Department Of Environmental Science And Technology

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Author: search.filters.author.Kumar, Rakesh

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    Uranium and Fluoride Accumulation in Vegetable and Cereal Crops: A Review on Current Status and Crop-Wise Differences
    (Multidisciplinary Digital Publishing Institute (MDPI), 2023-09-19T00:00:00) Sachdeva, Saloni; Powell, Mike A.; Nandini, Girish; Kumar, Hemant; Kumar, Rakesh; Sahoo, Prafulla Kumar
    Uranium (U) and fluoride (F?) contamination in agricultural products, especially vegetable and cereal crops, has raised serious concerns about food safety and human health on a global scale. To date, numerous studies have reported U and F? contamination in vegetable and cereal crops at local scales, but the available information is dispersed, and crop-wise differences are lacking. This paper reviews the current status of knowledge on this subject by compiling relevant published literatures between 1983 and 2023 using databases such as Scopus, PubMed, Medline, ScienceDirect, and Google Scholar. Based on the median values, F? levels ranged from 0.5 to 177 mg/kg, with higher concentrations in non-leafy vegetables, such as Indian squash �Praecitrullus fistulosus� (177 mg/kg) and cucumber �Cucumis sativus� (96.25 mg/kg). For leafy vegetables, the maximum levels were recorded in bathua �Chenopodium album� (72.01 mg/kg) and mint �Mentha arvensis� (44.34 mg/kg), where more than 50% of the vegetable varieties had concentrations of >4 mg/kg. The concentration of U ranged from 0.01 to 17.28 mg/kg; tubers and peels of non-leafy vegetables, particularly radishes �Raphanus sativus� (1.15 mg/kg) and cucumber �Cucumis sativus� (0.42 mg/kg), contained higher levels. These crops have the potential to form organometallic complexes with U, resulting in more severe threats to human health. For cereal crops (based on median values), the maximum F? level was found in bajra �Pennisetum glaucum� (15.18 mg/kg), followed by chana �Cicer arietinum� (7.8 mg/kg) and split green gram �Vigna mungo� (4.14 mg/kg), while the maximum accumulation of U was recorded for barley �Hordeum vulgare� (2.89 mg/kg), followed by split green gram �Vigna mungo� (0.45 mg/kg). There are significant differences in U and F? concentrations in either crop type based on individual studies or countries. These differences can be explained mainly due to changes in geogenic and anthropogenic factors, thereby making policy decisions related to health and intake difficult at even small spatial scales. Methodologies for comprehensive regional�or larger�policy scales will require further research and should include strategies to restrict crop intake in specified �hot spots�. � 2023 by the authors.
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    Rice husk biochar - A novel engineered bio-based material for transforming groundwater-mediated fluoride cycling in natural environments
    (Academic Press, 2023-05-24T00:00:00) Kumar, Rakesh; Sharma, Prabhakar; Sharma, Pushpa Kumari; Rose, Pawan Kumar; Singh, Rakesh Kumar; Kumar, Nishant; Sahoo, Prafulla Kumar; Maity, Jyoti Prakash; Ghosh, Ashok; Kumar, Manish; Bhattacharya, Prosun; Pandey, Ashok
    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 (F?) cycling, performance feasibility was tested at various governing factors, contact time (0�120 min), initial F? 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 F? 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 F? removal mechanisms. Pseudo-second-order and Freundlich were the best fit kinetic and isotherm for F? sorption, respectively. Increased biochar dose drives an increase in active sites due to F? 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 F? contamination, and has been performed multiple times after systematic adsorption-desorption experiments. Lastly, techno-economic analysis was analyzed for biochar synthesis and F? treatment performance costs. Overall, our results revealed worth output and concluded with recommendations for future research on F? adsorption using biochar. � 2023 Elsevier Ltd
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    Co-transport and deposition of fluoride using rice husk-derived biochar in saturated porous media: Effect of solution chemistry and surface properties
    (Elsevier B.V., 2023-02-10T00:00:00) Kumar, Rakesh; Sharma, Prabhakar; Rose, Pawan Kumar; Sahoo, Prafulla Kumar; Bhattacharya, Prosun; Pandey, Ashok; Kumar, Manish
