Residual Iron Concentration Research Articles

Applications of Fenton Coagulation for wastewater treatment: a review

The most diverse forms of pollution and contamination, especially from the industrial sector, reinforce the need to optimize industrial processes in the search for reducing waste generated or even creating and improving appropriate techniques for removing organic compounds in solid waste and effluents. Wastewater resulting from chemical processes, in general, has a complex composition and causes environmental problems when not treated appropriately. An efficient proposal for the treatment of effluents of high chemical complexity and high concentration of suspended solids is Fenton Coagulation. This process reconciles the coagulation process with iron ions and reuses the residual iron concentration to apply a subsequent treatment, the Fenton process. Therefore, the objective of this work is to address the hybrid Fenton coagulation process and discuss important aspects of its use for the treatment of effluents.

Role of solution acidity on ferrous ions mineralization process at low temperature of 393.15 K, 408.15 K, and 423.15 K

Here, a clean, low-temperature hematite process using a neutralizer was proposed to remove iron ions from a zinc leaching solution and reutilize iron removal residue. The results showed that the solution acidity played a crucial role in this process. For a ZnSO4 solution with an Fe2+ concentration of 12–14 g/L and an initial pH > 3.0, the iron ion concentration decreased to 20 mg/L within 95 min when using the low-temperature hematite process with pure ZnO (10–13 g/L) added as a neutralizer in the temperature range of 408.15–423.15 K. The iron removal efficiency reached 99%. Increasing the initial pH of the initial solution significantly improved the iron removal efficiency, and it was necessary to control the pH above 3.0. After ferrous ion mineralization, the residual iron concentration in the solution was inversely proportional to the final pH. The precipitated hematite products contained an Fe content of >55%, with a Zn loss of <1% and S contamination level of <3%. These hematite products can be sold as raw materials for ironmaking to solve the environmental issues associated with the storage of iron removal residue. The results showed that zinc oxide dust could not be used as a neutralizer because it resulted in the loss of valuable metals such as Pb, Ag, and In. Compared with the hematite process (453.15–473.15 K, reaction time of 3.0 h) used by the Iijima Refinery of Akita Zinc Co. in Japan, the ferrous ion mineralization in this study was shortened to <100 min. This significantly increased the treatment capacity of the low-temperature hematite process for zinc leaching solutions. The low-temperature hematite process could be performed at 393.15 K, 408.15 K, and 423.15 K, which can realize energy savings and consumption reduction.

REMOVAL OF IRON COMPOUNDS FROM MECHANICAL FILTERS HOUSEHOLD REVERSE OSMOTIC SYSTEMS WATER PURIFICATION

Today, the most convenient and widespread option for cleaning and purifying drinking water is to install reverse osmosis systems directly at the water intake points. However, the use of reverse osmosis systems has disadvantages associated with the frequent need to replace their elements. The article discusses the competitiveness of negative impact on the environment of reverse osmosis systems and ways to regenerate filters with the possibility of their reuse. Currently, there are no companies or organizations in Ukraine that would collect and dispose of such filters. This direction is undeveloped. There are practically no corresponding data in the scientific literature. If you take into account the fact that, according to our calculations, about 88,000 domestic reverse osmosis systems are in use today in Kyiv alone, it is easy to calculate that 176,000 polypropylene cartridges with a total volume of 105 m3 of polypropylene enter the environment during the year. &#x0D; The article presents method of regeneration of mechanical filters from iron compounds and other harmful impurities deposited on the surface and pores of the filter during operation. Studies of the jet sulfuric acid as a cleaner have confirmed its effectiveness and sufficient safety for further processing of cleaning products as an additive to cement. To establish the minimum residual concentration of iron in the mother liquor, a cycle of experiments was conducted and it was established that pH 4.0-4.5 can be considered optimal, at which the content of iron ions is at the level of their content in drinking water. There was made an estimation of acid. Technologies of large-scale cleaning used filters can be beneficial and cost-effective..&#x0D; The results of the experimental study make it possible to develop a treatment plant with an automated system for dosing acid and measuring acidity.

