Search

Iron and manganese in groundwater impair the quality of drinking water; however, the rates of iron and manganese removal with conventional aeration and rapid sand filtration (RSF) processes vary extensively. Five full-scale aeration–RSF processes in Nepal also showed varying efficiencies of iron and manganese removal; while the iron concentration was below the national standard (0.30 mg/L) in 31 out of the 37 treated waters, the manganese concentration was higher than the standard (0.20 mg/L) in all of the treated waters. Re-aeration and stirring of the treated water did not oxidize soluble manganese, and this caused the poor removal rates for manganese. Bench-scale dual-media filters comprising anthracite on top of sand/ceramic layers with dosages of poly aluminum chloride and chlorine worked well by removing coagulated iron in the anthracite layer and then removing manganese in the sand/ceramic layers. A manganese-oxide-coated ceramic filter provided the highest manganese removal from 1.10 mg/L to <0.01 mg/L, followed by manganese-oxide-coated sand and quartz sand. Increasing the pH from 7.5 to 9.0 stabilized the manganese removal. Therefore, we propose a re-design of the present treatment processes and the selection of suitable filter media for better removal of iron and manganese. [ABSTRACT FROM AUTHOR]

The aim of this work is to develop a simple, sensitive, and reliable colorimetric test method for the visual detection of Fe(II) and Fe(III) in water. The sample solution of Fe(III) was initially complexed with chromeazurol S (CAS) followed by ion-pair association with cetyltrimethylammonium bromide (CTAB) in the presence of perchlorate ions. This led to the formation of a bulky and insoluble fluffy precipitate involving the physical entrapment of the ternary complex of Fe-CAS-CTAB, which floats on the top of the solution. Depending on the concentration of Fe(III), this type of ternary complex produces an impressive color change from reddish magenta to purple and then to cyan-blue, easily detectable with the naked eye without the need for expensive instrumentation. The ternary-colored complex was formed instantly and remained stable for at least 8 h with constant absorbance. For the determination of total iron and Fe(II), complete oxidation of Fe(II) to Fe(III) was carried out using 100 μL of KMnO4 (0.005%). The minimal response with the test method was found to be about 5 ng/mL of Fe(III) in 2 min of the total sample testing procedure. However, Fe(III) could be quantified using a spectrophotometer after dissolving the fluffy precipitate in toluene solvent. The calibration graph was linear in the range of 5–30 ng/mL of Fe(III) with a correlation coefficient of 0.9931 and a limit of detection of 0.9 ng/mL. The relative standard deviation was found to be less than 6%. At the end of the study, the efficacy of the method was evaluated by its application to groundwater and thermal power plant coolant waters. [ABSTRACT FROM AUTHOR]

Providing the population with high-quality drinking water is one of the main state tasks. Rural water supply systems and water supply systems of small settlements in the region require special attention, namely, the development of technologies for individual, small-sized water treatment equipment, as well as equipment for collective use, designed to purify groundwater for drinking purposes. In many areas, there are groundwaters containing excess levels of several pollutants, which makes their purification much more difficult. Elimination of shortcomings in the known methods of water iron removal is possible by reconstructing existing water supply systems from underground sources in small settlements. A rational solution is to search for groundwater treatment technologies that make it possible to provide the population with high-quality drinking water at a lower cost. The result of increasing the concentration of oxygen in water was obtained in the process of modifying the filter by changing the excess air exhaust system, which was made in the form of a perforated pipeline located in the lower half of the granular filter layer connected to the upper branch pipe. At the same time, high-quality groundwater treatment, sufficient simplicity and reliability in operation are ensured, local conditions and the inaccessibility of many objects and settlements in the region are taken into account as much as possible. After the filter was upgraded, the concentration of iron decreased from 4.4 to 0.27 mg/L and ammonium nitrogen from 3.5 to 1.5 mg/L. [ABSTRACT FROM AUTHOR]

Lithogenic materials such as terrigenous lithogenic particles (TLP) can efficiently promote the formation and sinking of mineral‐associated marine organic matter, acting as important ballast and potentially playing an important role in the global carbon cycle. To assess the influence of TLP on fluxes of particulate organic carbon (POC) and other biogeochemical cycles, we construct TLP forcing fields based on global riverine suspended sediment data and then apply them to the Community Earth System Model, version 2 (CESM2) modified with the TLP ballasting effect term. Simulations forced by different concentrations of TLP transported in the surface ocean or along the bottom of continental shelves and slopes are conducted. When the TLP transports seaward along the bottom, simulated POC fluxes at 100 and 2,000 m decrease about 11% and 19%, respectively, for the global ocean, and about 9% and 12%, respectively, for the oceanic regions of continental margins. The initial abiotic ballast processes triggered by TLP input increase POC fluxes, causing additional removal and burial of dissolved iron in continental margins. This further enhances the accumulation of macronutrients in the upwelling regions and their advection transport to neighboring subtropical gyres, thus altering regional productivity when simulations reach quasi‐equilibrium. When consider the impacts of TLP in simulations, the simulated POC flux exhibits an increase in subtropical gyres but a decrease in tropical Pacific and mid‐high latitude regions. The present work highlights the importance of TLP in global biogeochemical cycles, suggesting that the amount of carbon sequestration might be overestimated without TLP in models. Key Points: The ballast effect of terrigenous lithogenic particles has been incorporated into a community earth system modelCarbon sequestration might be overestimated without terrigenous lithogenic particles in the modelWith terrigenous lithogenic ballast, simulated POC flux increases in subtropics but decreases in tropical Pacific and mid‐high latitudes [ABSTRACT FROM AUTHOR]

Urbanization and industrialization had decreased the drinking water quality to a greater extent. Iron contamination is a serious issue in many open well and bore well samples of Kerala, India. Intake of large amount of iron causes serious health issues to humans. There were several methods for the removal of iron from drinking water. But the cost of these treatments is not affordable to common people. Use of eco-friendly materials for the effective removal of iron from water samples is the major concern for this study. Different plant materials which are easily available in Kerala were used in this study for the effective removal of iron. Clitoria ternatea, which is a climber was selected as the adsorbent material. The extracts of this plant materials were incorporated in Magnesium based Metal-Organic-Framework (MOF) and used for water treatment. Among the prepared MOFs, that modified with flower extract of Clitoria ternatea, was found to be more effective at an adsorbent dosage of 40ppm. The adsorption process was analyzed using different isotherms and found suitable for Langmuir adsorption. Hence a mono-layer of adsorption was formed on the adsorbent surface by physical adsorption. [ABSTRACT FROM AUTHOR]

