A new efficient indigenous material for simultaneous removal of fluoride and inorganic arsenic species from groundwater

Remediation of arsenic and fluoride from groundwater: a critical review on bioadsorption, mechanism, future application, and challenges for water purification

In the past few decades, the excessive and inadequate use of technological advances has led to groundwater contamination, mainly caused by organic and inorganic pollutants, which are highly harmful to human health, agriculture, water bodies, and aquaculture. Among all toxic pollutants, As and F- play a significant role in groundwater contamination due to their excellent reactivity with other elements. To mitigate the prevalence of arsenic and fluoride within the water system, the use of biochar gives an attractive strategy for removing them mainly because of the substantial surface area, pore size, pH, aromatic structure, and functional groups inherent in biochar, which are primarily dependent upon its raw material and pyrolysis temperature. Researcher develops different methods like physiochemical and electrochemical for treating arsenic and fluoride contamination. Among all removal methods, bioadsorption using agricultural waste residues shows effective/feasible removal of As and F- due to its low cost, ecofriendly nature, readily available, and efficient reuse compared with several other harmful synthetic materials that demand costly design specifications. This study discusses current developments in bioadsorption methods for As and F- that use agricultural-based biomaterials and describes the prevailing state of arsenic and fluoride removal strategies that use biomaterials precisely.

Transformative and sustainable insights of agricultural waste-based adsorbents for water defluoridation: Biosorption dynamics, economic viability, and spent adsorbent management

With the progression of civilization, the harmony within nature has been disrupted, giving rise to various ecocidal activities that are evident in every spheres of the earth. These activities have had a profound and far-reaching impact on global health. One significant example of this is the presence of fluoride in groundwater exceeding acceptable limits, resulting in the widespread occurrence of "Fluorosis" worldwide. It is imperative to mitigate the concentration of fluoride in drinking water to meet safety standards. While various defluoridation techniques exist, they often have drawbacks. Biosorption, being a simple, affordable and eco-friendly method, has gained preference for defluoridation. However, its limited commercialization underscores the pressing need for further research in this domain. This comprehensive review article offers a thorough examination of the defluoridation potential of agro-based adsorbents, encompassing their specific chemical compositions and preparation methods. The review presents an in-depth discussion of the factors influencing fluoride biosorption and conducts a detailed exploration of adsorption isotherm and adsorption kinetic models to gain a comprehensive understanding of the nature of the adsorption process. Furthermore, it evaluates the commercial viability through an assessment of regeneration potential and a cost analysis of these agro-adsorbents, with the aim of facilitating the scalability of the defluoridation process. The elucidation of the adsorption mechanism and recommendations for overcoming challenges in large-scale implementation offer a comprehensive outlook on this eco-friendly and sustainable approach to fluoride removal. In summary, this review article equips readers with a lucid understanding of agro-adsorbents, elucidates their ideal conditions for improved performance, offers a more profound insight into the fluoride biosorption mechanism, and introduces the concept of effective spent adsorbent management.

Amino-functionalized novel biosorbent for effective removal of fluoride from water: process optimization using artificial neural network and mechanistic insights

Aqueous fluoride (F - ) pollution is a global threat to potable water security. The present research envisions the development of novel adsorbents from indigenous Limonia acidissima L. (fruit pericarp) for effective aqueous defluoridation. The adsorbents were characterized using instrumental analysis, e.g., TGA-DTA, ATR-FTIR, SEM-EDS, and XRD. The batch-mode study was performed to investigate the influence of experimental variables. The artificial neural network (ANN) model was employed to validate the adsorption. The dataset was fed to a backpropagation learning algorithm of the ANN (BPNN) architecture. The four-ten-one neural network model was considered to be functioning correctly with an absolute-relative-percentage error of 0.633 throughout the learning period. The results easily fit the linearly transformed Langmuir isotherm model with a correlation coefficient( R 2 ) > 0.997. The maximumF - removal efficiency was found to be 80.8 mg/g at the optimum experimental condition of pH 7 and a dosage of 6 g/L at 30 min. The ANN model and experimental data provided a high degree of correlation (R 2 = 0.9964), signifying the accuracy of the model in validating the adsorption experiments. The effects of interfering ions were studied with realF - water. The pseudo-second-order kinetic model showed a good fit to the equilibrium dataset. The performance of the adsorbent was also found satisfactory with field samples and can be considered a potential adsorbent for aqueous defluoridation.

Efficient groundwater defluorination over a wide concentration gradient through capacitive deionization with a three-layer structured membrane coating electrode

Fluoride (F-) pollution in groundwater is an important environmental issue and capacitive deionization (CDI) holds promise for defluorination at moderate concentrations (e.g., 200 -1000 mg L-1). However, existing electrodes suffer from the overlap of electrical-double-layer (EDL) and severe co-ion effects at low (e.g., <200 mg L-1) and high sodium fluoride (NaF) concentrations (e.g., >1000 mg L-1), respectively, exhibiting poor salt adsorption capacity (SAC). Hence, a three-layer structured electrode, "membrane/carbon nanotube (CNT)/activated carbon (AC)" (CNT-MCE), was prepared through electrospinning CNT onto AC, followed by a polymer membrane coating. Compared to AC and membrane coated electrode, CNT-MCE with mesopore-dominated structure prevented EDL overlap, achieving a higher SAC of 40.8 mg g-1 at 100 mg L-1 NaF. At 1500 mg L-1 NaF, the positively charged CNT-MCE exhibited an improved SAC of 58.8 mg g-1 by inhibiting co-ion effects. Meanwhile, CNT-MCE consistently demonstrated superb SACs at 200 - 800 mg L-1 NaF and maintained excellent stability over a wide concentration gradient by inhibiting severe oxidation. Notably, CNT-MCE successfully decreased the F- concentration in simulated groundwater from 3.4 to 1.1 mg L-1. Overall, our work provides an efficient strategy of electrode design to broaden the applicability of CDI for groundwater defluorination over a wide concentration gradient.

