Ferrous Concentration Research Articles

Toward Continuous Electrochemical Synthesis of Ferrate

AbstractFerrate (Fe(VI)) is of great interest in energy storage solutions, organic synthesis, and wastewater treatment due to its decent oxidation potential and non‐toxic end‐product formation, making it a green oxidizer. The electrochemical generation of ferrate in NaOH at current densities of j ≥ 100 mA cm−2 is presented using low‐cost sacrificial iron anodes, mild steel, and spheroidal graphite cast iron (ductile iron). Under optimized reaction parameters with 40 wt.% (14 m) NaOH and a ZrO2‐based diaphragm, spheroidal graphite cast iron shows no signs of passivation in 5 h experiments even at j = 150 mA cm−2. The results are used in a novel electrolysis cell with a combined geometric anode surface area of 230 cm2, incorporated in a mini‐plant suitable for continuous synthesis. This setup produces a peak ferrate concentration of 10.1 g L−1 (84 mm) after 5 h in 1.6 L anolyte volume, resulting in a total ferrate mass of 16.2 g. Optimal electrolysis temperatures are between 35 and 50 °C. The highest current efficiency is 63.0%, and the lowest specific energy consumption is 9.2 kWh kg−1 ferrate. The presented work is an essential step toward the continuous electrochemical synthesis of ferrate using sacrificial anodes under basic conditions.

A new spectrophotometric method for measuring ceruloplasmin ferroxidase activity: an innovative approach.

Ferroxidases are enzymes that participate in the iron metabolism of different organisms. They catalyze the oxidation of ferrous iron, Fe2⁺, into ferric iron, Fe3⁺, which is essential in iron homeostasis and physiological functioning. The present study describes a novel spectrophotometric method of serum ceruloplasmin ferroxidase activity. This method is easy to perform; it is also sensitive, specific, and rapid. In this method, ferrous ions are used as a substrate for the enzyme, with either salicylic acid or sulfosalicylic acid being taken as a chromogenic compound. These chromogens easily form a colored complex with ferric ions but are not formed with ferrous ions. In the enzymatic reaction, the ceruloplasmin ferroxidase enzyme catalyzes the oxidation of ferrous to ferric ions. The resulting increase in ferric ion concentration is then measured spectrophotometrically, following the formation of the colored complex. The complex formed has maximum absorbance at 540 nm in the case of salicylic acid and 490 nm in the case of sulfosalicylic acid. Comparatively, it was tested against the standard method to ascertain the new method's effectuality and reliability for assaying ferroxidase activity. The determined correlation coefficient amounted to 0.99, showing a strong correlation between the results obtained by the two methods. This new spectrophotometric technique offers a simplified, sensitive, specific, and fast means of estimating ferroxidase activity. It avoids using concentrated strong acids in the procedure and correlates excellently with the standard technique. This sets up a potential alternative for accurately determining ferroxidase activity in biological samples.

Sulfur oxidation of ferrate synthesized from sludge in the aspect of desulfurization: A parametric study

Abstract The emission of sulfur in the atmosphere poses a significant threat to human health and the environment. To address this issue, stringent regulations have been implemented to limit the sulfur content in diesel, and novel desulfurization technologies are being developed. One notable technology is oxidative desulfurization (ODS), which employs oxidants to transform sulfur compounds into their corresponding sulfones, which are relatively easier to recover. The application of high-shear mixing in ODS has been studied to increase sulfur-to-sulfone conversion by creating smaller droplets and reducing mass transfer resistance. This research investigates the application of potassium ferrate derived from drinking water treatment sludge (DWTS), in the mixing-assisted oxidative desulfurization (MAOD) of a dibenzothiophene (DBT) model fuel. Potassium ferrate was synthesized using the wet oxidation method. The study evaluated the effects of ferrate concentration (400 to 600 ppm), agitation speed (4,400 to 10,800 rpm), and temperature (40 to 60 °C) on the efficiency of DBT conversion. The results revealed that 493.2 ppm DBT conversion was achieved at 550 ppm Fe(VI) concentration, 7,600 rpm agitation speed, and 50 °C temperature. Notably, increasing Fe(VI) concentration, agitation speed, and temperature had significant effects on sulfur reduction. This study demonstrates the potential of using potassium ferrate derived from DWTS in MAOD for effective desulfurization and discusses insights into the effects of operating conditions to enhance desulfurization efficiency. Ultimately, the study contributes to the development of environmentally friendly and cost-effective desulfurization technologies.

