## 2 Starch Modification Processes
### Applications of Modified Starch
#### 2.5.3 Applications of Chemically Modified Starch
[129] reported that oxidation of corn starch nanocomposites could improve water resistance in agricultural mulch films. In contrast, [PERSON] and coworkers prepared liquid starch-based mulchting materials (LSMM) by grafting polyacrylic acid (PAA) onto starch and then crosslinked with \(N\), \(N^{\prime}\)-methylene-bisacrylamide (MBA). This study demonstrated high relative hygroscopicity, water retention, and degradability of LSMM [130]. Moreover, chemically modified starch also acts as a superabsorbent. Starch-based superabsorbents have been considered in personal care products, agriculture, forestry, chemical industry, and drug delivery systems. For instance, [PERSON] and [PERSON] [131] prepared starch hydrogels crosslinked with acrylic monomers as a superabsorbent. They revealed that the water absorption capacity of hydrogels was 0.9%. [PERSON] et al. [132] synthesized a superabsorbent polymer for agricultural applications using modified starch. The starch was modified using zinc oxide and tetraethyl orthosilicate and then graft-copolymerized with potassium acrylate monomer. The modified starch showed enhanced reusability, biodegradation, provided support as a soil conditioner, and aided against transient drought. Recently, [PERSON] and coworkers investigated the removal of cationic, methylene blue (MB), and anionic, methyl orange (MO) dyes present in water using succinylated starch. This study indicated that succinylated starch was superabsorbent material while being sensitive to changes in pH and the ionic strength of the medium. They also showed the removal of MB from an aqueous solution using succinylated starch [133]. [PERSON] et al. [134] displayed the effectiveness of dual-modified cassava starch in removing Pb\({}^{2+}\) ions in aqueous solutions. During starch modification, tetraethylorthosilicate (TEOS) was used as the chemical modifying agent, whereas Pluronic 123 was used as the structure-directing agent. The modified starch exhibited a maximum adsorption capacity of 330.3 mg/g while performing a higher desorption efficiency of over 97%. Figure 8 shows the adsorption mechanism of Pb\({}^{2+}\) ions onto modified starch. This adsorption behavior can be well explained using [PERSON]'s hard-soft acid-base (HSAB) principle. According to Figure 8, it is evident that the electron pairs in oxygen atoms in hydroxyl groups can donate electrons to the Pb\({}^{2+}\), resulting in interactions between the lead ions and hydroxyl groups in modified cassava starch [134]. Table 5 summarizes the recent applications of modified starch relevant to packaging, pharmaceutical, agriculture, and sorption. Apart from the above, [PERSON] et al. [135] and [PERSON] et al. [136] prepared an adsorbent for the removal of Cd\({}^{2+}\) from aqueous solution using facile esterification reaction and graft copolymerization, respectively. Facile esterification reaction was used to prepare graphene-starch, and the results showed excellent adsorption towards Cd\({}^{2+}\) ions at low concentrations from aqueous solutions [135]. Furthermore, [PERSON] et al. [136] grafted amylose and amylopectin using sodium polyacrylate. According to the reported data, the starch-based superabsorbent showed 347.46 mg/g of monolayer adsorption capacity. Figure 8: Pb\({}^{2+}\) adsorption mechanism of modified cassava starch. Reprinted with permission from reference [134], Copyright 2021 MDPI.