Amount Of Arsenic Research Articles

Facile synthesis of Co/rGO, Au/rGO, and CoAu/rGO nanocomposites for precise determination of Arsenic(III) in water systems

Cobalt (Co), gold (Au), and cobalt-gold (CoAu) nanoparticles were deposited on reduced graphene oxide (rGO) by a facile and scalable procedure. The synthesised nanocomposites (Co/rGO, Au/rGO, and CoAu/rGO) were used as electrode materials for detecting trace amounts of arsenic (As(III)) ions in water samples. All three electrodes responded to the presence of As(III) in an acidic medium (different acids of the same concentration, then chosen acid at different concentrations). A detailed optimization of the conditions was continued with the CoAu/rGO electrode which showed the best response in terms of the best defined peak indicating the oxidation of As(0) to As(III) and the highest current. The electrode was tested in a wide range of concentrations (30–1000 µM), where two areas of linearity and limits of detection were obtained (for low- and high- concentrations). Moreover, this electrode showed the ability to detect As(III) ions in the presence of Cu(II), as an interference model as well as a satisfactory electrochemical response, in terms of a clear peak corresponding to the oxidation of As(0) to As(III) in a real sample.

Environmental contamination of arsenic: pathway analysis through water-soil-feed-livestock in Nadia District (India) and potential human health risk.

This study investigated arsenic (As) concentrations in diverse environmental components and their potential impact on the health risks faced by residents of the arsenic (As)-contaminated Nadia district in West Bengal, India. A random selection of 182 cattle and 255 goats from 40 livestock farmers in the district revealed that both animals and humans were naturally exposed to elevated arsenic levels through contaminated drinking water, foods, grasses, concentrate feeds, various fodder tree leaves, and other food/feed resources. The mean As concentration in roughages (483.18µg/kg DM) was significantly higher (p < 0.001) than in tree leaves (391.53µg/kg DM), and concentrate feed/ingredients (186.66µg/kg DM). Pond water exhibited higher arsenic levels (106.11µg/L) compared to shallow tube well water (47.96µg/L) and deep tube well water/tap water (10.64µg/L and 10.04µg/L, respectively). The mean arsenic concentration in soils DM of fodder fields, crop fields, and grassland was 10.25, 10.58, and 10.20mg/kg, respectively. It was observed that protein-rich feeds had lower levels of arsenic accumulation (p < 0.048), while fiber-rich feeds containing more cellulose, hemicellulose, and lignin had higher arsenic levels (p < 0.017). Goats consumed 73.46% more arsenic per kg body weight compared to dairy cows. Although chronic and sub-chronic arsenic exposure in the district did not typically manifest symptoms or visible signs in ruminant animals, concentrations in the hair and feces of both cattle and goats exceeded normal values. Cattle feces had significantly higher arsenic (410.43µg/kg DM) levels (p < 0.001) than goat feces (227.00µg/kg DM), and arsenic concentration in cattle hair (1917.74µg/kg DM) was also significantly greater (p < 0.001) than goat hair (1435.74µg/kg DM). Arsenic levels in milk samples from both species were below 10µg/kg. Liver (356.02µg/kg DM) and kidney (317.22µg/kg DM) contained significantly higher (p < 0.001) levels of arsenic compared to muscle (204.23µg/kg DM), and bone (161.98µg/kg DM) in local meat-type adult male goats. The skin accumulated the highest amount of arsenic (576.24µg/kg DM) among the non-edible parts of the goat carcass. The cumulative cancer risk value for adults was 4.96 × 10-3, exceeding the threshold value (1 × 10-6). This suggests a significant risk of cancer development for the population in arsenic-affected areas. Non-cancer risks (hazard indexes) were estimated at 11.01 for adults. Our observations revealed that the highest bioaccumulation of arsenic occurred in the hair of cows, and goats in the examined localities. The biotransformation factor (BTF) for hair was much higher compared to other excreted samples from both species. The calculated BTF followed the order: hair > feces > milk for cows and goats. Livestock farmers in Nadia district are advised to carefully select feed resources, prioritizing those high in crude protein and low in neutral detergent fiber, and they should provide drinking water from deep aquifers to ensure the safety of milk and meat for human consumption.