Copper and zinc sulfides bioleaching by an extremely thermophilic archaeon in high NaCl concentration

Chloride bioleaching has received attention of several mineral processing industries, particularly in countries where there is scarcity of freshwater and only chloride-containing waters can be used. Therefore, the present work investigated the effect of NaCl (1.0 mol L−1) on the bioleaching of three sulfide minerals: chalcopyrite, bornite, and sphalerite by the thermophilic archaea Sulfolobus acidocaldarius. Chalcopyrite dissolution was only 25 % in the biotic experiment in the absence of chloride, but reached 90 % in the presence of both microorganisms and chloride, while less than 60 % extraction was observed in the abiotic experiment with chloride. In the experiments of bornite bioleaching, 86 % and 77 % of copper were extracted in the biotic and abiotic tests with chloride, respectively. In the absence of NaCl, the biotic and abiotic experiments presented similar copper dissolution (∼35 %). Finally, bioleaching experiments carried out with sphalerite showed zinc extractions below 35 % in all conditions tested. The main contribution from the archaea was its ability to produce low concentrations of ferric ion, which was partially precipitated as jarosite, resulting in low redox potential values (< 450 mV vs. Ag/AgCl), and efficiently bioleached bornite and chalcopyrite. Furthermore, XRD and SEM-EDS analyses demonstrated that sphalerite was practically not leached while bornite was transformed into new copper sulfide phases (CuS and Cu3FeS4). Jarosite and elemental sulfur were products of chalcopyrite and bornite bioleaching in the presence of chloride.

Treatment of Organic Pollutant by Advanced Oxidation Processes

The investigation involved the oxidation of urea (UR) in a batch reactor, employing Fenton's reagent. Various parameters, namely reaction time, pH level, ferrous ion dose, and hydrogen peroxide dose, were scrutinized. The reaction time spanned from 30 minutes to 3 hours, revealing a notably positive impact. An optimal pH of 3 was identified for the medium. The concentrations of ferrous ions ranged from 0.2 g/l to 0.53 g/l, with hydrogen peroxide levels ranging from 1 g/l to 2.65 g/l. The impact of hydrogen peroxide was notably significant at a ferrous ion concentration of 0.3 g/l and a pH of 3. Evaluating urea removal efficiency through chemical oxygen demand (COD) calculations showed a maximum efficiency of 86.8%, with a minimum ammonia yield of 6%. Overall, the outcomes underscored the efficacy of the Fenton process in urea treatment.

Diffusion Correction in Fricke Hydrogel Dosimeters: A Deep Learning Approach with 2D and 3D Physics-Informed Neural Network Models.

In this work an innovative approach was developed to address a significant challenge in the field of radiation dosimetry: the accurate measurement of spatial dose distributions using Fricke gel dosimeters. Hydrogels are widely used in radiation dosimetry due to their ability to simulate the tissue-equivalent properties of human tissue, making them ideal for measuring and mapping radiation dose distributions. Among the various gel dosimeters, Fricke gels exploit the radiation-induced oxidation of ferrous ions to ferric ions and are particularly notable due to their sensitivity. The concentration of ferric ions can be measured using various techniques, including magnetic resonance imaging (MRI) or spectrophotometry. While Fricke gels offer several advantages, a significant hurdle to their widespread application is the diffusion of ferric ions within the gel matrix. This phenomenon leads to a blurring of the dose distribution over time, compromising the accuracy of dose measurements. To mitigate the issue of ferric ion diffusion, researchers have explored various strategies such as the incorporation of additives or modification of the gel composition to either reduce the mobility of ferric ions or stabilize the gel matrix. The computational method proposed leverages the power of artificial intelligence, particularly deep learning, to mitigate the effects of ferric ion diffusion that can compromise measurement precision. By employing Physics Informed Neural Networks (PINNs), the method introduces a novel way to apply physical laws directly within the learning process, optimizing the network to adhere to the principles governing ion diffusion. This is particularly advantageous for solving the partial differential equations that describe the diffusion process in 2D and 3D. By inputting the spatial distribution of ferric ions at a given time, along with boundary conditions and the diffusion coefficient, the model can backtrack to accurately reconstruct the original ion distribution. This capability is crucial for enhancing the fidelity of 3D spatial dose measurements, ensuring that the data reflect the true dose distribution without the artifacts introduced by ion migration. Here, multidimensional models able to handle 2D and 3D data were developed and tested against dose distributions numerically evolved in time from 20 to 100 h. The results in terms of various metrics show a significant agreement in both 2D and 3D dose distributions. In particular, the mean square error of the prediction spans the range 1×10-6-1×10-4, while the gamma analysis results in a 90-100% passing rate with 3%/2 mm, depending on the elapsed time, the type of distribution modeled and the dimensionality. This method could expand the applicability of Fricke gel dosimeters to a wider range of measurement tasks, from simple planar dose assessments to intricate volumetric analyses. The proposed technique holds great promise for overcoming the limitations imposed by ion diffusion in Fricke gel dosimeters.