Heavy metals are considered hazardous elements because they are not biodegradable in the environment. Exposure to heavy metals leads to serious problems that affect human health and the aquatic environment. Removal of heavy metal ions from simulated water was employed for chitosan/iron nanocomposites (C-Fe2O3NPs). C-Fe2O3 was prepared from chitosan solution and iron salt. The characterization of C-Fe2O3 was carried out using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), and X-ray diffractometry (XRD). To determine the morphological structure, functional groups, and physicochemical properties. Determination of the optimum operating experimental conditions that result in the highest efficiency for heavy metal ions was investigated, such as contact duration (0-60 min), concentration (0.5, 1, 2, 3, and 5 mg/L), and adsorbent dose (0.1-0.5 g/L). Subsequently, the application of modified C-Fe2O3 in batch system for the elimination of Cu, Cr, Pb, Zn, and Se from simulated water was carried out. The results showed that EDX displayed the existence of iron, indicating the presence of iron nanoparticles. Also, the XRD and XRF showed the presence of iron oxide in the crystalline phase. The optimal conditions of the breakthrough curve, such as column height, flow rate, and contact time, were also examined. The results showed that the optimal conditions in the column system were a height of 10 cm, a flow rate of 5 mL/min, and a concentration of 3 mg/L. The kinetic information obtained was best modeled with the pseudo second-order model, and the experimental results fit the Langmuir model. High removal rates for Cu, Cr, Zn, Se, and Pb reached 99.8%, 93.8%, 98.8%, 99.8%, and 97.8%, respectively were achieved. The regeneration study indicated the good shelf life of iron magnetic NPs, which was 4.2%. In conclusion, C-Fe2O3 NPs are a potential adsorbent for heavy metal decontamination from water. [ABSTRACT FROM AUTHOR]

In some regions, underground water contains dissolved arsenic and this is a health risk for the population. In this work, arsenic was reduced to acceptable levels. Water from Zacatecas, Mexico, containing 1.58, 1.72 and 2.03 mg/L of As, Fe and Mn respectively, and pH 2.0, was treated with Fe from electrolytic dissolution, then with a mixture of ozone and air. The parameters considered during the treatment were agitation rate, ozone flux, pH, temperature, and dissolution time of iron. The concentration of As was reduced by co-precipitation with Fe from the electrolytic dissolution and by co-precipitation with Mn contained in the water when ozone was injected. The results indicated that the co-precipitation reactions depended on the mass transport. The ozone oxidizes the Mn in two steps (pH 2): firstly, the Mn (II) is oxidized to Mn (IV) and precipitated and secondly, the precipitated Mn (IV) is oxidized and dissolved as Mn (VII). Arsenic co-precipitated in the first Mn oxidation step, and then it turned into a solution together with the Mn at high flow of ozone. The residual concentrations of Fe, Mn and As in the water at pH 7 are 0.014, 0.07 and 0.00512 mg/L, respectively. [ABSTRACT FROM AUTHOR]

In order to explore the enhancement effect of biochar on anaerobic digestion, oxytetracycline residue was used as the substrate for anaerobic digestion, and biochar was added to solve the problems of low efficiency and weak stability of traditional anaerobic digestion. The strengthening effects of biochar and zero-valent iron modified biochar were illustrated by the changes of gas production, stability and microbial community. The results show that adding biochar alone and nano-scale zero-valent iron modified biochar can reduce the concentration of ammonia nitrogen in the system, reduce the influence of ammonia inhibition on anaerobic digestion, promote the transformation and consumption of VFAs, and improve the stability of the system. The gas production efficiency increased by 20.74% and 15.49% respectively, reaching above 115.20 mL/g. In addition, biochar can also strengthen the removal of residual oxytetracycline, and its removal efficiency is increased by 2.37% and 4.82% respectively compared with the control group, and the content of residual oxytetracycline in the final system can be reduced to below 10 mg/L. After adding zero-valent iron to biochar, the abundance of acid-producing bacteria and methano-genic archaea increased in different degrees, thus strengthening the process of anaerobic digestion and methanogenesis. [ABSTRACT FROM AUTHOR]

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. When operating reverse osmosis systems, most owners are not concerned about the negative consequences of using such systems. After 3-6 months of using mechanical filters in the first stage of water treatment, such filters are thrown out together with other household waste. They pose a significant threat to the environment. Currently, companies in Ukraine would not collect and dispose of such filters. This direction is undeveloped. There are no corresponding data in the scientific literature. According to authors' calculations, about 20,000 household reverse osmosis systems are operated per 1 million people today, so it is easy to calculate that 44,000 cartridges with a total polypropylene volume of 26 m3 enter the environment during the year. It is difficult to imagine the real environmental damage from the cartridges of even one city. Therefore, the regeneration of mechanical filters of reverse osmosis systems is quite relevant and essential today. This work aimed to develop an environmentally safe technology for regenerating mechanical filters with the possibility of repeated use. Filter lifespan can be prolonged by special cleaning with sulfuric acid with a fixed pH level. This article highlights the research results on the regeneration the mechanical filters, describes the characteristics of the cleaning process using sulfuric acid and shows the options for environmentally safe waste processing from such regeneration. [ABSTRACT FROM AUTHOR]

The chromium (Cr) limit values are currently tightened to 25 μg L−1 (EU), 5 μg L−1 (Germany), and possibly 10 μg L−1 Cr(VI) (California). The combined process of chemical reduction, coagulation, and biotic filtration (RCbF) efficiently removes Cr(VI) in drinking water. In this study, redox-active substances (O2, NO3−, Fe2+, MnO2) were investigated concerning their effect on the RCbF process. The experiments were performed at two-stage pilot waterworks for biological iron and manganese removal. O2 or NO3− as oxidants affected the RCbF process, neither by consumption of the reductant Fe(II) nor by re-oxidation of already formed Cr(III) in the supernatant of the filter bed. However, the oxidation of Cr(III) by O2 to Cr(VI) with MnO2 as a mediator was identified as potential risk for Cr breakthrough. Up to one third of the initial Cr(III) concentration was oxidized to Cr(VI) in the second filter bed within a contact time of only 5 min. The kinetically relevant mechanism seemed to be the formation of Cr(III)Fe(III)-hydroxides and not the reduction of Cr(VI) by Fe(II). Further, the mixing of Cr(VI) containing raw water with Fe(II) containing groundwater was determined as a chemical-free alternative for the RCbF process, depending on the resulting Fe(II) concentration after mixing. [ABSTRACT FROM AUTHOR]

This study proposed an AO-SBR (Anaerobic Aerobic Sequencing Batch Reactor) combined with iron-carbon micro-electrolysis (ICME) particles system for sewage treatment at low temperature and explored the dephosphorisation mechanism and microbial community structure. The experimental results illustrated that ICME particles contributed to phosphorus removal, metabolic mechanism of poly-phosphorus accumulating organism (PAO) and microbial community structure in the AO-SBR system. The optimal treatment effect was achieved under the conditions of pH 7, DO 3.0 mg/L and particle dosage of 2.6 g Fe-C/g MLSS, and the removal rates of COD, TP, NH4+-N and TN reached 80.56%, 91.46%, 69.42% and 57.57%. The proportion of phosphorus accumulating organisms (PAOs) increased from 4.54% in the SBR system to 10.89% in the ICME-SBR system at 10°C. Additionally, the metabolic rate of PAOs was promoted, and the activities of DHA and ETS both reached the maximum value of 13.34 and 102.88 μg·mg−1VSS·h−1. These results suggest that the ICME particles could improve the performance of activated sludge under low-temperature conditions. This technology provides a new way for upgrading the performance of sewage treatment in the cold area. [ABSTRACT FROM AUTHOR]

