Study on the Adsorption of Chromium (VI) by Hydrolyzed Keratin/Polyamide 6 Blend Nanofibres

Abstract

In this study, nanofibre mats for chemical adsorption of heavy metals were prepared by electrospinning blends of hydrolyzed keratin (HK) and polyamide 6 (PA6) in formic acid. Viscosity measurements of the spinning solutions and morphological analyses of the fracture sections of the same polymer blends cast into films, suggested intermolecular interactions and good compatibility between HK and PA6. The mats made of continuous randomly oriented blend nanofilaments of HK/PA6 50/50 wt, with a mean diameter of about 200 nm, were tested as chromium (VI) ion adsorbents. The parameters investigated included initial chromium ion concentration, pH, contact time and adsorbent dosage. The maximum adsorption capacity occurred at acidic pH. The pseudo-first order, the pseudo-second order and the intraparticle diffusion models were used to describe the kinetics of adsorption process. It was found that kinetic data fit the pseudo-second order model and follow the intraparticle diffusion model, although diffusion is not the only rate control step. Adsorption data fit well the Freundlich isotherm model and the maximum adsorption capacity was found 55.9 mg/g. Moreover, the mean free energy (E) of adsorption ranges between 8 and 16 kJ/mol, so that the adsorption mechanism for HK-based nanofibres was explained as an ion-exchange process.

Keratinous Materials as Novel Absorbent Systems for Toxic Pollutants

“…The structural changes of the membrane are significantly affected by the pH of keratin or biofiber solutions, which influenced metal ion removal . While testing with Cr 6+ ion with hydrolyzed keratin/polyamide nano-fibrous membrane, the adsorption capacity increased from 2.1 to 55.9 mg/g for the initial Cr 6+ ion concentration of 5 to 200 ppm, which is attributed to the high driving force for mass transfer of the highly concentrated starting solutions 26 . In contrast, the removal Cr 3+ is low, around 0.7 mg/g with the nanofibrous membrane with keratin content of 30 wt%.…”

“…Electrospinning is used commonly to create nano-fibrous membranes using an electric field. In general, nano-structured systems with high porosity, surface area and small inter-fiber pore size, exhibit good filtration efficiency, removing tiny particles (˂0.3 micron) 5,26 . One potential disadvantage of extracted keratinderived fibers is the poor physico-mechanical properties of the finished fiber, especially in the wet state.…”

“…Therefore, particularly for applications requiring high mechanical performance, recent research has focused on blending of keratin with other polymeric materials using a common solvent system 11,27 . For instance, solubilized keratins can be blended with polymers such as polyamide 6, polyethylene-oxide and polyhydroxybutylateco-hydroxyvalerate to produce materials with good mechanical properties and performance 5,6,26,28,29 .…”

Low-cost sorbents for the removal of acid dyes from aqueous solutions

“…Efforts have been lately made for the valorization of these renewable resources, mainly by keratin solubilization and regeneration into useful materials, from biomaterials with medical applications (Rouse and Van Dyke, 2010) to soil fertilizers (Zoccola et al, 2015). Due to their ability to adsorb heavy metals from aqueous solutions, native or processed keratinous materials can find promising applications for the treatment of heavy metal pollution (Aluigi et al, 2012;Evangelou et al, 2008;Khosa and Ullah, 2014;Wen et al, 2010). Little research has been dedicated to investigating their potential utilization for color removal from aqueous solution (Gupta et al, 2006;Mittal et al, 2013;Saleem et al, 2005).…”

Removal of hexavalent chromium by using red mud activated with cetyltrimethylammonium bromide

“…Adsorbents such *Corresponding author. Emails: lideliang@henu.edu.cn, lidelianglu@126.com as carbon, [6,7] red mud, [8] coal, [9] fertilizer industrial waste, [10] polymers, [11,12] and activated sludge biomass [13] are attracted increasingly.…”