Removal of Arsenic(III) from Water with a Combination of Graphene Oxide (GO) and Granular Ferric Hydroxide (GFH) at the Optimum Molecular Ratio

The occurrence of arsenic in water is a global problem for public health. Several removal technologies have been developed for arsenic removal from water, and adsorption onto iron oxy-hydroxides is the most widely used technique. Granular ferric hydroxide (GFH) has been used mainly for As(V) removal, but it has the disadvantage that it can create a problem with the residual concentration of iron in the water. Moreover, graphene oxide (GO), which contains a large amount of reactive oxygen, exhibits high adsorbing capacity. In this study, the combined use of GO and GFH as adsorbent materials in different molar ratios was investigated in order to achieve the maximum As(III) removal from aqueous solutions. The effect of the adsorbent’s dosage, pH value, contact time, initial As(III), and different molar ratios of GO/GFH was examined. As depicted, the presence of GFH enhances the use of GO. In particular, the molar ratio of GO/GFH 2:1 (i.e., 0.2 g/L GO and 0.1 g/L GFH) is chosen as optimal at pH value 7.0 ± 0.1, while the removal percentage increased from 10 % (absence of GFH) to 90% with the simultaneous addition of GFH. Freundlich isotherm and pseudo-second-order kinetic models described the experimental data adequately and the highest adsorption capacity that was achieved was 22.62 μg/g.

Research of the Process of Purification of Sulfate Zinc Solution from Iron Ions Using Anodic Oxidation

The possibility of using a membrane electrolytic cell for the electrochemical oxidation of Fe(II) and purification from impurities of real industrial solutions obtained by atmospheric leaching of low-grade zinc concentrates is considered. The average indicators for carrying out the electrooxidation process are given. The principal possibility of conditioning a zinc sulfate solution by hydrolytic purification with preliminary oxidation of iron in a membrane electrolytic cell with an anion-exchange membrane MA-41 TU 2255-062-05761695-2009 is considered. Carrying out direct electrooxidation of iron (II) in sulfate zinc solutions in the anode chamber of a flow membrane electrolyzer ensures good filterability of precipitates after hydrolytic precipitation of iron, since this solution does not contain Fe(II) ions, the presence of which leads to significant difficulties in the operations of separating solid and liquid phases. This makes it possible to exclude the thickening operation from the technological scheme. The degree of oxidation of iron during the test period was 99.8–99.9%. The residual concentration of iron after precipitation from solutions obtained after electrochemical oxidation in the form of oxide and hydroxide compounds was less than 0.01 g/dm3.

Integrated photo-Fenton and membrane-based techniques for textile effluent reclamation

The complexity of textile effluents demands innovative treatment capable to promote the water reuse and by-products recovery. Taking this into account, an advanced oxidation process (AOP, photo-Fenton) was combined with microfiltration (MF) and nanofiltration (NF) in two distinctive processes: (1) MF-NF-AOP(c) and (2) MF-AOP-NF; aiming for the NF concentrate treatment in the first, and as a NF pre-treatment in the second. The MF was able to reject > 99.1% of the indigo blue, which can be reused in the dyeing process. The AOP applied to MF permeate had a higher COD degradation (78%, compared to 69% when applied to NF concentrate treatment), but the residual iron content resulted in a pronounced concentration polarization effect in the NF. Due to that fact, the NF in the second treatment systems had a higher fouling rate and lower permeate flux (average value: 19 L/m2h) compared to the first (average value: 38 L/m2h). In both cases, the residual iron concentration in the NF concentrate and in the AOP effluent prevented their reuse. However, the NF permeate from both treatment processes can be considered for yarn washing-off and equipment washing down. Furthermore, for the combination MF-NF-AOP(c), the NF permeate met the requirements to be recycled back to the process. The better performance of the first system (MF-NF-AOP(c)) in textile wastewater treatment was reassured by its lower operating expenditure (0.421 US$/m3) compared to MF-AOP-NF (0.736 US$/m3). Overall, the treatment combining MF-NF-AOP(c) was considered the most cost-effective alternative for textile wastewater treatment reuse.