HCl-induced emulsion and sludge formation affected by asphaltene type

Asphaltene may cause severe challenges during acid stimulation of oil wells. In the course of contact between crude oil and the injected acid (i.e. HCl), dispersed asphaltene molecules in the organic medium chemically adsorb and accumulate onto the surface of acid droplets due to interaction with acid ions. This causes forming a shear-resistance interfacial layer, known as acid-induced sludge, that prevents droplet coalescence and stabilizes the unwanted acid in oil emulsion. In this study, a set of compatibility tests was conducted to discern the emulsion stabilizing affinity of various asphaltene samples and sludge formation as a function of experimental variables including acid-to-mixture volumetric ratio (AMR) and pH, ferric ion, and asphaltene concentrations, aromaticity of the model oil, and shear (mixing speed). The utilization of heptol model oils (a mixture of heptane, toluene, and asphaltene) would help to focus on asphaltene behavior while isolating the other crude oil components. Five asphaltene samples (A1 to A5) having different structures were used in this study. Regardless of asphaltene properties, the emulsion stability was decreased approximately 70 % by increasing AMR. In addition, more aromaticity of the model oil resulted in 80 % less emulsion stability. There is a minimum range for emulsion stability in the interval of 500–1000 ppm asphaltene concentration for all samples. Up to 50 % emulsion stability was detected in the case of asphaltene A3 because of basic properties and higher colloidal instability. The effect of ferric ion concentration on intensifying emulsion stability and sludge formation was noticeable up to 500 ppm. HCl-model oil emulsion and the formed sludge had no sensitivity to shear force in the range of 500–1500 rpm due to the very low viscosity of the model oil. Therefore, in the studied shear range, emulsion and sludge formation have been more chemically controlled instead of being physically limited due to mixing. Moreover, sludge formation is not affected by pH of the HCl solution higher than 2 and mixing speed.

A Two-Step Leaching Process Using Thiourea for the Recovery of Precious Metals from Waste Printed Circuit Boards

The development of efficient recovery methods for waste printed circuit boards (WPCBs) not only tackles the environmental risks of disposal but also promotes the conservation of resources within the electronics industry. This study proposes a two-step leaching approach for recovering metals from WPCBs. Initially, transition metals are leached using nitric acid, followed by the recovery of precious metals with thiourea in the second stage. In the first stage, dissolution rates exceeding 90 wt% were achieved for transition metals, including Cu, Fe, Ni, Pb, and Sn. In this stage, the dissolution of precious metals (i.e., Au and Pd) was insignificant. In the second stage, the effect of four parameters was investigated, including the impact of temperature, concentrations of ferric ions, sulfuric media, and thiourea on the recovery of Au and Pd. Precise control over sulfate concentration played a vital role in achieving maximum Au recovery. The optimal acid concentration was 0.2 M, resulting in a recovery rate of ~50 wt%. Ferric ion concentration positively affects Au recovery, whereas, in extracting Pd, optimal conditions imposed the absence of ferric ions. Thiourea concentration positively impacted Au and Pd recovery rates, peaking at 49 wt% for Au at 1 M and 44 wt% for Pd at 1.5 M. Prolonged leaching resulted in declining Au recovery rates, indicating a decrease in reagent concentration. Temperature variation yielded similar outcomes, with 50 °C resulting in peak recovery rates of 53 wt% for Au and 54 wt% for Pd. Metal dissolution kinetics during leaching were analyzed using pseudo-first-order and pseudo-second-order models. The second-order model proved suitable for transition metals in the first stage, while only for Au and Pd in the second stage (with R2 = 0.99).

