Designing a regenerable stimuli-responsive grafted polymer-clay sorbent for filtration of water pollutants

Abstract

A novel, stimuli-responsive composite, based on poly(4-vinylpyridine) (PVP) brushes, end-grafted to montmorillonite clay (GPC), was designed as a regenerable sorbent for efficient removal of pollutants from water. We characterized the novel composite sorbent and its response to pH, employing Fourier transform infrared, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetry analysis and zeta potential measurements. In comparison with conventional, electrostatically adsorbed PVP composites (APC), the GPC presented superior characteristics: higher polymer loading without polymer release, higher zeta potential and lower pH/charge dependency. These superior characteristics explained the significantly higher removal of organic and inorganic anionic pollutants by this composite, in comparison with the removal by APC and by many reported sorbents. For example, the filtration (20 pore volumes) of selenate by GPC, APC and a commercial resin column was complete (100%), negligible (0%) and reached 90% removal, respectively. At low–moderate pH, the grafted polymer undergoes protonation, promoting pollutant adsorption, whereas at high pH, the polymer deprotonates, promoting pollutant desorption. Indeed, ‘in-column’ regeneration of the GPC sorbents was achieved by increasing pH, and upon a second filtration cycle, no reduction in filter capacity was observed. These findings suggest the possible applicability of this stimuli-responsive sorbent for water treatment.

Dissolved organic matter adsorption from surface waters by granular composites versus granular activated carbon columns: An applicable approach

“…One of the most common polymer studied is chitosan (Jang and Lee, 2019;Mukhopadhyay et al, 2020;Shi et al, 2019;Vakili et al, 2019) followed by many studies on the fabrication and use of polydiallyldimethylammonium chloride (PDADMAC)-clay composites as sorbents (Ganigar et al, 2010a;Gunister et al, 2013;Radian and Mishael, 2012;Ray et al, 2019;Sabarish and Unnikrishnan, 2018;Zadaka et al, 2008). Studies have also focused on new and advanced polymers for the development of composite sorbents (Ganigar et al, 2010a;Gardi and Mishael, 2018;Jean Serge et al, 2019;Ravi et al, 2020;Mishael, 2018, 2016;Zadaka et al, 2008). However, most of the studies did not address operational and applicable aspects of composite employment for water treatment such as: 1. the composites, as powder, cannot be employed in filtration columns, due to their low hydraulic conductivity 2. the polymers are not cheap and not necessarily approved for treating drinking water use 3. sorbent regeneration was not demonstrated 4. studying pollutant removal from real contaminated water (not synthetic) 5.…”

Current Advances of Polymer Composites for Water Treatment and Desalination

“…However, at elevated pH, the stimuli-responsive polymer lost the protons, leading to desorption of the pollutants. Also, the elimination of micropollutants, e.g., sulfentrazone, arsenate, and atrazine, from wastewater was explored by this composite [50]. In a similar work, exfoliated and intercalated montmorillonites were grafted with different stimuli-responsive polymers, i.e., sodium 2-acrylamido-2-methylpropane sulfonate and Nisopropylacrylamide, using a surfactant-free technique.…”

Preprogrammed Dynamic Microstructured Polymer Interfaces

“…[64] Another priority area is extraction of valuable or toxic substances from liquid media. For example, particles decorated with poly(4-vinylpyridine) were used as a recyclable sorbent for water purification when pollutants were adsorbed by the polymer in its protonated form and subsequently released upon deprotonation [65] . Furthermore, multi-responsive PDMPI exploiting a combination of changes in pH and temperature were used for separation of antibodies, [66] recycling of Cd-ions, [67] extraction of bisphenol A [68] , and uptake and release of trivalent lanthanum ions [69] and therapeutic drugs.…”