Mexico is characterized as a mining country since it is the world's main silver producer. During its extraction, wastewater (mining tailings) is generated which contains cyanide and heavy metals. The purpose of this research was to determine whether a bacterial consortium isolated from a tailings dam can use cyanide as a source of nitrogen and carbon to carry out its biodegradation. The study determined the effects of three physicochemical factors (pH, temperature and inoculum concentration) and three metals (copper, iron and nickel) on cyanide biodegradation. The results showed that the highest cyanide removals were obtained when working with a pH of 9.5, a temperature of 25 °C and 15% v/v of inoculum (88%), while the optimum values for copper, iron and nickel were 0, 7.7 and 0.46 mg·L−1, respectively, showing that copper causes an inhibitory effect (cyanide biodegradation of 68%) on the bacteria and consequently on the biological degradation of cyanide and that iron can promote the biodegradation of the pollutant by 91%. [ABSTRACT FROM AUTHOR]

Manganese (Mn) control in surface water systems is a challenge for the drinking water industry, especially through a sustainability framework. Current methods for removing manganese from surface water use strong oxidants that embed carbon and can be expensive and harmful to human health and the environment. In this study, we used a simple biofilter design to remove manganese from lake water, without conventional surface water pre-treatments. Biofilters with aerated influent removed manganese to concentrations below 10 µg/L when receiving influent water containing > 120 µg/L of dissolved manganese. Manganese removal was not inhibited by high iron loadings or poor ammonia removal, suggesting that removal mechanisms may differ from groundwater biofilters. Experimental biofilters also achieved lower effluent manganese concentrations than the full-scale conventional treatment process, while receiving higher manganese concentrations. This biological approach could help achieve sustainable development goals. [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron (nZVI) has received more attention due to its high reactivity in removing contaminants. However, assessing reactivity requires time and cost savings to improve the potential applicability of nZVI. In this study, a model for Cr(VI) removal by nZVI was established to simulate the changes of various ions during the reaction. The aim was to elucidate the reduction mechanism and provide a new method for calculating electron efficiency. And we calibrated the parameters through experimental data and characterization analysis, which improved the reliability of the model. In addition, we discussed the specific effects of the initial concentration and initial pH of Cr(VI) on electron efficiency and reactivity. The results indicated that the initial concentration and initial pH primarily affected the electron efficiency by altering the utilization efficiency of active sites and the corrosion degree of nZVI. At pH values of 3, 5, 7, 9, and 11, the electron efficiencies were 39.18%, 47.56%, 58.81%, 59.12%, and 84.19%, respectively. We found that both nZVI and Fe(II) had reduction effects, but which one played the major role depended on the reaction conditions. Finally, the possible reaction mechanisms were analyzed by combining experiments, models, and characterizations. The whole reaction process was divided into three stages: pollutant adsorption, electron transfer process, and mass transfer process. [ABSTRACT FROM AUTHOR]

According to Council Directive 98/83/EC on the quality of water intended for human consumption, concentration of the manganese in the drinking water should not exceed 0.05 mg/l. However, this level of manganese concentration is higher in groundwater of a community (Vitia town) in Kosovo. Groundwater is used for drinking supply of some villages and is only chlorified continuing to the reservoir from where is gravitationally disseminated to the villages. The manganese level of the water is at the range 0.3 to 0.6 mg/l. Limestone has been proven by many researchers to be a very effective filter material in manganese removal for groundwater. A miniature filtration unit was modeled to investigate the removal efficiency of manganese. The unit consists of local limestone, where a single material is folded in three layers of different grainsizes. In fact, the aim of this paper was to assess whether limestone as a single material acting as a "multi-media filter" can reduce the manganese concentration in groundwater. On the basis of the analysis of the single snapshot sample, the removal of manganese achieved more than 95% in filtered water. Particularly, this study demonstrates that filtering the water through three layers of different grain sizes of limestone ("multi-media limestone filter") can be a good alternative for manganese removal in groundwater. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the removal of Cu2+ using eggshells and iron-modified eggshells. Batch adsorption experiments were conducted to assess the impact of various operational parameters, including contact time, pH, isotherms, and kinetics. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). XRD analysis confirmed the presence of crystalline phases, specifically trigonal and hexagonal structures, in both eggshell samples. The addition of iron resulted in a reduction in the average crystallite size from 33.157 nm to 16.086 nm. The FTIR spectra exhibited a carbonyl peak at 1804 cm-1. The results indicated that Cu2+ adsorption on eggshells occurred rapidly, reaching equilibrium within 80 min, with an optimal pH range of 6.0 to 7.0. Furthermore, the modified eggshells demonstrated superior Cu2+ removal compared to unmodified eggshells due to the increased external surface area. The copper concentration on the eggshell surface increased from 0% to 94.58%, suggesting an ion exchange between iron and copper within the modified eggshell. The experimental data exhibited a better fit with the Freundlich isotherm model, indicating the presence of heterogeneous adsorption sites for Cu2+. The kinetics of adsorption followed a pseudo-second-order rate equation. This study highlights the efficacy of using eggshells, particularly iron-modified eggshells, as a cost-effective and accessible method for the efficient removal of heavy metals like Cu2+ from drinking water or industrial wastewater. [ABSTRACT FROM AUTHOR]

The development of zero-valent iron in-situ reactive zone technology is restricted by the poor mobility and reactivity of zero-valent iron. Hence，hollow micron zero-valent iron (H-mZVI) was prepared through rapid liquid reduction and used to remove Cr(VI) from aqueous solution. Scanning electron microscopy confirmed that H-mZVI had a hollow structure, particle size of approximately 1 µm, and rough surface. X-ray diffraction indicated that H-mZVI was mainly composed of ZVI. Brunauer–Emmett–Teller results showed that H-mZVI had a large specific surface area (25.54 m2/g) and pore volume (0.12 cm3/g). The Cr(VI) removal efficiency of H-mZVI was 6.18 times that of solid micron zero-valent iron (S-mZVI), and the removal reaction conformed to first-order reaction kinetics. Electrochemical test results revealed that the electron transport efficiency was stronger, Fe2+ concentration in aqueous solution was larger, and the decrease in oxidation–reduction potential was more obvious in H-mZVI than in S-mZVI. Desorption experiment and X-ray photoelectron spectroscopy showed that H-mZVI removed Cr(VI) primarily through reduction and secondarily through adsorption. The effects of conventional ions and humic acid (HA) on Cr(VI) removal by H-mZVI were in the order of PO 4 3->HA>NO 3 ->CO 3 2->HCO 3 ->Cl-=Mg2+=Ca2+. The corrosion products and their proportions varied in the presence of different ions. [Display omitted] • H-mZVI is synthesized by liquid phase reduction in a closed reactor. • H-mZVI removes Cr(VI) through adsorption and reduction. • The types and proportions of mineralized products of H-mZVI vary under different ions. [ABSTRACT FROM AUTHOR]

