Fluoride is widely found in soil–water systems due to anthropogenic and geogenic activities that affect millions worldwide. Fluoride ingestion results in chronic and acute toxicity, including ...skeletal and dental fluorosis, neurological damage, and bone softening in humans. Therefore, this review paper summarizes biological processes for fluoride remediation, i.e., bioaccumulation in plants and microbially assisted systems. Bioremediation approaches for fluoride removal have recently gained prominence in removing fluoride ions. Plants are vulnerable to fluoride accumulation in soil, and their growth and development can be negatively affected, even with low fluoride content in the soil. The microbial bioremediation processes involve bioaccumulation, biotransformation, and biosorption. Bacterial, fungal, and algal biomass are ecologically efficient bioremediators. Most bioremediation techniques are laboratory-scale based on contaminated solutions; however, treatment of fluoride-contaminated wastewater at an industrial scale is yet to be investigated. Therefore, this review recommends the practical applicability and sustainability of microbial bioremediation of fluoride in different environments.
Competitive biosorption of Cd(II), Cr(III) and Ni(II) on unmodified shelled
Moringa oleifera seeds (SMOS) present in ternary mixture were compared with the single metal solution. The extent of ...adsorption capacity of the ternary metal ions tested on unmodified SMOS was low (10–20%) as compared to single metal ions. SMOS removed the target metal ions in the selectivity order of Cd(II)
>
Cr(III)
>
Ni(II). Sorption equilibria, calculated from adsorption data, explained favorable performance of biosorption system. Regeneration of exhausted biomass was also attempted for several cycles with a view to restore the sorbent to its original state.
Aim: The objective of this study was to evaluate and compare canal transportation (CT) and centering ability (CA) in the curved canals prepared using HyFlex CM (HCM) and TruNatomy (TN) rotary file ...systems with the help of cone-beam computed tomography (CBCT).
Materials and Methods: Forty extracted single-rooted mandibular premolars with 10°-30° of curvature were selected and divided into two groups. In Group 1, the canals were prepared with HCM files (Coltene Whaledent) and in Group 2 the canals were prepared with TN Prime rotary files (Dentsply Sirona). Pre- and postinstrumentation scans were performed at the same position using CBCT to evaluate CT and CA at three levels 3 mm, 6 mm, and 9 mm from the apex and were compared using CBCT software (On Demand 3D software).
Statistical Analysis Used: The two groups were statistically analyzed with Mann-Whitney U-test.
Results: There was no significant difference among the tested groups regarding the canal centering ratio (P > 0.05). At 6- and 9-mm levels, there was no significant difference in CT among the two groups (P > 0.05). However, at 3 mm from apex, there was a statistically significant difference (P = 0.006) with TN files exhibiting lesser CT.
Conclusion: Both the file systems respected the canal anatomy, although in the apical third, TN files exhibited better results. Hence, this file system can be considered for instrumentation of canals with moderate apical curvatures. In regard to CA, no significant differences were found among the file systems.
Arsenic (As) is a ubiquitous carcinogen element, occurring due to geogenic and anthropogenic actions and posing major global public health concerns. This review work significantly summarized the ...current state of knowledge for arsenic-contaminated water treatment. Firstly, this paper insight a brief understanding of arsenic speciation, toxicity, and accumulation in the food chain, and secondly, explains the adsorption techniques for As remediation from the contaminated water. Arsenic adsorption, using biochar-based sorbents, is summarized as an efficient and economically feasible approach. Biochars, renewable carbonaceous and sustainable materials, synthesized through pre/post-pyrolysis treatment of biomass under limited oxygen supply conditions, resulting in high surface area, dual-porosity, surface charge, and enhanced functional groups. Thirdly, this review discusses various factors, such as acidic pH, initial concentration, biochar dose, co-existing ions, and temperature, including regeneration and reusability of biochar-based sorbents. Arsenic adsorption increases at 2–6 pH and decreases until pH 10. In aqueous solution, pH-influenced As species, as H2AsO4− and HAsO42− dominate in the range of 3–6 pH, and AsO43− are primarily present in alkaline solution. Thus, electrostatic interactions and surface complexation are dominating mechanisms occurring at arsenic-biochar interfaces in aqueous solutions. Lastly, mechanistic understanding for arsenic adsorption onto biochar materials has been discussed, considering equilibrium adsorption isotherms, kinetics, and thermodynamics analysis. In conclusion, this review also highlighted major challenges and future scope relevant for implications of biochar sorbents in continuous flow systems to scale up for commercial and industrial purposes.
