Removal of the Water Pollutant Ciprofloxacin Using Biodegradable Sorbent Polymers Obtained from Polysaccharides

Abstract

Water use has been increasing globally by 1% per year, and recycling and re-use are critical issues compromised by the presence of pollutants. In this context, the design of novel materials and/or procedures for the large scale-removal of pollutants must be economically and environmentally feasible in order to be considered as part of the solution by emerging economies. We demonstrate that the cross-linking of biodegradable polysaccharides such as starch, dextrin, or dextrin and β-cyclodextrin with divinyl sulfone is an innovative strategy for synthesizing insoluble and eco-friendly sorbent polymers, including pSt, pDx and pCD-Dx. The evaluation of these polymers’ ability to remove ciprofloxacin (CIP), a prime example of antibiotic pollution, revealed that pSt, with a Kd of 1469 L/kg and a removal rate higher than 92%, is a favorable material. Its sorption is pH-dependent and enhanced at a mildly alkaline pH, allowing for the desorption (i.e., cleaning) and reuse of pSt through an environmentally friendly treatment with 20 mM AcONa pH 4.6. The facts that pSt (i) shows a high affinity for CIP even at high NaCl concentrations, (ii) can be obtained from affordable starting materials, and (iii) is synthesized and regenerated through organic, solvent-free procedures make pSt a novel sustainable material for inland water and seawater remediation, especially in less developed countries, due to its simplicity and low cost.

Removal of Erythromycin from Water by Ibuprofen-Driven Pre-Organized Divinyl Sulfone Cross-Linked Dextrin

“…The search for sorbent materials is driven not only by their affinity for pollutants but also by the sustainability of their production. We previously reported that it is feasible to obtain sorbent polymers by cross-linking biodegradable carbohydrates with DVS and the ecofriendly material resulting from the cross-linking of starch shows a high affinity for CIP, making it suitable for inland water and seawater remediation [ 14 , 15 , 16 ]. Nevertheless, this approach failed to yield sorbent materials capable of capturing IBU despite both CIP and IBU showing a certain degree of structural similarity ( Figure S1 ).…”

“…Natural polymers such as chitosan, cyclodextrin, sodium alginate, starch, cellulose, lignin, and their derivatives have been used to prepare molecular imprinted polymers (MIPs) [ 20 ]. In addition, along with our previous research, we have generated a library of polymers using starch, Dx, and/or β-cyclodextrin as building blocks [ 14 , 15 , 16 ]. However, for the purposes of this work, we have focused on Dx because, unlike starch, it exhibits excellent water solubility and, as a linear molecule, it is more flexible than cyclodextrins because the cavities are not preformed.…”

“…The XRPD analysis ( Figure S2 ) of the starting material Dx revealed dispersive broad peaks centered at 2θ 17° and 22°, indicating the amorphous structure of the materials resulting from its cross-linking with DVS, regardless of the pre-incubation with IBU. FTIR spectra ( Figure 1 A) display the broad signal of the O-H stretching at 3500 cm −1 and the expected double signal at 1282 and 1313 cm −1 , which are distinctive of the sulfone group and of the DVS cross-linked carbohydrates [ 16 , 21 ]. The spectra of pDx1 and pDx5 obtained in the presence of IBU do not show the signature of the C=O stretching, supporting the idea that IBU is not trapped after cross-linking but that it is released during washes in the isolation process, resulting in the synthesis of IBU-free polymers.…”

“…The maximum rate of decomposition occurs between 108 °C and 120 °C (Tp1), which is consistent with the expected values for DVS cross-linked carbohydrate polymers. This temperature range is associated with the vaporization of bound water [ 16 ]. A second mass loss occurs due to the depolymerization and decomposition of both the polymers and the structure of Dx.…”

“…In the context of antibiotic removal, we have reported that the cross-linking of starch with DVS yields a low-cost and eco-friendly sorbent polymer. This polymer effectively traps CIP from water with a Kd of 1469 L/kg and removal rates exceeding 92% [ 16 ].…”