Desulfurization of coal pyrite tailings with ozone

Mining is an important sector of the economy, and in the southern region of Brazil, coal mining stands out. This activity generates waste with a high pyritic content, which causes environmental problems such as acid mine drainage (AMD). Therefore, studies that aim to beneficiate or treat this waste are of high relevance. In this study, an alternative for desulfurizing pyritic waste using ozone was investigated. Ozone treatment of mining tailings suspension was evaluated as a new strategy for sulfur removal. Particle size analysis, sulfate content, ferrous ion concentration (and total iron), pH, Eh, conductivity, and X-ray fluorescence were performed. Furthermore, a kinetic analysis of ozone consumption was established. The behavior of sulfate and hydrogen ion concentrations indicates that sulfuric acid is the main reaction product, and conductivity suggests that ion release is continuous over the ozonation time. A reaction kinetics with ??1.2 was found for ozone depletion, which aids in predicting the dosage to be applied on a larger scale. This study represents a contribution to the search for alternatives for treating pyritic waste and contributes to the understanding of the reaction rate of ozone consumption in this type of reaction.

Application of the sono-Fenton/UV process on the treatment of table olive processing wastewater

AbstractThe Mediterranean Basin economies of Spain, Italy, Greece, and Turkey depend on the table olive and olive oil industries. Table olive processing wastewater characteristics and quantity depend on olive varietal and processing methods. Olives and processing methods provide phenol, suspended particles, dissolved inorganic solids, and refractory organics. Due of its complexity, conventional methods struggle to tackle table olive processing wastewater. A novel approach to enhanced oxidation processes integrates many ways to boost hydroxyl radical formation and scale up efficiency. UV assisted sono-Fenton process as a modified Fenton process was applied to table olive washing wastewater to achieve high formation of hydroxyl radicals. When UV assisted sono-Fenton experiments executed to determine the optimum reaction conditions, the effects of hydrogen peroxide, ferrous ion concentrations and reaction time on the oxidation of table olive washing wastewater investigated by using a statistical experimental design. Chemical oxygen demand (COD), total organic carbon (TOC) and phenol removal efficiencies were examined by keeping the pH constant. The UV assisted sono-Fenton process achieved 53% phenol, 68% TOC, and 80% COD removal efficiencies. The results show that the UV assisted sono-Fenton process can treat effectively table olive processing wastewater. Optimum reaction conditions for the UV assisted sono-Fenton process were determined. UV assisted sono-Fenton process provides a significant reduction in reaction time and minimizes the costs of process associated with low chemical requirements. So, these optimum reaction conditions were resulted in low sludge production at the UV assisted sono-Fenton process while treating table olive processing wastewater.

Enhancing oxidative desulfurization using sludge-derived ferrate (VI) for dibenzothiophene: An optimization study

Sulfur emissions pose a substantial threat to human health and the environment. To address this, stringent regulations limit sulfur content in fuels, and innovative desulfurization technologies are under active investigation. Oxidative desulfurization (ODS) employs oxidants to convert sulfur compounds into more readily recoverable sulfones. This study explores high-shear mixing in ODS, known as mixing-assisted oxidative desulfurization (MAOD), focusing on dibenzothiophene (DBT) oxidation in model fuels and pyrolysis oil. Fe(VI) derived from drinking water treatment sludge via wet oxidation is utilized in the MAOD process. The research evaluates the impact of ferrate concentration (400–600 ppm), phase transfer agent (PTA) concentration (100–300 mg per 50 mL of fuel), agitation speed (4,400 to 10,800 rpm), and temperature (40–60 °C) on % DBT conversion. Experimental sulfur conversions range from 63.4 % to 99.6 %. Through response surface methodology, optimal parameters of 537 ppm Fe(VI), 114 mg PTA per 50 mL of model fuel, 8,157 rpm agitation speed, and 41.7 °C are determined. These parameters are applied to pyrolysis oil, achieving a desulfurization efficiency of 53.2 %. Notably, increasing Fe(VI) concentration, agitation speed, and temperature significantly enhances sulfur reduction. The study underscores the potential of using potassium ferrate derived from drinking water treatment sludge in MAOD for effective desulfurization and provides insights into the impact of operating conditions on desulfurization efficiency. Ultimately, the research contributes to advancing environmentally friendly and cost-effective desulfurization technologies.

