Acidic Chloride Solutions Research Articles

The Contribution of Galvanic Coupling with Tin, Tialn, and Crn to the Corrosion of Steel in Neutral and Acidic Chloride Solutions

The Contribution of Galvanic Coupling with Tin, Tialn, and Crn to the Corrosion of Steel in Neutral and Acidic Chloride Solutions

COUPLED SOLUBILITY OF Cu and Ag IN CHLORIDE-BEARING HYDROTHERMAL FLUIDS (350-650 °С, 1000 - 1500 BAR)

The coupled solubility of Cu(cr) and Ag(cr) was measured in acidic chloride solutions at 350 °С/1000 bar, 450 °С/1000 bar and 653 °С/1450 bar in a wide range of chloride concentrations (0.02m HCl + (0-15m) NaCl). The experiments were performed using autoclave (350, 450 °С) and ampoule (653 °С) techniques, the dissolved metal concentrations were measured after quenching the experimental system. The equilibrium constants of the reaction combining the dominant forms of transport of the metals are determinedCu(cr) + AgCl2- = Ag(cr) + CuCl2- K°(Cu-Ag) . The calculated reaction constant is independent of chloride concentration. It is known that AgCl2- predominates in the studied chloride concentration range. Therefore, the main cupper form of occurrence is CuCl2- in all experimental fluids with chloride content up to 47 wt.%, which is close to the NaCl saturation limit. The constant of the coupled Cu and Ag solubility was determined for the experimental PT-parameters as lg K°(Cu-Ag) = 2.65±0.20 (350 °С/1000 bar), 2.28±0.10 (450 °С/1000 bar), 1.49±0.34 (653 °С/1450 bar). These data, together with values from the literature for temperatures from 200 to 900 °С and pressure up to 2000 bar were fitted to the density model equation: lg K°(Сu-Ag) = 1.066 + 1.108∙103∙T(K)-1 + 3.585lgd(w) – 1.443∙lg d(w)103T(K)-1, where d(w) is the pure water density. According to these data, copper is much more soluble in chloride solutions compared to silver, but the difference in the solubility decreases with the temperature increase. Reliable literature data on the silver solubility constant allow to calculate the copper solubility oneCu(к) + HCl° + Cl- = CuCl2-+ 0.5H2(р-р) K°(Cu) ,lg K°(Cu) = 1.39±0.20 (350 °С, 1000 bar), 1.91±0.10 (450 °С, 1000 bar), 2.06±0.34 (653 °С, 1450 bar). The new values of K°(Cu) are combined with reliable literature data to calculate the density model parameters. The obtained density model equation can be used to calculate the copper solubility constant up to 800 °C and pressures to 2000 bar: lg K°(Сu) = 6.889 – 3.298∙103∙T(K)-1 + 8.694∙lg d(w) – 4.807∙lg d(w)∙103∙T(K)-1. The solubility of chalcopyrite in the system with mineral buffer assemblages pyrite-hematite-magnetite and K-feldspar-muscovite-quartz is discussed.

The effect of tartrate on the mild leaching of low-grade polymetallic complex chalcopyrite ore in acidic ferric chloride solution

The mild leaching of low-grade polymetallic complex chalcopyrite ore (LPCCO) is of great significance, but is limited by the passive film.

Nanostructured Co-doped BiVO4 for efficient and sustainable photoelectrochemical chlorine evolution from simulated sea-water.

The co-production of hydrogen and chlorine from sea-water splitting could be a potential, sustainable and attractive route by any method. However, challenges to overcome are many, and critically, the sustainability and operating potential of the electrocatalyst are important. In this work, we report on Co-doping in the BiVO4 (Co-BV) crystal lattice and employed the same as the photoanode; Co-BV exhibits a photocurrent of 190 μA cm-2 at 1.1 V vs. RHE (the reversible hydrogen electrode) in the acidic sodium chloride solution (pH 2.3) under one sun illumination. The best-performing photoanode, with 0.05 mol% of Co doping (0.05 Co-BV), selectively produced active chlorine with 92% faradaic efficiency at 1.1 V vs. RHE by successfully suppressing the kinetically sluggish oxygen evolution reaction (OER) and the stability of the catalyst was demonstrated for up to 20 h. This is the lowest operating potential reported for the chlorine evolution reaction (CER), thus far. The overpotential required for CER with 0.05 Co-BV is lower than that of OER, which leads to selective CER at 1.1 V (vs. RHE). Co-doping into the BiVO4 lattice decreases the charge transfer resistance and enhances the CER kinetics due to its structural and electronic integration with the BV lattice. We demonstrate that Co-doping also improves the lifetime of the charge carrier and enhances the current density of CER and sustainability of the catalyst.