Remediation of water tainted with noxious aspirin and fluoride ion using UiO-66-NH2 loaded peanut shell

One green adsorbent, UiO-66-NH2 modified peanut shell (c-PS-MOF), was prepared in a green synthetic route for improving the capture level of aspirin (ASP) and fluoride ion (F-). The adsorption properties of c-PS-MOF were evaluated by batch experiments and its physicochemical properties were explored by various characterization methods. The results showed that c-PS-MOF exhibited a wide range of pH applications (ASP: 2-10; F-: 3-12) and high salt resistance in the capturing processes of ASP and F-. The unit adsorption capacity of c-PS-MOF was as high as 84.7 mg·g-1 for ASP as pH = 3 and 11.2 mg·g-1 for F- under pH = 6 at 303 K from Langmuir model, respectively. When the solid-liquid ratio was 2 g·L-1, the content of ASP (C0 = 100 mg·L-1) and F- (C0 = 20 mg·L-1) in solution can be reduced to 0.48 mg·L-1 and 1.05 mg·L-1 separately. The recycling of c-PS-MOF can be realized with 5 mmol·L-1 NaOH as eluent. Analysis of simulated water samples showed that c-PS-MOF could be used to remove ASP and F- from actual water. The c-PS-MOF is promising to bind ASP and F- from rivers, lakes, etc.

Seasonal characteristics of particle size distribution of organic markers in atmospheric particulate matters in Beijing

Beijing is a metropolis that is quickly growing, which has significant and unusual air pollution issues. In Beijing, organic matter makes up about 40%-60% of the total mass of fine particles, making it the most prevalent portion and highlighting its crucial role in reducing air pollution. However, a thorough chemical analysis of particulate organic matter has never been reported in Beijing. In this work, the organic components of fine particles in Beijing's urban environment were examined by the Gas Chromatography and Mass Spectrometry (GC/MS) method. In 30 p.m. (Particulate matter) 2.5, more than 101 unique chemical compounds were identified and measured. Seven samples from the 2015-2016 summer, including harvest, cold, Aromatic hydrocarbons, unsaturated fats, ferulic acid, polyaromatic, and some tracer substances (hopanes, present in environmental samples, and corticosteroids) were the main ingredients, with their total concentrations being 489, 1369, and 1366 ng*m-3 in the summer, respectively. Due to their various primary pollution sources, such as combustion processes, fuel combustion, and culinary emissions, various organic compounds displayed ostensibly varied seasonal tendencies. Discussion of these organic chemicals' prevalence and a source reveals Beijing's seasonal air pollution patterns.

In-situ modified biosynthetic crystals with lanthanum for fluoride removal based on microbially induced calcium precipitation: Characterization, kinetics, and mechanism

In this research, in-situ modified biosynthetic crystals with lanthanum (BC-La) were synthesized based on anaerobic microbially induced calcium precipitation (MICP) and investigated its capacity for groundwater defluoridation under various operational conditions. The kinetic and thermodynamic models were simulated to explore the effect of the material on the removal of fluoride ion (F^-) under various parameters (pH, initial concentration of F^-, and temperature). BC-La had the maximum F^- adsorption capacity of 10.92 mg g^-1 and 96.66% removal efficiency. The pseudo-second-order kinetic model and Langmuir isotherm model were the best kinetic and isotherm models for F^- removal from BC-La, which indicated that F^- were mainly spontaneously removed through chemisorption and adsorption processes. The specific surface area was 54.26 m² g^-1 and the average pore size was 9.0670 nm. BC-La mainly contained LaCO₃OH, LaPO₄, CaCO₃, Ca₅ (PO₄)₃OH, and F^- was mainly removed through ion exchange with the material surface. Moreover, OH^-, PO₄^3-, and CO₃^2- significantly influenced the F^- removal. This work suggested a novel method for in-situ modification of anaerobic biosynthetic crystals, which improved the defluoridation effect of traditional biosynthetic crystals, increased the stability of the BC-La and allowed to remove F^- from groundwater consistently.

Zirconium/lanthanum-modified chitosan/polyvinyl alcohol composite adsorbent for rapid removal of fluoride

A novel and easily separable adsorbent in the shape of a membrane for the rapid removal of fluoride from water was prepared after testing Zr, La and LaZr to modify a chitosan/polyvinyl alcohol composite adsorbent (CS/PVA-Zr, CS/PVA-La, CS/PVA-LA-Zr). The CS/PVA-La-Zr composite adsorbent can remove a large amount of fluoride within 1 min of contact time, and the adsorption equilibrium can be reached within 15 min. The fluoride adsorption behavior of the CS/PVA-La-Zr composite can be described by pseudo-second-order kinetics and Langmuir isotherms models. The morphology and structure of the adsorbents were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The adsorption mechanism was studied using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and which showed that ion exchange occurred mainly with hydroxide and fluoride ions. This study showed that an easily operable, low-cost and environmentally friendly CS/PVA-La-Zr has the potential to remove fluoride effectively from drinking water in a short time.