Photovoltaic performance of pristine and arsenic doped hybrid perovskite

Under the scope of all-solid-state perovskite solar cells, the important role of methylammonium lead halide film lies in facilitating the formation of a photo-generated electronrich film, which directly affects the overall photovoltaic performance. This study introduces a novel chemical strategy aimed at increasing the quality of perovskite film through minimal arsenic doping. The result of the inclusion of arsenic is characterized by high crystalline grains in the attainment of a homogeneous, uniform and ancient perovskite film. The analysis of the UV-Visible spectra indicates that the perovskite film, which is produced under sequential conditions, displays light extraction of electrons for light absorption, more effective electron transport, and adjacent electron transport layer. Different morphology obtained through customized perovskite conditions contribute to a better short-circuits current, which improves overall cell performance. Arsenic-doped perovskite-based solar cells demonstrate a 1.55% increase in power conversion efficiency compared to their nondecorated counterparts, exhibiting 0.20% efficiency. The outcomes not only offer a straightforward method for enhancing perovskite films but also introduce an innovative perspective on constructing high-performance perovskite solar cells using minimal amounts of arsenic, thereby minimizing toxicity in the fabricated solar cells.

The Impact of Induced Industrial and Urban Toxic Elements on Sediment Quality

Abstract: The increasing population has subjected rivers and streams to high levels of both industrial and domestic pollution. Significant environmental challenges have been brought about by their effects, particularly with regard to biota, ecosystem processes, soil quality, and groundwater pollution. This study examined the effects of human activity by applying pollution index models to evaluate the input of toxic elements in river sediments. Prior to sediment quality analysis, the total amount of arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), thorium (Th), and uranium (U) was determined in the concentration range of 1.09–10.0 mg/kg, 8.53–475 mg/kg, 0.12–0.16 mg/kg, 4.85–77.5 mg/kg, 3.14–5.9 mg/kg and 0.93–2.86 mg/kg, respectively. The enrichment factor, contamination factor, pollution load index, and geo-accumulation index revealed alarmingly high levels of Pb and Hg contamination at some sampling points, which are related to possible human input, ranging from severe enrichment to considerable contamination. The low ranges of pollution indices of some toxic elements suggest enrichment through the natural weathering process and atmospheric deposition. The Pearson correlation coefficient revealed a significant correlation between Pb-Fe and As-Fe, suggesting the possibility of acid mine contamination. Continual monitoring of river sediment is essential to minimize the impact of toxic elements to sustain sediment health and quality.

Effect of soaking in plasma-activated liquids (PALs) on heavy metals and other physicochemical properties of contaminated rice

In this study, plasma-activated liquids (PALs) were produced by a cold plasma gliding arc device at two different exposure times (7.5 and 15 min) and compared with deionized water (DW) as a control. The results showed that the amount of arsenic (As: 98 %), cadmium (Cd: 93 %), and lead (Pb: 93.3 %) were significantly decreased in all samples after soaking in PALs and DW than raw rice (p < 0.05). However, 15-min PALs were more successful. All soaked samples did not exceed the maximum residue limits (MRLs). A softer and easier chewing texture was observed for rice samples soaked in PALs than the sample soaked in DW. The samples treated with PALs also showed a lower gelatinization temperature and enthalpy. The color parameters and microstructure of rice samples were affected by treatment with PALs. Therefore, soaking rice in PALs before cooking can be considered an effective method to reduce the heavy metals in rice.