Efficacy of natural and consumer-friend applications to control Aeromonas hydrophila growth in Bluefish

Fish is one of the main transmission routes of Aeromonas (A.) hydrophila, an emerging pathogen that threatens public health due to its high antibiotic resistance. This study aimed to control the growth of A. hydrophila in cold-stored Bluefish (Pomatomus saltatrix) using natural, consumer-friendly practices. Samples were inoculated with A.hydrophila, dipped or sprayed with acetic acid, citric acid, ascorbic acid, sodium lactate, or sodium chloride solutions (4%), and stored at 4°C. Dipping was very effective since the growth of A. hydrophila was inhibited by all dipping treatments and remained below the inoculation dose after 72 hours. During this time, dipping in acetic acid, ascorbic acid, and citric acid reduced the initial load of A. hydrophila (7.03 log cfu/g) to 5.27, 5.51, and 5.64 log cfu/g, respectively. Acetic acid, ascorbic acid, and citric acid dipping treatments reduced the A. hydrophila number 1 log/cfu more than other treatments (P<0.05). Acetic acid and ascorbic also provided the best results for the sprayed samples. Our results showed that dipping in natural acids such as acetic acid, ascorbic acid, and citric acid yielded successful results in inhibiting A. hydrophila growth. Using consumer-friendly, natural substances to ensure food safety by controlling the growth of this emerging pathogen will provide significant benefits for the food industry.

Theoretical Analysis of the pH Dependence of Evolution of the System Composition in the Course of Electrolysis of Acidic Aqueous Chloride Solutions

Theoretical Analysis of the pH Dependence of Evolution of the System Composition in the Course of Electrolysis of Acidic Aqueous Chloride Solutions

Corrosion Behavior of Sensitized AISI 304 Stainless Steel in Acid Chloride Solution.

Corrosion resistance of sensitized austenitic stainless steel (SS) in chloride environments is currently the subject of numerous studies. Most of them are focused on neutral chloride solutions at room temperature and the experiments are carried out on ground stainless steels surfaces. This paper deals with the corrosion behavior of sensitized AISI 304 stainless steel in acid 1 M chloride solution (pH = 1.1) at the temperatures of 20 ± 3 °C and 50 °C. The specimens after sensitization are tested as covered by high-temperature surface oxides ("heat tinted"), and also after their chemical removal to assess the impact of the surface state on corrosion resistance. Potentiodynamic polarization (PP) and exposure immersion test are used as the independent corrosion tests. Microstructure before/after exposure immersion test is evaluated by optical microscopy (OM) and SEM. The results obtained showed that sensitization significantly conditions corrosion regardless of the removal of high-temperature oxides, and the elevated temperature mainly acts as its accelerating factor.

Electrodeposition of Ni-Co-Fe-P Alloy Coating on Q345 Steel Welded Joint and Its Corrosion Resistance in Acidic Chloride Solution

Electrodeposition of Ni-Co-Fe-P Alloy Coating on Q345 Steel Welded Joint and Its Corrosion Resistance in Acidic Chloride Solution

Catalytic selective separation of chloride ions from acidic wastewater

A new two-step technique was developed for selective separation of chloride ions from acidic aqueous solutions. The process is operated at ambient temperature and pressure, and it is powered by H2 gas and atmospheric oxygen. The Pt-Ag-AC catalyst comprises activated carbon (AC) loaded with platinum (Pt) nano size crystals and metallic silver (Ag) particles. The aeration of acidic chloride solution results in the oxidation of Ag0 to Ag+, which in turn reacts with chloride ions to form an insoluble AgCl precipitate on the catalyst. The regeneration of the Pt-AgCl-AC is performed by hydrogenation, that leads to reduction of AgCl into Ag0, followed by the release of Cl− ions. The process was studied in a batch mode system using acidic NaCl-H2SO4 solutions (500 mgCl/L, [H2SO4]0 = 0.5 M) and Pt-Ag-AC made of granular activated charcoal. The carbon was loaded with 0.5 %Pt and 3.22, 6.25 or 9.09 % of metallic silver. A maximal chloride adsorption capacity of 16.31 mgCl/g was recorded. Full (100 %) separation of Cl− ions from NaCl solutions with [Cl−]0 = 200 mg/L and [H2SO4]0 = 0.5 M was demonstrated.

