RESUMEN
Water contaminated with arsenic presents serious health risks, necessitating effective and sustainable removal methods. This article proposes a method for removing arsenic from water by impregnating biochar with iron oxide (Fe2O3) from brown seaweed (Sargassum polycystum). After the seaweed biomass was pyrolyzed at 400 °C, iron oxide was added to the biochar to increase its adsorptive sites and surface functional groups, which allowed the binding of arsenic ions. Batch studies were conducted to maximize the effects of variables, including pH, contact time, arsenic concentration, and adsorbent dosage, on arsenic adsorption. The maximum arsenic adsorption efficiency of 96.7% was achieved under optimal conditions: pH 6, the adsorbent dosage of 100 mg, the initial arsenic concentration of 0.25 mg/L, and a contact time of 90 min. Langmuir and Freundlich's isotherms favored the adsorption process, while the kinetics adhered to a pseudo-second-order model, indicating chemisorption as the controlling step. Column studies revealed complete saturation after 200 min, and the adsorption behavior fits both the Adams-Bohart and Thomas models, demonstrating the potential for large-scale application. The primary mechanism underlying the interaction between iron-modified biochar and arsenic ions is surface complexation, enhanced by increased surface area and porosity. This study highlights the significant contribution of iron-modified biochar derived from macroalgae as an effective and sustainable solution for arsenic removal from water.
Asunto(s)
Arsénico , Carbón Orgánico , Compuestos Férricos , Algas Marinas , Contaminantes Químicos del Agua , Purificación del Agua , Arsénico/química , Arsénico/aislamiento & purificación , Carbón Orgánico/química , Algas Marinas/química , Adsorción , Compuestos Férricos/química , Purificación del Agua/métodos , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/aislamiento & purificación , Cinética , Concentración de Iones de HidrógenoRESUMEN
This research uses a novel TiO2@CSC.Alg composite sponge was created by encasing TiO2 nanoparticles in the natural polymers alginate and chitosan, resulting in a nanocomposite that is both ecologically friendly and biocompatible. Using the generated nanocomposite as a new environmentally friendly adsorbent, As(V) heavy metal ions were effectively removed from aqueous media. The following techniques were used to analyse the physicochemical properties of the obtained materials: pHZPC, FTIR, XRD, BET, SEM, and XPS. Utilizing nitrogen adsorption/desorption isotherms, the TiO2@CSC.Alg composite sponge's textural properties were identified. This revealed a BET surface area of 168.42 m2/g and a total pore volume of 1.18 cc/g, indicating its porous nature and potential for high adsorption capacity. Examine the effects of temperature, pH, dose, and beginning concentration on adsorption. The adsorption characteristics were determined based on equilibrium and adsorption kinetics measurements. The adsorption process was both pseudo-second-order (PSOE) and Langmuir isothermally fit. Chemisorption was the adsorption method since the adsorption energy was 25.45 kJ·mol-1. An endothermic and spontaneous adsorption process was indicated by more metal being absorbed as the temperature increased. The optimal conditions for adsorption were optimized via Box-Behnken design software to be pH of 5 in the solution, a dosage of 0.02 g of the TiO2@CSC.Alg composite sponge per 25 mL, and an arsenate (As(V)) solution the adsorption capacity was 202.27 mg/g are ideal for efficient adsorption. These parameters are critical in achieving the maximum adsorption capacity of the composite sponge for arsenate, which could be beneficial for water purification applications. Utilizing Design-Expert software's response surface methodology (RSM) and Box-Behnken design (BBD), the adsorption process was optimized with the fewest planned tests. After six successive cycles of adsorption and desorption, the adsorbent stability was confirmed by the adsorbent reusability test without any noticeable decrease in removal efficacy. Additionally, it displayed good efficiency, the same XRD and XPS data before and after reuse, and no change in chemical composition.
