Investigation of complex formation between (sodium alginate/acrylamide) semi-interpenetrating polymer networks and lead, cadmium, nickel ions

On the performance of Sargassum-derived calcium alginate ion exchange resins for Pb2+ adsorption: batch and packed bed applications

Driven by climate change and human activity, Sargassum blooming rates have intensified, producing copious amount of the invasive, pelagic seaweed across the Caribbean and Latin America. Battery recycling and lead-smelter wastes have heavily polluted the environment and resulted in acute lead poisoning in children through widespread heavy metal contamination particular in East Trinidad. Our study details a comprehensive investigation into the use of Sargassum (S. natans), as a potential resource-circular feedstock for the synthesis of calcium alginate beads utilized in heavy metal adsorption, both in batch and column experiments. Here, ionic cross-linking of extracted sodium alginate with calcium chloride was utilized to create functional ion-exchange beads. Given the low quality of alginates extracted from Sargassum which produce poor morphological beads, composite beads in conjunction with graphene oxide and acrylamide were used to improve fabrication. Stand-alone calcium alginate beads exhibited superior Pb2+ adsorption, with a capacity of 213 mg g-1 at 20 °C and pH 3.5, surpassing composite and commercial resins. Additives like acrylamide and graphene oxide in composite alginate resins led to a 21-40% decrease in Pb2+ adsorption due to reduced active sites. Column operations confirmed Alginate systems' practicality, with 20-24% longer operating times, 15 times lower adsorbent mass on scale-up and 206% smaller column diameters compared to commercial counterparts. Ultimately, this study advocates for Sargassum-based Alginate ion-exchange beads as a bio-based alternative in Trinidad and developing nations for dealing with heavy metal ion waste, offering superior heavy metal adsorption performance and supporting resource circularity.

Muscle-inspired anisotropic carboxymethyl cellulose-based double-network conductive hydrogels for flexible strain sensors

Conductive hydrogels are considered one of the most promising materials for preparing flexible sensors due to their flexible and extensible properties. However, conventional hydrogels' weak mechanical and isotropic properties are greatly limited in practical applications. Here, the internal structure of the hydrogel was regulated by pre-stretching synergistic ion crosslinking to construct a carboxymethyl cellulose-based double network-oriented hydrogel similar to muscle. The introduction of pre-stretching increased the tensile strength of the double-network hydrogel from 1.45 MPa to 4.32 MPa, and its light transmittance increased from 67.3 % to 84.5 %. In addition, the hydrogel's thermal stability and electrical conductivity were improved to a certain extent. Its good mechanical properties and conductive properties can be converted into stable electrical signal output during deformation. The carboxymethyl cellulose-based double network oriented hydrogels were further assembled as flexible substrates into flexible sensor devices. The hydrogel sensors can monitor simple joint movements as well as complex spatial movements, which makes them have potential application value in the research field of intelligent response electronic devices such as flexible wearables, intelligent strain sensing, and soft robots.

Novel synthesis of natural cation exchange resin by crosslinking the sodium alginate as a natural polymer with 1,6-hexamethylene diisocyanate in inert solvents: Characteristics and applications

Novel synthesis of natural polymeric cation exchanger from sodium alginate reagent as natural polymer (CAlg-Na)_n has been developed. This procedure takes place by crosslinking the solid sodium alginate with 1,6-hexamethylene diisocyanate (HDI) in dryness benzene as inert solvent (DB). The experimental results for crosslinking the alginate using different degrees of crosslinking of HDI/DB (w/w) showed that the capacity of the synthesized resin for binding the polyvalent metal ions reached its maximum at 30% of (HDI/D) ratio. This work aims to present a novel synthesis of cation exchange resin from natural polymers as an alternative promising competitor of low-cost, high performance and non-toxicity for removal of the toxic heavy metal ions in wastewater remediation and radionuclide pollutants from environmental contaminated media. The results obtained from various applied techniques for determining the bounded metal ion concentrations with (CAlg-Na)_n indicated that the resin capacity was followed the order U(VI) > Cu(II) > Sr(II) > Ca(II) at 25 °C, respectively. The factors influenced the alginate affinity for chelating the metal ions were explained in some correlation terms between the alginate capacity and some physicochemical properties of chelated metal ions and its respective formed complexes. Speculated geometrical configurations for chelation were suggested and discussed.

Raman spectroscopy and WAXS method as a tool for analysing ion-exchange properties of alginate hydrogels

Hydrogels are cross-linked three-dimensional macromolecular networks that contain a large fraction of water within their structure. One of the most important properties of alginate hydrogels, leading to their broad versatility, is their ability for controlled uptake, release and retention of molecules. This ability, in turn, is due to specific interactions of the macromolecular network with the diffusing or retained molecule. Raman spectroscopy has been employed to characterize the diffusion properties of solutes in hydrogels. Besides their application in the food sector, they are used in many biomedical, pharmaceutical and technical areas; for example, as a natural tissue or drug carriers. In the latter case, controlled release of drugs from a wound dressing is of particular interest-or ion exchange between the drug and the structure of the dressing. Raman active vibrations were used to show the areas responsible for the penetration of the model azo-dyes (based on non-genotoxic benzidine analogs) within Ca-alginate/carboxymethylcellulose Medisorb A wound dressing. In this case, the intensity of the stretching bands was used to obtain the concentration profiles of the model dye in alginate/carboxymethylcellulose gel (Medisorb A). The characteristic band at 1511 cm(-1) indicates that new band positions were observed following dye adsorption on wound dressing. The Raman spectra of alginate immersed for different times in Ringer's solution reveal peak shifts. Differences in peak shapes and the appearance of new bands are observed as the sodium content increased. Raman spectra give direct information on the exchange process. There are also new peaks appearing at 1034-1016 and 850 cm(-1) regions in the spectra after the release studies. This could, therefore, correspond to a partial bonding between sodium and oxygen atoms (the guluronic units originate a band at approximately 1025 cm(-1)). The aim of the examination in this paper also was to investigate the crystallinity index of Medisorb A wound dressing dyed (or undyed) and Medisorb A wound dressing after the release process in Ringer's solution (the crystallinity index is about 65%). In WAXS curves we can observed additional peaks (2theta at 32 degrees and 45 degrees ).