Novel Synthesis of Carbon Dots from Coconut Wastes and Its Potential as Water Disinfectant

Subramani Krishnaraj Rajkishore (), Krishnagounder Padmanaban Devadharshini, Ponnuraj Sathya Moorthy, Vanniya Sreeramulu Reddy Kiran Kalyan, Rajkishore Sunitha, Mohan Prasanthrajan, Muthunalliappan Maheswari, Kizhaeral Sevathapandian Subramanian, Nalliappan Sakthivel and Ruben Sakrabani
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Subramani Krishnaraj Rajkishore: Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore 641003, India
Krishnagounder Padmanaban Devadharshini: Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore 641003, India
Ponnuraj Sathya Moorthy: Centre for Agricultural Nanotechnology, Tamil Nadu Agricultural University, Coimbatore 641003, India
Vanniya Sreeramulu Reddy Kiran Kalyan: Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore 641003, India
Rajkishore Sunitha: Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore 641003, India
Mohan Prasanthrajan: Centre for Agricultural Nanotechnology, Tamil Nadu Agricultural University, Coimbatore 641003, India
Muthunalliappan Maheswari: Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore 641003, India
Kizhaeral Sevathapandian Subramanian: Centre for Agricultural Nanotechnology, Tamil Nadu Agricultural University, Coimbatore 641003, India
Nalliappan Sakthivel: Agricultural Research Station, Tamil Nadu Agricultural University, Bhavanisagar 638451, India
Ruben Sakrabani: Cranfield Soil and Agrifood Institute, School of Water, Energy & Environment, Cranfield University, Cranfield MK43 0AL, UK

Sustainability, 2023, vol. 15, issue 14, 1-16

Abstract: This paper presents a facile and effective method for the large-scale production of carbon dots (CDs) from diverse coconut wastes (fronds, husk and shell). On comparing two different methods, namely (i) hydrothermal carbonization and (ii) novel sequential synthesis processes (pyrolysis followed by sonication), the latter procedure recorded a higher recovery of CDs (14.0%) over the hydrothermal method (2.33%). Doping agents such as urea, polyethyleneimine (PEI) and hexamethylenetetramine (HMTA) were chosen at varying concentrations to synthesize surface-modified CDs (SMCDs) for enhanced antibacterial properties. Among these SMCDs, urea-doped CDs (1:1) @ 1000 ppm registered significantly higher cytotoxicity (20.6%) against Escherichia coli ( E. coli ). Subsequently, to assess the applicability of CDs as a disinfectant in water purification systems, two products, namely (i) CD-infused chitosan beads and (ii) pelletized CDs, were developed to ensure the immobilization of CDs. Studies with lab-scale prototypes have revealed that CDs infused chitosan beads reduced the colonies of E. coli from 5.41 × 10 2 CFU/mL (control group) to 2.16 × 10 2 CFU/mL, in comparison with pelletized CDs that decreased to 3.30 × 10 2 CFU/mL. The biosafety of CDs was assessed against Eisenia fetida for 21 days, and the observations revealed no mortality, even at 2000 ppm. Overall, this research demonstrated that a waste biomass can be effectively transformed into a novel water disinfectant. Furthermore, this scientific endeavor opens up research avenues to evolve advanced water purifiers using low-cost and eco-friendly nanomaterials.

Keywords: coconut waste; carbon dots; cytotoxicity; Escherichia coli; Eisenia fetida; water disinfectant (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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