    Fluoride (F?) contamination in water is a global health concern, threatening the well-being of millions. This study investigated the role of ZnCl2/FeCl3-rice husk-modified biochar (Zn-BC and Zn/Fe-BC) in treating F?-contaminated surface and groundwater under the influence of varying solution chemistry, co-existing ions, and biochar-amended through column transport experiments. Modified biochar showed maximum F? adsorption, 99.01% and 91.90% using Zn/Fe-BC and Zn-BC, respectively, than 85.87% using raw biochar (R-BC). Raw/modified biochars were characterized with FESEM-EDAX, FTIR, XRD, particle size, surface area, electro-kinetic potential, and point of zero charge analyses. Langmuir and pseudo-second-order kinetic could explain that F?-biochar interactions are dominated by chemisorption at ambient temperature while physisorption at higher temperatures. The influence of salt concentrations and co-occurring ions reduced F? sorption using Zn/Fe-BC. Increased salt strengths led to reduced electrophoretic mobility of biochar particles, i.e., biochar�biochar particles attract each other and increase the hydrodynamic diameter, which ultimately reduces the active sites on biochar for F? adsorption. Co-transport and deposition of biochar and F? in saturated porous media revealed lower mobility of biochar, and maximum F? adsorption was observed at 10 mM salt strength. Biochar transport is governed by electrostatic interactions, whereas F? transport mainly occurs through chemisorption. In rural areas, hand pumps and tube wells are generally used as source of potable water for drinking and cooking purposes; thus, biochar-mediated sand columns can be utilized for defluoridation. Thus, Zn/Fe-BC can be utilized as a potential bio-adsorbent for F?-contaminated natural surface and groundwater with optimum preparation and treatment costs. � 2023 The Authors
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    Recent advances in biochar amendments for immobilization of heavy metals in an agricultural ecosystem: A systematic review
    (Elsevier Ltd, 2023-01-03T00:00:00) Sachdeva, Saloni; Kumar, Rakesh; Sahoo, Prafulla Kumar; Nadda, Ashok Kumar
    Over the last several decades, extensive and inefficient use of contemporary technologies has resulted in substantial environmental pollution, predominantly caused by potentially hazardous elements (PTEs), like heavy metals that severely harm living species. To combat the presence of heavy metals (HMs) in the agrarian system, biochar becomes an attractive approach for stabilizing and limiting availability of HMs in soils due to its high surface area, porosity, pH, aromatic structure as well as several functional groups, which mostly rely on the feedstock and pyrolysis temperature. Additionally, agricultural waste-derived biochar is an effective management option to ensure carbon neutrality and circular economy while also addressing social and environmental concerns. Given these diverse parameters, the present systematic evaluation seeks to (i) ascertain the effectiveness of heavy metal immobilization by agro waste-derived biochar; (ii) examine the presence of biochar on soil physico-chemical, and thermal properties, along with microbial diversity; (iii) explore the underlying mechanisms responsible for the reduction in heavy metal concentration; and (iv) possibility of biochar implications to advance circular economy approach. The collection of more than 200 papers catalogues the immobilization efficiency of biochar in agricultural soil and its impacts on soil from multi-angle perspectives. The data gathered suggests that pristine biochar effectively reduced cationic heavy metals (Pb, Cd, Cu, Ni) and Cr mobilization and uptake by plants, whereas modified biochar effectively reduced As in soil and plant systems. However, the exact mechanism underlying is a complex biochar-soil interaction. In addition to successfully immobilizing heavy metals in the soil, the application of biochar improved soil fertility and increased agricultural productivity. However, the lack of knowledge on unfavorable impacts on the agricultural systems, along with discrepancies between the use of biochar and experimental conditions, impeded a thorough understanding on a deeper level. � 2023 Elsevier Ltd
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    Uranium and Fluoride Removal from Aqueous Solution Using Biochar: A Critical Review for Understanding the Role of Feedstock Types, Mechanisms, and Modification Methods
    (MDPI, 2022-12-13T00:00:00) Thakur, Anjali; Kumar, Rakesh; Sahoo, Prafulla Kumar
    Uranium (U) and fluoride (F?) are the major global geogenic contaminants in aquifers and pose serious health issues. Biochar, a potential adsorbent, has been widely applied to remediate geogenic and anthropogenic contaminants. However, there is a lack of research progress in understanding the role of different feedstock types, modifications, adsorption mechanisms on physico-chemical properties of biochar, and factors affecting the adsorption of U and F? from aqueous solution. To fill this lacuna, the present review gives insight into the U and F? removal from aqueous solution utilizing biochar from various feedstocks. Feedstock type, pyrolysis temperature, modifications, solution pH, surface area, and surface-charge-influenced biochar adsorption capacities have been discussed in detail. Major feedstock types that facilitated U and F? adsorption were crop residues/agricultural waste, softwood, grasses, and animal manure. Low-to-medium pyrolyzing temperature yielded better biochar properties for U and F? adsorption. Effective modification techniques were mainly acidic and magnetic for U adsorption, while metal oxides, hydroxides, alkali, and magnetic modification were favourable for F? adsorption. The major mechanisms of U adsorption were an electrostatic attraction and surface complexation, while for F? adsorption, the major mechanisms were ion exchange and electrostatic attraction. Lastly, the limitations and challenges of using biochar have also been discussed. � 2022 by the authors.