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Starches of different botanical origin, namely potato, wheat, and corn are cross‐linked with epichlorohydrin (EPI) at cross‐linking agent to starch molar ratios of 0.0005:1, 0.0017:1, 0.0055:1, and 0.01:1. The degree of cross‐linking is evaluated by determining the solubility in aqueous 1 m KOH solution and assessing pasting properties of aqueous starch suspensions. It is found that the size of starch microgranules affects the degree of cross‐linking and the smaller the granules are, the more cross‐linking agent is required to achieve the same solubility or viscosity characteristics. The assessment of two methods reveals that solubility in alkali solution method can be used when determining the degree of cross‐linking of starch in a wide range, meanwhile, a viscoamylography approach is only suitable when the amount of EPI in the modification reaction is increased to 0.01 mol per mole of starch. The peculiarities of both methods are discussed and may be useful when determining the degree of cross‐linking of different starches with potential application as thickeners or sorbents.

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Ultrasound activated (U‐CCS) and non‐activated microgranular cross‐linked cationic starch sorbents (CCS) of different degree of substitution (DS) of quaternary ammonium groups are developed and used for binding of ibuprofen (IB) via adsorption and removal from aqueous solution. Ultrasonic treatment results in the formation of some fissures and cracks on the exterior of the modified starch granules as observed by a scanning electron microscopy studies. The equilibrium adsorption of IB onto both types of granules is investigated. The parameters of the Langmuir, Freundlich, and Dubinin‐Radushkevich adsorption models are calculated and showed that driving forces of adsorption are electrostatic interaction between quaternary ammonium groups of modified starches and carboxylic groups of IB. The sorption capacities of CCS with DS of quaternary ammonium groups equal to 0.21 and 0.42 are 232 and 345 mg g−1, respectively. The ultrasound activation increases the sorption capacities of U‐CCS to 574 and 579 mg g−1, accordingly. Therefore, the ultrasound activation allows to achieve high‐level binding of IB by using low amounts of chemical agent to modify starch granules. The ultrasound activation method presents a great potential to improve the CCS sorption properties and generating a promising sorbent for the removal of IB from aqueous media.