materials Article Medical Plant Extract Purification from Cadmium(II) Using Modified Thermoplastic Starch and Ion Exchangers Yi-Gong Chen 1 , Qian Wang 2 , Anna Wolowicz 3 , Agnieszka Gladysz-Plaska 3 , Monika Wawrzkiewicz 3 , Weronika Sofi ´ nska-Chmiel 4 , Gui-Yuan Lv 5 , Dorota Kolody ´ nska 3, * and Su-Hong Chen 1, *   Citation: Chen, Y.-G.; Wang, Q.; Wolowicz, A.; Gladysz-Plaska, A.; Wawrzkiewicz, M.; Sofi ´ nska-Chmiel, W.; Lv, G.-Y.; Kolody ´ nska, D.; Chen, S.-H. Medical Plant Extract Purification from Cadmium(II) Using Modified Thermoplastic Starch and Ion Exchangers. Materials 2021, 14, 4734. https://doi.org/10.3390/ma14164734 Academic Editors: Beata Podko´ scielna, Malgorzata Maciejewska and Marta Grochowicz Received: 17 June 2021 Accepted: 19 August 2021 Published: 22 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Chaowang Road 18, Hangzhou 310014, China; yigongchen@hotmail.com 2 Hangzhou Fang Hui Chun Tang Group Co., Ltd., Hangzhou 310052, China; wangq@fhct.com 3 Department of Inorganic Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie Sklodowska Sq. 2, 20-031 Lublin, Poland; anna.wolowicz@poczta.umcs.lublin.pl (A.W.); a.gladysz-plaska@poczta.umcs.lublin.pl (A.G.-P.); m.wawrzkiewicz@poczta.umcs.lublin.pl (M.W.) 4 Analytical Laboratory, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie Sklodowska Sq. 2, 20-031 Lublin, Poland; wschmiel@poczta.umcs.lublin.pl 5 College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou 310053, China; zjtcmlgy@163.com * Correspondence: d.kolodynska@poczta.umcs.lublin.pl (D.K.); chensuhong@zjut.edu.cn (S.-H.C.) Abstract: Pure compounds extracted and purified from medical plants are crucial for preparation of the herbal products applied in many countries as drugs for the treatment of diseases all over the world. Such products should be free from toxic heavy metals; therefore, their elimination or removal in all steps of production is very important. Hence, the purpose of this paper was purification of an extract obtained from Dendrobium officinale Kimura et Migo and cadmium removal using thermoplastic starch (S1), modified TPS with poly (butylene succinate); 25% of TPS + 75% PBS (S2); 50% of TPS + 50% PLA (S3); and 50% of TPS + 50% PLA with 5% of hemp fibers (S4), as well as ion exchangers of different types, e.g., Lewatit SP112, Purolite S940, Amberlite IRC747, Amberlite IRC748, Amberlite IRC718, Lewatit TP207, Lewatit TP208, and Purolite S930. This extract is used in cancer treatment in traditional Chinese medicine (TCM). Attenuated total reflectance-Fourier transform infrared spectroscopy, thermogravimetric analysis with differential scanning calorimetry, X-ray powder diffraction, gel permeation chromatography, surface analysis, scanning electron microscopy with energy dispersive X-ray spectroscopy, and point of zero charge analysis were used for sorbent and adsorption process characterization, as well as for explanation of the Cd(II) sorption mechanism. Keywords: cadmium; Dendrobium officinale Kimura et Migo; thermoplastic starch; ion exchange resin; plant extract purification 1. Introduction Medicinal plants, being a part of conventional medicine, have been used in therapy throughout the world for a long time. They have been trusted globally for thousands of years for their accessibility and limited side-effects [1]. The World Health Organization (WHO) estimates that 65–80% of the world’s population, especially in Africa, Asia, Latin America, and the Middle East use herbal products [2]. Recently, greater attention has also been paid to herbal medicine in developed countries. The methods generally called natural medicine, based on herbal extracts, are not favored [3–6]. In fact, these are proven and non-contradictory to conventional medicine. They are not only a ‘green’ alternative to most pharmaceuticals used for the treatment of diseases all over the world, but also the source of a wide variety of natural antioxidants. Their medicinal value is usually due to the presence of very important phytochemicals, such as alkaloids and tannins, as well as flavonoids and phenolic compounds. However, they should be free from heavy metal ions. For this Materials 2021, 14, 4734. https://doi.org/10.3390/ma14164734 https://www.mdpi.com/journal/materials