Browsing by Author "Sweta Mohan"

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Effective removal of fluoride from water by coconut husk activated carbon in fixed bed column: Experimental and breakthrough curves analysis
(Elsevier B.V., 2018) Mahe Talat; Sweta Mohan; Viney Dixit; Devendra Kumar Singh; Syed Hadi Hasan; Onkar Nath Srivastava
The bio-waste coconut husk was converted into activated carbon through merely treating with KOH and thus obtained activated carbon was characterized by XRD, TGA, SEM and TEM analysis. The prepared activated carbon having very high surface area (1448 m2/g) was utilized as an adsorbent for the removal of fluoride (F-) from water. Fluoride adsorption experiments were performed on the laboratory-scale column at different bed height, flow rates, and F- concentrations to explore the potential of prepared adsorbent and it was found to be very efficient adsorbent as it showed high adsorption capacity 6.5 mg/g at pH 5, F- concentration 10 mg/L and adsorbent dose 1.4 g/L. Various breakthrough models i.e. Bed Depth Service Time (BDST), Thomas and Yoon–Nelson were applied on breakthrough data to analyze the breakthrough curves. The high R2 values obtained for the BDST model revealed its validity for this adsorption system. Breakthrough curves were successfully analyzed and described by both Thomas and Yoon–Nelson models. The exhausted adsorbent was efficiently regenerated with the 10% NaOH solution and regenerated adsorbent showed remarkable uptake capacity with a slight reduction in adsorption performance up to the 3 cycles. Life factor calculation indicated that adsorbent bed would have sufficient bed capacity up to 8.3 cycles to avoid breakthrough at time t = 0 and the bed would be completely exhausted after 9.0 cycles. © 2018
Introduction to Microplastics: Origin, Environmental Pathways, and Impacts on Ecosystems and Human Health
(Springer Science+Business Media, 2025) Vijay Kumar; Anupam Sunny; Khushaboo Verma; Ambneesh Mishra; Md Izhar Alam; Hira Lal Yadav; Javed Alam; Sweta Mohan; Devendra Kumar Singh
The plastics which were valued for their durability and versatility, have become ubiquitous in modern applications, from packaging to medicine. However, their non-biodegradable nature and poor waste management have led to severe environmental pollution, with over 430 million tons produced annually, which is projected to double by 2040. The improper disposal of such a huge plastic waste results in the release and accumulation of microplastics (MPs, < 5 mm) and nanoplastics (NPs, < 100 nm) in air, water, soil, and biota, which is being produced from both intentional production and degradation of larger plastics. These persistent MPs contaminate the various ecosystems, enter into the food chains through ingestion, inhalation, and dermal contact, and act as vectors for several toxic chemicals like heavy metals and polycyclic aromatic hydrocarbons, and increase their ecological and health impacts. In aquatic systems, MPs cause physical harm through ingestion and entanglement and reduces the growth and survival of organisms. In terrestrial environments, MPs disrupt soil structure, microbial activity, and nutrient cycling and impairs the health of plants. Human exposure to MPs is linked to respiratory, immune, and reproductive health issues, exacerbated by toxic additives like phthalates and flame retardants. The current chapter explores the sources, pathways, and impacts of MPs and NPs, emphasizing the urgent need for improved waste management, biodegradable alternatives, and global cooperation to mitigate plastic pollution and safeguard ecosystems and human health. © 2025 The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.
Synthesis of highly fluorescent nitrogen-rich carbon quantum dots and their application for the turn-off detection of cobalt (II)
(Elsevier B.V., 2019) Daraksha Bano; Vijay Kumar; Subhash Chandra; Vikas Kumar Singh; Sweta Mohan; Devendra Kumar Singh; Mahe Talat; Syed Hadi Hasan
In this study, we have reported easy and economical synthesis of highly fluorescent nitrogen-rich carbon quantum dots (N-CQDs). The as-prepared N-CQDs displayed strong blue color emission along with CIE co-ordinate index (0.15, 0.14). The N-CQDs possess comparatively high QY of 57% using quinine sulfate as a standard. Furthermore, the as-prepared N-CQDs defend against the high salt strength and longtime photostability over the six months of incubation. Apart from this, the as-prepared N-CQDs responded as a sensor for the ‘turn-off’ detection of Co2+ along with the detection limit of 0.12 μM over a linear range from 0.5 to 3 μM. The mechanistic study proved the detection of Co2+ was based on the IFE, static quenching, aggregation, and complex formation between the amino group of N-CQDs and Co2+. Moreover, the fluorescence of the quenched N-CQDs can reappear and get ‘turn-on’ by using GSH, AA, EDTA, and cyst; thus, the prepared N-CQDs could further execute as a probe for the Co2+ detection. Inspired by these outstanding properties, the as-prepared N-CQDs were also successfully employed for the practical application toward monitoring the trace level of Co2+ in a vitamin B-12 sample. © 2019 Elsevier B.V.