Asunto(s)
Alginatos , Quitosano , Nanocompuestos , Titanio , Contaminantes Químicos del Agua , Purificación del Agua , Titanio/química , Quitosano/química , Nanocompuestos/química , Adsorción , Alginatos/química , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/aislamiento & purificación , Cinética , Purificación del Agua/métodos , Concentración de Iones de Hidrógeno , Agua/química , Arsénico/química , Arsénico/aislamiento & purificación , Temperatura , Iones/químicaRESUMEN
Arsenic (As) speciation analysis is scientifically relevant due to the pivotal role the As chemical form plays in toxicity, which, in turn, directly influences the effect it has on the environment. The objective of this study was to develop and optimize a method tailored for studying As compounds in plant samples. Different extraction procedures and HPLC methods were explored to assess their efficiency, determine mass balance, and improve the resolution of compounds in the chromatograms. Conventionally applied anion-exchange chromatography facilitated the separation of well-documented As compounds in the extracts corresponding to 19 to 82% of As present in extracts. To gain insight into compounds which remain undetectable by anion chromatography (18 to 81% of As in the extracts), but still possibly metabolically relevant, we explored an alternative chromatographic approach. The procedure of sample purification and preconcentration through solid-phase extraction, facilitating the detection of those minor As compounds, was developed. The system was further refined to achieve an online 2D-RP-HPLC system, which was employed to analyze the extracts more comprehensively with ICP and ESI MS. Using this newly developed method, As(III)-phytochelatins, along with other arseno-thio-compounds, were detected and identified in extracts derived from the tree roots of seedlings grown in the presence of As(III) and As(V), and a group of arseno lipids was detected in the roots of plants exposed to As(V).
Asunto(s)
Arsénico , Espectrometría de Masa por Ionización de Electrospray , Cromatografía Líquida de Alta Presión/métodos , Espectrometría de Masa por Ionización de Electrospray/métodos , Arsénico/análisis , Arsénico/aislamiento & purificación , Extracción en Fase Sólida/métodos , Arsenicales/análisis , Arsenicales/química , Arsenicales/aislamiento & purificación , Extractos Vegetales/química , Raíces de Plantas/química , Plantas/química , Fitoquelatinas/química , Fitoquelatinas/metabolismoRESUMEN
For the removal of arsenic from marine products, iowaite was prepared and investigated to determine the optimal adsorption process of arsenic. Different chemical forms of arsenic (As(III), As(V)) with varying concentrations (0.15, 1.5, 5, 10, 15, and 20 mg/L) under various conditions including pH (3, 5, 7, 9, 11) and contact time (1, 2, 5, 10, 15, 30, 60, 120, 180 min) were exposed to iowaite. Adsorption isotherms and metal ions kinetic modeling onto the adsorbent were determined based on Langmuir, Freundlich, first- and second-order kinetic models. The adsorption onto iowaite varied depending on the conditions. The adsorption rates of standard solution, As(III) and As(V) exceeded 95% under proper conditions, while high complexity was noted with marine samples. As(III) and As(V) from Mactra veneriformis extraction all decreased when exposed to iowaite. The inclusion morphology and interconversion of organic arsenic limit adsorption. Iowaite can be efficiently used for inorganic arsenic removal from wastewater and different marine food products, which maybe other adsorbent or further performance of iowaite needs to be investigated for organic arsenic.
Asunto(s)
Arsénico/aislamiento & purificación , Compuestos Inorgánicos/aislamiento & purificación , Agua de Mar/química , Contaminantes Químicos del Agua/aislamiento & purificación , Concentración de Iones de Hidrógeno , Cinética , TermodinámicaRESUMEN
Desulfurized gypsum (DG) as a soil modifier imparts it with bulk solid sulfite. The Fe(III)-sulfite process in the liquid phase has shown great potential for the rapid removal of As(III), but the performance and mechanism of this process using DG as a sulfite source in aqueous solution remains unclear. In this work, employing solid CaSO3 as a source of SO32-, we have studied the effects of different conditions (e.g., pH, Fe dosage, sulfite dosage) on As(III) oxidation in the Fe(III)-CaSO3 system. The results show that 72.1% of As(III) was removed from solution by centrifugal treatment for 60 min at near-neutral pH. Quenching experiments have indicated that oxidation efficiencies of As(III) are due at 67.5% to HOâ¢, 17.5% to SO5â¢- and 15% to SO4â¢-. This finding may have promising implications in developing a new cost-effective technology for the treatment of arsenic-containing water using DG.