Modeling and Optimization of Electrochemical Advanced Oxidation of Clopidogrel Using the Doehlert Experimental Design Combined with an Improved Grey Wolf Algorithm

In this research, the optimization of the electrochemical advanced oxidation treatment for the degradation of Clopidogrel was investigated. This study examined the influence of various experimental parameters including applied current, initial Clopidogrel concentration, and ferrous ion concentration by the use of the Doehlert design within a response surface methodology framework. The improved grey wolf optimizer was applied in order to define the optimum operating conditions. The monitoring of clopidogrel concentration during treatment revealed that complete disappearance of clopidogrel was achieved under an initial clopidogrel concentration of 0.02 mM, current intensity of 0.55 A, Fe2+concentration of 0.7 mM, and a reaction time of 20 min in a solution containing 50 mM Na2SO4 at pH 3. A quadratic polynomial model was developed, and its statistical significance was confirmed through the analysis of variance, demonstrating a high level of confidence in the model (R2 = 0.98 and p-value &lt; 0.05). Furthermore, following electrolysis treatment for 480 min, the synthetic clopidogrel solutions underwent mineralization, achieving a 70.4% removal rate of total organic carbon. Subsequently, the applicability of the optimized process was tested on real pharmaceutical wastewater, and mineralization was investigated under the identified optimal conditions, resulting in a total organic carbon removal rate of 87% after 480 min of electrolysis time. The energy consumption for this system was calculated to be 1.4 kWh·kg−1 of the total organic carbon removed. These findings underscore the effectiveness and potential applicability of the electrochemical advanced oxidation for industrial wastewater treatment.

Magnetic bio-based Fe3O4@urushiol-Fe polymeric nanoparticles for efficient photothermal sterilization

Many advantages of photothermal sterilization make it very promising in the field of sterilization. Biomass micro-nanoparticles with photothermal properties are considered worthy of development as photothermal sterilization materials. Urushiol, the main component of natural sap from lacquer tree, was applied to react with green-vitriol by the adjusted the concentrations of ferrous ion through the chemical synthesis method to prepare a novel magnetic composite nanoparticle with Fe3O4 as the central core wrapped by urushiol-Fe chelate polymer. Under 808 nm near-infrared irradiation (0.12 W cm−2), the Fe3O4@urushiol-Fe polymeric nanoparticles were rapidly heated up to a maximum temperature of 104.9 ℃, implying good photothermal conversion performance. The nanoparticles were applied for the effective inactivation of bacteria such as Escherichia coli and Staphylococcus aureus. The optimal dose and irradiation power for sterilization were 0.5 mg and 1 W cm−2, respectively. The composite nanoparticles exhibited good photothermal conversion stability even after multiple photothermal heating and photothermal sterilization. The biomass magnetic composite Fe3O4@urushiol-Fe polymer nanoparticles had the advantages of simple preparation, high efficiency of photothermal conversion, significant sterilization effect, and easy collection, which demonstrated a broad application prospect in the field of photothermal sterilization.

Development of an artificial neural network (ANN) for the prediction of a pilot scale mobile wastewater treatment plant performance

