Eco-Friendly Sustainable Fluorescent Carbon Dots for the Adsorption of Heavy Metal Ions in Aqueous Environment

Abstract

The materials and substances required for sustainable water treatment by adsorption technique, are still being researched widely by distinguished classes of researchers. Thus, the need to synthesize substances that can effectively clean up pollutants from the environment cannot be overemphasized. So far, materials in bulk forms that are rich in carbon, such as biochar and varieties of activated carbon have been used for various adsorptive purposes. The use of bulk materials for such purposes are not efficient due to minimal surface areas available for adsorption. This study explores the adsorption task at nano dimension using carbon dots (CDs) from tapioca. The properties of carbon structure and its influence on the adsorptive efficacy of carbon nanoparticles were investigated by energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HrTEM), and atomic force microscopy (AFM). The results implied carbon present in CDs are good adsorbents for effective adsorption of heavy metal ions (lead) with removal efficiency of 80.6% in aqueous environment. The adsorption process as explored by both Langmuir and Freundlich isotherms have proven favorability of the adsorption process. Langmuir form two and three have correlation coefficients R2 at 0.9922 and 0.9912, respectively. The Freundlich isotherm confirms CDs as having defined surface heterogeneity and the exponential distribution of active sites. The adsorption of lead unto CDs obeyed the second order kinetic model with coefficient of determination, R2 of 0.9668 and 0.9996 at an initial lead concentration of 20 mg/L and 100 mg/L, respectively. The findings validated the efficiency of CDs derived from tapioca as an excellent material for further utilization in the environmental fields of wastewater pollution detection and clean up, bio-imaging, and chemical sensing applications.

Equilibrium and Kinetic Studies for The Adsorptive Removal of Lead (II) Ions from Aqueous Solution Using Activated Plantain Peel Biochar

“…Consequently to measure the sorption kinetics, 0.01 M lead solution was used while varying time between 30-150 min. To get sorption isotherms, 0.1 g of the activated biochar was added to different concentrations of lead solution (4,8,12,16 and 20 mg/ml) and the mixtures equilibrated for 120 seconds each. Similar method was applied for pH varied between 2-10.…”

“…Various techniques are available for the removal heavy metals from wastewaters, surface and underground waters. These methods are chemical precipitation, ion exchange, filtration, evaporation, reverse osmosis, solvent extraction, electrochemical treatment, membrane separation and activated carbon adsorption [7][8][9]. However, all these methods are either inefficient or not economical when heavy metal exists in lower concentrations [8].…”

“…These methods are chemical precipitation, ion exchange, filtration, evaporation, reverse osmosis, solvent extraction, electrochemical treatment, membrane separation and activated carbon adsorption [7][8][9]. However, all these methods are either inefficient or not economical when heavy metal exists in lower concentrations [8]. For instance, activated carbon a commonly used adsorbent for removal of various pollutants from wastewater has been jettisoned due to its high cost [9].…”

Hydrothermal Synthesis of Fluorescent Schiff Base Functionalized Carbon Dot Composite for The Removal Of Cd(II) Ions From Aqueous Solution: Equilibrium and Kinetic Studies.

“…Deleterious heavy metals such as cadmium pose serious harmful health and environmental hazard as they are regarded as destructive contaminant due to their bio-accumulative and non-degradable properties (1).…”

“…The development of excellent functionalized carbon quantum dot nanomaterial for the adsorption of cadmium from aqueous solution has been reported, however, carbon quantum dot is potentially toxic compared to carbon dot (7). The use of hydrothermal synthetic technique in the preparation of carbon dot is advantageous because of relatively mild operating conditions (reaction temperatures < 300 °C), one-step synthetic procedure, environmental friendliness, and good dispersion in solution (1). Studies have noted that carbon dots with surface immobilization exhibit high fluorescent properties whereas the nonfunctionalized carbon nanoparticles are weakly fluorescent.…”