Treatment of mature landfill leachate by electrocoagulation followed by Fenton or UVA-LED photo-Fenton processes

The main objective of this study is to optimize a two-step treatment for mature landfill leachate consisting of electrocoagulation (EC) followed by Fenton or UVA-LED photo-Fenton processes aiming to provide a more efficient and feasible alternative treatment strategy that also increases biodegradability and decreases conductivity. Although 5 mA cm−2 EC is cheaper than 10 mA cm−2 EC per kg of removed COD (0.63 vs. 0.89 € kgCOD−1), it achieved the half total COD removal (13% compared to 26%), and the low residual iron concentration (100 mg L−1) that remained at the end of the process made necessary a long treatment time to perform the posterior Fenton (48 h) or UVA-LED photo-Fenton (6 h) process. When EC was performed at 10 mA cm−2, the residual iron concentration (220 mg L−1) was high enough to reduce treatment time by one half for both Fenton processes. Consequently, treatment cost decreases from 5.91 to 3.48 € kgCOD−1 for the EC + UVA-LED photo-Fenton ([H2O2]/COD = 1.063) treatment combination; whereas it slightly decreases from 1.68 to 1.61 € kgCOD−1 for the alternative EC + conventional Fenton combination. In both cases, total COD removal was around 87%. In addition, SUVA removal was >40%, conductivity was reduced about 20–30%, and biodegradability (BOD5/COD) increased over 0.3.

Residual Concentration of Lead, Iron and Calcium in Chicken Meat Paste: Indicative Parameters for Identifying Deboning Procedure and Health Risk Assessment

Residual Concentration of Lead, Iron and Calcium in Chicken Meat Paste: Indicative Parameters for Identifying Deboning Procedure and Health Risk Assessment

Assessing desalination pretreatment conditions towards pilot scale‐up using Box‐Behnken experimental design

AbstractThe purpose of this study is to optimize the operating conditions in batch mode using Box‐Behnken Design (BBD), for the coagulation‐flocculation line sizing prior the sand filter in the pilot scale. Three coagulants were employed to achieve a high turbidity removal with a low concentration of residual metals. The results showed that the best turbidity removal was obtained with FeCl3. Using BBD (15 experiments), the optimal parameters were: coagulant dose = 5.5 mg FeCl3/L, slow stirring time = 33 min and slow stirring velocity = 45 rpm, in these conditions, the turbidity removal reached 94.89% and the residual iron concentration was 0.449 mg/L. Regarding the model fit, the obtained R2 values were 99.67% for turbidity removal and 99.47% for residual iron concentration. The optimum conditions obtained from this study could be scaled up and applied to desalination plants. BBD approach is of great interest because it allows the prediction of the response value without performing experiments.

Simultaneous Removal of Arsenate and Chromate from Ground- and Surface- Waters by Iron-Based Redox Assisted Coagulation

Arsenic (As) and chromate (Cr(VI)) contamination of ground and surface waters is a major problem worldwide. Given that a new drinking water limit is anticipated for Cr(VI) and that the limit of arsenic in drinking water is quite low (10 μg/L), there is an urgent need for evaluating technologies that could be efficient for removal of both contaminants simultaneously. In this work, the use of Fe(II) redox assisted coagulation was investigated to simultaneously remove the contaminants of interest. The basic principle of this technology is that Fe(II) could react with Cr(VI) and form Fe(III)-hydroxides and insoluble Cr(III) species, while the freshly formed Fe(III) hydroxides are very efficient adsorbents for As(V). The effect of pH, the water matrix composition, Fe(II) dose, initial contaminant concentrations, NOM presence and phosphate concentration were the examined parameters. The results revealed that with a dose of 2 mg/L Fe(II), residual As(V) and Cr(VI) concentrations were both below 10 μg/L, from initial concentrations of 50 μg/L. Though, this is effective only at circumneutral pH values. This is however not a big obstacle, since most natural waters, especially groundwaters, have near neutral pH values. At these pH values, residual iron concentration was far below 200 μg/L. The presence of phosphate anions inhibited As(V) removal but had no effect on Cr(VI) removal. Increasing Fe(II) concentrations eliminated the effect of phosphate and provided simultaneous phosphate removal. Therefore, Fe(II) coagulation can be applied, with secured results, for simultaneous As(V), Cr(VI) and phosphate removal from waters.