Productive activities such as pig farming are a fundamental part of the economy in Mexico. Unfortunately, because of this activity, large quantities of wastewater are generated that have a negative impact in the environment. This work shows an alternative for treating piggery wastewater based on advanced oxidation processes (Fenton and solar photo Fenton, SPF) that have been probed successfully in previous works. In the first stage, Fenton and SPF were carried out on a laboratory scale using a Taguchi L9-type experimental design. From the statistical analysis of this design, the operating parameters: pH, time, hydrogen peroxide concentration [H2O2], and iron ferrous concentration [Fe2+] that maximize the response variables: Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and color were chosen. From these, a cascade forward neural network was implemented to establish a correlation between data from the variables to the physicochemical parameters to be measure being that a great fit of the data was obtained having a correlation coefficient of 0.99 which permits to optimize the pollutant degradation and predict the removal efficiencies at pilot scale but with a projection to a future industrial scale. A relevant result, it was found that the optimal values for maximizing the removal of physicochemical parameters were pH = 3, time = 60 min, H2O2/COD = 1.5 mg L−1, and H2O2/Fe2+ = 2.5 mg L−1. With these conditions degradation percentages of 91.44%, 47.14%, and 97.89% for COD, TOC, and color were obtained from the Fenton process, while for SPF the degradation percentage increased moderately. From the ANN analysis, the possibility to establish an intelligent system that permits to predict multiple results from operational conditions has been achieved.

PbO2 /graphite and graphene/carbon fiber as an electrochemical cell for oxidation of organic contaminants in refinery wastewater by electrofenton process; electrodes preparation, characterization and performance

The electro-Fenton oxidation process was used to treat organic pollutants in industrial wastewater as it is one of the most efficient advanced oxidation processes. The novel cell in this process consists of a prepared PbO2 electrode by electrodeposition on graphite substrate and carbon fiber modified with graphene as a cathode. X-ray diffraction, fluorescence, analysis system, atomic force microscopy, and scan electron microscopy were used to characterize the prepared anode and cathode. XRD patterns clearly show the characteristic reflection of the mixture of  - and β phases of PbO2 on graphite and carbon fiber, and AFM results for cathode and anode present that PbO2 on graphite substrate and graphene on carbon fiber surface are on a nanoscale. Contact angle measurement was determined for the carbon fiber cathode before and after modification. The anodic polarization curve showed a higher anodic current when utilizing the PbO2 anode than the graphite anode. Phenol in simulated wastewater was removed by electro-Fenton oxidation at 8 mA/cm2 current density, 0.4 mM of ferrous ion concentration at 35 °C up to 6 h of electrolysis. Chemical oxygen demand for the treated solution was removed by 94.02 % using the cell consisting of modified anode and cathode compared with 81.23% using modified anode and unmodified cathode and 79.87 % when using unmodified anode and modified cathode.

Iron toxicity in lowland rice influenced by application of high potassic fertilizer with suitable cultivars enhanced productivity and climate resilience

Iron poisoning in low-land rice in India develops gradually and is primarily caused by anaerobic conditions in submerged rice fields. A high concentration of ferrous ions in the soil solution disrupts the potassium balance in rice plants, leading to adverse effects on crop growth. In the 2021–2022 period, an experiment was conducted in non-saline, iron-rich soil (pH–4.82, Fe–458.6 mg kg–1) to mitigate iron toxicity in rice cultivars through potassium nutrition. The experiment involved 4 potassium application doses (K-40, K-80, K-100 and K-120) and 32 rice cultivars, replicated twice using a split-plot design. Higher potassium doses led to increased tiller counts, but gradually decreased root length. Notably, cultivars like Kanchan, Indravati, Jagabandhu, Santepheap and Salibahan exhibited the lowest iron concentration in their grains compared to susceptible cultivars. Administering K-120 resulted in a yield increase of over 36.70 q ha-1. Grain yield increased with higher K dosage, although it did not affect total iron content. However, K doses did influence specific fractions of iron in the soil. Hence, potassium nutrition appears crucial in managing iron toxicity in inceptisols, especially when paired with cultivars tolerant to iron toxicity.

Comparison of river and coastal water as potential sources of bioavailable iron

The assimilation of dissolved iron by phytoplankton depends on its chemical speciation and/or oxidation state. In this study river and coastal water was irradiated with a sunlight simulator and monitored for photoproduction of bioavailable reduced iron using a colorimetric method. The 0.01 μΜ steady-state concentration of ferrous ion was detected in river water during irradiation. The apparent quantum yield, an estimate of process efficiency, suggests qualitative differences between organic iron complexes in river and coastal water. The amount of photoproduced bioavailable iron may be of importance in relieving iron stress in potentially toxic diazotrophs in the area affected by the river plume.