In this work, an iron-rich residue, which is widely obtained as a by-product in the iron mining industry, and macauba endocarp, waste from the extraction of vegetable oil for the production of biofuels, were used in the preparation of different composites based on iron and carbon. The composites were obtained by manual grinding of the calcined iron residue and activated carbon prepared by the macauba endocarp followed by thermal treatment under nitrogen atmosphere. The effect of the thermal treatment was analyzed by Mössbauer spectroscopy and X-ray diffraction and showed that the increase in the treatment temperature promoted the formation of different reduced iron phases in the final composite, such as Fe3O4, FeO, and Fe0. These composites were used in a combined adsorption/oxidation process through photocatalysis to remove up to 93% of amoxicillin from aqueous phase. The formation of possible reaction intermediates was monitored by electrospray ionization mass spectrometry (ESI–MS) and a mechanism of amoxicillin degradation was proposed. Afterward, the Fe/C composites were conducted to evaluate the impact of several parameters on phosphate adsorption processes and showed a maximum adsorption capacity of 40.3 mg g−1. The adsorption capacity obtained for all the materials were greater than those found in the literature. [ABSTRACT FROM AUTHOR]

This work uses a new nanoadsorbent after chemically synthesis from chicken eggshell wastes for removing amoxicillin (AMX) from aqueous solution. This removal was examined as a time function, initial concentration of AMX, pH, agitation speed, and adsorbent dosage. The study achieved the optimum time for equilibration in (90) min, at pH = 7 with an adsorbent dosage of 1.2 g. We applied many kinetic models to the sorption kinetic data where the pseudo-second-order model ( R 2 = 0.9924) was used to interpret the gained data at a rate constant K2 of (0.0077) g/(mg. min) at 200 rpm. Moreover, the adsorption calculated amount reached the experimentally required value and isotherm data best fitted the Langmuir model with R 2 (≥0.9486) than the Freundlich model. The intraparticle diffusion model revealed a diffusion dependent process. The different functional sets on the calcium/iron-surface as a layered double hydroxide (Ca/Fe)-LDH were important in sorpting the selected antibiotic. Forming (Ca/Fe)-LDH nanoparticles in the manufactured beads interacted with polluted water confirming that the nanoparticles own the prospective for acting as a latent sorbent to remove contaminants from aquatic media. [ABSTRACT FROM AUTHOR]

1,1,1-Trichloroethane (1,1,1-TCA) is a typical organochloride solvent in groundwater that poses threats to human health and the environment due to its carcinogenesis and bioaccumulation. In this study, a novel composite with nanoscale zero-valent iron (nZVI) supported by polycaprolac-tone (PCL)-modified biochar (nZVI@PBC) was synthesized via solution intercalation and liquid-phase reduction to address the 1,1,1-TCA pollution problem in groundwater. The synergy effect and improvement mechanism of 1,1,1-TCA removal from simulated groundwater in the presence of nZVI@PBC coupling with Shewanella putrefaciens CN32 were investigated. The results were as follows: (1) The composite surface was rough and porous, and PCL and nZVI were loaded uniformly onto the biochar surface as micro-particles and nanoparticles, respectively; (2) the optimal mass ratio of PCL, biochar, and nZVI was 1:7:2, and the optimal composite dosage was 1.0% (w/v); (3) under the optimal conditions, nZVI@PBC + CN32 exhibited excellent removal performance for 1,1,1-TCA, with a removal rate of 82.98% within 360 h, while the maximum removal rate was only 41.44% in the nZVI + CN32 treatment; (4) the abundance of CN32 and the concentration of adsorbed Fe(II) in the nZVI@PBC + CN32 treatment were significantly higher than that in control treatments, while the total organic carbon (TOC) concentration first increased and then decreased during the culture process; (5) the major improvement mechanisms include the nZVI-mediated chemical reductive dechlorination and the CN32-mediated microbial dissimilatory iron reduction. In conclusion, the nZVI@PBC composite coupling with CN32 can be a potential technique to apply for 1,1,1-TCA removal in groundwater. [ABSTRACT FROM AUTHOR]

The efficiency of using zeolite nano-clay and silica sand in removing iron from groundwater is investigated experimentally as an application of in situ remediation technique using permeable reactive barrier (PRB). In the first stage of the study batch experiments were conducted on coarse silica sand and fine silica gravel to determine their iron removal efficiency from contaminated water. The results showed that the removal efficiency was about 51.90% for coarse silica sand while fine silica gravel failed to reduce the iron concentration in water. A mix of zeolite nano-clay and coarse silica sand with a ratio of 1:30 was tested. It was found that iron removal efficiency significantly increases to about 99.70%. The linear adsorption isotherm was found to be the most representative for the adsorption of iron onto coarse silica sand and the mix of nano-clay and coarse silica sand with distribution coefficients equal 0.0009 and 0.001, respectively. In the second stage a glass sand tank with coarse silica sand and a mix of zeolite nano-clay and coarse silica PRBs was constructed. The sand tank was used to investigate the effect of sampling time, head difference, iron concentration, nano-clay dosage, and thickness of permeable reactive barrier on the iron removal efficiency. The results indicated that increasing iron concentration and head difference decreases iron removal efficiency. The mix of zeolite nano-clay and coarse silica sand improves iron removal efficiency. Furthermore, increasing nano-clay dosage slightly increases the removal efficiency. However, increasing the thickness of filter layer (i.e., PRB) significantly improves the removal efficiency. Finally, the experimental model data were used to test the capability of a numerical contaminant transport model to predict the removal efficiency. The MT3DMS numerical model included within the Groundwater Modeling System (GMS) was used along with the different experimental data to obtain reaction rate values as calibration parameters for linear isotherm. Reaction rates that yield modeling results matching experimental data were obtained. [ABSTRACT FROM AUTHOR]