Asunto(s)
Arsénico/química , Calcio/química , Hierro/química , Sulfitos/química , Contaminantes Químicos del Agua/química , Agua/química , Arsénico/aislamiento & purificación , Oxidación-Reducción , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del AguaRESUMEN
Synthesis and application of a task-specific ionic liquids (TSILs) as extracting solvents or chelating agents in dispersive liquid-liquid micro-extraction (DLLME) was evaluated. The developed method was based on the use of an ammonium pyrrolidine dithiocarbamate (APDC) bonded ionic liquid for chelation with As(III), followed by conversion of the As(III) chelated TSIL to a hydrophobic ionic liquid using KPF6 as an anion-exchange reagent. As(V) was reduced to As(III), using a 2/1 w/w blend of KI and Na2S2O3 and then the total amount of As was measured through ETAAS analysis. Under optimal conditions, linear dynamic ranges of 0.2-15 ng mL-1 and 0.2-20 ng mL-1 were observed in the determination of As(III) and total As respectively. The relative standard deviations (RSD%, n = 5) for the determination of As(III) (10 ng mL-1) was 3.2% and the limits of detection and quantitation were determined to be 0.01 ng mL-1 and 0.0.034 ng mL-1; respectively.
Asunto(s)
Arsénico/análisis , Arsénico/aislamiento & purificación , Líquidos Iónicos/química , Microextracción en Fase Líquida/métodos , Espectrofotometría Atómica/métodos , Límite de DetecciónRESUMEN
The correct immobilization and orientation of enzymes on nanosurfaces is a crucial step either for the realization of biosensors, as well as to guarantee the efficacy of the developed biomaterials. In this work we produced two versions of a chimeric protein, namely ArsC-Vmh2 and Vmh2-ArsC, which combined the self-assembling properties of Vmh2, a hydrophobin from Pleurotus ostreatus, with that of TtArsC, a thermophilic arsenate reductase from Thermus thermophilus; both chimeras were heterologously expressed in Escherichia coli and purified from inclusion bodies. They were characterized for their enzymatic capability to reduce As(V) into As(III), as well as for their immobilization properties on polystyrene and gold in comparison to the native TtArsC. The chimeric proteins immobilized on polystyrene can be reused up to three times and stored for 15 days with 50% of activity loss. Immobilization on gold electrodes showed that both chimeras follow a classic Langmuir isotherm model towards As(III) recognition, with an association constant (KAsIII) between As(III) and the immobilized enzyme, equal to 650 (± 100) L mol-1 for ArsC-Vmh2 and to 1200 (± 300) L mol-1 for Vmh2-ArsC. The results demonstrate that gold-immobilized ArsC-Vmh2 and Vmh2-ArsC can be exploited as electrochemical biosensors to detect As(III).
