenes, carbonyl, and hydroxyl groups are present in SPWAC. The iron ions concentration in treated water is below the allowable threshold (0.3 mg/L) based on World Health Organization (WHO) guidelines for drinking water. Therefore, the SPWAC is promising technology to be applied for treating industrial wastewater.

Development of siderophore-based rhizobacterial consortium for the mitigation of biotic and abiotic environmental stresses in tomatoes: An in vitro and in planta approach.

Tomato-associated plant-growth-promoting rhizosphere bacteria were screened for effective antagonistic activity against the fungal vascular wilt pathogens; tolerance to heavy metals; and enhancing the bioavailability of iron for tomato plants through in vitro and in vivo approaches. Among the 121 rhizobacteria screened for siderophores, 25 isolates were observed to be siderophore producers and out of these, seven isolates chelate copper and iron thus exhibiting in vitro antagonism against the virulent strains of Fusarium oxysporum f. sp. lycopersici MTCC10270 (Fol), Fusarium equiseti MFol and Sarocladium sp. SWL isolated from infected tomatoes. Pseudomonas stutzeri KRP8 was identified to be the most potent strain among the siderophore producers and its siderophores were chemically characterized by mass spectra as metal bound and metal-free forms. Upon bio-inoculation of fortified bacterial consortium (siderozote) into the rhizosphere of vermiculite pot cultured tomatoes supplied with varying concentrations of iron and copper ions, we observed in planta growth improvements, antagonism, enhancement of bioavailability of iron and heavy metal tolerance using Inductively Coupled Plasma-Optical Emission Spectrometry. Our rhizobacterial consortium provides an opportunity for soil reclamation through an ecofriendly method for a heavy metal-free agricultural landscape.

A Novel Method for Removal of Iron Ion Contamination in Patchouli Essential Oil

Nowadays, in the aromatic and cosmetics industries, as well as an additive for food flavoring, patchouli essential oil (PEO) is a significantly crucial raw material. This oil is extracted from Pogostemon cablin, a plant from the Lamiaceae family. The standard method to obtain this oil is steam distillation. However, applying this method, the oil has a relatively high iron content. A contaminated iron ion can arise in the PEO for some reasons, i.e., the distillation practice used in a non-stainless steel tank, the PEO stored in an iron drum, or even the water for steam production was not appropriately treated. Activated carbon adsorbents can be used to remove contaminants from liquids or gasses by adsorbing ions, complexes, and molecules from aqueous solutions. Although fine adsorbent particles offer advantages in terms of adsorption capacity and kinetics, the application of the adsorbent to remove iron ions contaminated in PEO is not simple work. It is because a problem with these particles is widely dispersed in the oil and challenging to recover and contaminates the final product of PEO. This study developed a novel method to remove iron ions contaminated in a PEO using a modified activated carbon, i.e., magnetic activated carbon (MAC). For practical applications, using MAC material will reduce operating costs and solve the problems related to the quality of the end product, i.e., contamination by the adsorbent. The result shows that the MAC material improved the quality of PEO by reducing iron ion concentration in the oil from the initial concentration of 194 mg/L to around 87 mg/L. As expected, the adsorbent allows rapid removal from the PEO by using a magnetic source. Based on this study, MAC material enables the reduction of iron ion contamination in PEO and produces a free-adsorbent in the final product.

Mechanochemically activated microscale zero-valent iron with carboxymethylcellulose for efficient sequestration of phosphate in aqueous solution

This study modified microscale zero valent iron (mZVI) using hydrophilic sodium carboxymethyl cellulose (CMC) via mechanical ball milling method, which was donated as CMC-mZVI, and compared the phosphate removal performance of mZVI and CMC-mZVI. Characterization results of X-ray powder diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), EDS-mapping images of CMC-mZVI demonstrated that the dominant crystalline structure of mZVI did not alter significantly after the ball-milling process and CMC could be adsorbed on the surface of mZVI. Further phosphate (PO43-) removal experimental results revealed that the PO43- removal percentage of CMC-mZVI within 360 min was 99.99 %, which was much higher than that of mZVI (75.23 %). Subsequently, this study analyzed the concentration of ferrous ions and total iron ions dissolved by mZVI and CMC-mZVI, compared the high resolution X-ray photoelectron spectroscopy (HR-XPS) of mZVI and CMC-mZVI before and after the phosphate removal, and characterized the affinity of CMC-mZVI (or mZVI) to water by testing the static contact angle between CMC-mZVI (or mZVI) and water. The above results suggested that the existence of CMC on the surface of mZVI could promote the hydrophilic property of mZVI, resulting the enhancement of ferrous ions and total iron ions dissolution by 8 and 8.78 times than that of mZVI, and the rapid co-precipitation of phosphate. This study provided an environmentally friendly and effective method to improve the reactivity of commercial mZVI powder, and contributed to the wide application of mZVI technology in the field of environmental remediation.