Synthesis, characterization and As(III) scavenging behaviours of mango peel waste loaded with Zr(IV) ion from contaminated water

Raw mango peel (RMP) was first saponified to yield saponified mango peel (SMP), which was then loaded with Zr(IV) ions to form a biosorbent for As(III) scavenging.The biosorption behaviors and mechanisms of As(III) scavenging using RMP and Zr(IV)-loaded saponified mango peel (Zr(IV)-SMP) were investigated batchwise. The As(III) scavenging efficiency of RMP increased from 20.13 % to 87.32 % after Zr(IV) loading. Optimum contact time of 6 h has been investigated for As(III) scavenging by Zr(IV)-SMP, and the data on kinetics is well fitted to the pseudo-second-order (PSO) model. Similarly, isotherm data of Zr(IV)-SMP fitted well to the Langmuir isotherm model with the maximum As(III) scavenging potential of 45.52 mg/g. Chloride (Cl−) and nitrate (NO3−) have negligible influence on As(III) scavenging, but sulphate (SO42−) interferes significantly. The exhausted Zr(IV)-SMP could be easily regenerated by treating with 2MNaOH. A mechanistic study indicates that As(III) scavenging is primarily contributed to electrostatic interaction and ligand exchange, which is confirmed from both instrumental and chemical characterizations techniques. Tubewell underground water polluted with a trace amount of arsenic (98.63 μg/L) could be successfully lowered down to the WHO standard (10 μg/L) by applying a small amount of Zr(IV)-SMP. Therefore, the Zr(IV)-SMP investigated in this work can be a low-cost, environmentally benign, and promising alternative for scavenging trace levels of arsenic from contaminated water.

Recycling of arsenic residue to basalt fiber via vitrification

The management of arsenic residue (AR) poses a significant environmental challenge globally. Conventional methods such as landfill, adsorption, and purification often fail to prevent arsenic migration, leading to uncertainties about the final disposition of AR and risks of secondary pollution. Vitrification offers a more stable approach for solidifying AR. This study explores the vitrification mechanism of AR using basalt and evaluates the performance of the resulting fibers. Our findings indicate that increasing the arsenic concentration decreases the high-temperature viscosity of basalt, making fiber drawing more energy-efficient. Incorporating a small amount of arsenic (approximately 0.4 mol%) significantly enhances the tensile strength of basalt fibers (BFs) by 10 %, attributed to reduced viscosity and improved fiber formation with fewer internal defects. Additionally, the flexural strength and stiffness modulus of asphalt mixtures are notably improved with the addition of AR-BF composites. We also examined the solidification and leaching mechanisms of arsenic in the basalt glass system. BFs containing up to 0.4 mol% As2O3 exhibited arsenic leaching levels below the standard threshold (<67.7 μg/dm2) under strong acid/alkali immersion conditions. These results highlight the potential for in-situ curing and recycling of hazardous AR, particularly in the development of mechanically reinforced materials.

Analysis of arsenic in rice and domestic water supply in Baguio City, Philippines

Numerous studies have found that rice and water, as components of the human diet, are potential pathways of arsenic exposure in humans. Due to the negative health effects linked with arsenic exposure, the quality of drinking water and rice samples must be continually monitored. This research was carried out in Baguio City, a small urban center in the Philippines. Following microwave digestion, arsenic in rice and water samples were determined using Atomic Absorption Spectrometry. The results showed that the National Food Authority (NFA) rice samples had arsenic content below the detection limit, indicating that this commercially available rice does not pose any health risk to Filipino consumers in terms of arsenic exposure. The arsenic value in other rice samples ranged from 8 μg/L to 27 μg/L, with the lowest and highest values found in organic brown rice and white rice varieties, respectively. Despite detectable arsenic in all 20 rice samples, all values were less than the maximum contaminant level (MCL) of 150 μg/L. Despite higher arsenic content in mixed rice than in white and organic colored rice, the mean differences are not significant, as proven by the Kruskal Wallis Test. All drinking water samples bought from water refilling stations had no detectable arsenic, while eight of the 18 (44%) of the spring water samples showed detectable amounts but are far below MCL of arsenic in drinking water. The findings suggest that the amount of arsenic in rice and spring water samples are too low to pose health risks over a short period of time.