Asunto(s)
Arseniato Reductasas/química , Arsénico/aislamiento & purificación , Técnicas Biosensibles , Proteínas Fúngicas/química , Proteínas Recombinantes de Fusión/química , Arsénico/toxicidad , Enzimas Inmovilizadas/química , Escherichia coli/genética , Humanos , Pleurotus/química , Pleurotus/enzimología , Thermus thermophilus/enzimologíaRESUMEN
In this study, complex nickel-aluminum hydroxides were prepared at different molar ratios (NA12, NA11, NA21, NA31, and NA41), and their adsorption capability on arsenic ions (As(III)) from aqueous media was assessed. The physicochemical properties such as morphology, X-ray diffraction pattern, specific surface area, numbers of hydroxyl groups, and surface pH were investigated. In addition, the effect of contact time, temperature, and pH on the adsorption capability on As(III) was also evaluated. NA41 exerted the highest adsorption capability on As(III) comparable to other prepared adsorbents. However, the specific surface area and numbers of hydroxyl groups did not significantly affect the adsorption capability on As(III). The equilibrium adsorption of As(III) using NA41 was achieved within 24 h, and the obtained results corresponded to a pseudo-second-order model with correlation coefficient value of 0.980. Additionally, the adsorption isotherms were well described by both the Langmuir and Freundlich equations. The optimal pH condition for removal of As(III) using NA41 was found to be approximately 6-8. Finally, the adsorption mechanism of As(III) was assessed by analyzing the binding energy and elemental distribution, which indicated that the electrostatic interaction and ion exchange influenced the adsorption of As(III) under experimental conditions. These results demonstrated the potential candidate of NA41 as an effective adsorbent on As(III) removal from aqueous media.
Asunto(s)
Aluminio/química , Arsénico/aislamiento & purificación , Hidróxidos/química , Níquel/química , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Arsénico/química , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Propiedades de Superficie , Contaminantes Químicos del Agua/químicaRESUMEN
As one of the most significant natural polymer with the highest annual yield, lignin has been applied in the treatment of wastewater to remove heavy metal ions. However, there are still some shortages, such as low reactivity, difficulties in adsorbing oxyanions and low selectivity on specific oxyanions. To improve its adsorption properties, a novel lignin-based adsorbent was prepared in this study, doped with nitrogen by Mannich reaction, using triethylenetetramine (TETA) as N source, and further modified with Ca2+. The adsorption of Ca, N-co-doped lignin (Ca@N-Lig) for As (V), Cr (VI) and P (V) was studied. The Ca@N-Lig shows high capacity, excellent selectivity and prominent regeneration ability for As (V) adsorption. The adsorption of Ca@N-Lig for As (V) followed the Langmuir isotherm model and the pseudo-second-order kinetics model, yielding a maximum adsorption capacity of 681.59 mg·g-1 and a fast adsorption equilibrium within 30 min. Ca@N-Lig has an excellent regeneration ability on the adsorption of As (V) with a decrease of about 15.60% after 5 adsorption/desorption cycles. This study offers an efficient way to remove As (V) from polluted water.
Asunto(s)
Arsénico/aislamiento & purificación , Calcio/química , Lignina/química , Nitrógeno/química , Trientina/química , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Equipo Reutilizado , Agua Dulce/química , Humanos , Cinética , Bases de Mannich/química , Aguas Residuales/química , Purificación del Agua/métodosRESUMEN
Ti (IV)-modified vinyl phosphate magnetic nanoparticles (Fe3 O4 @SiO2 @KH570-PO4 -Ti (IV)) was prepared for simultaneous extraction of multiple arsenic species, followed by high performance liquid chromatography (HPLC)- inductively coupled plasma mass spectrometry (ICP-MS) analysis. Inorganic arsenic (iAs), dimethyl arsenic acid (DMA), monomethyl arsenic acid (MMA), p-amino phenyl arsenic acid (p-ASA), 4-hdroxyphenylarsenic acid (4-OH), phenyl arsenic acid (PAA), and 3-nitro-4-hydroxyphenylarsenic acid (ROX) were investigated as interest analytes. It was found that they were quantitatively adsorbed on Fe3 O4 @SiO2 @KH570-PO4 -Ti (IV) at pH 5, and desorbed completely with 0.1 mol/L sodium hydroxide solution. Enrichment factor of 100-fold was obtained by consuming 100 mL sample solution. Under the optimal conditions, the method combining MSPE with HPLC-ICP-MS presented a linear range of 1-5000 ng/L for seven arsenic species. The limits of detection were 0.39, 0.60, 0.23, 1.85, 0.54, 0.48, and 0.84 ng/L for DMA, MMA, p-ASA, iAs, 4-OH, PAA, ROX, with the relative standard deviations (c = 10 ng/L, n = 7) of 3.6, 3.9, 5.5, 12.4, 6.1, 5.8, 5.0, respectively. The accuracy of the method was validated by analyzing BCR 627 Tuna fish. The application potential of the method was further evaluated by chicken muscle and liver samples. No target arsenic species were detected in these samples, and good recoveries (80.6-123%) were obtained for the spiked samples at low, medium, and high concentration levels.