Efficient removal of total arsenic (As3+/5+) from contaminated water by novel strategies mediated iron and plant extract activated waste flowers of marigold

In this investigation, marigold flower-waste was activated with iron salts (MG-Fe), subsequently marigold plant extract (MG-Fe-Ex) for the adsorptive elimination of As³⁺ and As⁵⁺ from contaminated water. The governing factor such as medium pH, temperature, pollutant concentration, reaction time, adsorbent dose were considered for the study. The complete elimination of As^3+/5+ was recorded with MG-Fe-Ex at pH 8.0, 90 min, 30 °C, dose 4 g/L, 20 mg/L of As^3+/5+ and shaking rate 120 rpm, while under the identical experimental condition, MG-Fe exhibited 98.4% and 73.3% removal for As⁵⁺ and As³⁺, respectively. The MG-Fe-Ex contains iron oxides (Fe₂O₃ and Fe₃O₄) as a result of iron ions reaction with plant bioactive molecules as evident from x-ray diffraction analysis (XRD), energy dispersive x-ray spectroscopic (EDS) and Fourier transform infrared (FTIR) spectroscopic study. The adsorption data of As^3+/5+ on MG-Fe and MG-Fe-Ex was best fitted by pseudo-first order kinetic and freundlich isotherm except As⁵⁺ adsorption on MG-Fe-Ex that can be described by langmuir isotherm model. The prevailing mechanism in adsorption of As^3+/5+ on both adsorbent might be hydrogen bonding, electrostatic attraction and complexation. From the above, it is confirmed that MG-Fe-Ex adsorbent has high potential and can be used for the adsorptive elimination of As^3+/5+ from contaminated water in sustainable and environmentally friendly way.

Lignocellulosic Biomass as Sorbent for Fluoride Removal in Drinking Water

Water supply to millions of people worldwide is of alarmingly poor quality. Supply sources are depleting, whereas demand is increasing. Health problems associated with water consumption exceeding 1.5 mg/L of fluoride are a severe concern for the World Health Organization (WHO). Therefore, it is urgent to research and develop new technologies and innovative materials to achieve partial fluoride reduction in water intended for human consumption. The new alternative technologies must be environmentally friendly and be able to remove fluoride at the lowest possible costs. So, the use of waste from lignocellulosic biomasses provides a promising alternative to commercially inorganic-based adsorbents-published studies present bioadsorbent materials competing with conventional inorganic-based adsorbents satisfactorily. However, it is still necessary to improve the modification methods to enhance the adsorption capacity and selectivity, as well as the reuse cycles of these bioadsorbents.

Adsorption of As(III) and As(V) from aqueous solution by magnetic biosorbents derived from chemical carbonization of pea peel waste biomass: Isotherm, kinetic, thermodynamic and breakthrough curve modeling studies

The purpose of this research was to investigate the adsorption of arsenic (As) from aqueous solutions using MPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum (pea) pyrolyzed at 500 °C and 600 °C temperatures, respectively). The potential of both biosorbents for As adsorption was determined in batch and column mode. The characterization of both biosorbents was performed by energy dispersive spectroscopy, scanning electron microscope, pHZPC, particle size distribution, X-ray diffraction, zeta potential and Fourier-transform infrared spectroscopy. It was found that the efficiency of MPAC-600 was better than MPAC-500 for the adsorption of As(III) and As(V) ions. The adsorption capacities of MPAC-500 and MPAC-600 in removing As(III) were 0.7297 mg/g and 1.3335 mg/g, respectively, while the values of Qmax for As(V) on MPAC-500 and MPAC-600 were 0.4930 mg/g and 0.9451 mg/g, respectively. The Langmuir isotherm model was found to be the best fit for adsorption of As(III) by MPAC-500 and MPAC-600, as well as adsorption of As(V) by MPAC-500. The Freundlich isotherm model, on the other hand, was optimal for As(V) removal with MPAC-600. With R2 values close to unity, the pseudo-second-order kinetics were best fitted to the adsorption process of both As species. The Thomas model was used to estimate the breakthrough curves. The effects of coexisting oxyanions and regeneration studies were also carried out to examine the influence of oxyanions on As adsorption and reusability of biosorbents.

As and [Formula: see text] cooccurrence in drinking water: critical review of the international scenario, physicochemical behavior, removal technologies, health effects, and future trends

Drinking water contaminated with As and [Formula: see text] is increasingly prevalent worldwide. Their coexistence can have negative effects due to antagonistic or synergistic mechanisms, ranging from cosmetic problems, such as skin lesions and teeth staining, to more severe abnormalities, such as cancer and neurotoxicity. Available technologies for concurrent removal include electrocoagulation ~ adsorption > membranes > chemical coagulation > , and among others, all of which have limitations despite their advantages. Nevertheless, the existence of competing ions such as silicon > phosphate > calcium ~ magnesium > sulfate > and nitrate affects the elimination efficiency. Mexico is one of the countries that is affected by As and [Formula: see text] contamination. Because only 10 of the 32 states have adequate removal technologies, more than 65% of the country is impacted by co-presence problems. Numerous reviews have been published concerning the elimination of As or [Formula: see text]. However, only a few studies have focused on the simultaneous removal. This critical review analyzes the new sources of contamination, simultaneous physicochemical behaviors, available technologies for the elimination of both species, and future trends. This highlights the need to implement technologies that work with actual contaminated water instead of aqueous solutions (55% of the works reviewed correspond to aqueous solutions). Similarly, it is necessary to migrate to the creation of pilot, pre-pilot, or prototype scale projects, because 77% of the existing studies correspond to lab-scale research.

