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

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.