Arsenic Species Distribution and Toxicity in the Environment, Bioaccumulation, Biomethylation and Bioremediation by Microalgae: A Review

Arsenic (As) is a noxious metalloid that has been designated a priority pollutant and is present in the environment as a consequence of both anthropogenic and natural processes. Its toxicity in environmental and biological systems depends strongly on the chemical species. Interest in arsenic and microalgae interactions is important because microalgae are at the base of the aquatic food chain, are used in animal nutrition and has potential for As phytoremediation. This paper reviewed the current information on As species distribution in the environment especially as it relates to its toxicity to microalgae as well as its bioaccumulation, biomethylation and bioremediation by microalgae using appropriate methods. Information obtained revealed that Microalgae have evolved mechanisms for dealing with As in the environment with arsBHC operon mediating the reduction and extrusion of arsenite from the cells. They accumulate large amounts of arsenic from their surroundings which could lead to toxicity, As excretion from cells, reduction, methylation or complexation with metal binding peptides like glutathione and phytochelatins. This has made them suitable as ecological indicators to give an indication of As bioavailability and also in possible applications for the process of As remediation. Microalgae are been proposed for bioremediation purposes in aquatic environment since they show a high capacity for biosorption and bioconcentration of As and most importantly since they are able to methylate inorganic As to non-toxic organic and volatile As.

Electrical properties of A-site Ca-doped LaNb1-xAsxO4-δ ceramics

The electrical properties of A-site Ca-doped LaNbO4 with the addition of As in the B-site, have been investigated. Total, grain- and specific grain boundary electric conductivities in different oxygen partial pressure, and water vapour partial pressure were determined. Additional conductivity measurements were performed in nitrogen, to suppress the possible p-type conductivity, focusing on protonic conductivity. The maximum measured total conductivity was recorded for La0.99Ca0.01Nb0.9As0.1O4-δ at 800 °C, which was equal to 1.2·10−4 S·cm−1 in H2O- humidified air, and 2.2·10−5 S·cm−1 in H2O- humidified N2. From the deconvoluted data, the lowest activation energies for grain conduction were obtained in both atmospheres for La0.99Ca0.01Nb0.7As0.3O4-δ. In the temperature range 400 °C – 550 °C it was 0.23 eV and 0.13 eV respectively for H2O- humidified air and H2O- humidified N2. The results show that the increasing arsenic amount mainly influences the activation energies, whereas the calcium addition slightly improves the grain conductivity. The pO2 experiments revealed that in oxidizing atmospheres, electron holes contribute to the conductivity. The high proton transfer numbers were obtained for each sample, peaking at tH+ = 0.91 for LaNb0.7As0.3O4 at 400 °C. Interestingly, even at elevated temperatures relatively high values are obtained where tH+ = 0.87 was recorded at 800 °C for La0.99Ca0.01Nb0.9As0.1O4-δ.