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•Biochar is a novel, eco-friendly and efficient carbon material for As removal.•Solution chemistry, pyrolysis, and feedstock type govern the As removal potential.•Electrostatic attraction and surface complexation are prominent mechanisms for As adsorption.•To reduce arsenic-loaded sludge, recyclability and reusability of biochar are necessary.
Biochar, a promising carbon-rich and carbon-negative material, can control water pollution, harness the synergy of sustainable development goals, and achieve circular economy. This study examined the ...performance feasibility of treating fluoride-contaminated surface and groundwater using raw and modified biochar synthesized from agricultural waste rice husk as problem-fixing renewable carbon-neutral material. Physicochemical characterizations of raw/modified biochars were investigated using FESEM-EDAX, FTIR, XRD, BET, CHSN, VSM, pHpzc, Zeta potential, and particle size analysis were analyzed to identify the surface morphology, functional groups, structural, and electrokinetic behavior. In fluoride (Fˉ) cycling, performance feasibility was tested at various governing factors, contact time (0–120 min), initial Fˉ levels (10–50 mg L−1), biochar dose (0.1–0.5 g L−1), pH (2–9), salt strengths (0–50 mM), temperatures (301–328 K), and various co-occurring ions. Results revealed that activated magnetic biochar (AMB) possessed higher adsorption capacity than raw biochar (RB) and activated biochar (AB) at pH 7. The results indicated that maximum Fˉ removal (98.13%) was achieved using AMB at pH 7 for 10 mg L−1. Electrostatic attraction, ion exchange, pore fillings, and surface complexation govern Fˉ removal mechanisms. Pseudo-second-order and Freundlich were the best fit kinetic and isotherm for Fˉ sorption, respectively. Increased biochar dose drives an increase in active sites due to Fˉ level gradient and mass transfer between biochar-fluoride interactions, which reported maximum mass transfer for AMB than RB and AB. Fluoride adsorption using AMB could be described through chemisorption processes at room temperature (301 K), though endothermic sorption follows the physisorption process. Fluoride removal efficiency reduced, from 67.70% to 53.23%, with increased salt concentrations from 0 to 50 mM NaCl solutions, respectively, due to increased hydrodynamic diameter. Biochar was used to treat natural fluoride-contaminated surface and groundwater in real-world problem-solving measures, showed removal efficiency of 91.20% and 95.61%, respectively, for 10 mg L−1 Fˉ contamination, and has been performed multiple times after systematic adsorption-desorption experiments. Lastly, techno-economic analysis was analyzed for biochar synthesis and Fˉ treatment performance costs. Overall, our results revealed worth output and concluded with recommendations for future research on Fˉ adsorption using biochar.
•Activated magnetic biochar (AMB) significantly reduces 10 mg L−1 fluoride at pH 7.•Mass transfer rates were analyzed for fluoride-biochar interactions.•Salt strength reduces adsorption due to electrostatic attraction and agglomeration.•Total interaction energies due to biochar-biochar interaction were investigated.•AMB synthesis and treatment costs were 0.01 $ g−1 and 5.96 $ mol−1, respectively.
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•Arsenic exposure from wheat is substantial and increasing.•The home-made bread (chapati) contributed most of the wheat intake in Bihar, India.•Arsenic concentration in the wheat ...flour was not lower than in the grains.•Arsenic exposure from wheat-based food intake is of concern.
In arsenic (As) endemic areas of south-east Asia, where a subsistence rice-based diet is prevalent, As exposure from food is mainly focused on rice intake. However, consumption of wheat is substantial and increasing. We present a probabilistic assessment of increased cancer risk from wheat-based food intake in a study population of rural Bihar, India where As exposure is endemic. Total As in wheat grains (43.64 ± 48.19 µg/kg, n = 72) collected from 77 households across 19 villages was found to be lower than reported As in wheat grains from other south-east Asian countries but higher than a previous study from Bihar. This is the first study where As concentration in wheat flour was used for risk estimation, bearing in mind that it was the flour obtained after indigenous household processing of the grains that was used for making the home-made bread (chapati) which contributed 95% of wheat intake for the studied population. Interestingly, while 78% of the surveyed participants (n = 154) consumed rice every day, chapati was consumed every day by 99.5% of the participants. In contrast to previous studies, where As concentration in wheat grains was found to be lower than the flour due to the removal of the bran on grinding, we did not find any appreciable lowering of arsenic in the wheat flour (49.80 ± 74.08 µg/kg, n = 58), most likely due to external contamination during processing and grinding. Estimated gender adjusted excess lifetime cancer risk of 1.23 × 10−4 for the studied rural population of Bihar indicated risk higher than the 10−4–10−6 range, typically used by the USEPA as a threshold to guide regulatory values. Hence, our findings suggest As exposure from wheat-based food intake to be of concern not only in As endemic areas of rural Bihar but also in non-endemic areas with similar wheat-based diet due to public distribution of the wheat across India.