Zr-Based Biocomposite Materials as an Alternative for Fluoride Removal, Preparation and Characteristics

The development of biocomposite materials used as adsorbents to remove ions in aqueous media has become an attractive option. The biomasses (base materials) are chemically treated and impregnated with metal cations, becoming competitive for fluoride-capture capacity. In this research, Valence orange (Citrus sinensis) and Red Delicious apple (Malus Domestica) peels were modified by alkaline treatment, carboxylation, and impregnation with zirconium (Zr). These materials were characterized morphologically and structurally to understand the modifications in the treated biomasses and the mechanism of fluoride adsorption. The results show changes in surface area and composition, most notably, an increment in roughness and Zr impregnation of the bioadsorbents. After batch experimentation, the maximum capacity of the materials was determined to be 4.854 and 5.627 mg/g for the orange and apple peel bioadsorbent, respectively, at pH 3.5. The experimental data fitted the Langmuir model, suggesting that chemisorption occurs in monolayers. Finally, the characterization of the bioadsorbents in contact with fluoride allowed the replacement of OH species by fluoride or the formation of hydrogen bonds between them as an adsorption mechanism. Therefore, these bioadsorbents are considered viable and can be studied in a continuous system.

NLRP3 inflammasome is involved in the mechanism of the mitigative effect of lycopene on sulfamethoxazole-induced inflammatory damage in grass carp kidneys

Freshwater environmental antibiotic pollution is becoming more severe because of the irregular use of sulfonamide antibiotics. Sulfamethoxazole (SMZ) is a kind of antibiotic that can cause harm to the urinary systems of organisms. However, the toxic impacts of environment-related concentrations of antibiotics in fish have not been thoroughly studied. Lycopene (LYC) has the property of alleviating antibiotic toxicity by diminishing oxidative stress and inflammation. This investigation is intended to examine the instrument of the mitigative part of LYC on SMZ-caused renal inflammatory injury in grass carp. Grass carp were born with SMZ (0. 3 μg L^-1) and LYC (10 mg/kg body weight) for 30 days. Serum was used to measure creatinine (CREA) and urea nitrogen (BUN) contents; what is more, kidneys were used to measure histological structure, oxidative stress indicators, relative expressions of cytokines, and inflammatory factors. We found that SMZ exposure significantly increased oxidative stress, characterized by decreased catalase activity (CAT) and superoxide dismutase (SOD). In addition, inflammation-related factors: interleukin (IL-18, IL-6, and IL-1β), an apoptotic speck-containing protein with a card (ASC), NOD-like receptor protein3 (NLRP3), cysteinyl aspartate specific proteinase-1 (caspase-1), tumor necrosis factor-α (TNF-α), and nuclear factor-activated B cells (NF-κB) expression increased significantly contrasted with those control group. Inflammatory reactions and ultrastructural changes accompany. LYC administration alleviated the changes mentioned above. In conclusion, In conclusion, these results suggest a protective effect of LYC dietary supplements against kidney damage caused by SMZ. LYC is expected to prevent and treat oxidative stress and chronic inflammation caused by antibiotics as a critical component in the fish breeding diet.

Performance of a novel iron infused biochar developed from Raphanus sativus and Artocarpus heterophyllus refuse for trivalent and pentavalent arsenic adsorption from an aqueous solution: mechanism, isotherm and kinetics study

Fabrication of magnetic biochar was done by pyrolysis of waste leaves of Raphanus sativus (MRB) and Artocarpus heterophyllus (MJB) peel pretreated with FeCl₃ was examined for As(III and V) adsorption from an aqueous solution. The synthesized bioadsorbents were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), particle size analysis (PSA), scanning electron microscope (SEM), energy dispersive x-ray (EDX), zeta potential, Vibrating sample magnetometer (VSM) and point of zero charge (pH_ZPC). MRB-800 exhibits greater efficiency toward the removal of both As species with q_max value 2.08 mg/g for As(III) and 2.03 mg/g for As(V). Whereas, the q_max value was 1.13 mg/g for As (III) and 1.26 mg g^-1 for As (V) adsorption using MJB-800. Temkin and Freundlich isotherm were best fitted to the adsorption of As(III) and As(V) by MRB-800, respectively. Langmuir isotherm was best followed to the adsorption of As (III and V) by MJB-800. Pseudo-second-order kinetics was well simulated by the experimental data of As adsorption using both the bioadsorbents. Surface complexation and electrostatic attraction was dominant mechanism for As (III) and As (V) adsorption. Thermodynamic study shows that removal of As (III) was exothermic while the As (V) adsorption was endothermic for MRB-800 and MJB-800.

Comprehensive and critical appraisal of plant-based defluoridation from environmental matrices

Fluoride is recognized as one of the global environmental threats because of its non-biodegradable nature and long-term persistence in the environment. This has created the dire need to explore various defluoridation techniques (membrane process, adsorption, precipitation, reverse osmosis, ion exchange, and electrocoagulation). Owing to their cost ineffectiveness and high operational costs, these technologies failed to find any practical utility in fluoride remediation. Comparatively, defluoridation techniques involving the use of low-cost plant-derived adsorbents and fluoride phytoremediators are considered better alternatives. Through this review, an attempt has been made to critically synthesize information about various plant-based bioadsorbents and hyperaccumulators from existing literature. Moreover, mechanisms underlying the fluoride adsorption and accumulation by plants have been thoroughly discussed that will invigorate the researchers to develop novel ideas about process/product modifications to further enhance the removal potential of the adsorbents and plants. Literature survey unravels that various low-cost plant-derived adsorbents have shown their efficacy in defluoridation, yet there is an urgent need to explore their pragmatic application on a commercial scale.