Morphology of the bronze objects from the Pinchuga-6 burial ground

The article is concerned with bronze objects of the end of the Early Iron Age from the fully excavated burial ground of Pinchuga-6 in the Lower Angara River region. The cemetery is dated to the 3rd–4th centuries BC. All burials were made following the rite of burial on the side. Three categories of copper alloy products have been distinguished: belt set parts, jewelry, and cult castings. The components of the belt sets include flat openwork buckles, hoops and bird-shaped overlays. Flat openwork buck-les have no analogues in the neighbouring territories. They appeared on the basis of the circle of post-Hunnic cultures of South-ern Siberia and were used in the Angara taiga until the mid-1st millennium AD. One belt hoop with volutes and an openwork patch is of a typical Tashtyk Culture appearance. At the end of the Early Iron Age, bird-headed belt plates were used across a vast territory that stretched from the Ural Mountains in the west to the banks of the Yenisei and Angara Rivers in the east. The jewelry includes tubular cast and spiral beads, stripes and pendants. The majority of items are multi-functional — they could be worn different ways. All of them were widespread in the first half of the 1st millennium AD, and they do not have a clear cultural and chronological reference. At Pinchuga-6, various objects of cult casting were found, including ornitho-, zoo- and ichthyomor-phic images, and disks with a circular ornament. These items have similarities among the Ishim and Kholmogory collections, materials from the Aidashinskaya cave, and Tomsk and Ust-Abinsk burial grounds. Pinchuga-6 is currently the farthest north-eastern site where such objects have been found. The grave goods of the cemetery contain items of different cultural attribution made of copper-based alloys. In this single complex in the Angara River region, objects from Western Siberia, Khakass-Minusinsk depression, and, possibly, of local origin have been found. XRF analysis of the items has been carried out. Lead-tin and tin bronze prevail, although being in approximately equal quantities, individual objects are made of copper, a small amount of arsenic is traced in two buckles, one ornithomorphic image is cast from an alloy with a significant amount of silver. The clo-sest in this feature, as well as in the amount of tin and lead in the alloys, are the products of the Tomsk burial ground.

Purification of Copper Concentrate from Arsenic under Autoclave Conditions

This study presents the results of a two-stage autoclave processing of a copper–arsenic concentrate. Copper concentrate is an important raw material to produce copper and other metals. However, in some cases, the concentrate may contain increased amounts of arsenic, which makes further processing difficult. Therefore, the development of modern hydrometallurgical methods for processing copper concentrate with a high arsenic content is an urgent task, which could lead to the optimization of the raw material processing process and the improvement of the quality of the concentrate. It has been established that the optimal conditions for the sequential two-stage autoclave processing of copper–arsenic concentrate are: t = 220–225 °C, τoxidation = 20 min, τtot = 90 min, Po2 = 0.4 MPa, and L:S = 10:1, [H2SO4]initial = 40 g/dm3; in this case, 85% of zinc, 44% of iron, and 78% of arsenic, respectively, are extracted into the solution during both stages and the loss of copper was about 0.01%. This is explained by the fact that at the first stage (oxidation) of the autoclave processing of the copper–arsenic concentrate, copper, together with iron, leaches into the solution, and at the second stage (reduction), copper precipitates out of the solution in the form of chalcocite. Copper in the residue after autoclave leaching is in the form of Cu2S, iron is in the form of pyrite (FeS2), and lead is in the form of anglesite (PbSO4), respectively. The obtained micrographs and EDX mappings clearly show no iron arsenates. This confirms that at the oxidative stage of the developed process, arsenic, removed by 78%, remains in the solution. The remaining arsenic is associated with tennantite, indicating the effectiveness of the treatment process in removing arsenic from the copper–arsenic concentrate. A second important observation is the presence of pronounced areas of copper sulfides in the microphotos without iron and arsenic impurities. This confirms that copper is deposited as chalcocite during the reduction phase of the process, which is the desired result.

The probable reasons of arsenic susceptibility in a chronically exposed population of West Bengal

Arsenic is potent human carcinogen which affects millions of people across the globe. Arsenic induced pre-cancerous and cancerous skin lesions are hall marks of chronic arsenic toxicity. Even then, only 15%–20% of the population manifest arsenic-induced skin lesions but the rest do not, the reason for which in not very clear. Not only that, conjunctival irritations of the eyes, peripheral neuropathy and respiratory distress are the non-dermatological health effects which are often manifested in them in addition to the cancers of skin and other internal organs. In this work we have considered 233 arsenic exposed individuals with skin lesions and 205 arsenic exposed individuals without skin lesions from the highly arsenic affected Murshidabad district of West Bengal. We have compared arsenic exposure in the two groups through drinking water. Both the study groups have similar levels of arsenic exposure, drinking same arsenic laden water. Results show that higher amounts of arsenic were retained in the nails and hair of the skin lesion group compared to the no skin lesion group. Significant higher amounts of chromosomal aberration and micronucleus formation were found in the skin lesion group, than the no skin lesion group. Incidences of conjunctival irritations of the eyes, peripheral neuropathy and respiratory distress were much higher in the former group compared to the later. We, thus found that one group was more susceptible than the other, even with similar levels of arsenic exposure. We have tried to identify and discuss the probable reasons for this observation with reference to our previous works in the exposed population from West Bengal, India.