Asunto(s)
Arsénico , Arsenicales , Cromatografía Líquida de Alta Presión/métodos , Nanopartículas de Magnetita/química , Espectrometría de Masas/métodos , Animales , Arsénico/análisis , Arsénico/química , Arsénico/aislamiento & purificación , Arsenicales/análisis , Arsenicales/química , Arsenicales/aislamiento & purificación , Pollos , Límite de Detección , Modelos Lineales , Hígado/química , Carne/análisis , Músculos/química , Compuestos Organofosforados/química , Reproducibilidad de los Resultados , Titanio/química , Atún , Compuestos de Vinilo/químicaRESUMEN
In the lowlands of Nepal (Terai), the WHO drinking water guideline concentration of 10 µg/L for arsenic (As) is frequently exceeded. Since their introduction in 2006, iron-assisted bio-sand filters (Kanchan filters) are widely used to treat well water in Nepal. The filters are constructed on the basis of As-removal with corroding zero-valent iron (ZVI), with water flowing through a filter bed of iron nails placed above a sand filter. According to several studies, the performance of Kanchan filters varies greatly and depends on the size of the iron nails, filter design, water composition, and operating conditions, leading to concerns about their actual efficiency. This study examined 38 Kanchan household filters for which insufficient As-removal was reported, to evaluate the reasons for limited removal efficiency and to define measures for improved performance. The measured arsenic removal ranged from 6.3% to 98.5%. The most relevant factors were the concentrations of As and Fe in the raw water, with the best removal efficiency observed for water with low As (123 µg/L) and high Fe (5.0 mg/L). Although the concentrations of other elements, pH, flow rates, and contact time with ZVI also played a role, the combined evidence indicated that the reactivity of the frequently drying nail beds between filtrations was insufficient for efficient As-removal. Optimized filters with added top layers of sand and raised water outlets with flow restrictions to keep nails permanently immersed and to increase contact times, should be able to achieve higher and more consistent arsenic removal efficiencies.
Asunto(s)
Arsénico/aislamiento & purificación , Filtración/métodos , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Arsénico/análisis , Arsénico/química , Composición Familiar , Filtración/instrumentación , Hierro/análisis , Hierro/química , Nepal , Agua/química , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/química , Purificación del Agua/instrumentaciónRESUMEN
A novel adsorbent Mn-Fe layered double hydroxides intercalated with ethylenediaminete-traacetic (EDTA@MF-LDHs) was synthesized by a low saturation coprecipitation method. The behavior and mechanism of As(III) removed by EDTA@MF-LDHs were investigated in detail in comparison with the carbonate intercalated Mn-Fe layered double hydroxides (CO3@MF-LDHs). The results showed that EDTA@MF-LDHs had a higher removal efficiency for As(III) than As(V) with a broader pH range than CO3@MF-LDH. The large adsorption capacity of EDTA@MF-LDHs is related to its large interlayer spacing and the high affinity of its surface hydroxyl groups. The maximum adsorption capacity for As(III) is 66.76 mg/g at pH 7. The FT-IR and XPS characterization indicated that the removal mechanism of the As(III) on EDTA@MF-LDHs include surface complexation, redox, and ion exchange.