Synthesis and Characterization of the Mixed Metal Oxide of ZnO-TiO2 Decorated by Polyaniline as a Protective Film for Acidic Steel Corrosion: Experimental, and Computational Inspections.

In this work, the preparation, characterization, and evaluation of a novel nanocomposite using polyaniline (PANi) functionalized bi-metal oxide ZnO-TiO2 (ZnTiO@PANi) as shielding film for carbon steel (CS)-alloy in acidic chloride solution at 298 K was studied. Different spectroscopic characterization techniques, such as UV-visible spectroscopy, dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) approaches, as well as other physicochemical methods, such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and field emission scanning electron microscope (FESEM), were used to describe the produced nanocomposites. The significance of these films lies in the ZnO-TiO2 nanoparticle's functionalization by polyaniline, a material with high conductivity and electrochemical stability in acidic solutions. The mechanistic findings of the corrosion inhibition method were obtained by the use of electrochemical methods including open-circuit potentials (OCP) vs. time, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The results indicate that the synthesized ZnTiO@PANi is a powerful acidic corrosion inhibitor, and its inhibition effectiveness is 98.86% in the presence of 100 ppm. Additionally, the charge transfer resistance (Rp) value augmented from 51.8 to 432.7, and 963.7 Ω cm2 when the dose of PANi, and ZnTiO@PANi reached 100 ppm, respectively. The improvement in Rp and inhibition capacity values with an increase in nanocomposite dose is produced by the nanocomposite additives covering a larger portion of the surface, resulting in a decrease in alloy corrosion. By identifying the probable regions for molecule adsorption on the steel substrate, theoretical and computational studies provided significant details regarding the corrosion mitigation mechanism. The possibility of substituting old poisonous small substances with inexpensive and non-hazardous polymeric materials as shielding layers for utilization in the oilfield sectors is an important suggestion made by this research.

Assessing the efficacy of non-destructive testing methods to detect pitting corrosion

ABSTRACT Calibration of the non-destructive testing (NDT) methods for pipeline inspections is commonly done via machined defects with simple shapes and known sizes. However, such defects do not represent, e.g. an actual pit morphology observed in the field, which could lead to the unreliable interpretation of the inspection results. This work proposed a systematic approach to create and characterise real pits in stainless steel pipe specimens to assess the sensitivity of selected NDT methods. Pipe samples with three different diameters and thicknesses were used. Pits of different geometries and dimensions were generated by electrochemical methods, and immersion in an acidic ferric chloride solution filled in pre-drilled holes on the external surface of the specimens. NDT methods including radiography, Eddy current and dye penetrant testing were used for detecting and sizing the pits. The results were then compared with true pit depths obtained from cross-section analysis. Radiography and Eddy current methods failed to detect small pits with depths less than 70 µm. The porous metal cover on the pit mouth affected the detectability of radiography, while it had little impact on Eddy current testing. The findings of this investigation could be used to design training and calibration blocks for NDT methods.

Formation and Long-Time Exposure Aging of Oxides on Ni-Cr and Ni-Cr-X (Mo, W) Alloys in Acidic Chloride Solutions: Ramifications Towards Local Corrosion Resistance