THE INFLUENCE OF THE ANODE MATERIAL ON THE COURSE OF COMBINED PROCESSES DURING THE REGENERATION OF SULPHATE-ACID SOLUTIONS

The existing methods of regeneration of sulfo-acidic solutions, which contain iron sulfate, formed after technological operations for the preparation and etching of metal parts at metalworking enterprises are not effective and therefore are not used at Ukrainian enterprises. They are either aimed at sedimentation of the sludge of sparingly soluble iron compounds after neutralization of unreacted sulfuric acid or at dilution of the formed spent sulfo-acid solutions. The electrochemical method of regeneration of such spent sulfo-acid solutions is not properly researched. A feature of the development of technology and equipment for regeneration is a decrease in the content of iron ions and an increase in the concentration of sulfuric acid during the regeneration process. The process of electrochemical regeneration of spent steel etching solutions is characterized by a significant change in the composition of the etching solution and the temperature of the etching process. At the beginning of work, the initial solution of sulfuric acid reaches a concentration of 2.0 mol·dm-3 and does not contain iron (II) sulfate. In the process of digestion, the concentration of sulfuric acid decreases to 0.5 mol·dm-3, and the concentration of iron (II) sulfate increases accordingly. Therefore, the course of the anodic process was studied for the following solution compositions: 0.5 mol·dm-3; 1.0 mol·dm-3 and 1.5 mol·dm-3 H2SO4. Under the conditions of a decrease in the concentration of sulfuric acid, its chemical activity also decreases when interacting with iron oxides and hydroxides. An increase in the temperature of the entire process is used to increase the reactivity of the pickling solutions. The main process at the platinum anode is the release of oxygen in a wide range of current densities and a significant overvoltage of the entire process. Taking into account the obtained voltage-voltage dependences, it can be seen that the current rises when reaching potentials that significantly exceed the standard potential for obtaining oxygen from water. The advantage of the platinum anode is the slight influence of the concentration of sulfuric acid on the kinetics of the anode process. The obtained results were used for comparison with other alternative anode materials. Manganese dioxide was obtained by the method of pyrolysis of a coating solution of manganese monoacid applied to a titanium current lead, which can be represented by reaction (5) of the decomposition of manganese nitrate on a titanium plate. Due to the developed surface, the real current density was more than an order of magnitude lower on the TDMA than on the platinum anode with the same geometric dimensions. A lower current density contributed to a decrease in the steady-state potentials of oxygen release. The current density can be increased by an order of magnitude if surfactants are added to the working solution. A comparison of voltage-voltage dependences on platinum and TDMA indicates that the use of TDMA gives a more significant gain in energy consumption during the regeneration process. Taking into account that the range of current densities of 4-5 A/dm2 was determined for the cathode process according to the research results, the difference in the reduced polarization of the anode on TDMA, compared to platinum, is more than 400 mV, which will significantly reduce costs during unit operation. The use of TDMA is expedient in the galvanostatic mode of operation of the electrode unit for the process of electrochemical regeneration of spent sulfo-acid solutions of steel pickling.

Preparation of ferric oxide powders by ultrasonic‐assisted impinging stream reaction

AbstractIn this paper, Fe3O4 powder was prepared by the chemical precipitation method using impinging stream technology. The influences of feed flow rate, L/D, reactant concentration, ratio of iron ion concentration, reaction temperature, and impact time on the size and distribution of particles were investigated by the orthogonal experiment method. The microstructure and morphology of Fe3O4 powders were characterized by scanning electron microscopy, X‐ray diffractometer, and granulometer. The results showed that when ratio of iron ion concentration c(Fe2+):c(Fe3+) = 0.75, reactant concentration c(Fe3+) = 0.4 mol · L−1, feed flow rate Q = 800 L · h−1, L/D = 3, reaction temperature T = 20°C, impact time t = 50 min, the prepared Fe3O4 had an average particle size of 1.815 μm and the most uniform distribution. The influence of ultrasonic enhancement on the mixing process and powder preparation in an impinging stream reactor was investigated. The size and distribution of the powders were significantly affected by ultrasonic enhancement. With the increase in ultrasonic power, the particle size of the powders decreased and the distribution became narrower. The particle size was reduced by 68.78%, and the particle distribution range was narrowed by 84.34% under ultrasound enhancement. This study promised the effective utilization of ultrasonic cavitation in the optimization of experimental equipment and the preparation of ultrafine powder, which provides a basis for process optimization of powder preparation.

Energy-saving technology for processing of exhausted etching solutions with obtaining of ferromagnetic compounds

Exhausted etching solutions are the waste of industrial enterprises and contain toxic pollutants that have a detrimental effect on the environment. Currently, the processing of these solutions to obtain marketable products is important. The paper presents the results of research on the application of the ferritization method for processing of exhausted etching solutions of steel surfaces. Energy-saving activation of the process by alternating magnetic fields was used, which has undeniable advantages compared to traditional thermal activation. The influence of the initial concentration of iron ions in the reaction mixture of ferritization process and the methods of its activation on the treatment quality of exhausted etching solutions was studied. It was established that the best degree of extraction of heavy metal ions from exhausted etching solutions by ferritization is achieved when the reaction mixture is activated by alternating magnetic fields at an initial concentration of iron ions of 6.6 g/dm3 . At the same time, the residual concentration of iron ions in purified solutions does not exceed 0.03 mg/dm3 , that corresponds to degree of purification of solutions of 99.999%. Those solutions can be reused in situ. The qualitative and quantitative composition of ferritization sediments was studied. Phases of ferroxygite δ-FeOОН, magnetite Fe3O4 and maghemite ɣ-Fe2O3 were detected by X-ray phase analysis in the sediments. It was established that at the initial concentration of iron ions of 26.6 g/dm3 with thermal activation of the reaction mixture and 16.6 g/dm3 with alternating magnetic fields activation, the sediment exclusively contains the magnetite phase. The results of the study indicate the possibility of further use of sediments for the production of important industrial products and materials containing ferromagnetic compounds. The implamitation of improved ferritization process in industrial enterprises will allow to achieve decrease of energy consumption compared to known technologies of exhausted etching solutions processing.