Sources, controls, and probabilistic health risk assessment of fluoride contamination in groundwater from a semi-arid region in Gujarat, Western India: An isotope-hydrogeochemical perspective

Fluoride contamination in groundwaters of a rural region in semi-arid Western India has been studied using combination of geochemical-and-isotopic techniques, in conjunction with Health Quotient assessment approach. The objective of this study is to determine the sources and controls on fluoride content and to evaluate probabilistic non-carcinogenic risk associated with its long-term consumption. F^- ranges from 0.3 to 12 mg L^-1, shows high spatial variability, and ~ 35% of the samples have F^-  > 1.5 mg L^-1 (WHO maximum limit for drinking). Two sources are identified: high F^- results from water-rock interaction of F-bearing minerals in granites and gneisses, while phosphate fertilizers can contribute up to ~ 0.46 mg L^-1 of groundwater F^- that can be significant for low F^- samples. High F^- samples are characterized by high pH, Na and alkalinity, and low Ca. Calcite precipitation drives the solubility of F-bearing minerals. Kinetic fractionation of water isotopes (¹⁸O and ²H) demonstrates that evaporation plays role in enriching groundwater F^-. Non-carcinogenic risk, estimated by Hazard Quotient ([Formula: see text]), ranges from 0.13-5.72 to 0.26-11.86 for adult and children, respectively. Conservative estimate shows that ~ 0.467 million of adults and~0.073 million of children in four sub-districts are under the risk of fluorosis-while the residents of other five sub-districts remain safe from it. Finally, we suggest stakeholders to install F^- treatment plants to ensure the health safety of local residents in the high-risk zones, create awareness in farmers for optimum use of fertilizers, and promote rainwater harvesting, for better management of groundwater resources and quality in the region.

Effective adsorption of quadrivalent cerium by synthesized laurylsulfonate green rust in a central composite design

The layered laurylsulfonate intercalated green rust (lauryl-S GR) was synthesized to evaluate the influence of synthesis parameters and aqueous conditions on the adsorption of Ce^IV. The maximum adsorption capacity of 305.58 mg/g by lauryl-S GR was predictably obtained. The pseudo-first-order kinetic model was appropriate in fitting the whole uptake process in a weak acid environment. Three isotherm models including Langmuir, Freundlich, and Tempkin were all reliable in depicting the isotherm adsorption process. The maximum monolayer adsorption capacity of lauryl-S GR towards Ce^IV was 315.46 mg/g. Ce species including CeO and Ce₂O₃ besides CeO₂ were matched in the XPS distribution, directly indicating the reduction reaction brought by Fe^II in the GR occurred to hydrated Ce^IV ions during the adsorption. Nano-sized Ce particles attached to the lauryl-S GRs after the adsorption experiments were observed in the morphological characterization. Flocculated materials were formed on the surface of the lauryl-S GR at a pH of 7, which further reduced the active sites and disrupted the continuous uptake of Ce^IV to the lauryl-S GR. This study expands the application of GRs and supplies an ideal iron-based material for the construction of the affiliated recovery pathway to the traditional separation of Ce.

Arsenic and Fluoride in Groundwater, Prevalence and Alternative Removal Approach

Contamination of drinking water by arsenic and fluoride is a global problem, as more than 300 million people in more than 100 countries have been affected by their presence. These elements are considered the most serious contaminants in drinking water and their removal is a worldwide concern. Therefore, the evaluation of three alternative approaches—electrocoagulation, adsorption by biomaterials, and adsorption by metal oxide magnetic nanoparticles (MNPs)—was performed for arsenic and fluoride removal from groundwater. Arsenic removal from synthetic and groundwater (well water) was accomplished with the three processes; meanwhile, fluoride removal from groundwater was only reported by two methods. The results indicate that an electrocoagulation process is a good option for As (>97%) and F (>90%) removal in co-occurrence; however, the operational conditions for the removal of both pollutants must be driven by those used for fluoride removal. As (80–83%) and F (>90%) removal with the biomaterials was also successful, even when the application objective was fluoride removal. Finally, MNPs (Co and Mn) were designed and applied only for arsenic removal and reached >95%. Factors such as the pH, the presence of interfering ions, and the initial concentration of the contaminants are decisive in the treatment process’s efficiency.

Characterizations and fluoride adsorption performance of wattle humus biosorbent

Considering the serious health effects of fluoride contamination, an environment friendly bioadsorbent was derived from wattle humus for fluoride removal by conventional thermal activation process. Analytical characterizations revealed that heterogeneous morphological textured wattle humus enabled remarkable adsorption capacity. XPS analysis substantiated that fluoride had been successfully adsorbed on to the carbonized wattle humus surface through chemisorption. Fluoride adsorption efficiency was systematically rationalized via batch adsorption studies. Experiments were performed at different initial fluoride concentration and scrutinized the impact of contact time (10-120 min), adsorbent dosage (0.5-2.5 g), pH (2.0-9.0), and interfering co-existing ions (SO₄^2-, NO₃^-, Cl^-, and HCO₃^-) on fluoride removal. Even at different adsorbate dosage (2-10 mg/L), 98% fluoride removal efficiency was achieved under pH > 6. The competitive anions do not interfere the wattle humus fluoride adsorption capacity. Moreover, the adsorption isotherms and kinetics studies inferred that monolayer and multilayer adsorption behavior by wattle humus leads to noticeable fluoride adsorption. Adsorbent regeneration test affirms that regenerated adsorbent found higher (>95%) fluoride removal efficiency even at five recycle runs.