Ni-Cr-based alloys are considered amongst the most corrosion-resistant when utilized in aqueous marine applications. The superior corrosion resistance of these alloys is known to depend on the presence of a homogeneous solid solution and the desirable attributes of their oxide films. However, the scientific basis for excellent passivation and protection against localized corrosion initiation remains uncertain and insights are often based on short term laboratory testing under limited conditions even though exposures are long-term. The engineering basis for alloy choice often relies on lab testing, field exposures or empirical metrics such as the PREN that do not even consider exposure time. Both highly engineered legacy and emerging alloys lack information on the precise attributes of protective passive films after long-time exposures. However, relevant field exposure periods are nearly infinite in time.The focus of the current work was on solid solution Ni-22Cr, Ni-22Cr-6Mo, and Ni-22Cr-6Mo-3W alloys. Potential step passivation studies in 0.1 NaCl pH 4 solutions in the passive range were investigated over 10s to 10 days at select potentials. To characterize the formation and exposure aging of oxide films, electrochemical methods were used as well as XPS and three-dimensional APT. Improvements in passive films protectiveness was correlated Cr3+ enrichment and aliovalent cation accumulation (Figure 1), and minimal morphological roughening. There is possibility of either oxide doping and/or phase separation promoted by aliovalent cations associated with alloying with Mo and W. Ni2+ rich oxides and hydroxides were preferentially dissolved with time. The most corrosion resistant alloys possess passivating films that are efficacious not only just after formation, but that self-healing capabilities and improve over long exposure times as evident from impedance spectroscopy and metastable pit studies. Such alloys were observed to be the most resistant when interrogated for local corrosion after various periods of exposure compared to other alloys whose impedance response degraded over exposure time. The latter alloys eventually arrived at conditions favoring breakdown.This work contributes to the scientific understanding of the long-term passivation process in Ni-based alloys in acidic chloride-containing environments. The presence of Mo and W as minor alloying elements on aqueous passivation and localized corrosion resistance initiation and stabilization correlated with certain features of electrochemically grown oxide films. Oxide exposure aging time, potential, and oxide “transformation” diagrams are introduced and shown to provide valuable insights on alloy. Passivated films may form as solute captured solid solutions after short term passivation or when grown quickly but are gradually enriched in Cr, Mo and W over long time. Can such Cr enrichment continue during exposure without limits? Factors affecting and limiting Cr enrichment are discussed as time allows.This work was supported by the Office of Naval Research under MURI “Understanding Atomic Scale Structure in Four Dimensions to Design and Control Corrosion Resistant Alloys” through Northwestern University #SP0028970-PROJ0007990-MURI ONR N00014-16-1-2280. Figure 1

Cathodic Boronitrocarburising and Anodic Polishing of Mild Steel 20 in Electrolitic Plasma

The paper discusses a possibility of increasing the wear and corrosion resistance of a low carbon steel surface after cathodic plasma electrolytic boronitrocarburising in a solution of boric acid, glycerin, and ammonium chloride, with the subsequent anodic plasma electrolytic polishing in an ammonium sulfate solution due to the formation of a modified structure consisting of a dense oxide layer and a diffusion layer below it, which contains up to 0.87% carbon, 0.80% nitrogen, and 0.87% boron upon reaching microhardness up to 970±20 HV. The competitive influence of the surface erosion under the action of discharges and high-temperature oxidation on the morphology and roughness of the surface is revealed. A positive effect of reducing the surface roughness during the formation of a dense oxide layer on the surface and a hardened diffusion layer under it on reducing the friction coefficient and mass wear, as well as reducing the roughness and additional oxidation of the surface during polishing on reducing the corrosion current density, has been established.

Alkaloid content and taste profile assessed by electronic tongue of Lupinus albus seeds debittered by different methods

Lupin seeds are rich in proteins, lipids and bioactive compounds, but before consumption must be debittered to remove toxic alkaloids. Traditionally, debittering is a water-intensive and protracted process, lasting up to six days. To develop a more efficient procedure, different washing solutions (0.5% and 1% NaCl or citric acid), with or without the use of ultrasound, were applied on Lupinus albus seeds and compared to two control methods, the first with water and the second with a sodium chloride solution. The sonication did not accelerate debittering, while the sodium chloride and citric acid solutions significantly shortened debittering time, reduced water consumption and decreased alkaloid content to commercial values (0.31–1.03 g/kg dry matter). Debittering with a 1% citric acid solution saved 88 h and 65 L water/kg dry lupin compared to the water control method, and 13 h and 31 L water/kg dry lupin compared to the salt solution control method. The electronic tongue grouped the experimental and commercial samples in well-defined clusters; bitter and umami tastes were the main factors, well correlated with alkaloid content. The proposed procedure, either with citric acid or sodium chloride, could be easily adopted by the industry to reduce time and costs of lupin debittering.

