Cross-linked-substituted (esterified/etherified) starch derivatives as aqueous heavy metal ion adsorbent: a review

Abstract

Starch is a biopolymer with outstanding economic and environmental friendly attributes which has driven technological innovations to enhance its applications in food and nonfood industries. Starch is constituted by O-H groups with valency and electronic characteristics that can initiate adsorption of aqueous heavy metal ions (AHMIs). However, this can be enhanced using various modification sequences. A common procedure is the cross-linking and substitution of the O-H groups via esterification and/or etherification reactions to produce starch derivative adsorbents (SDAs) with improved structural and functional properties for adsorption of AHMIs. The efficiency of SDAs developed using these procedure depends on the botanical source of the native starch base, porosity and structural stability of the derivative (i.e. degree of cross-linking), substituted functional group(s), degree of substitution (DS) and the steric/conformation effects of the substituted groups. Many works have been done to optimize these factors, and this review highlighted some of the tailored procedures and the results obtained.

Interpretation of the adsorption process of toxic Cd2+ removal by modified sweet potato residue

“…This may be due to the fact that starch was hydrolyzed by NaOH, which changed the morphology of the starch and produced more available functional groups. 43 The surface of the SPR was smooth and had fewer voids. After modification, the material appeared corrugated, wrinkled, and loose, forming an irregular layered shape and a microporous structure that might help create more adsorption sites for Cd 2+ binding.…”

Dual Enzymolysis Assisted by Acrylate or Phosphate Grafting: Influences on the Structural and Functional Properties of Jujube Residue Dietary Fiber

“…In the case of JRDF-EAG, the peaks at 1742 cm −1 (corresponding to asymmetric bending of the acetyl group) and 1100 cm −1 (representing the stretching vibration of C–O–C) transferred to 1752 and 1085 cm −1 , respectively; and the peak at 1525 cm −1 (indicative of the stretching vibration of –C=O) transferred to 1519 cm −1 , evidencing the introduction of the propenyl ester group [ 19 ]. Moreover, a new peak at around 2395 cm −1 (corresponding to the stretching vibration of the phosphate group) appeared in the spectrum of JRDF-EPG [ 10 , 30 ], demonstrating that the phosphate group had been grafted with JRDF. Similar results were obtained by Djordjević et al [ 31 ].…”

Influences of superfine-grinding and mix enzymatic hydrolysis combined with hydroxypropylation or acetylation on the structure and physicochemical properties of jujube kernel fiber

“…Moreover, the peaks at wavenumbers of 1,632 and 1,110, 1,378 cm −1 (separately indicative of the asymmetric bend of acetyl group, C-H, and -C=O, respectively, Gil-López et al, 2019) in the spectrum of JKF separately presented at wavenumbers of 1,622, 1,107, and 1,369 cm −1 in the spectrum of JKE-SGEA, demonstrating that acyl ester groups have been introduced into JKF molecules after acetylation. Additionally, compared with the spectrum of JKF, the spectrum of JKF-SGEH has two new peaks appearing at wavenumber of 913 and 2,734 cm −1 (indicative of the stretching and flexion of C-O and C-H, respectively), and the peak at 2850 cm −1 transferred to 2,845 cm −1 (indicative of the flexion of C-H), which is attributed to the introduction of hydroxypropyl group after hydroxypropylation (Tapia-Hernández et al, 2019b;Akinterinwa et al, 2020). Previous studies shown that superfine-grinding, acetylation and hydroxypropylation all could influence the structure of fibers via changing their chemical bonds (Shaikh et al, 2019;Zheng et al, 2022).…”