Global groundwater is frequently discovered to have high arsenic (As) concentrations, critically endangered and potentially toxic to aquatic organisms and humans. This work investigates As(V) ...adsorption using raw nanobiochar (RnBC) and activated magnetic nanobiochar (AMnBC), which are synthesized via pre-treating rice straw biomass with ZnCl2 and FeCl3 and pyrolyzing at 500 °C, followed by ball milling. The highest adsorption capacity for AMnBC and RnBC was 130 μg/g and 38.67 μg/g, respectively, at alkaline water chemistry to mimic natural groundwater conditions. Different functional groups contributed by modifications are evident with As(V) adsorption using RnBC and AMnBC. Multilayer chemisorption may explain the adsorption of As(V) on biochar surfaces, as Freundulich isotherm and pseudo-second-order kinetic model are suggested. The synthesis cost for AMnBC and RnBC was $0.0147/g and $0.0099/g, respectively, which helped to determine the most effective and efficient method for As(V) adsorption. In this study, natural As-contaminated groundwater collected from Patna, Bihar (India), was treated for As(V) removal using AMnBC in natural environments. Thus, this study recommends that cost-effective modified biochar can effectively be used for As(V) elimination from naturally contaminated groundwater as well as surface water.
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•Activated magnetic nanobiochar, AMnBC, synthesized from rice straw in single-step.•Optimum arsenic(V) removal of 130 μg/g was obtained using AMnBC in alkaline water.•Comparative analysis for synthesis cost was analyzed for raw and modified biochar.•Natural contaminated groundwater collected from Patna, Bihar treated using AMnBC.
The present study explores the unexploited sorption properties of the plant
Moringa oleifera Lam. for decontamination of Cd at laboratory scale. Sorption studies using standard practices were carried ...out in batch experiments as functions of biomass dosage, contact time, metal concentrations, particle size and pH. Percentage sorption in each case was computed on the basis of Cd estimation using a planar NaI (TI) detector coupled to a 4
K MCA (Canberra Accuspec Card with PC-AT 386). The adsorption data accurately in a Freundlich isotherm. Sorption studies resulted in the standardization of optimum conditions for removal of Cd (85.10%) as follows: biomass dosage (4.0
g), metal concentration (25
μg/ml), contact time (40
min) and volume of the test solution (200
ml) at pH 6.5. Fourier transform infrared (FTIR) spectrometry highlighted amino acid–Cd interactions responsible for sorption phenomenon. The findings open up new avenues in the removal of toxic metals by shelled
Moringa oleifera seeds (SMOS) from water bodies as low cost, domestic and environmentally friendly safe technology.
Purpose of Review
The purpose of this review is to evaluate the effectiveness of biochar in immobilizing arsenic (As) in contaminated paddy soils and its impact on As availability and bioaccumulation ...in rice, as well as rice plant biomass.
Recent Findings
Recent studies have focused on managing As contamination in agricultural fields, with a particular focus on South and Southeast Asia, where rice, a primary food source and As accumulator, is of significant concern. Biochar, a product of biomass pyrolysis, has emerged as a viable solution for environmental remediation due to its effectiveness in immobilizing metal(loid)s in water and soil. The successful implementation of biochar as a soil amendment strategy has led to growing interest in its use as an effective means of reducing the bioaccumulation and availability of metal(loid)s, including As.
Summary
A meta-analysis of 25 studies revealed that biochar generated from maize and sewage sludge successfully reduced As availability and bioaccumulation in rice grains. In addition, the use of biochar led to higher biomass and yield of rice crops compared to control groups. Modified biochar was more effective in decreasing As availability, likely due to interactions with iron and calcium phases or complexes occurring in or on the biochars. Nevertheless, at elevated biochar dosages, As mobilization was noted in field conditions which warrants further investigation.
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