Efficient Recycling and Utilization Strategy for Steel Spent Pickling Solution

Before steel can be utilized, pickling is necessary to remove surface oxidation products. However, as the ferrous ion concentration in the pickling solution increases, the pickling rate significantly diminishes, necessitating the treatment of spent pickling solution (SPS) to mitigate its hazardous effects prior to disposal. Current industrial methods predominantly rely on neutralization and precipitation techniques, which are cost-prohibitive and generate substantial by-products, thus failing to meet environmental protection standards. In this study, a new method, which is based on the formation of FeC2O4·2H2O precipitate in a strong acid solution, is proposed to treat the SPS. Initially, the SPS undergoes a two-step impurity removal process, followed by the controlled addition of oxalic acid dihydrate (H2C2O4·2H2O) to precipitate iron. The resulting precipitate is filtered, washed, and vacuum-dried, and the regenerated acid is recycled back into the pickling tank. When 1 g/10 mL of H2C2O4·2H2O is used, the iron removal rate achieves 60%, and the acidity of the regenerated acid increases by 11.3%. X-ray diffraction pattern (XRD) and thermogravimetric–differential scanning calorimetry (TG-DSC) characterization showed that the precipitate was α-FeC2O4·2H2O, with an average particle size of about 3.19 μm and a purity of 95.24%. This process innovatively achieves efficient recycling of acid and iron resources, offering a potential solution to the industrial challenge of difficult SPS treatment in the steel industry and meeting the urgent need for sustainable development.

Pristine and UV-Weathered PET Microplastics as Water Contaminants: Appraising the Potential of the Fenton Process for Effective Remediation

Polyethylene terephthalate (PET) microplastics constitute a significant portion of plastic pollution in the environment and pose substantial environmental challenges. In this study, the effectiveness of the Fenton process and post-oxidation coagulation for the removal of non-weathered and UV-weathered PET microplastics (PET MPs) were investigated. A response surface methodology was used to investigate the interplay between PET concentration and ferrous ion (Fe2+) concentration. The models revealed an intricate interplay between these variables, highlighting the need for a balanced system for optimal PET MP removal. For non-weathered PET, the simultaneous increase in the concentrations of both PET microplastics and Fe2+ was found to enhance the removal efficiency. However, this synergistic effect was not observed in UV-weathered PET, which also demonstrated a more pronounced effect from the Fe2+ concentration. The statistical analysis provided a strong basis for the validity of the models. X-ray photoemission spectroscopy (XPS) further elucidated the mechanisms behind these findings, revealing that UV weathering results in surface changes, which facilitate hydroxyl radical oxidation. These findings underline the complexity of the Fenton process in PET microplastic removal and the different behavior of non-weathered and UV-weathered microplastics. This has significant implications for tailoring remediation strategies and underscores the importance of considering environmental weathering in these strategies.

Selective leaching of lead from complex polymetallic sulfide secondary concentrate with ferric methanesulfonate and methanesulfonic acid solution

The selective leaching of lead from complex polymetallic sulfide secondary concentrate (CPSSC) with the solution mixed by ferric methanesulfonate and methanesulfonic acid (Fe(MS)3-MSA) was investigated by leaching experiments, analysis of solids, and electrochemical characterizations. The leaching results showed that stirring rate, liquid–solid ratio, temperature, and ferric concentration greatly influenced Pb extraction rate. At the optimum leaching conditions, 93.1 % Pb, while 3.8 % Cu and 18.8 % Fe were extracted. The selective leaching mechanism was related to the activity of PbS in Fe(MS)3-MSA solution and the galvanic effect between sulfides. XRD and SEM-EDS results of leaching residues verified the selective decreases in PbS, and retainment of most Cu, Fe, and Zn. Electrochemical characterizations demonstrated a more stable and higher open-circuit potential, and an increase/decrease in A0 peak potential/current in LSV curve for the residue’s electrode, suggesting the selective decreases in active components (e.g. PbS). After selective leaching, Cu could be easily extracted from residues by pressurized water leaching, and Fe(MS)3-MSA solution could be regenerated for recycling used in leaching. These results indicate the great potential of Fe(MS)3-MSA solution to selectively leach and separate Pb from CPSSC, and unveil a method to effectively treat refractory CPSSC.