Dynamics of Spatiotemporal Variation of Groundwater Arsenic in Central Rift Vally of Ethiopia: A Serial Cross-Sectional Study.

Arsenic is a well-known, highly poisonous metalloid that affects human health and ecosystems and is widely distributed in the environment. Nevertheless, data on the spatiotemporal distribution of arsenic in groundwater sources in Ethiopia are scarce. The principal aim of this study was to assess the extent of arsenic in groundwater sources and analyze the spatiotemporal variations in the central rift valley of Ethiopia. The study employed a serial cross-sectional study design and census sampling methods. The concentrations of arsenic in the groundwater samples were determined using inductively coupled plasma mass spectrometry (ICP-MS) at the Ethiopian Food and Drug Authority laboratory. Descriptive statistical analyses were performed using IBM SPSS version 29 software. Additionally, ArcGIS software was utilized to map the spatiotemporal distribution of arsenic. Furthermore, Minitab statistical software version 21.4 was employed to assess the correlation between spatiotemporal variations of arsenic concentrations in groundwater sources. The mean values of arsenic in the groundwater samples were 11.2 µg/L during the dry season and 10.7 µg/L during the rainy season. The study results showed that 18 wells (42.2%) and 22 wells (48.8%) had higher arsenic concentrations (>10 µg/L) during the dry and rainy seasons, respectively. Thus, arsenic levels in 42.2% and 48.8% of the samples exceeded the maximum threshold limit set by WHO, USEPA, and Ethiopian standards (10 µg/L), respectively, during the dry and rainy seasons. Furthermore, our analysis revealed a significant positive correlation between arsenic in groundwater and well depth (r = .75, P < .001), indicating a strong association between higher arsenic concentrations and deeper wells. Similarly, we observed a substantial positive correlation between arsenic concentration in groundwater and season (r = .9, P < .001), suggesting notable variations in arsenic levels between dry and rainy seasons. The majority of the groundwater sources in the studied area are unfit for human consumption because they contain high amounts of arsenic, which poses a significant risk to human health. Moreover, the arsenic concentration varied spatially and temporally. Therefore, special attention is needed to reduce arsenic exposure and associated health risks.

Rapid and selective trace determination of arsenic in rice samples by using functionalized conductive polymer dots as fluorescent probe with comparable results to ICP-MS analysis

Rice, a staple diet across most countries, has been identified as one of the significant sources of arsenic accumulation, which occasions public severe health issues. Therefore, developing a rapid method for the selective detection of arsenic in rice is of great importance. Toward this goal, in this paper, an application of a fluorescent probe constructed from functionalized conductive polymer dots (FCPDots) was performed to discriminate arsenic in rice samples. In the presence of arsenic, the intense emission of the FCPDots probe at 395 nm under an excitation wavelength of 334 nm substantially decreased because of the formation of the As_S linkage. The probe represented an outstanding performance toward arsenic at linear concentrations between 0.25 and 2.00 nM with an excellent detection limit of 0.107 nM. As a final step, ICP-Mass analysis confirmed that the probe is applicable and reliable to detect trace amounts of arsenic in real samples. Interestingly, the FCPDots probe was able to detect arsenic rapidly, accurately, and selectively in several rice samples despite the heavy metal ions interferences.