Nano-zero-valent iron (nZVI) can be used to remove nitrate nitrogen (NO3-N) from groundwater. However, it has low reduction efficiency owing to its oxidation and aggregation characteristics. Thus, nZVI-loaded material is used to alleviate these drawbacks. In this study, nZVI-coated attapulgite (ATP) was prepared for the removal of NO3-N from groundwater. ATP-nZVI was prepared using the chemical liquid deposition-coreduction method. The prepared materials were characterized by SEM, XRD, and XPS analyses, which confirmed that the aluminum silicate particles in the ATP structure are effective carriers of nZVI and effectively inhibit self-consumption caused by the oxidation and aggregation of nZVI. The batch experiments examined experimental samples containing 30 mg/L nitrate and analyzed the effects of various parameters, including the material, mass ratio, initial pH, initial temperature, and coexisting anions on the NO3-N removal efficiency. The results showed that the optimal removal rate of the composite was 78.61%, which is higher than that using the same amount of ATP, iron powder, and nZVI. When the mass ratio of ATP to nZVI was 1 : 1, the NO3-N removal efficiency was the highest. When the pH value increased from 3 to 9, the NO3-N removal rate decreased, while an increase in the reaction temperature promoted NO3-N removal. The order of the inhibitory effect of coexisting anions on NO3-N removal by various nanoions was PO43–>CO32–>SO42–>Cl–. The adsorption kinetic model fitting results indicated that the chemisorption of electron exchange between ATP and nZVI in NO3-N removal was the main rate-limiting step in the reaction. This study demonstrates the potential of the prepared ATP-nZVI composite for NO3-N removal from groundwater. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electrochemical advanced oxidation processes are the most promising methods for destroying and degrading organic and inorganic pollutants present in produced water effluents. This study presents the electro‐oxidation process using graphite electrodes and electro‐Fenton process using iron electrodes for the treatment of real produced water. The effect of operating parameters such as current density on chemical oxygen demand (COD) removal efficiency was addressed. The result showed that electro‐Fenton process was more efficient than electro‐oxidation process where it gave 98% as maximum COD removal efficiency with energy consumption of 1.9 kWh/dm3 at H2O2 concentration of 12 mM, current density of 10 mA/cm2, temperature of 25°C, pH of 3, and treatment time of 80 min compared with 96.9% as maximum COD removal efficiency with energy consumption of 3 kWh/dm3 at pH of 6, current density of 10 mA/cm2, temperature of 40°C, and reaction time of 80 min when using electro‐oxidation process. These results demonstrated that electrochemical technologies are very promising methods for the treatment of produced water from oil/gas industry, so it can be safely disposed of or effectively reused for injection and irrigation. [ABSTRACT FROM AUTHOR]

Waste management and energy generation are the foremost concerns due to their direct relationship with biological species and the environment. Herein, we report the utilization of iron rust (inorganic pollutant) as a photocatalyst for the photodegradation of methylene blue (MB) dye (organic pollutant) under visible light (economic) and water oxidation (energy generation). Iron rust was collected from metallic pipes and calcined in the furnace at 700 °C for 3 h to remove the moisture/volatile content. The uncalcined and calcined rust NPs are characterized through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared (FTIR) analysis, X-ray Diffraction (XRD), and thermogravimetric analysis (TGA). The morphological study illustrated that the shape of uncalcined and calcined iron rust is spongy, porous, and agglomerated. The XRD and DLS particle sizes are in a few hundred nanometers range. The photodegradation (PD) investigation shows that calcined rust NPs are potent for the PD of modeled MB, and the degradation efficiency was about 94% in a very short time of 11 min. The photoelectrochemical (PEC) measurements revealed that calcined rust NPs are more active than uncalcined rust under simulated 1 SUN illumination with the respective photocurrent densities of ~0.40 and ~0.32 mA/cm2. The density functional theory simulations show the chemisorption of dye molecules over the catalyst surface, which evinces the high catalytic activity of the catalyst. These results demonstrate that cheaper and abundantly available rust can be useful for environmental and energy applications. [ABSTRACT FROM AUTHOR]

Iron (III) contaminant removal from aqueous solution of iron trioxonitrate (III) using chicken eggshell adsorbent was investigated in this study. The objective was to assess the efficacy of chicken eggshell adsorbent in treatment of wastewater. Standard methods were in conducting laboratory experiments. Results indicated 85.58% carbon content and particle size range 0.075 - 4.75 mm, characteristics of good adsorbents. Maximum removal of 91.16% was observed at 1.0 g dosage of adsorbent. Optimum adsorption of Fe3+ occurred at slightly acidic pH of 6 corresponding to 91.157% removal. Contaminant removal decreases with increase in initial metal concentrations from 10 - 40 mg/l corresponding to 91.16 -76.77%, while between 20 - 60° optimum removal of 92.58% was observed at 40 °C. Adsorption increased with increase in contact time between 67.84 -91.16% and equilibrium was attained at 90 minutes. The adsorption process best fits the Redlich-Peterson isotherm with highest R2-value of 0.9996, with the least errors in SSE, SAE and ARE of 0.00988, 0.15171 and 0.74788 respectively. The pseudo second-order kinetics best described the equilibrium adsorption and FTIR spectra for loaded and unloaded cases indicate that adsorption has taken place. It is concluded that eggshell is a good adsorbent. However, more research are recommended. [ABSTRACT FROM AUTHOR]

The serious environmental risks caused by Pb(II) and Sb(V) co-contamination increase the need for their efficient and simultaneous removal. In this study, the remediation feasibility by Fe-doped phosphogypsum (FPG) was elucidated for single systems with Pb or Sb pollutant and coexisting systems with both from water. As for single systems, Fe doping effectively enhanced the Pb(II) removal performance by phosphogypsum (PG) at low Pb(II) concentrations of below 100 mg/L via the combination of precipitation and complexation. The optimal removal rate of Sb(V) by FPG increased by 2.08–3.31 times as compared to that of by PG (10–120 mg/L), mainly due to the strong affinity of iron hydroxyl (≡Fe–O–H) towards Sb(V). Compared with the single systems, the coexistence greatly enhanced the Pb(II) and Sb(V) removal performance by FPG, and the interaction behavior between Pb(II) and Sb(V) on the FPG was concentration dependent. Briefly, the sorption of FPG controlled the elimination of low coexisting concentrations of Pb(II) and Sb(V), whereas the co-precipitation process between Pb(II) and Sb(V) predominated with high ions concentration. The significant synergistic effects were found during the removal of Pb(II) and Sb(V) on FPG in the coexisting system, which mainly attributed to precipitation, bridging complexation and electrostatic attraction. Considering the advantages such as facile preparation, low cost and high removal capacity, FPG is a promising material to uptake Pb(II) and/or Sb(V) from contaminated water. [ABSTRACT FROM AUTHOR]

In this study, a new type of phosphorylated chitosan-supported nano iron (CSP/Fe0) composite material. CSP/Fe0 had a high adsorption rate (99.25%) and a maximum adsorption capacity (627.34 mg g−1) when the conditions were pH = 6, 308.15 K and 12 h. CSP/Fe0 had a specific surface area of CSP/Fe0 was 6.02 m2 g−1, and has a mesoporous structure with more active sites (average pore size is 9.67 nm). The primary mechanism may be the complexation of U(VI) with abundant –OH, –NH2, P=O on the surface of the material and the reduction of nanoscale zero-valent iron. Therefore, it is indicated that the material has good potential in remediation of uranium-contaminated groundwater environment. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The power industry is one of the most water-consuming industries, therefore water management in this sector of the economy is a very important element of sustainable development. The analysis of the management of water streams at the surface water treatment plant (WTP) with decarbonization and ion exchange for water softening and demineralization was done. The main emphasis was placed on the effect of recycling of water used for the WTP's own purposes on the quantity of water taken from the river and the quality of treated water. The article shows that water savings should also be sought at WTP in combined heat and power plants. Accurate distribution of used technological water streams and determination of their quality allows for the appropriate indication of the points of their return to the main technological line without additional treatment or only with the use of basic technological processes, e.g. sedimentation. In the analysed WTP, the quality of the backwash water returned after treatment was in terms of parameters, i.e. conductivity, hardness, alkalinity, CODKMnO4 and iron concentration, better than the quality of raw surface water. The reduction in the amount of water abstracted due to recycling of water treatment plant technological waters was about 8.3% (approximately 130 000 m³/year). [ABSTRACT FROM AUTHOR]