Modified activated carbon for deironing of underground water

Successful water treatment is one of the most important aspects for a healthy human life and environmental protection. This study deals with the investigation of a modified catalytic material that is used in water treatment as one of the most promising filter media for water deironing. The activated carbon granules were coated with iron oxide by solution combustion synthesis (SCS) method in a muffle furnace oven. We investigated obtained samples using different diffraction and spectroscopic methods. The elemental composition of the surface and phases of produced materials and the results of comparative analysis with initial samples of the raw material used for the underground water deironing were presented. Using the SCS method, active coal granules were modified with a formation of fine dispersed and crystalline structures of magnetite on their surface. This had a positive effect on the catalytic capacity of the material for deironing of underground water as well as for the specific surface area increase. The residual concentration of total iron in the first portions of the filtrate when using modified samples was almost 3 times lower than for initial material.

Coagulation and dissolved air flotation as a harvesting method for microalgae cultivated in wastewater

Microalgae harvesting is the major bottleneck for biomass production on a large-scale. In this study, coagulation followed by dissolved air flotation (DAF) was used as a harvesting method for Chlorella sorokiniana cultivated in wastewater. The harvesting performance was evaluated using four coagulants (aluminum sulphate, ferric chloride, Tanfloc SG and Zetag 8185) usually used in water or wastewater treatment. All coagulants tested showed high flotation efficiency at different conditions of dosage, pH and flotation velocity. The optimal doses were 10 mg L−1 Zetag 8185; 75 mg L−1 Tanfloc SG; 500 mg L−1 Al2(SO4)3, and 1000 mg L−1 FeCl3 at pH 7, which showed the maximum efficiency of 98.4, 94.5, 95.4, 96.7% at 8 cm·min−1, respectively. Moreover, the photobioreactor effluent quality significantly improved after harvesting tests using the optimal doses. High removal was reached for turbidity (93.7–96.2 %), apparent color (91.7–92.3 %), TKN (90.2–92.6%), total phosphorus (89.4–90.9 %) and TSS (88.6–92.5 %). The use of metal salts requires caution due to the high residual concentration of iron and aluminum in the final effluent.

Potabilidade da água de poços artesianos: diagnóstico de amostras dos municípios do Rio Grande do Sul

A água potável é toda água própria para consumo. Deve ter certa quantidade de sais minerais dissolvido, estar livre de materiais tóxicos e micro-organismos. É considerada um recurso indispensável ao homem. Um dos principais problemas está relacionado à contaminação da água, ou seja, este recurso vem sendo poluído de tal maneira que já não se pode consumi-lo em seu estado natural. Contudo, apesar de todos os esforços para armazenar e diminuir seu consumo, está se tornando um bem escasso e sua qualidade se deteriora cada vez mais rápido. Dessa forma, as águas subterrâneas vêm se constituindo como uma importante alternativa para abastecimento hídrico de comunidades. Considerando a relevância deste tema, este estudo busca fazer um diagnóstico da qualidade da água de poços artesianos da Região Central do Estado do Rio Grande do Sul, a fim de comprovar a potabilidade perante aos parâmetros da legislação vigente. Para isto os procedimentos experimentais realizados foram: determinação do valor de pH; turbidez; temperatura; sólidos totais dissolvidos; cor; dureza e concentração residual de ferro. A avaliação dos resultados obtidos neste estudo foi baseada nos padrões de potabilidade estabelecidos na Portaria nº 518, de 25 de março de 2004, do Ministério da Saúde.

A sequential process to treat a cashew-nut effluent: Electrocoagulation plus electrochemical oxidation

The treatment of a real cashew-nut effluent has been studied using a pioneering sequential process involving electrocoagulation (EC) and electrochemical oxidation (EO) approaches. The performance of the system was analyzed in terms of chemical oxygen demand removal, by-products evolution, toxicity and energy consumption. Preliminary EC tests with Fe electrodes were performed at different current densities (8.33–100mAcm−2), yielding COD removals among 17–51%. The residual iron concentration detected was below the Brazilian legal limits of discharge. The sludge obtained from the experiments at 8.33 and 100mAcm−2 revealed a heterogeneous morphology with interconnected laminar plates. Regarding their structure, the powders showed a mixture of poorly crystalline phases. The main elements identified were oxygen, carbon and iron, which allow proposing an alternative use of this powder for construction and building materials. Sequential experiments, using EC at 8.33 or 100mAcm−2 plus EO, intensified COD removals up to 51% and 80%, corresponding to 5 and 65kWhm−3 of energy consumption, respectively. To evaluate the by-products generated during EO treatment, the evolution of carboxylic acids and inorganic species (PO43−, NH4+, NO3−, NO2−) was followed. After that, phytotoxicity analyses were performed in order to assess water quality and its reuse in irrigation activities. Based on these results, the sequential experiment with EC by applying 8.33mAcm−2 plus EO (35.5mAcm−2) was considered the most efficient and viable to depurate the real cashew-nut effluent.