K2CO3-Activated Pomelo Peels as a High-Performance Adsorbent for Removal of Cu(II): Preparation, Characterization, and Adsorption Studies

Activated carbons (ACs) were prepared from pomelo peels by K2CO3 activation and used as an adsorbent (PAC) for the removal of Cu(II) from aqueous solutions. BET, SEM, and FT-IR were employed for the characterization of the obtained ACs. The optimum ACs were reported at activation temperature of 850°C, activation time of 60 min, and impregnation ratio of 3, which had a high surface area (1213 m2/g) and total pore volume (0.57 cm3/g). The resulting ACs were used for the adsorption of Cu(II) from aqueous solutions in the batch mode and yielded a superior adsorption capacity of 139.08 mg/g. The pH of optimum adsorption was determined as 5. Pseudo first-order model, pseudo second-order model, and intraparticle diffusion model were applied to describe the adsorption processes. The adsorption kinetic data were found to follow the pseudo second-order model. The adsorption isotherms data were analyzed using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. The Langmuir model was found to provide the best fit, and the calculated adsorption capacity was 151.35 mg/g.

Lycopene alleviates sulfamethoxazole-induced hepatotoxicity in grass carp (Ctenopharyngodon idellus) via suppression of oxidative stress, inflammation and apoptosis

Antibiotics are used worldwide to treat diseases in humans and other animals; most of them and their secondary metabolites are discharged into the aquatic environment, posing a serious threat to human health. However, the toxicity of antibiotics on aquatic organisms, especially the effects on the detoxification system and immune system, has not been thoroughly studied. Lycopene (LYC) is a naturally occurring hydrocarbon carotenoid, which has received extensive attention as a potential antioxidant. The aim of this study was to investigate whether LYC alleviates exogenous toxicity in carp induced by sulfamethoxazole (SMZ) and the underlying molecular mechanisms. The grass carp were treated with SMZ (0.3 μg L-1) and/or LYC (10 mg per kg body weight) for 30 days. Indexes, such as hepatic function-related including histopathological changes and biochemical parameters, detoxification system-related including the cytochrome P450 enzyme system and antioxidant system, and immune system-related including inflammatory and apoptosis processes were detected. The results showed that SMZ stress leads to significant pathological damage of the liver and induction of oxidative stress. LYC coadministration recovered the cytochrome p450-1A1 homeostasis and decreased SMZ-induced accumulation of intracellular reactive oxygen species (ROS). Mechanistically, indicators in the innate immune system (such as toll like receptors (TLRs), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6 and IL-8) and the apoptosis pathway (p53, PUMA, B-cell lymphoma-2 (Bcl-2), BCL2-associated X (Bax), and Caspase-9/3) disclosed adaptive activation under SMZ exposure; these anomalies returned to normal or close-to-normal levels after LYC coadministration. Therefore, LYC dietary supplement possesses liver protective function against exogenous toxic compounds like SMZ, making LYC a functional aquatic feed ingredient for aquiculture.

Arsenic behavior across soil-water interfaces in paddy soils: Coupling, decoupling and speciation

The sharp redox gradient at soil-water interfaces (SWI) plays a key role in controlling arsenic (As) translocation and transformation in paddy soils. When Eh drops, As is released to porewater from solid iron (Fe) and manganese (Mn) minerals and reduced to arsenite. However, the coupling or decoupling processes operating within the redox gradient at the SWI in flooded paddy soils remain poorly constrained due to the lack of direct evidence. In this paper, we reported the mm-scale mapping of Fe, As and other associated elements across the redox gradient in the SWI of five different paddy soils. The results showed a strong positive linear relationship between dissolved Fe, Mn, As, and phosphorus (P) in 4 out of the 5 paddy soils, indicating the general coupling of these elements. However, decoupling of Fe, Mn and As was observed in one of the paddy soils. In this soil, distinct releasing profiles of Mn, As and Fe were observed, and the releasing order followed the redox ladder. Further investigation of As species showed the ratio of arsenite to total As dropped from 100% to 75.5% and then kept stable along depth of the soil profile, which indicates a dynamic equilibrium between arsenite oxidization and arsenate reduction. This study provides direct evidence of multi-elements' interaction along redox gradient of SWI in paddy soils.

Isolation of biosynthetic crystals by microbially induced calcium carbonate precipitation and their utilization for fluoride removal from groundwater

Biosynthetic crystals (BC) were prepared through microbially induced calcium carbonate precipitation (MICP) for fluoride (F^-) removal from the groundwater. Batch experiments were conducted to evaluate the fluoride adsorption capacity and the impacts of critical factors (organic matter, pH, initial fluoride concentration and BC dosage) on defluorination efficiency of BC. The maximum adsorption amount and defluorination efficiency were recorded as 5.10 mg g^-1 and 98.24%, respectively. The adsorption kinetics and isotherms studies showed that pseudo-second-order kinetic model and Freundlich isotherm model were best fitting to the reaction. Adsorption thermodynamic parameters indicated a spontaneous, endothermic and thermodynamically favorable adsorption process. Moreover, the mechanism of F^- removal by BC was further analyzed by SEM, XPS, XRD and FTIR. The method can cope with the problem of applying the external organic substances in MICP, and avoid the microbial safety risk in the effluent. As an economically and environmentally friendly adsorbent, BC can be used for F^- removal from groundwater.