Iron is one of the groundwater contaminants that negatively impact health and the environment. This study is attempted at introducing low cost natural adsorbent for that adsorbs iron from synthetically prepared iron water. Sawdust and barley husks were used as a filter media, either alone or at different mixing ratio of sawdust/barley husks (1:1, 0.5:1, 1:0.5), to study the effect of adsorbent dose on the removal efficiency. Synthetic water of iron was used at different initial concentrations (10, 25, 40, 65, and 80) mg/L to study the effect of initial iron concentration on the removal efficiency. The filtration process was conducted at a surface loading rate of 3 m3/m2.hr. The results showed higher removal efficiency with the increase of iron initial concentration. The results indicated that removal of iron ranged (90-99.34%) for all types of filter media. The best removal was found to be 99.34% at a mixing ratio of 0.5:1 (sawdust/barley husks) at 80 mg/L initial concentration. As a conclusion, Removal of iron was very successfully observed with absorbent materials sawdust and barley husk, which makes the treatment of iron even possible in rural areas and when high concentration of iron is present. [ABSTRACT FROM AUTHOR]

This study used modified manganese sand as an adsorbent to explore its adsorption effect on iron and manganese ions from groundwater. The effects of pH, manganese sand dosage, and the initial concentration of Fe/Mn on the removal rate of iron and manganese ions were studied through single-factor experiments. Based on the above three factors, a quadratic polynomial model between the adsorption rate and the above factors was established to determine the optimal adsorption conditions. The response surface analysis showed that pH had the most significant effect on the adsorption process. The optimum conditions for the adsorption of iron and manganese ions by modified manganese sand were pH = 7.20, the dosage of manganese sand = 3.54 g/L, and the initial concentration ratio of Fe/Mn = 3.80. The analysis of variance showed that the RSM model could accurately reflect the adsorption process of manganese sand. In addition, we confirmed that the relative error between model predictions and experimental values was close to 1%, proving that the response surface model was reliable. The kinetic data of the manganese sand were described well with the pseudo-second-order model. The isothermal adsorption of iron and manganese ions by modified manganese sand was fitted well using the Langmuir equation. [ABSTRACT FROM AUTHOR]

• Mild aeration (reduced pH and O 2) enabled Fe2+ oxidation at twice the rate compared to the intensively aerated filter. • Biological Fe2+ oxidation dominated in the filter with mild aeration producing characteristic twisted iron oxide stalks. • Filter clogging was slower for these biogenic iron oxides than for chemical iron oxides. • Less clogging (allowing lower backwash frequencies) combined with higher flow rates yielded four times more water per run. Rapid sand filters are established and widely applied technologies for groundwater treatment. In these filters, main groundwater contaminants such as iron, manganese, and ammonium are oxidized and removed. Conventionally, intensive aeration is employed to provide oxygen for these redox reactions. While effective, intensive aeration promotes flocculent iron removal, which results in iron oxide flocs that rapidly clog the filter. In this study, we operated two parallel full-scale sand filters at different aeration intensities to resolve the relative contribution of homogeneous, heterogeneous and biological iron removal pathways, and identify their operational controls. Our results show that mild aeration in the LOW filter (5 mg/L O 2, pH 6.9) promoted biological iron removal and enabled iron oxidation at twice the rate compared to the intensively aerated HIGH filter (>10 mg/L O 2, pH 7.4). Microscopy images showed distinctive twisted stalk-like iron solids, the biosignatures of Gallionella ferruginea , both in the LOW filter sand coatings as well as in its backwash solids. In accordance, 10 times higher DNA copy numbers of G. ferruginea were found in the LOW filter effluent. Clogging by biogenic iron solids was slower than by chemical iron flocs, resulting in lower backwash frequencies and yielding four times more water per run. Ultimately, our results reveal that biological iron oxidation can be actively controlled and favoured over competing physico-chemical routes. The production of more compact and practically valuable iron oxide solids is of outmost interest. We conclude that, although counterintuitive, slowing down iron oxidation in the water before filtration enables rapid iron removal in the biofilter. [Display omitted] [ABSTRACT FROM AUTHOR]

Microbial advanced oxidation, a fundamental process for pollutant degradation in nature, is limited in efficiency by the weak respiration of indigenous microorganisms. In this study, an electric field was employed to enhance microbial respiration and facilitate the microbial advanced oxidation of p-nitrophenol (PNP) in simulated wetlands with alternation of anaerobic and aerobic conditions. With intermittent air aeration, an electric field of 0.8 V promoted extracellular electron transfer to increase Fe2+ generation through dissimilatory iron reduction and the production of hydroxyl radicals (•OH) through Fenton-like reactions. As a result, the PNP removal rate of the electrically-stimulated group was higher than that of the control (72.15 % vs 46.88 %). Multiple lines of evidence demonstrated that the electrically-induced polarization of respiratory enzymes expedited proton-coupled electron transfer within the respiratory chain to accelerate microbial advanced oxidation of PNP. The polarization of respiratory enzymes with the electric field hastened proton outflow to increase cell membrane potential for adenosine triphosphate (ATP) generation, which enhanced intracellular electron transportation to benefit reactive oxygen species generation. This study provided a new method to enhance microelectrochemical remediation of the contaminant in wetlands via the combination of intermittent air aeration. [Display omitted] • Electrical stimulation promoted •OH generation to degrade pollutants in wetlands. • Polarized amide groups improved sediment electroactivity after electrical stimulation. • Polarized proteins benefited PCET in microbial respiration chains. • Accelerated PCET promoted Fe2+ generation to support microbial advanced oxidation. [ABSTRACT FROM AUTHOR]

Iron (Fe2+) is the major ground water pollutant which demands its efficient elimination. Iron availability in groundwater bespeak assorted geochemical processes along with subsurface contamination in distinct locale. Vulnerability of ground water due to Fe2+ contamination cannot be overlooked as this trace metal causes aesthetic issues, health issues and distribution networks deterioration. Although numerous techniques for recovery of iron have been developed and advanced, it was nevertheless not effectively removed. Biosorption technique is stand-alone technique which had the potential for the removal of Iron, and it deploys the mechanism of sorption. The present study aims to investigate the potential of Purolite resins as a low-cost adsorbent for the removal of Fe from ground water. The present study deals with the characterization of Purolite as specific resin adsorbent using SEM and FTIR. The study also investigates the effects of various parameters such as pH, adsorbent dosage, contact time and, initial ion concentration (ionic strength) on the adsorption system. Moreover, adsorption isotherms and kinetics were also evaluated for the process. [ABSTRACT FROM AUTHOR]

