Titania Nanofibers: A Potential Adsorbent for Mercury and Lead Uptake

Abstract

Abstract-The present investigation focuses on testing the adsorptive behaviour of laboratory synthesized titania nanofibers towards Hg(II) and Pb(II) in the aqueous system. The BET analysis confirmed that the electrospinned nanofibers were confirmed to possess a large surface area of 740 m 2 /g. The fiber mats were analysed by EDX, which confirmed the adsorption of the metals on the fiber surface. SEM revealed the smooth morphology and continuous nature of the fibers. The effect of pH, contact time and adsorbent dose is compared for both the metals. At the most optimized conditions, highest uptake of 95.5% was observed for 0.01 mg/L Hg(II) concentration while it was 83.8% for 0.5 mg/L Pb(II) concentration. Since the rate limiting steps in adsorption are of vital importance in order to define the rate parameters for design purposes, the present study takes into account Weber and Morris and Boyd mass transfer diffusion models for both Hg(II) and Pb(II) adsorption on titania nanofibers. The equilibrium data were then analyzed using Langmuir and Freundlich sorption models and the characteristic sorption parameters for each isotherm were determined. The discussion also focuses on few of the recently used adsorbents for heavy metal uptake and their comparison with the present study.Index Terms-Adsorption, heavy metals, isotherm, mass transfer, nano adsorbent.

Cationization of Cellulose Nanofibers for the Removal of Sulfate Ions from Aqueous Solutions

“…Pseudo-first-order (PFO; Figure 6b) and pseudo-secondorder (PSO; Figure 6c) kinetic models describe the adsorption rate and the factors that influence the rate in the attainment of equilibrium in a reasonable amount of time. 36,37 The equations for these models can be expressed as follows PFO model…”

Heavy metal pollution and the role of inorganic nanomaterials in environmental remediation

“…At very low pH values, the high concentration of H + ions compete with the metal ions for available active sites of the adsorbent material, whereas at high pH values, the OH − ions tend to precipitate the metal ions, preventing their adsorption. The maximum adsorption of Hg 2+ has been achieved within pH values of 5-7.5 (figure 6) [8,75,105,134]. Chitosan-bound Fe 3 O 4 nanoparticles were able to remove 92.4% of Hg 2+ ions even at a low pH of 3 [72].…”

“…The Hg 2+ ion is highly toxic even at low concentrations and can accumulate in ecosystems, in particular apex predators, causing several disorders and diseases. Methyl mercury (CH 3 Hg + ) is another form of mercury that bioaccumulates in organic tissues, poisoning the food chain [8,9]. The Minamata Convention on Mercury established in October 2013 saw over 130 countries signing, and declared mercury pollution as a global problem that no country can solve alone is a classic example of food poisoning by heavy metals [10].…”

“…Open Sci. 8: 201485 adsorbents possess (i) high surface area to volume ratio, (ii) surface functional groups tailored for a specific application, (iii) short diffusion route or absence of internal diffusion resistance, (iv) high porosity, (v) enhanced structural properties, and (vi) catalytic properties [8,72,73,[77][78][79]. These properties make nanoadsorbents highly selective, and with the capacity to achieve efficient adsorption of a variety of water pollutants including heavy metals.…”

“…Heavy metal removal strategies from water include chemical precipitation, ion exchange, solvent extraction, cloud point extraction, ultrafiltration, reverse osmosis, crystallization, evaporation, photocatalysis and adsorption techniques. Apart from adsorption, the rest of the techniques suffer disadvantages such as (i) sludge production, (ii) high energy requirements, (iii) high operational costs, (iv) requirement for the use of solvents, (v) possible inefficiency at removing trace concentrations of some toxic metal ions, (vi) solubility limitations, (vii) possible use of high-pressure operations, and (viii) requirement of expensive analytical instrumentation [8,[71][72][73][74]. However, the adsorption technique is simple and effective; the adsorbents are usually easy to handle, and the operation and design are flexible [8,75].…”