Land-use change caused by anthropogenic activities increase fluoride and arsenic pollution in groundwater and human health risk

Groundwater pollution is becoming a more serious issue because of various anthropogenic activities. A large proportion of the population living in the urbanized and industrialized world is exposed daily to hazardous materials. However, despite the knowledge that protecting groundwater is necessary, little is known about the role of land-use change for human health risks. In this study, we analyzed the temporal and spatial variation of groundwater fluoride (F) and arsenic (As) during 2010-2018 in Shanxi Province of Northern China. Distribution areas of high F and As increased from 2010 to 2018 and spread over time. We assessed human health risk by calculating carcinogenic risk and non-carcinogenic risk. The results showed that F exposure, frequency of high concentration, and risk from 2016 to 2018 were higher than that in 2010-2015, and similar results were obtained for As exposure. Further, land-use change caused by anthropogenic activities increased F and As pollution in groundwater and placed humans at a higher health risk. Our study sheds light on anthropogenic activities that could increase human health risks caused by groundwater F and As via changing land-use. The study provides supports and suggestions for policy-makers to reduce groundwater pollution and prevent adverse health risks to residents.

A critical review on recent developments in MOF adsorbents for the elimination of toxic heavy metals from aqueous solutions

Effective and substantial remediation of contaminants especially heavy metals from water is still a big challenge in terms of both environmental and biological perspectives because of their adverse effects on the human health. Many techniques including adsorption, ion exchange, co-precipitation, chemical reduction, ultrafiltration, etc. are reported for eliminating heavy metal ions from the water. However, adsorption has preferred because of its simple and easy handlings. Several types of adsorbents are observed and documented well for the purpose. Recently, highly porous metal-organic frameworks (MOFs) were developed by incorporating metals and organic ligands together and claimed as potent adsorbents for the remediation of highly toxic heavy metals from the aqueous solutions due to their unique features like greater surface area, high chemical stability, green and reuse material, etc. In this review, the authors discussed systematically some recent developments about secure MOFs to eliminate the toxic metals such as arsenic (both arsenite and arsenate), chromium(VI), cadmium (Cd), mercury (Hg) and lead (Pb). MOFs are observed as the most efficient adsorbents with greater selectivity as well as high adsorption capacity for metallic contamination. Graphical abstract.

Bifunctional iron-modified graphitic carbon nitride (g-C3N4) for simultaneous oxidation and adsorption of arsenic

Iron-modified graphitic carbon nitride (FG materials) was prepared through a simple and cost-effective method using iron oxide and melamine to achieve simultaneous oxidation and adsorption of arsenic. We hypothesized that graphitic carbon nitride oxidizes As(III) to As(V) under light irradiation, and the converted As(V) is adsorbed by the amorphous iron phase on FG materials. FG materials were characterized by X-ray diffraction, Fourier transform infrared spectra, field-emission scanning electron microscopy, specific surface area, ultraviolet-visible light spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy. As(III) was efficiently transformed to As(V) due to the photocatalytic-oxidation ability of graphic carbon nitride under visible and UV light irradiation, the oxidized As(V) was adsorbed by the amorphous iron phases, and As species were removed from the system. The removal efficiency of As(III) decreased from 50%, 41%, and 33% under UV light, visible light and dark, respectively. FG materials exhibited the photocatalytic-oxidation ability and adsorption capacity, and a synergistic effect was observed between graphitic carbon nitride and iron oxide. Removal of As can be achieved even under visible light, confirming the field applicability of low-cost FG materials.

Engineering a Biopolymer-Based Ultrafast Permeable Aerogel Membrane Decorated with Task-Specific Fe-Al Nanocomposites for Robust Water Purification

The present work demonstrates an innovative strategy for robust water purification using an engineered aerogel membrane fabricated from biopolymers and task-specific Fe-Al-based nanocomposites. The as-prepared ethylenediaminetetraacetate dianhydride cross-linked chitosan- and agarose (7:3 weight ratio)-based aerogel membrane decorated with α-FeOOH- and γ-AlOOH-based nanocomposites was characterized using various analytical tools, which suggested formation of a highly stable network interconnected through covalent and electrostatic interactions. The optimized bionanocomposite-based aerogel (BNC-AG-0.1) membrane showed macroporous and partial unidirectional short-range channels with an ultralow density of 0.021 g·m^-2, a high swelling ratio of 1974%, and a remarkable pure water flux of 19,228 L·m^-2·h^-1 (>6-fold higher flux compared to the reported aerogel membranes). The aerogel membranes were successfully utilized for purification of diverse pollutants such as dyes, emerging pollutants (EPs), arsenate, and fluoride in a continuous flow method under gravitational force. The BNC-AG-0.1 membrane exhibits high rejection (95-98.6%) for both cationic and anionic dyes with a flux rate of 1150-1375 L·m^-2·h^-1 and a rejection of 89-92% for EPs with a flux rate of 1098-1165 L·m^-2·h^-1. Moreover, the BNC-AG-0.1 membrane showed a q_max of 102.45 mg·g^-1 (at pH 6.5) for As(V) with >93% rejection at a flow rate of 1000 L·m^-2·h^-1. Furthermore, the aerogel membrane showed an excellent removal efficiency (92%) of arsenic up to the 10th cycle and hence demonstrated as a potential adsorption-based membrane for arsenic-free potable water. On the other hand, the BNC-AG-0.1 membrane showed a q_max of 81.56 mg·g^-1 (at pH 6.5) for F^- removal with >99% rejection at a flow rate of 250 L·m^-2·h^-1. When applied for real-water purification, approximately 4734 L of safe drinking water (the F^- concentration is less than the WHO permissible limit) per square meter of the aerogel membrane can be obtained with a flux rate of 250 L·m^-2·h^-1. Overall, the prepared aerogel membrane showed robust removal of a variety of contaminants with ultrafast water permeation and established excellent recyclability.