Asunto(s)
Aniones , Arsénico , Técnicas de Química Analítica , Ácido Edético , Hierro , Magnesio , Aniones/síntesis química , Arsénico/aislamiento & purificación , Técnicas de Química Analítica/métodos , Ácido Edético/química , Concentración de Iones de Hidrógeno , Hidróxidos/química , Hierro/química , Magnesio/química , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Fractionation information on arsenic (As) in complex samples, particularly solid samples, is of immense interest. Herein, selective extraction of various As species adsorbed onto ferrihydrite as the model substrate was online-adapted to inductively coupled plasma-mass spectrometry (ICP-MS) for sensitive detection. The As-adsorbed ferrihydrite sample was loaded into a homemade online sequential elution device using two commercially available micropipette tips, and then, each fraction of As including nonspecifically adsorbed, specifically adsorbed, iron oxide bonded, and residual species was successively extracted for ICP-MS detection, with H2O, NH4NO3, NH4H2PO4, ammonium oxalate, and HF as the eluents, respectively. While no water-soluble As was detected, the fraction of As bonded to iron oxide was detected as the dominant species (>80%), and the specifically adsorbed As and residual As also accounted for a substantial amount (10%). The method had a detection limit of 0.008 µg/kg for As(III) and 0.013 µg/kg for As(V), with merits such as extremely low sample consumption, high throughput, and minimized experimental manipulation, presenting an alternative strategy for sensitive fractionation analysis of As adsorbed onto solid substrates (e.g., iron oxides, etc.).
Asunto(s)
Arsénico/análisis , Arsénico/aislamiento & purificación , Fraccionamiento Químico/métodos , Compuestos Férricos/química , Espectrometría de Masas , Adsorción , Arsénico/química , Límite de Detección , Propiedades de SuperficieRESUMEN
Films made from neat chitosan and chitosan with magnetic nanoparticles (MNPs) were tested as adsorbents of arsenate ions. Sorption equilibrium and sorption kinetics studies are reported, including different models applied to enlighten experimental observations and predict results. The sorption of As (V) was reasonably explained using Freundlich isotherm for neat chitosan film although it was better represented by Langmuir equation for the composite sample. The experimental kinetics results showed that the adsorption of arsenate ions is very fast during the first minutes and then the composite seems to reach saturation, while a slow desorption in the chitosan film was observed and acceptably fitted with a pseudo first order reversible model. The adsorbent containing MNPs presented higher adsorption capacity, which was associated to the additional adsorbent capacity provided by the MNPs and its much more irregular surface area that leads to an enhanced adsorption surface. For instance, at 10 mg/L equilibrium concentration, which corresponds to an initial concentration of As (V) much higher than the normal concentration of arsenate in natural water, chitosan-MNP sample exhibits a removal capacity of 10.4 mg/g that is more than six times higher than the 1.6 mg/g shown by the chitosan film.
Asunto(s)
Arsénico/aislamiento & purificación , Quitosano/química , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Adsorción/efectos de los fármacos , Arsénico/toxicidad , Compuestos Férricos/química , Cinética , Nanopartículas/química , Agua/química , Contaminantes Químicos del Agua/toxicidadRESUMEN
Natural groundwater from the towns of Wabana and Freshwater and treated well water from the town of Wabana in Newfoundland and Labrador, Canada were tested separately and together in sand columns to study the removal of arsenic. The most ideal conditions for arsenic removal appeared to include an arsenic concentration of approximately 35 µg/L and lower, an Fe:As mass ratio in the order of 65 and lower, and aeration of the sand media. Active aeration by pumping air though the filter, passive aeration by scraping off top layers of sand and virtual aeration by diluting the strength of the water being treated, were employed and compared. For tests where groundwater from the towns of Wabana and Freshwater was combined, arsenic removal was optimized and other elements, in addition to iron, were also correlated with effluent arsenic. Further, for these same tests there was a gradual increase in effluent pH that could have been due to oxygen depletion or gradually more reducing conditions in the sand column. Where Ni, Mn and Zn were correlated with effluent arsenic it was concluded that the increase in pH increased heavy metal removal and arsenic release. In the test where the treated Wabana water made up a greater proportion of the mix than the Wabana groundwater, lithium was also correlated with arsenic.