This work describes an experimental and machine learning approach for the prediction of selenite removal on chemically modified zeolite for water treatment. Breakthrough curves were constructed using iron-coated zeolite adsorbent and the adsorption behavior was evaluated as a function of an initial contaminant concentration as well as the ionic strength. An elevated selenium concentration in water threatens human health and aquatic life. The migration of this metalloid from the contaminated sites and the problems associated with its high releases into the water has become a major environmental concern. The mobility of this emerging metalloid in the contaminated water prompted the development of an efficient, cost-effective adsorbent for its removal. Selenite [ Se (IV) ] removal from aqueous solutions was studied in laboratory-scale continuous and packed-bed adsorption columns using iron-coated natural zeolite adsorbents. The proposed adsorbent combines iron oxide and natural zeolite's ability to bind contaminants. Breakthrough curves were initially obtained under variable experimental conditions, including the change in the initial concentration of Se   (IV) , and the ionic strength of solutions. Investigating the effect of these parameters will enhance selenite mobility retardation in contaminated water. Continuous adsorption experiment findings will evaluate the efficiency of this economical and naturally-based adsorbent for selenite removal and fate in water. Multilinear and non-linear regressions approaches were utilized, yet low coefficients of determination values were respectively obtained. Then, a comparative analysis of five boosted regression tree algorithms for a selenite breakthrough curve prediction was performed. AdaBoost, Gradient boosting, X G B o o s t , L i g h t G B M , and C a t B o o s t models were analyzed using the experimental data of the packed-bed columns. The performance of these models for the breakthrough curve prediction under different operation conditions, such as initial selenite concentration and ionic strength, was discussed. The applicability of these models was evaluated using performance metrics (i.e., Mean Absolute Error ( M A E ), Root Mean Square Error ( R M S E ), Mean Absolute Percentage Error ( M A P E ), and coefficient of determination ( R 2 ). The C a t B o o s t model provided the best fit for a breakthrough prediction with a coefficient of determination R 2 equal to 99.57. The k-fold cross-validation technique and the statistical metrics verify this model's accurateness. A feature importance assessment indicated that Se   (IV) initial concentration was the most influential experimental variable, while the ionic strength had the least effect. This finding was consistent with the column transport results, which observed Se   (IV) sorption dependency on its inlet concentration; simultaneously, the ionic strength effect was negligible. This work proposes implementing machine learning-based approaches for predicting water remediation-associated processes. The significance of this work was to provide an alternative method for investigating selenite adsorption behavior and predicting the breakthrough curves using a machine-based approach. This work also highlighted the importance of management practices of adsorption processes involved in water remediation. [ABSTRACT FROM AUTHOR]

Directly from the coasts of Mediterranean and Red Seas in Egypt by sieving; the Amphistegina tests (hard parts or shells) were accumulated in main size of 1.2 mm. While after 18 d of seawatersoftening, a definite calcite ooids were formed within an assembled semi-pilot seawater-softening unit with mesh size varying from 0.5 to 3.0 mm. For the first time, we used the Amphistegina tests and the fabricated calcite ooids as dual filtration media and iron removal from the groundwater sample presented from Al-Qurayyat, Jouf Governorate, Kingdom of Saudi Arabia. At temperatures of 293 and 313 K and different pumping speeds; 0.02, 0.03, 0.04, 0.05 and 0.06 m3/h, the filtrate of raw groundwater sample was achieved by different filtration media such as ooids, Amphistegina and dual Amphistegina-ooids filter. The maximum bed capacity for the dual-media filter vessel, which desired to full of is 13.2 L. This vessel has two layers of media includes ooids (2.28 L) and Amphistegina (5.97 L). At lower velocity (0.02 m3/h) and higher temperature (313 K), the iron removal efficiency reached to 74.15% by new dual-media filter from 1.47 mg/L in raw groundwater sample in the absence of chlorine injection. [ABSTRACT FROM AUTHOR]

The treatment of wastewater containing organic pollutants has become a serious issue, and one of the advanced oxidation process, Fenton oxidation is recognized as an ideal way owing to its universality and environmental friendliness, thus efficient and economic catalysts are in great demand. Herein by incorporating Fe2+ containing compound as ligand, a tremella-like iron containing metal–organic framework (TFMOF) was synthesized with zirconium acetate and 1,1′-ferrocene-dicarboxylic acid though a facile solvothermal method. The TFMOF combined the merits of both ferrocene moiety with well dispersed Fe2+ sites in the molecular level and MOF films with large surface areas and exposed sites. And the morphology and crystal structure of TFMOF were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Moreover, employed as an effective catalyst in Fenton oxidation, over 99%, 95% and 97% of rhodamine B, methyl orange and reactive black V were rapidly degraded without the assistance of additional irradiation, and degradation conditions like pH, H2O2 and initial pollutant concentrations as well as the reaction kinetic was investigated, indicating the hydroxyl radical generated in the presence of TFMOF and H2O2 was able to degrade the pollutants into non-toxic molecular. Besides, the catalytic activity of TFMOF maintained well after three cycles. The good activity and universality of TFMOF make it a promising catalyst for the treatment of wastewater. [ABSTRACT FROM AUTHOR]

Since the early twentieth century, disinfecting water has been an essential process to prevent the introduction of harmful organisms, especially pathogenic organisms. Due to the reaction between anthropogenic contaminants present in water and the chemicals used to disinfect water, compounds known as disinfection by-products (DBPs) are formed during the water disinfection process. Chlorination, the most dominant water disinfection method, produces DBPs that have drawn a lot of attention and health concerns. The most commonly used removal technology for trichloromethane (TCM) is adsorption, and the use of activated carbon, iron oxides, and nanoparticles has been widely investigated. Studies have found that using nano-zero valent iron with nano-catalytic metals (Cu, Ni etc.) to synthesize bimetallic nanoparticles increases the removal of organic pollutants. The current study investigates the adsorption of trichloromethane (TCM) by synthesized Fe/Cu bimetallic nanoparticles. The response surface methodology (RSM) was used to investigate the effect of independent variables on the removal of TCM. According to the CCD results, TCM concentration and reaction time were determined as the most effective parameters. The lowest TCM concentrations have low removal efficiencies, while the lowest TCM concentration (50 µg/L) can be removed up to 60%. The highest TCM concentration can be 500 µg/L to achieve a removal below the limits with 500 mg/L Fe/Cu concentration and 24 min of reaction time. Life cycle assessment (LCA) was applied to Fe/Cu nanoparticle synthesis, and results indicated that the highest environmental impact was from the mixture of reactant stage. [ABSTRACT FROM AUTHOR]

This work presents the fabrication, characterization, and application of iron-coated carbon fiber (Fe@CF), synthesized in a facile in situ iron reduction, for As(III) removal from an aqueous solution. The physico-chemical properties of the composite were characterized using Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy. Adsorption studies were evaluated in batch experiments with respect to reaction time, the dose of adsorbent, As(III) initial concentration, pH, and co-existing ions. The results showed that the BET surface area and pore volume of Fe@CF slightly decreased after Fe coating, while its pore size remained, while the SEM and XRD analyses demonstrated that the Fe was successfully anchored on the CF. A maximum As(III) adsorption of 95% was achieved with an initial As concentration of 1.5 mg/L at optimum conditions (30 min of reaction time, 1 g/L of dose, 1 mg/L of As(III) concentration, and pH 3.5). Since the treated effluents could not meet the strict discharge standard of ≤10 μg/L set by the World Health Organization (WHO), a longer reaction time is required to complete the removal of remaining As(III) in the wastewater effluents. As compared to the other adsorbents reported previously, the Fe@CF composite has the highest As(III) removal. Overall, the findings suggested that the use of Fe@CF as an adsorbent is promising for effective remediation in the aquatic environment. [ABSTRACT FROM AUTHOR]