Removal of arsenic from realgar-containing water by Spirogyra: Implications for in situ remediation of arsenic in the mine area

Realgar (As4S4) is an arsenic sulfide mineral, occurring widely in metamorphic-hydrothermal deposits, reductive soil and wetland sediments. The dissolution of realgar releases arsenic, which is toxic to the environment, so the process that causes this problem deserves attention. Native Spirogyra sp. was collected and cultured from a realgar mine area and used to create varying concentrations of algae to investigate the dissolution of realgar using a photosynthesis microcosm. Separately the dynamic adsorption and uptake processes of arsenic (III) and arsenic (V) were investigated. The dissolution rate equation of realgar under Spirogyra sp. is R = 10−6.36[DO]1.84[H+]−0.60. The diurnal growth of Spirogyra sp. increases arsenic release by as much as three times than the control group and significantly changes aqueous arsenic species by varying the dissolved oxygen and pH. The amounts of arsenic (III) and arsenic (V) removed from living Spirogyra sp. were 14605 μg⋅g−1⋅h−1 and 6511 μg⋅g−1⋅h−1. Increasing amounts of –COOH, CO and carbonyl groups from the live Spirogyra sp. also promoted the dissolution of realgar. The results suggest that filament Spirogyra sp. would be an effective method for in situ acceleration of arsenic sulfide dissolution and remediation of arsenic pollution in environments such as paddy soil.

Degradation of roxarsone and simultaneous immobilization of inorganic arsenic by L-cys modified FeMnNi-LDH activated persulfate system

A series of novel L-cysteine (L-cys) modified iron-manganic-nickel hydrotalcite (L-cys-LDH) were synthesized and used for heterogeneous catalytic activation of monopersulfate (PMS) to degrade roxarsone (ROX) and adsorption of released inorganic arsenic. The catalyst was characterized by TEM, XRD, FTIR, XPS, and other characterization techniques to analyze its structure and functional properties. The degradation experiment results showed that the activity of the catalyst was effectively improved after L-cys loading on LDH. In the pH range of 3–9, 0.2 g/L L-cys-LDH and 0.2 mM PMS could degrade more than 90 % of ROX in 20 min, three times higher than that of ordinary FeMnNi-LDH. Besides, the residual amount of inorganic arsenic in the solution was less than 0.01 mg/L. The electron paramagnetic resonance (EPR) test and quenching investigation identified surface-bound SO4-· and surface-bound ·OH as the main contributors to organic degradation. Mechanism studies have shown that cysteine embedded in LDH accelerated the conversion rate of Fe(III)/Mn(III) to Fe(II)/Mn(II) by self-oxidation to cystine, thereby improving the efficiency of catalyst activation of PMS. In addition, the main degradation products were obtained by LC-MS analysis, and the possible pathway of ROX degradation was given in L-cys-LDH/PMS system combined with DFT theoretical calculation. The work showed that L-cys-LDH exhibited excellent catalytic performance and inorganic arsenic adsorption capacity. It provides an idea for the improvement of hydrotalcite-based catalysts. It also sheds some light on the degrade of novel hydrotalcite-based catalysts for the one step degradation and adsorption of ROX.

Biochar potentially enhances maize tolerance to arsenic toxicity by improving physiological and biochemical responses to excessive arsenate