Asunto(s)
Arsénico/aislamiento & purificación , Filtración/métodos , Agua Subterránea/química , Hierro/análisis , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Aire , Arsénico/análisis , Filtración/instrumentación , Laboratorios , Terranova y Labrador , Oxígeno , Arena , Contaminantes Químicos del Agua/análisis , Purificación del Agua/instrumentación , Pozos de AguaRESUMEN
Tooeleite is the only known ferric arsenite sulfate mineral and has environmental significance for arsenic remediation. This study investigated the formation and stability of biogenic tooeleite in Fe(II)-As(III)-SO42- environment using Acidithiobacillus ferrooxidans under the ambient conditions. The results show that bacteria facilitated the formation and crystallization of tooeleite owing to the microbial oxidation of Fe(II) to Fe(III). Due to the better growth of bacteria, the higher removal of As(III) by tooeleite formation was achieved under 8.978-10.806 g/L initial Fe(II) concentration and 2.00-3.00 initial pH, and the highest efficiency was ~95%. Fe(III) and As(III) precipitated simultaneously into two types of tooeleite. The relatively stable tooeleite is featured by the developed (020) crystal face and the bulk-like structure with thick flakes. This study yields a better understanding of biogenic tooeleite, and the importance of tooeleite formation in As(III)-rich environment for arsenic remediation.
Asunto(s)
Acidithiobacillus/metabolismo , Arsénico/metabolismo , Compuestos Férricos/química , Hierro/metabolismo , Acidithiobacillus/química , Arsénico/química , Arsénico/aislamiento & purificación , Cristalización , Concentración de Iones de Hidrógeno , Hierro/química , Oxidación-ReducciónRESUMEN
Arsenic is one of the inorganic pollutants typically found in natural waters, and its toxic effects on the human body are currently of great concern. For this reason, the search for detoxifying agents that can be used in a so-called "chelation therapy" is of primary importance. However, to the aim of finding the thermodynamic behavior of efficient chelating agents, extensive speciation studies, capable of reproducing physiological conditions in terms of pH, temperature, and ionic strength, are in order. Here, we report on the acid-base properties of meso-2,3-dimercaptosuccinic acid (DMSA) at different temperatures (i.e., T = 288.15, 298.15, 310.15, and 318.15 K). In particular, its capability to interact with As(III) has been investigated by experimentally evaluating some crucial thermodynamic parameters (ΔH and TΔS), stability constants, and its speciation model. Additionally, in order to gather information on the microscopic coordination modalities of As(III) with the functional groups of DMSA and, at the same time, to better interpret the experimental results, a series of state-of-the-art ab initio molecular dynamics simulations have been performed. For the sake of completeness, the sequestering capabilities of DMSA-a simple dithiol ligand-toward As(III) are directly compared with those recently emerged from similar analyses reported on monothiol ligands.
Asunto(s)
Arsénico/aislamiento & purificación , Líquidos Corporales/química , Quelantes/química , Succímero/química , Arsénico/química , Humanos , Concentración de Iones de Hidrógeno , Ligandos , Simulación de Dinámica Molecular , Estructura Molecular , TermodinámicaRESUMEN
Innovative iron/calcium in-situ-impregnated mesoporous activated carbons (GL100 and GL200) have been prepared by iron/calcium in-situ-impregnation and Multistage Depth-Activation. Arsenic adsorption kinetics, isotherms, thermodynamics, and re-usability were investigated. Effects of surface-absorbed (ST-HA) and dissolved states humic acid (DHA) on the arsenic adsorption were also determined. Results suggested in-situ iron/calcium impregnation caused the well-development of mesoporous structures during ranges of 2.0-5.0 nm in GL100 and 5.0-50 nm in GL200, respectively. The increase of iron/calcium ensured surface basicity and high ash contents on GL100/GL200, and As(III)/As(V) can be better adsorbed in neutral conditions with higher kinetics in comparison with regular mesoporous carbon XHIT. Maximum adsorption capacities of As(III)/As(V) by GL100 and GL200 were 2.985/3.385 mg/g and 2.516/2.807 mg/g, respectively. Arsenic desorption and carbon re-usability of GL100/200 was improved. As(III)(As (V)) adsorption capacities by GL100 and GL200 were 2.437(1.672) mg/g and 1.740(1.308) mg/g, respectively, after eight cycles. Arsenic adsorption capacities on GL100 were proved to be promoted with the presence of low-level of ST-HA or DHA, and be inhibited at a high-level. As(V) was bound more strongly than As(III) in the presence of ST-HA. As(III)/As(V) uptakes increased slightly and decrease gradually to 1.75/1.86 mg/g in the presence of DHA (0-10 mg DOC/L). Physisorption and chemisorption mechanisms dominant in arsenic adsorption on GL100 in presence of humic acid, forming inner-sphere complexation with metallic oxide, functional groups on carbon surface and humic acid structure, or ternary surface complexation via cationic metal ions as cation bridge.
