Facile synthesis and characterization of ZnS polymorphs/Halloysite composite for efficiently selective adsorption of Al(III) from acidic rare earth ions solution

Investigation of adsorption potential of acid violet 90 dye with chitosan/halloysite/boron nitride composite materials

In this study, composite adsorbents consisting of a mixture of chitosan (CTS), boron nitride (h-BN) and halloysite (HNT) were used for the adsorption of Acid Violet 90 (AV90) dye in a batch system. Adsorbents CTS, CTS/HNT, CTS/h-BN and CTS/h-BN/HNT beads were prepared by simple dropping method and dried in a freeze dryer. The beads were characterized by FT-IR, SEM and zeta potential analysis. The effects of pH (2-8) and dye concentration (50-250 mg/L) on AV90 adsorption properties of beads were investigated. In addition, Langmuir, Freunlich, Temkin and Henry adsorption isotherm models were used to examine the dye adsorption mechanism. It was observed that the Langmuir and Freundlich adsorption isotherm models were in good agreement with the experimental data. In the dye concentration range studied, the qm values of CTS, CTS/h-BN1, CTS/h-BN3, CTS/HNT/h-BN1, CTS/HNT/h-BN3, CTS/HNT obtained from the Langmuir isotherm model was 27.62, 17.80, 10.11, 8.71, 32.57, 19.96 mg/g, respectively. Pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models were used to examine the adsorption kinetics of adsorbents. As a result, it is thought that the use of this study in the field of dye adsorption can be an innovative and important study.

Ion-imprinted chitosan prepared without cross-linking agent for efficient selective adsorption of Al(III) from rare earth solution

In the aqueous phase, ion-imprinted materials exhibit excellent selective adsorption properties for specific ions, but their complicated preparation process and large amount of crosslinker consumption limit their application. In this study, ion-imprinted chitosan (IIP-CS) was prepared by a simple one-step hydrothermal method without a cross-linking agent for the efficient adsorption of trace amounts of Al(III) from a rare earth solution. The structures and morphology of IIP-CS were analyzed by FT-IR, SEM, and XRD. The Al(III) adsorption characteristics of IIP-CS were investigated under various preparation processes and adsorption conditions. It was found that the optimum mass ratio of IIP-CS is 3 : 1 and pH is 3 and the adsorption capacity reaches up to 40.36 mg g-1. In addition, three different isothermal models-Temkin, Freundlich, and Langmuir-were used to analyze the equilibrium adsorption of IIP-CS in aqueous solution. The results obtained are consistent with the Langmuir model. The adsorption process of Al(III) on IIP-CS follows a pseudo-secondary kinetic model, suggesting that electron sharing or exchange between IIP-CS and Al(III) is a key factor affecting its adsorption rate. IIP-CS shows high selectivity coefficients for Al(III) in mixtures of La(III), Y(III), and Gd(III), which are 792.50, 163.26, and 55.16, respectively. The mechanism of action is the formation of a complex via amidation between Al(III) and IIP-CS. IIP-CS is an adsorbent with excellent regeneration and selective adsorption performance in aqueous solution.

Preparation of chitosan mesoporous membrane/halloysite composite for efficiently selective adsorption of Al(III) from rare earth ions solution through constructing pore structure on substrate

The removal of impurity Al(III) from rare earth ion solution by selective adsorption method was one of the challenging tasks. Herein, calcination and acid dissolution treatment were used to construct the pore structure for the halloysite substrate (Hal-650-H) and provide conditions for the formation of the chitosan mesoporous membrane to prepare composite (Hal-H-2CS). The selective adsorption properties and mechanism of the Hal-H-2CS for Al(III) in the rare earth ion solution were studied. The results showed that the formation of mesoporous structures for chitosan provided abundant sites for the adsorption of Al(III). Hal-H-2CS showed remarkable selective adsorption properties for Al(III) in a wide pH range and the binary mixtures with high content of Al(III) or La(III). The maximum adsorption capacity of Al(III) was 106 mg/g, while the adsorption capacity of La(III) was only 1.41 mg/g at pH 4.0. In addition, the Hal-H-2CS exhibited excellent regeneration and structural stability. The remarkable selective properties of Hal-H-2CS was achieved by the synergistic effect between chitosan mesoporous membrane and Hal-650-H, the main adsorption sites were the OH, NH2, CONH2 of chitosan and the oxygen sites of the Hal-650-H. This work provides a new strategy for the design and preparation of outstanding selective adsorbent for Al(III).