Metalloid pollution, including arsenic poisoning, is a serious environmental issue, plaguing plant productivity and quality of life worldwide. Biochar, a carbon-rich material, has been known to alleviate the negative effects of environmental pollutants on plants. However, the specific role of biochar in mitigating arsenic stress in maize remains relatively unexplored. Here, we elucidated the functions of biochar in improving maize growth under the elevated level of sodium arsenate (Na2AsO4, AsV). Maize plants were grown in pot-soils amended with two doses of biochar (2.5% (B1) and 5.0% (B2) biochar Kg−1 of soil) for 5 days, followed by exposure to Na2AsO4 ('B1 + AsV'and 'B2 + AsV') for 9 days. Maize plants exposed to AsV only accumulated substantial amount of arsenic in both roots and leaves, triggering severe phytotoxic effects, including stunted growth, leaf-yellowing, chlorosis, reduced photosynthesis, and nutritional imbalance, when compared with control plants. Contrariwise, biochar addition improved the phenotype and growth of AsV-stressed maize plants by reducing root-to-leaf AsV translocation (by 46.56 and 57.46% in ‘B1 + AsV’ and ‘B2 + AsV’ plants), improving gas-exchange attributes, and elevating chlorophylls and mineral levels beyond AsV-stressed plants. Biochar pretreatment also substantially counteracted AsV-induced oxidative stress by lowering reactive oxygen species accumulation, lipoxygenase activity, malondialdehyde level, and electrolyte leakage. Less oxidative stress in ‘B1 + AsV’ and ‘B2 + AsV’ plants likely supported by a strong antioxidant system powered by biochar-mediated increased activities of superoxide dismutase (by 25.12 and 46.55%), catalase (51.78 and 82.82%), and glutathione S-transferase (61.48 and 153.83%), and improved flavonoid levels (41.48 and 75.37%, respectively). Furthermore, increased levels of soluble sugars and free amino acids also correlated with improved leaf relative water content, suggesting a better osmotic acclimatization mechanism in biochar-pretreated AsV-exposed plants. Overall, our findings provided mechanistic insight into how biochar facilitates maize’s active recovery from AsV-stress, implying that biochar application may be a viable technique for mitigating negative effects of arsenic in maize, and perhaps, in other important cereal crops.Graphical

NiFe2O4–TiO2 magnetic nanoparticles synthesized by the thermal decomposition of 8-hydroxyquinolinates as efficient photocatalysts for the removal of As(III) from water

NiFe2O4–TiO2 magnetic nanoparticles were synthesized by the chemical coprecipitation of 8-hydroxyquinolinates method and calcined at three temperatures (500, 700 and 900 °C). The synthesized samples presented five crystalline phases: NiFe2O4, α-Fe2O3, NiO and the allotropic forms of TiO2. The sample calcined at 900 °C still showed a sixth phase, Fe2TiO5. The samples showed particles formed by agglomerates of granules and the coating of NiFe2O4 by TiO2 was not completely homogeneous. Band gap values for the magnetic nanoparticles ranged from 1.72 to 1.93 eV and were lower than those reported in the literature for TiO2 (3–3.2 eV), indicating that the association of nickel ferrite and TiO2 was efficient to reduce the band gap and also to extend energy absorption towards visible radiation. Magnetic nanoparticles were applied in the photocatalytic removal of As(III) from the aqueous medium under visible and ultraviolet radiation. The sample calcined at 900 °C was able to remove the greatest amount of arsenic from the medium, about 94.7 % using visible radiation. This sample showed the lowest band gap value and also the appearance of the Fe2TiO5 phase, which can be active in the reaction. A reuse test was also performed, showing that the photocatalyst can remove more As(III) than photolysis in three consecutive cycles of use.

Signal amplification strategy by chitosan-catechol hydrogel modified paper electrode for electrochemical detection of trace arsenite

Arsenic contamination is widespread in water bodies and poses a significant risk to human health, thus developing a rapid and inexpensive in situ method for the detection of arsenic is urgently needed. In this study, a chitosan-catechol carbon paper electrode was fabricated by electrodeposition of chitosan on a conductive carbon paper and subsequential electro-oxidative grafting of catechol. This chitosan-catechol modified electrode demonstrated good performance in detecting trace amounts of arsenic, which is mainly due to the significantly amplification of oxidation signals generated by ferrocene (Fc) on chitosan-catechol hydrogel. The interaction of As(III) with quinone and semiquinone radicals results in the decrease of electronic transmission nodes. The modified electrode exhibited a good detection capability of low concentration As(III) with a detection limit 0.82 ppb by differential pulse voltammetry (DPV). In addition, the chitosan-catechol modified sensor has the merits of high reproducibility, durability and strong resistance to ionic interference. Further successful detection of As(III) in actual rice and soil samples suggests its good potential in the field of in situ detection.