Bio-Based Hydrogels With Ion Exchange Properties Applied to Remove Cu(II), Cr(VI), and As(V) Ions From Water

Cellulose-Based Hydrogels for Wastewater Treatment: A Focus on Metal Ions Removal

The rapid worldwide industrial growth in recent years has made water contamination by heavy metals a problem that requires an immediate solution. Several strategies have been proposed for the decontamination of wastewater in terms of heavy metal ions. Among these, methods utilizing adsorbent materials are preferred due to their cost-effectiveness, simplicity, effectiveness, and scalability for treating large volumes of contaminated water. In this context, heavy metal removal by hydrogels based on naturally occurring polymers is an attractive approach for industrial wastewater remediation as they offer significant advantages, such as an optimal safety profile, good biodegradability, and simple and low-cost procedures for their preparation. Hydrogels have the ability to absorb significant volumes of water, allowing for the effective removal of the dissolved pollutants. Furthermore, they can undergo surface chemical modifications which can further improve their ability to retain different environmental pollutants. This review aims to summarize recent advances in the application of hydrogels in the treatment of heavy metal-contaminated wastewater, particularly focusing on hydrogels based on cellulose and cellulose derivatives. The reported studies highlight how the adsorption properties of these materials can be widely modified, with a wide range of adsorption capacity for different heavy metal ions varying between 2.3 and 2240 mg/g. The possibility of developing new hydrogels with improved sorption performances is also discussed in the review, with the aim of improving their effective application in real scenarios, indicating future directions in the field.

Fabrication of EVOH/PANI Composite Nanofibrous Aerogels for the Removal of Dyes and Heavy Metal Ions

Water pollution caused by the leakage and discharge of pollutants, such as dyes and heavy metal ions, can cause serious damage to the environment and human health. Therefore, it is important to design and develop adsorbent materials that are efficient and multifunctional for the removal of these pollutants. In this work, poly(vinyl alcohol-co-ethylene) (EVOH)/polyaniline (PANI) composite nanofibrous aerogels (NFAs) were fabricated via solution oxidation and blending. The aerogels were characterized by a scanning electron microscope, Fourier transform infrared spectrometry, a contact angle measuring instrument and a universal testing machine. The influences of the introduction of PANI nanorods on the structural properties of aerogels were investigated, and the adsorption performance of aerogels was also studied. The results showed that the introduction of PANI nanorods filled the fibrous network structure, reduced porosity, increased surface hydrophilicity and improved compressive strength. Furthermore, EVOH/PANI composite NFAs possess good adsorption performances for dyes and heavy metal ions: The adsorption capacities of methyl orange and chromium ions (VI) are 73.22 mg/g and 115.54 mg/g, respectively. Overall, the research suggests that EVOH/PANI NFAs have great potential as efficient and multifunctional adsorbent materials for the removal of pollutants from water.

Dual-functional lignin-based hydrogels for sustained release of agrochemicals and heavy metal ion complexation

An effective way of improving the efficiency of agrochemicals and improving crop yield and quality is by slow or sustained release, which is conducive to environmental protection. Meanwhile, the excessive amount of heavy metal ions in soil can create toxicity in plants. Here, we prepared lignin-based dual-functional hydrogels containing conjugated agrochemical and heavy metal ligands through free-radical copolymerization. The content of the agrochemicals (including plant growth regulator 3-indoleacetic acid (IAC) and herbicide 2,4-dichlorophenoxyacetic acid (DCP)) in the hydrogels were tuned by changing the hydrogel composition. The conjugated agrochemicals could slowly release through the gradual cleavage of the ester bond. As a result of the release of the DCP herbicide, the growth of lettuce was effectively regulated, thus confirming the feasibility and effectiveness of this system in application. At the same time, due to the presence of metal chelating groups (such as COOH, phenolic OH, and tertiary amine) the hydrogels could act as adsorbents or stabilizers towards heavy metal ions for improving the soil remediation and preventing the adsorption of these toxic metals by plant roots. Specifically, Cu(II) and Pb(II) could be adsorbed >380 and 60 mg/g, respectively.

Polysaccharide-based biopolymer hydrogels for heavy metal detection and adsorption

BACKGROUND

With rapid development in agriculture and industry, water polluted with heavy metallic ions has come to be a serious problem. Adsorption-based methods are simple, efficient, and broadly used to eliminate heavy metals. Conventional adsorption materials have the problems of secondary environmental contamination. Hydrogels are considered effective adsorbents, and those prepared from biopolymers are biocompatible, biodegradable, non-toxic, safe to handle, and increasingly used to adsorb heavy metal ions.

AIM OF REVIEW

The natural origin and easy degradability of biopolymer hydrogels make them potential for development in environmental remediation. Its water absorption capacity enables it to efficiently adsorb various pollutants in the aqueous environment, and its internal pore channels increase the specific surface area for adsorption, which can provide abundant active binding sites for heavy metal ions through chemical modification.

KEY SCIENTIFIC CONCEPT OF REVIEW

As the most representative of biopolymer hydrogels, polysaccharide-based hydrogels are diverse, physically and chemically stable, and can undergo complex chemical modifications to enhance their performance, thus exhibiting superior ability to remove contaminants. This review summarizes the preparation methods of hydrogels, followed by a discussion of the main categories and applications of polysaccharide-based biopolymer hydrogels.

Rare Earth Elements Uptake by Synthetic Polymeric and Cellulose-Based Materials: A Review

Contemporary industrial processes and the application of new technologies have increased the demand for rare earth elements (REEs). REEs are critical components for many applications related to semiconductors, luminescent molecules, catalysts, batteries, and so forth. REEs refer to a group of 17 elements that have similar chemical properties. REE mining has increased considerably in the last decade and is starting an REE supply crisis. Recently, the viability of secondary REE sources, such as mining wastewaters and acid mine drainage (AMD), has been considered. A strategy to recover REEs from secondary water-related sources is through the usage of adsorbents and ion exchange materials in preconcentration steps due to their presence in low concentrations. In the search for more sustainable processes, the evaluation of synthetic polymers and natural source materials, such as cellulose-based materials, for REE capture from secondary sources should be considered. In this review, the chemistry, sources, extraction, uses, and environmental impact of REEs are briefly described to finally focus on the study of different adsorption/ion exchange materials and their performance in capturing REEs from water sources, moving from commercially available ion exchange resins to cellulose-based materials.