Development of a Novel Cyclodextrin–Chitosan Polymer for an Efficient Removal of Pharmaceutical Contaminants in Aqueous Solution

Abstract

Introduction

The search for novel high-performance and specific materials has intensified in recent years, driven by the need for enhanced efficiency and selectivity. These materials have often been the subject of research in various fields, particularly in the environment. The growing presence of pharmaceutical residues, a class of emerging environmental contaminants [1,2], has raised concerns due to their potential toxicity to both ecological and human health. These residues have been the focus of numerous scientific investigations.

Progesterone and ibuprofen, widely consumed drugs worldwide, are often found in surface water, municipal and hospital waste, and effluents. Among the different methods used in the elimination of pharmaceutical residues [3,4,5,6,7,8,9], the adsorption process is one of the most attractive methods due to its efficiency, ease of implementation, and the availability of different adsorbents [10,11,12]. Biopolymers are considered innovative materials that can be modified physicochemically to improve their properties for specific applications.

Chitosan, a biopolymer derived from chitin, exhibits remarkable adsorption properties due to its numerous amino (–NH2) and hydroxyl (–OH) groups that act as active adsorption sites [13,14,15]. However, chitosan has limitations, such as its lack of selectivity, low mechanical strength, and solubility in acidic media, for practical application towards specific compounds [16]. To overcome these limitations, modifications of the functional groups of chitosan by crosslinking and grafting, the generation of nanoparticles and hydrogels, and the association of chitosan with other materials have been developed [17,18,19,20,21].

The grafting of cyclodextrins (CDs), cyclic oligosaccharides derived from starch, onto chitosan is a promising approach to improve its properties [18]. Insoluble CD polymers prepared by crosslinking with crosslinking agents such as glutaraldehyde, epichlorohydrin (Ep), HMDI, and citric acid [22,23,24] find many applications [25,26,27,28].
This study aims to develop a new bio-adsorbent material based on chitosan and three types of CDs (-α, -β, and -ɣ) crosslinked with citric acid for the selective removal of pharmaceutical pollutants in aqueous solution.
After characterization, the adsorption performance of the polymer was evaluated in the removal of two pharmaceutical contaminants, ibuprofen and progesterone, alone and in mixture. The effects of contact time, flow rate, pH of the solution, ionic strength, and temperature on the adsorption rate are studied.

Thermodynamic and kinetic studies were carried out to determine the nature of the adsorption reaction and the appropriate kinetic model. A thermogravimetric analysis (TGA) was undertaken to elucidate the mechanism of the adsorption of pollutants by the synthesized polymer. The results of this research will contribute to the valorization of chitosan and the development of new solutions for water decontamination.

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Materials

The progesterone and ibuprofen were obtained from UP John Company (Hastings, MI, USA) and Hubei Granules-biocause pharmaceutical Co., Ltd. (Wuhan, China), respectively, and were used without further purification.
The chitosan with molecular weight of 300 Da was obtained from SIGMA-ALDRICH and was put to use without further purification. The insoluble alpha–beta-gamma-cyclodextrin polymer was procured from start-up, In-Cyclo®, Rouen, France. All other reagents were of analytical grade.

Oughlis-Hammache, F.; Skiba, M.; Moulahcene, L.; Milon, N.; Bounoure, F.; Lahiani-Skiba, M. Development of a Novel Cyclodextrin–Chitosan Polymer for an Efficient Removal of Pharmaceutical Contaminants in Aqueous Solution. Materials 2024, 17, 3594. https://doi.org/10.3390/ma17143594

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Video: Chitosan as a natural excipient