The disinfection and natural organic matter removal performance of electro-synthesized ferrate (VI)

This study investigated the efficiency of electro-synthesized ferrate (VI) on the degradation of humic acid (HA) and removal of E. coli for different samples. For providing complete inactivation of E. coli, >1.5mgL−1 ferrate (VI) concentration should be applied for only E. coli containing samples. For only HA containing sample, 60% DOC removal was achieved with 25mgL−1 ferrate (VI). Ferrate (VI) was found to be more efficient at initial pH of 7 (pHi). For HA/E.coli containing samples, ferrate (VI) concentration should be increased to 260mgL−1 for complete inactivation of E. coli. Specific UV absorbance (SUVA) values of raw samples showed that the samples mostly consist of high molecular weight and high hydrophobicity. After the treatment by ferrate (VI); while almost all hydrophobic part was removed, a small portion of hydrophilic part was also removed for only HA containing sample. However, for treated HA/E. coli containing sample, the aromatic removal took place but lower and higher molecular weights of NOM was still in the media in the presence of bacteria. The electro-synthesized ferrate (VI) lowered the trihalomethane formation potential. The residual total iron concentration was 1.14mgL−1 at 1min of process time and then remained stable. This means that ferrate (VI) was consumed as soon as it was applied and reduced to Fe+3/Fe+2.

Removal of ferric hydroxide by flotation with micro and nanobubbles

Abstract This work presents results on the removal of Fe 3+ ions as precipitates and nanoparticles of Fe(OH) 3 , at pH 7, by nanobubbles (NBs) and by dissolved air flotation (DAF), a process which combines microbubbles (MBs) and NBs. DAF is a very well-known technology in the treatment of water and wastewater. Studies were conducted at low and high levels of saturation pressures (P sat of 2 and 4 bar) and with “isolated” (single) NBs. The latter were generated at 2.5 bar, after their separation from the MBs. Best results were obtained with flotation at 2 bar, when the concentration of MBs was low and NBs very high. The removal efficiency was 99% of the feed iron content (30 mg L −1 ), and the treated water had a residual total iron concentration of 0.3 mg L −1 and a turbidity of 0.6 NTU (95% reduction). The flotation at 4 bar (mostly by MBs) was faster (0.07 cm s −1 ) due to the high lifting power of the MBs but left a higher residual total iron content of 1.7 of mg L −1 . The flotation with isolated NBs (>10 8 bubbles mL −1 ) attained 91% iron removal due to “floatation” following NBs entrapment and the decrease of the relative density of the aggregates. Flotation of the nanoparticles with NBs was also studied and showed a removal efficiency of about 68%, considered high, for this difficult-to-separate system. All mechanisms involved were discussed in terms of physical, chemical and interfacial phenomena. It is believed that the combination of NBs and MBs has an excellent potential for future separation of particles, including nanoparticles, and will help to broaden applications in removing specific target pollutants from waters and wastewaters.