Asunto(s)
Arsénico/aislamiento & purificación , Carbón Orgánico/química , Frío , Purificación del Agua/métodos , Adsorción , Arsénico/química , Calcio/química , Sustancias Húmicas/análisis , Hierro/química , Cinética , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/aislamiento & purificaciónRESUMEN
Remediation of soil heavy metal by biochar has been extensively studied. However, few studies focused on the role of biochar on the co-immobilization of cadmium (Cd(II)) and arsenate (As(V)) and related soil nutrient availability. Remediation tests were conducted with three types of pristine and ferric trichloride (FeCl3) modified biochar (rice, wheat, and corn straw biochar) in Cd-As co-contaminated soil, with application rates of 1, 5, and 10% (w/w) and the incubation of 1, 7, 10, and 15 days. Using TCLP (Toxicity Characteristic Leaching Procedure) method, 10% of FeCl3 modified corn-straw derived biochar (FCB) had the highest immobilization efficiency of Cd(II) (63.21%) and As(V) (95.10%) after 10 days of the incubation. Iron-modified biochar immobilized higher fractions of water-soluble (F1) and surface-absorbed (F2) metal fractions than pristine biochar. For FCB amendment, Cd was mostly presented in the organic matter (OM) and sulfides associated (F4) and residual (F5) fractions (88.52%), as was found in the Fe-Al (oxides and hydroxides) (F3), F4, and F5 fractions (75.87%). FCB amendment increased soil pH values and available iron contents (p < 0.05), while no changes in soil available phosphorus content (p > 0.05). This study showed that FCB application reduces the environmental mobility of metals in Cd-As contaminated soil, while it also increases soil pH and available nutrient mobility, improving soil environmental quality and reducing remediation costs.
Asunto(s)
Arsénico/aislamiento & purificación , Cadmio/aislamiento & purificación , Carbón Orgánico , Hierro , Contaminantes del Suelo/aislamiento & purificación , SueloRESUMEN
The manganese sludge from laboratory biological manganese removal filter column backwashing residue was used to modify the Chitosan Alginate Fe-sludge Beads. The Chitosan Alginate Fe-sludge Beads strengthened with manganese sludge (CAFBs) get the oxidation ability and can removal As(III) effectively without a pre-oxidation process. It was characterized by SEM (scanning electron microscopy), XRD (X-ray diffraction), and BET (Brunauer-Emmett-Teller analysis). Batch adsorption experiments were carried out to study the mechanism of As(III) removal. SEM-EDS shows that the surface is rough and rich in iron and manganese element (32.8%). The BET data shows that it is porous and has large surface area (99.20 m2·g-1). XRD proves that the main components of CAFBs are amorphous iron oxide and MnO2.Neutral and weak alkaline conditions (pH = 7-9) were favorable for the adsorption and H2PO4- had obvious inhibitory effect on As(III) removal. The experimental data shows that the Pseudo-second kinetic model, intra-granular diffusion model and Freundlich isotherm can better describe the adsorption process of As(III) by CAFBs. At 298 K, the maximum adsorption capacity of As(III) is 20.16 mg/g. Regeneration studies find that CAFBs can be effectively regenerated by aeration into the NaOH solution.