Cassava Starch-Based Thermo-Responsive Pb(II)-Imprinted Material: Preparation and Adsorption Performance on Pb(II)

Multifunctional natural starch-based hydrogels: Critical characteristics, formation mechanisms, various applications, future perspectives

With the growth of the global population and increasing concern for environmental issues, the development of sustainable and eco-friendly materials has become increasingly important. Starch, as a renewable resource, is one of the most abundant polysaccharides in nature, with the advantages of good biocompatibility, high biodegradability, and low cost. Starch-based hydrogels (SBHs) have attracted widespread attention due to their unique physical and chemical properties. This article provides a comprehensive review of the latest research progress in SBHs, discussing their main characteristics, formation mechanisms, diverse applications, and future development trends. First, it outlines the biocompatibility, degradability, water absorption and retention, environmental responsiveness, and mechanical strength of SBHs. Then, it elaborates in detail on the formation mechanisms of SBHs, including physical crosslinking (hydrogen bonding, electrostatic interactions, host-guest and coordination interactions), chemical crosslinking (such as initiators, heat, light, radiation, and click reactions), and synergistic effects. Subsequently, it analyzes the applications of SBHs in cutting-edge fields such as flexible sensors, medical dressings, drug delivery, tissue engineering, soil protection, wastewater treatment, and food packaging. Finally, it summarizes the challenges in current research and provides an outlook on future development trends, emphasizing the importance of further optimizing the performance of SBHs to meet broader industrial needs and environmental protection goals. This review not only provides a systematic theoretical framework for the study of SBHs but also charts a course for their innovative applications in the field of sustainable materials, playing a significant role in advancing the continuous development of this area.

Study on the selective adsorption of Ag+ by thermosensitive poly(n-isopropylacrylamide)/guanylthiourea/chitosan composites

In this work, temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) and the ‌guanylthiourea (GLA) were used to modify chitosan (CS) to prepare a novel PNIPAM/GLA/CS adsorbent for Ag(I) ions. Temperature variations near the lower critical solution temperature (LCST) facilitate the adjustment of functional group distribution within the composite material, thereby influencing its adsorption performance for silver ions. The characteristics of this composite material were confirmed using a variety of techniques, including scanning electron microscopy (SEM), variable-temperature ultraviolet-visible near-infrared spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Studies on the adsorption of Ag(I) ions by the PNIPAM/GLA/CS adsorbent indicated that the optimal pH for adsorption is 6.0. The adsorption kinetics were best described by the pseudo-second order kinetic model, while the equilibrium adsorption data aligned more closely with the Langmuir adsorption isotherm model, achieving a maximum adsorption capacity of 336.33 mg/g at 40°C. Experimental results demonstrated that higher adsorption amounts were observed above the LCST, while desorption of target ions was more favorable below the LCST. This research provides valuable insights for the design of new structural adsorbents.

Starch-based hydrogels for environmental applications: A review

Water sources have become extremely scarce and contaminated by organic and inorganic industrial and agricultural pollutants as well as household wastes. Poisoning water resources by dyes and metals is a problem because contaminated water can leak into subsurface and surface sources, causing serious contamination and health problems. Therefore, developing wastewater treatment technologies is valuable. Today, hydrogels have attracted considerable attention owing to their broad applications. Hydrogels are polymeric network compositions with significant water-imbibing capacity. Hydrogels have potential applications in diverse fields such as biomedical, personal care products, pharmaceuticals, cosmetics, and biosensors. They can be prepared by using natural (biopolymers) and synthetic polymers. Synthetic polymer-based hydrogels obtained from petrochemicals are not environmentally benign; thus, abundant plant-based polysaccharides are found as more suitable compounds for making biodegradable hydrogels. Polysaccharides with many advantages such as non-toxicity, biodegradability, availability, inexpensiveness, etc. are widely employed for the preparation of environmentally friendly hydrogels. Polysaccharides-based hydrogels containing chitin, chitosan, gum, starch (St), etc. are employed to remove pollutants, metals, and dyes. Among these, St has attracted a lot of attention. St can be mixed with other compounds to make hydrogels, which remove dyes and metal ions to variable degrees of efficiency. Although St has numerous advantages, it suffers from drawbacks such as low stability, low water solubility, and fast degradability in water which limit its application as an environmental adsorbent. As an effective way to overcome these weaknesses, various modification approaches to form starch-based hydrogels (SBHs) employing different compounds have been reported. The preparation methods and applications of SBH adsorbents in organic dyes, hazardous materials, and toxic ions elimination from water resources have been comprehensively discussed in this review.

Fluorescent starch-based hydrogel with cellulose nanofibrils and carbon dots for simultaneous adsorption and detection of Pb(II)

The adsorption removal of lead (Pb) ions has become a crucial area of research due to the potential health hazards associated with Pb contamination. Developing cost-effective adsorbents for the removal of Pb(II) ions is significantly important. Hence, a novel fluorescent starch-based hydrogel (FSH) using starch (ST), cellulose nanofibrils (CN), and carbon dots (CD) was fabricated for simultaneous adsorption and detection of Pb(II). A comprehensive characterization of FSH, including its morphological features, chemical composition, and fluorescence characteristics, was conducted. Notably, FSH exhibited a maximum theoretical adsorption capacity of 265.9 mg/g, which was 13.0 times higher than that of pure ST. Moreover, FSH was employed as a fluorescent sensor for Pb(II) determination, achieving a limit of detection (LOD) of 0.06 μg/L. An analysis was further performed to investigate the adsorption and detection mechanisms of Pb(II) utilizing FSH. This study provides valuable insights into the production of a novel cost-effective ST-based adsorbent for the removal of Pb(II) ions.

Temperature responsive crosslinked starch-kraft lignin macromolecule

Starch is a natural polymer with a relatively simple structure and limited solubility in water. Kraft lignin (KL) is a complex biopolymer obtained as a by-product from the delignification of wood and grasses. The present work reports developing a temperature-responsive high molecular weight macromolecule from crosslinking KL and starch (KLS). The NMR and XPS analyses quantified the changes in the aromatic and anhydroglucose units of KL and starch, observing a higher content of C-O-C bonds, which confirms the presence of glycerol ether cross-linkages between starch and KL in KLS. The rheological analysis of KLS dispersions revealed the formation of a thermo-responsive structured network. The temperature-dependent water solubility and rheological characteristics of KLS were related to the presence of hydrophilic starch chains, crosslinking degree, and physicochemical characteristics of KL. The incorporation of KL and ether crosslinks increased the thermal stability of KLS. Because of its multiple functional groups and large molecular weight (3.6-4.2 × 10⁵ g/mol) that was arranged in an extended globular shape, KLS-5 formed a gel-like structure after a heating-cooling treatment. Overall, the results confirmed that incorporating lignin in starch would fabricate sustainable materials with potentially altered applications, such as temperature-responsive hydrogels and films.