In this paper, the chromium, Cr (VI), ion adsorption ability of oyster shell samples collected from two sea regions in Vietnam (Phu Yen province and Quang Ninh province) was investigated and compared. The oyster shell samples were calcined at different temperatures and denatured by using ethylenediaminetetraacetic acid (EDTA). The Cr (VI) ion adsorption ability of the prismatic (PP) and nacreous (NP) shell layers of oysters was also evaluated. The characteristics of oyster shell samples before and after treatment were determined by using analysis methods including XRD, IR, BET, UV-Vis, and FESEM. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models and fit statistic equations were used to study the adsorption isotherms of Cr (VI) ion adsorption by oyster shells. The Cr (VI) ions adsorption kinetic has been set up using four reaction models consisting of first-order, pseudo-first-order, second-order, and pseudo-second-order reaction models. Effects of experimental factors on the Cr (VI) ion adsorption process using oyster shells were also investigated and discussed in this work.

This study attempted to develop carrageenan/chitosan based microparticles loading α-mangostin which was extracted from Vietnamese mangosteen skin. The carrageenan/chitosan/α-mangostin microparticles were prepared by ionic gelation method by mixing chitosan, carrageenan with α-mangostin and subsequently crosslinking the mixtures with sodium tripolyphosphate crosslinking agent. The content of α-mangostin in microparticles was changed to evaluate the effect of α-mangostin content on physical, morphological properties, particles size and bioactivities of the carrageenan/chitosan/α-mangostin microparticles. The obtained results showed that carrageenan, chitosan was interacted together and with α-mangostin. The presence of polymers matrix improved the release ability of α-mangostin into ethanol/pH buffer solutions. The carrageenan/chitosan/ α-mangostin microparticles have antibacterial (gram (+) strains) and anti-oxidant activities. The results suggested that combination of chitosan and carrageenan in the microparticles can enhance the control release of αmangostin into solutions as well as keep the bioactivities of α-mangostin.

Yellow phosphorus is used widely in the world for production of phosphoric acid, various phosphates, flame retardant, detergent, water treatment, metal surface treatment, etc. After the production of yellow phosphorus, a large amount of phosphorus sludge is discharged to environment, causing environment pollution. This work focused on treatment of yellow phosphorus slag (YPS) and application of it as an absorbent for chromium (VI) ion and methylene blue. The YPS was first washed with water to remove phosphoferrite (FeP) and impurities and then being milled and transferred to a float sorting system to obtain YPS particles. The characteristics of YPS particles were determined by inductively coupled plasma-mass-spectrometry (ICP-MS), energy-dispersive X-ray spectroscopy (EDX), infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), zeta potential, and nitrogen adsorption methods. The YPS particles were retreated with NaOH, HNO3, and EDTA solutions to evaluate the influence of these agents on metal ion and organic compound adsorption ability by YPS. The adsorption parameters of chromium (VI) ion and methylene blue (MB) by treated YPS particles were recognized by the ultraviolet-visible (UV-Vis) spectrometer. The effects of temperature, pH solution, and initial concentration of absorbed substances on the adsorption ability were investigated. The adsorption isotherms and adsorption kinetics of chromium (VI) ion and MB by YPS particles were also determined. The obtained results confirmed that the green technology used to treat the YPS2 particles is suitable to obtain an effective absorbent. The adsorption efficiency of YPS2 particles for removal of chromium (VI) ions is smaller than that for removal of MB in aqueous solutions. The adsorption isotherm of MB adsorption process is complied with the Langmuir isotherm while the adsorption kinetic fits well with the pseudo-second-order reaction model. The thermodynamic parameters of MB adsorption processed on YPS2 were calculated and discussed.

This paper presents the characteristics, morphology, and properties of alginate/chitosan/polyphenol nanoparticles, in which polyphenols were extracted from Camellia chrysantha leaves collected in Tam Dao district, Vinh Phuc province (Vietnam). The alginate/chitosan/polyphenol nanoparticles were prepared by ionic gelation method at different polyphenol content. The characteristics and morphology of these nanoparticles were investigated using infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-Vis), and scanning electron microscopy (SEM). Release kinetic of polyphenols from the alginate/chitosan/polyphenol nanoparticles was conducted in simulated human body fluids. The release kinetics of polyphenols from the above nanoparticles were also evaluated and discussed. The experimental results showed that the release process of polyphenols from the nanoparticles was dependent on three factors: time, pH of solution, and amount of polyphenols.

This study attempted to develop carrageenan/chitosan based microparticles loading α-mangostin which was extracted from Vietnamese mangosteen skin. The carrageenan/chitosan/α-mangostin microparticles were prepared by ionic gelation method by mixing chitosan, carrageenan with α-mangostin and subsequently cross-linking the mixtures with sodium tripolyphosphate crosslinking agent. The content of α-mangostin in microparticles was changed to evaluate the effect of α-mangostin content on physical, morphological properties, particles size and bioactivities of the carrageenan/chitosan/α-mangostin microparticles. The obtained results showed that carrageenan, chitosan was interacted together and with α-mangostin. The presence of polymers matrix improved the release ability of α-mangostin into ethanol/pH buffer solutions. The carrageenan/chitosan/ α-mangostin microparticles have antibacterial (gram (+) strains) and anti-oxidant activities. The results suggested that combination of chitosan and carrageenan in the microparticles can enhance the control release of α-mangostin into solutions as well as keep the bioactivities of α-mangostin.