Ice-Template Crosslinked PVA Aerogels Modified with Tannic Acid and Sodium Alginate.

With the commitment to reducing environmental impact, bio-based and biodegradable aerogels may be one approach when looking for greener solutions with similar attributes to current foam-like materials. This study aimed to enhance the mechanical, thermal, and flame-retardant behavior of poly(vinyl alcohol) (PVA) aerogels by adding sodium alginate (SA) and tannic acid (TA). Aerogels were obtained by freeze-drying and post-ion crosslinking through calcium chloride (CaCl2) and boric acid (H3BO3) solutions. The incorporation of TA and SA enhanced the PVA aerogel’s mechanical properties, as shown by their high compressive specific moduli, reaching up to a six-fold increase after crosslinking and drying. The PVA/TA/SA aerogels presented a thermal conductivity of 0.043 to 0.046 W/m·K, while crosslinked ones showed higher values (0.049 to 0.060 W/m·K). Under TGA pyrolytic conditions, char layer formation reduced the thermal degradation rate of samples. After crosslinking, a seven-fold decrease in the thermal degradation rate was observed, confirming the high thermal stability of the formed foams. Regarding flammability, aerogels were tested through cone calorimetry. PVA/TA/SA aerogels showed a significant drop in the main parameters, such as the heat release rate (HRR) and the fire growth (FIGRA). The ion crosslinking resulted in a further reduction, confirming the improvement in the fire resistance of the modified compositions.

Conducting Polymer Hydrogel Driven By Sodium Chloride as High Performance Flexible Supercapacitor Electrode

With the rapid development of the wearable devices and flexible supercapacitors (FSCs), urgent demand for electrodes with high specific capacitance and excellent flexibility have been put forward. Herein, a self-standing conducting polymer hydrogel electrode has been successfully synthesized by in situ polymerization of aniline (ANI) in aqueous solution of polyvinyl alcohol (PVA), phytic acid (PA) and sodium chloride (NaCl). The prepared PANI/PVA/NaCl (PPN) hydrogel electrode shows high specific capacitance (1544 mF cm−2 at current density of 1 mA cm−2), good flexibility (elongation at fracture of 110%), satisfactory electrochemical stability (92% capacitance retention after 500 repeated bending cycles) and excellent cycling stability (78.2% capacitance retention after 10000 cycles) due to the uniform 3D interconnected structure driven by NaCl pseudo template. In order to further explore the potential application prospects of the synthesized hydrogel in flexible devices, a series of all-hydrogel-state FSCs are assembled based on the prepared PPN hydrogel electrodes and typical PVA/H2SO4 electrolyte. The assembled FSCs exhibit high energy density of 51.1 μWh cm−2 at power density of 250 μW cm−2 and long-life stability of 81.10% capacitance retention after 10000 charge/discharge cycles. This work provides a new synthesis strategy for the high performance energy storage electrodes and devices.

EXTRACTION OF IONS OF SOME TRANSITION ELEMENTS AND THEIR AMMONIA COMPLEXES FROM SOLUTIONS ON Na-CLINOPTYLOLITE AND Na-MORDENITE

Modified natural zeolites in the Na-form (clinoptilolite tuff of the Aydag and mordenite of the Chananab deposits in Azerbaijan) were studied in order to extract cations of the transition and heavy metals water and industrial liquid waste. The equilibrium and kinetic characteristics of the sorption process under static and dynamic conditions have been studied. Distribution isotherms of exchange ions between Na forms of zeolites with chloride (Ni2+, Co2+, Cu2+, Zn2+, Сd2+) and nitric acid (Hg+, Ag+) solutions have been obtained. It has been found that the increased selectivity of Na-zeolites to metal cations is due to their pronounced selectivity with respect to Ag+ ions over the entire range of concentration changes in solution and solid phase, as well as to cations in the ammonium form ([Ni(NH3)6]2+, [Co(NH3)6]2+, [Cu(NH3)4]2+, [Cd(NH3)6]2+, [Zn(NH3)4]2+) from low selectivity and selectivity to cations in the usual form. This fact makes it possible to extract the studied cations from the mixture in the form of ammonia, in accordance with the established range of selectivity of Na-zeolites to non-ferrous cations and their ammonia complexes