Use of Novel Composite Coagulants for Arsenic Removal from Waters—Experimental Insight for the Application of Polyferric Sulfate (PFS)

In the present study, several pre-polymerized coagulants of iron and aluminum were tested for their efficiency towards As(V) and As(III) removal from water sources. The results showed that the pre-polymerized coagulants of iron, such as poly-ferric sulfate and poly-ferric silicate chloride, were very efficient for As(V) removal. With regard to As(III) removal, among all examined coagulants, including the conventional ferric chloride, only the poly-ferric sulfate (PFS) was able to reduce As(III) to concentrations below the drinking water regulation limit of 10 μg/L. In contrast, all tested composite coagulants based on aluminum were not capable of removing efficiently both species of arsenic. PFS addition in water containing 4 mM of alkalinity and 25 μg/L of As(V) and As(III) (i.e., total arsenic concentration 50 μg/L) resulted in finished water with less than 5 μg/L arsenic, only by dosing 5 mg Fe-PFS/L at pH 7, whereas, simultaneously, the residual iron concentration was found well below its drinking water regulation limit of 200 μg/L. The use of PFS could provide a viable alternative for As(III) and As(V) removal at household treatment level for application in vulnerable communities, without the need of any additional treatment, such as oxidation of As(III) to As(V).

Evaluation of the electrode wear and the residual concentration of iron in a system of electrocoagulation

In this study, we evaluated the wear and tear experienced by electrodes and the residual concentration of iron in a system of electrocoagulation using effluent from a dairy industry. The experimental module was composed of iron electrodes, a 10 A source of direct current, and a 1,000 mL beaker. The tests were conducted with and without polarity inversion through the following variables: pH 4.5, time 60 min, and an electric current intensity of 1.5 A. In polarity inversion tests, the mass consumed in the electrode showed an average value of 0.2412 g/L of iron and residual iron presented a mean value of 2.10 mg/L. The treatment efficiency was 99% for turbidity, 95% for COD, and 90% for color. In the tests without polarity inversion, the wear of the electrodes was lower due to the effect of passivation, but residual iron presented high levels of concentration reaching 57.5 mg/L. Treatment efficiency was lower, mainly due to the reduction of color. The treated effluent presented reddish-brown color in some tests.

Separation of Fe&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; Nanoparticles from Water by Sedimentation in a Gradient Magnetic Field

Sedimentation dynamics of magnetite (γ-Fe3O4) nanopowders (10 - 20 nm) in water in the presence of a gradient magnetic field was studied by optical and Nuclear Magnetic Resonance (NMR) relaxometry methods. The magnetic field B ≤ 0.3 T, dB/dz ≤ 0.13 T/cm was produced by the system of permanent strip magnets. The initial sedimentation rate of the nanoparticles in water and under magnetic fields is higher for less concentrated suspensions (c0 = 0.1 g/l) than for more concentrated ones (c0 = 1 g/l). This might be connected with the formation of gel structures due to strong magnetic attraction between ferromagnetic nanoparticles. In the gravitation field, the suspensions of the particles (10 - 20 nm) remain stable for over 20 hours. The sedimentation process can be greatly accelerated by the action of a vertical gradient magnetic field, reducing the sedimentation time down to several minutes. In a gradient magnetic field enhanced by a steel grid, sedimentation of the nanopowder (c0 = 0.1 g/l) for 180 minutes resulted in reduction of the iron concentration in water down to 0.4 mg/l. In flowing water regime, the residual iron concentration in water 0.3 mg/l is reached after 80 minutes.

The effectiveness of polyaluminum ferric chloride (PAFCl) for turbidity and color removal from Isfahan raw water

In this study the performance of polyaluminum ferric chloride, a composite inorganic polymer of aluminum and ferric salt, was investigated for the removal of turbidity and color from Isfahan raw water. Water samples were collected from the main resource of Isfahan raw water. For the evaluation of the coagulation procedure, conventional Jar test apparatus was used according to the standard methods. Experiments were conducted in the School of Public Health, Isfahan University of Medical Science. The findings showed that the optimum pH for the coagulation of Isfahan raw water at August 2013 was 7.5–8 and the optimum dosage of the coagulant was 5 mg/L. Without filtration, the removal of turbidity, color and total coliform achieved was 85, 100, and 86%, respectively, at the above-mentioned dosage and pH. Residual turbidity, color, and UV254 dropped below 0.33 NTU, zero Pt.Co Units, and 0.022 cm−1, respectively. As, the residual concentration of aluminum and iron in treated water was 0.008 and 0.05 mg/L, respectively, this coagulant does not has any adverse health effect on consumers. The efficiency of this coagulant for the removal of turbidity, color, and organic matter in Isfahan raw water was very good and it has potential for selecting as a new coagulant for this city.