Arsenic adsorption by innovative iron/calcium in-situ-impregnated mesoporous activated carbons from low-temperature water and effects of the presence of humic acids

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.

As(III) and As(V) removal by using iron impregnated biosorbents derived from waste biomass of Citrus limmeta (peel and pulp) from the aqueous solution and ground water

Now a day's biosorbents with magnetic properties have been applied for water and wastewater treatment process, because of its magnetic nature it can be easily separated and can be reused more than one time. In the present study, two magnetic biosorbents were synthesized from waste biomass of Citrus limetta (peel and pulp) at 500 °C temperature represented as PAC-500 and PPAC-500. These biosorbents were effectively used for the removal of As(III) and As(V) from an aqueous solution and groundwater samples. The prepared biosorbents were characterized by using Brunauer Emmett Teller (BET), Zeta potential, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Disperssive X-ray (EDS), X-ray Diffraction (XRD) and Particle Size Analyzer (PSA). Isotherms, kinetics and thermodynamics were also applied to the obtained experimental data. The regeneration study revealed that the biosorbent can be recycled up to four cycles. The adsorbent capacity of PAC-500 and PPAC-500 for the sorption of As(III) was 714.28 μg/g and 526.31 μg/g, respectively, whereas the q_max value for As(V) sorption was 2000 μg/g for both the biosorbents (PAC-500 and PPAC-500). The effect of competitive ions was also studied that shows that the presence of H₂PO₄^- and CO₃² have negative effects on the sorption of As(III) and As(V). Arsenic is very toxic and it is a more important subject for consideration, therefore it is necessary to develop a low cost material that is very efficient in removing As from ground water contaminated with As water.

Synthesis of novel biochar from waste plant litter biomass for the removal of Arsenic (III and V) from aqueous solution: A mechanism characterization, kinetics and thermodynamics

The present study is focusing on utilization of a new feedstock material for the preparation of biochar. The dry waste leaves litter of Tectona and Lagerstroemia speciosa was used for synthesizing the biochar at 800 °C for 1 h in muffle furnace represents as TB 800 and LB 800 and then used for the removal of As(III) and As(V) from aqueous solution. The prepared biochar materials had a crystalline structure and was characterized by using Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), Brunaur emmit teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential, particle size and X-ray photoelectron spectroscopy (XPS). In regeneration study it was observed that prepared biochar material could be used up to four times with good removal percentage of Arsenic (III and V). The experimental data fitted well by Langmuir model for As(V) removal using TB 800 and LB 800, Freundlich model for As(III) removal by LB 800 and Temkin model for As(III) removal by TB 800. Pseudo-second-order kinetics was followed and best fitted with the obtained data of As(III) and (V) removal. Thermodynamics study revealed that the process of adsorption was endothermic for the removal of As(III) and exothermic for the adsorption of As(V) using TB 800 and LB 800. The adsorption capacity obtained for the removal of As(III) was 666.7 μg/g and 454.54 μg/g for TB 800 and LB 800, respectively and adsorption capacity for As(V) was 1250 μg/g for TB 800 and 714.28 μg/g was attained by LB 800.

Simultaneous biosorption of Arsenic (III) and Arsenic (V): Application of multiple response optimizations

In this work, simultaneous biosorption of As(III) and As(V) by Sargassum glaucescens was optimized using multiple response optimizations and Doehlert experimental design. The optimum condition for simultaneous biosorption of As(III) and As(V) were: biosorbent dosage 0.47 g L-1, pH 5.9 and initial concentration 120.34 mg L-1 with maximum overall desirability of 0.94. Different isotherms were fitted to biosorption equilibrium data and the Freundlich isotherm was the most suitable model. Based on thermodynamic study, the biosorption of arsenic species onto alga was endothermic and spontaneous. Kinetic results indicated that intraparticle diffusion model was the best kinetic model. Biosorption capacity of S. glaucescens and other biosorbents were also compared.

A critical review on arsenic removal from water using iron-based adsorbents

Intensive research efforts have been pursued to remove arsenic (As) contamination from water with an intention to provide potable water to millions of people living in different countries. Recent studies have revealed that iron-based adsorbents, which are non-toxic, low cost, and easily accessible in large quantities, offer promising results for arsenic removal from water. This review is focused on the removal of arsenic from water using iron-based materials such as iron-based nanoparticles, iron-based layered double hydroxides (LDHs), zero-valent iron (ZVI), iron-doped activated carbon, iron-doped polymer/biomass materials, iron-doped inorganic minerals, and iron-containing combined metal oxides. This review also discusses readily available low-cost adsorbents such as natural cellulose materials, bio-wastes, and soils enriched with iron. Details on mathematical models dealing with adsorption, including thermodynamics, kinetics, and mass transfer process, are also discussed. For elucidating the adsorption mechanisms of specific adsorption of arsenic on the iron-based adsorbent, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) are frequently used. Overall, iron-based adsorbents offer significant potential towards developing adsorbents for arsenic removal from water.