Mathematical modeling in the organization of the production process of leaching metals

The following will describe the process of how you can use mathematical modeling to organize the production of metal leaching. Mathematical models and results of computational experiments are presented. The results of studying the thickness of films of sulfuric acid-chloride solutions containing the addition of surfactants surface-active substance (SAS), which are formed when they pour out onto a frosted glass surface as a model of the surface of a piece of ore, are presented. A mathematical model how the film thickness changes depending on the feed rate of the solution and its composition, as well as on the angle of inclination of the glass surface has been determined. Underground leaching of metals from ores stimulates the search for ways and means of intensifying the process. Due to the addition of a surfactant, the leaching process is accelerated, since the thickness of the films of leaching solutions flowing over the surface of ore minerals decreases. This direction is relevant in modern science, and research in this direction the growth of indicators allows the national economy to improve and helps to improve and increase knowledge for further development of the metallurgical industry in Russia The article also discusses the results of studies on the electrochemical leaching of metals from polymetallic ore by sulfuric acid-chloride solutions with the addition of a surfactant with asymmetric current pulses. Mathematical models of the dependence of leaching indicators on the density and duration of the flow of direct and reverse polarity are presented. For ease of perception and better visualization, a table was compiled, which reflects the results of comparative analysis to assess the further possibility of processing secondary raw materials.

Computational, kinetic, and electrochemical studies of polyaniline functionalized ZnO and ZnO-SiO2 nanoparticles as corrosion protection films on carbon steel in acidic sodium chloride solutions

Two novel nanocomposites based on polyaniline functionalized ZnO and ZnO-SiO2 nanoparticles (ZnO@PANi and ZnSiO@PANi) were synthesized, characterized, and evaluated as protective films for steel pipelines in the pickling process at 25–55 °C. The prepared nanocomposites were described using different spectroscopic characterization methods including UV–vis, FTIR, DLS, XPS methods, and other physicochemical techniques including XRD, FESEM, and HR-TEM. The novelty of these films is in the fact that the ZnO and ZnO-SiO2 nanoparticles are functionalized by polyaniline which is electrochemically stable in acidic solution and has high conductivity. Electrochemical systems such as open circuit potentials (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) were utilized to attain the kinetics and mechanistic findings of the corrosion protection route. The outcomes indicate that the two fabricated ZnO@PANi and ZnSiO@PANi are efficient acidic corrosion inhibitors. The protection performance of ZnSiO@PANi (98.6%) was more pronounced at a dose (150 mg/L) than ZnO@PANi (92.3%) and individual PANi (83.4%) as achieved from PDP findings. The effect of temperature and flowing conditions reinforces further the performance of both nanocomposites. Surface characterization using FESEM/EDS delivered more indication for the steel surface protection with the ZnO@PANi and ZnSiO@PANi nanocomposites. Molecular modeling using DFT calculations and MC simulations supported the experimental findings. The binding energies of the compounds and Fe interface follow the order of ZnO@PANi > ZnSiO@PANi, which is in good agreement with the empirical results. An important suggestion of these results is the probability of substituting traditional toxic small molecules with cost-effective and non-toxic polymeric nanocomposites as protective films for use in the oil and gas industry.

Use of Ion-Exchange Resins to Adsorb Scandium from Titanium Industry’s Chloride Acidic Solution at Ambient Temperature

Scandium metal has generated a lot of interest during the past years. This is due to the various crucial applications it has found ground in and the lack of production in countries outside China and Russia. Apart from rare earth ores, scandium is present in a variety of wastes and by-products originating from metallurgical processes and is not currently being sufficiently valorised. One of these processes is the production of titanium dioxide, which leaves an acidic iron chloride solution with a considerably high concentration of scandium (10–140 ppm) and is currently sold as a by-product. This research aims to recover scandium without affecting the solution greatly so that it can still be resold as a by-product after the treatment. To achieve this, two commercial ion-exchange resins, VP OC 1026 and TP 260, are used in the column setup. Their breakthrough curves are plotted with mathematical modelling and compared. Results indicate that VP OC 1026 resin is the most promising for Sc extraction with a column capacity of 1.46 mg/mL, but Zr, Ti, and V coextract have high capacities, while Fe does not interfere with the adsorption.