In order to achieve efficient adsorptive and oxidative removal of pyrene, a persulfate oxidation system with composite nZVI-BC prepared by loading nano-zero-valent iron on coconut shell biochar as an activator was established and applied. The results of adsorption experiments showed that at pH 3, when the dosages of BC, nZVI and nZVI-BC were all 1.5 g/L, the removal efficiency of pyrene reached 64.9%, 19.0%, and 61.2%, respectively after 120 min of adsorption. The best performance of nZVI-BC-persulfate system was achieved at pH 3, nZVI-BC 1.2 g/L and persulfate concentration 6 mM, and after 60 min of degradation, the removal efficiency of pyrene reached 99.4%. The pre-adsorption process was a promoting-step for pyrene degradation. The conversion of nZVI to Fe2+ and Fe3+ played an important role in the activation of persulfate to produce SO 4 •− and •OH, both of which were responsible for non-selectively oxidization pyrene. The support of BC could improve the dispersibility and activity of nZVI and improve of the above conversion. The intermediates with relatively lower toxicity were identified during pyrene degradation, and they were successively oxidized into CO 2 and H 2 O finally. In summary, nZVI-BC can be a promising catalyst for persulfate activation to degrade PAHs in wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study innovated constructed an activated carbon-loaded nano-zero-valent iron (nZVI-C) enhanced membrane aerated biofilm reactor (MABR) coupled partial nitritation/anammox (PN/A) system for optimizing nitrogen and antibiotics removal. Results showed that nitrogen and antibiotic removal efficiencies of 88.45 ± 0.14% and 89.90 ± 3.07% were obtained by nZVI-C, respectively. nZVI-C hastened Nitrosomonas enrichment (relative abundance raised from 2.85% to 12.28%) by increasing tryptophan content in EPS. Furthermore, nZVI-C proliferated amo gene by 3.92 times and directly generated electrons, stimulating Ammonia monooxygenase (AMO) co-metabolism activity. Concurrently, via antibiotic resistance genes (ARGs) horizontal transfer, Nitrosomonas synergized with Arenimonas and Comamonadaceae for efficient antibiotic removal. Moreover, nZVI-C mitigated antibiotics inhibition of electron transfer by proliferating genes for PN and anammox electron production (hao, hdh) and utilization (amo, hzs, nir). That facilitated electron transfer and synergistic substrate conversion between ammonia oxidizing bacteria (AOB) and anaerobic ammonia oxidizing bacteria (AnAOB). Finally, the high nitrogen removal efficiency of the MABR-PN/A system was achieved. [Display omitted] • Nitrogen and antibiotic removal efficiencies of 88.45% and 89% were finally achieved. • nZVI-C enhanced tryptophan content to promote Nitrosomonas enrichment in biofilm. • nZVI-C stimulated AMO activity and enhanced Nitrosomonas co-metabolism ability. • Antibiotic removal relied on AMO and antibiotic resistance genes horizontal transfer. • Proliferation of electron transfer genes improved nitrogen removal efficiencye [ABSTRACT FROM AUTHOR]

Iron-based materials have garnered significant research interest due to their high surface reactivity, exhibiting potential for remediating metal(loid)s in groundwater. However, agglomeration and blockage limit its long-term and stability performance in application in permeable reactive barrier (PRB) technology. In this study, three innovative and low-cost iron composite fillers were prepared using a mass-producible impregnation method and applied as fillers for PRB. Static sorption and dynamic column experiments were conducted to assess the long-term performance of these composites to remediate multiple toxic metals(loids) contaminated groundwater. The results showed that the iron composite fillers had the excellent adsorption capacities for Co(II), Cu(II), Cr(VI) and As(III) from simulated contaminated groundwater even under the interference of Fe(III) and Mn(II). The pH of the influent favored the adsorption of toxic metals(loids) by the iron composite fillers in the order of 3.00＞5.00＞8.00＞7.00＞9.00＞6.00. The overall adsorption process was more consistent with the quasi-secondary kinetic equation. The corresponding constant values of Cr, Co, Cu, and As on CZ were 0.022, 0.093, 0.756, and 0.342 h−1, respectively. And that of CP-I and CP-II were 0.004, 0.022, 0.001, 0.126, 0.008, 0.041, 0.001, and 0.154 h−1, respectively. The specific surface area of the composite zeolite (Na 92 Al 92 Si 100 O 384) and composite pumice was 48.185 m2/g and 0.63 m2/g, respectively. The dynamic column experiment was run steadily for 40 days, during which the average removal rates of toxic metals(loids) were above 95% and approximate 20 times its own volume of contaminated water was purified. FeO(OH) on composite zeolite and Fe 3 O 4 on composite pumice played a dominant role in the removal of toxic metals(loids). The toxic metals(loids) adsorbed in the PRB were mainly in a stable phase of residual fraction and Fe-Mn oxide fraction, making them less likely to cause secondary pollution problems. [Display omitted] • Iron composite fillers applied for PRB were prepared based on pumice and zeolite. • The fillers exhibited an effective removal of toxic metals(loids) from groundwater. • Iron composite fillers were able to resist interference from iron and manganese ions. • The PRB columns filled with the fillers showed >95% removal of toxic metals(loids). • FeO(OH) and Fe 3 O 4 on fillers played a dominant role in removing heavy metal(loid)s. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new strategy for removing nutrient from wastewater at low C/N was proposed. • Fe(II) could significantly improve the robustness of MBBR. • Iron redox cycling and nitrogen removal in biofilm were realized by adding Fe(Ⅱ). • Interaction between pollutants and biofilm was reduced. • Correlation between environmental factors and functional bacteria was evaluated. A divalent iron-mediated moving bed biofilm reactor with intermittent aeration was developed to enhance the nitrogen removal at low carbon-to-nitrogen ratios. The study demonstrated that ammonia removal increased from 51 ± 4 % to 79 ± 4 % and nitrate removal increased from 72 ± 5 % to 98 ± 4 % in phases I-IV, and 2–5 mg·L-1 of divalent iron significantly increased the anoxic denitrification process. Divalent iron stimulated the secretion of extracellular polymeric substances, which facilitated the formation of cross-linked network between microbial cells. Furthermore, the cycle between divalent and trivalent iron decreased the energy barrier between the biofilm and the pollutant. The microbial community further revealed that Proteobacteria (relative abundance: 40–48 %) and Bacteroidota (relative abundance: 31–37 %) were the dominant phyla, supporting the synchronous nitrification and denitrification processes as well as the lower accumulation of nitrite. In conclusion, iron redox cycling significantly enhanced the nitrogen removal. This study proposes a viable strategy for the efficient treatment of nutrient wastewater. [ABSTRACT FROM AUTHOR]