Abstract
Heavy metals in water are a serious environmental problem due to their accumulation and toxicity; there are several processes we can use to address this issue, but adsorption is the most popular due to its simplicity and efficiency. Polysaccharides such as cellulose have received attention as adsorbents for heavy metals, and cotton–chitosan composites (CCs) were developed here with nontoxic reagents such as carboxylic acids as crosslinkers and NaH2PO4 as a catalyst to achieve chitosan covalent crosslinkage into oxidized cotton textiles with H2O2. The composites were characterized by fourier-transform infrared spectroscopy (FTIR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), atomic-force and scanning electron microscopy (AFM and SEM), and tensile strength; the adsorption of lead ions (Pb) was evaluated with cotton–chitosan composites and quantified by microwave plasma atomic emission spectroscopy (MP-AES). The composites showed a maximum incorporation of chitosan of 27.62 mg per gram of cotton textile. A tensile strength analysis of the composite showed a Young’s modulus approximately 1 MPa higher than that of cotton textile. The adsorption of lead ions with composites in an aqueous solution at pH 5 and 25 °C was circa 74% after 6 h of contact, as determined by MP-AES. This work is an approach to demonstrate the potential of these polysaccharides, modified by “green” procedures to remove pollutants from water.
Highlights
Heavy metals in water are a severe environmental problem that directly affects human health even at very low concentrations; most of them are considered persistent, nonbiodegradable, and toxic, and must be removed; an enormous amount of research into how to clean water at a lower cost and with less energy is needed
The Fourier transformed infrared analysis (FT-IR) spectra of composites 3 and 4 show those bands related to the primary amine group that are slightly visible at 1560 cm−1 ; the peaks at 2927 and 2839 cm−1 are attributed to C–H stretching of the alkyl group of cellulose as well as from the chitosan (Figure 1)
Cotton textiles presented a rough surface with an average height of circa 1.43 μm, and these values changed with chitosan incorporation, so the greater the chitosan concentration determined in composites, the smoother the surface analyzed
Summary
Heavy metals in water are a severe environmental problem that directly affects human health even at very low concentrations; most of them are considered persistent, nonbiodegradable, and toxic, and must be removed; an enormous amount of research into how to clean water at a lower cost and with less energy is needed. Adsorption is one of the most popular methods due to its simplicity, low cost, efficiency, the regeneration capacity of the adsorbent, no sludge generation, and simple recovery; some adsorption mechanisms are still not fully understood [3,6,7,8] Polysaccharides such as cellulose, cellulose derivates, cotton textiles, and chitosan have received significant attention over the last two decades because they are convenient for heavy metal adsorption and are environmentally friendly materials [1,3,5,9,10,11,12,13,14,15]. This work is an attempt to demonstrate the potential of “green” composites based on chitosan–cotton textiles that help to remove traces of toxic elements, can be reused and eventually biodegrade due to their natural composition
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