Replicating the key structural feature of calcium carbonate (CaCO 3 ) by biomolecules provides unique inspiration for synthesis of CaCO 3 suitable for industry application. The biomolecule-based morphological strategies generally contain the strong interaction between crystal and functional groups, such as carboxyl group and alcohol hydroxyl group. Here, a comparative study of low-molecular-weight organic acids (OAs) with structural similarity on calcite crystallization is presented. The morphological evolution of calcite from rhombohedron to ellipsoid is observed, needle-like or dumbbell-like in the presence of monohydroxy OAs of lactic acid, malic acid, or citric acid, suggesting carboxyl group shows more remarkable effect on the morphologies of calcite than that of Li + . The strong adsorption behavior of carboxyl group on calcite can decrease the crystallinity with increased number of carboxyl groups. In contrast, the dicarboxylic OA of tartaric acid showed stronger effects on the phase transition process from vaterite to calcite than that of succinic acid and monohydroxy OAs. These findings will aid in synthesizing CaCO 3 with specific morphology and polymorph by biochemical methods and are of great significance to the industrial application of CaCO 3 .
Xin Mi,Shuangxi Zhou,Ziming Zhou,Mohammadtaghi Vakili,Yue Qi,Ye Jia,Donghai Zhu,Wei Wang
Covalent organic frameworks (COFs) with great application potential in environmental remediation exist as the form of powder, which are difficult to separate and recycle. Two magnetic COFs with good recyclability were prepared through simple impregnation-precipitation method in this study. The prepared magnetic COFs were used for the adsorptive removal of diclofenac sodium (DCF). The introduction of hydroxyl group on magnetic COF (OH-MCOF) could greatly enhance its adsorption amount for DCF, and OH-MCOF was selected to study the effect of adsorption time, initial concentrations, solution pH and ionic strength on its adsorption for DCF, as well as its regeneration and reuse performance were investigated. In this study, the OH-MCOF had a high adsorption capacity for DCF of 203.4 mg/g based on the Langmuir model fitting, and exhibited quickly adsorption for DCF within 30 min. The adsorption efficiency was better than that of most reported adsorbents. Furthermore, the role of hydroxyl group on magnetic COF was highlighted through density functional theory (DFT) and electrostatic potential (ESP) calculation. After 5 cycles of regeneration, the OH-MCOF still maintained the same adsorption amount for DCF, showing good reusability and stability. This study reveals OH-MCOF with high removal and reusability in the further application of environmental remediation.
Wenyu Zhang,Le Wang,Yiguo Su,Zhiliang Liu,Chunfang Du
Indium oxide/halloysite nanotubes (In 2 O 3 /HNTs) composites used as adsorbents for tetracycline (TC) removal were synthesized through a simple hydrothermal method. The influences of adsorbent dosage, pH value, temperature and TC concentration on adsorption efficiency were investigated. The adsorption behavior of In 2 O 3 /HNTs toward TC could be described by Langmuir isotherm and pseudo second–order kinetic models. The adsorption results indicated that the adsorption efficiency and capacity of 20% In 2 O 3 /HNTs were 7 times and 10 times as those of In 2 O 3 as well as both 4 times as those of HNTs, respectively. Adsorption mechanism studies suggested that the electrostatic attraction was primarily responsible for the improvement of adsorption performance. The abundant hydroxyl groups of HNTs and the interfacial interaction between In 2 O 3 and HNTs contributed to more negative surface charges of In 2 O 3 /HNTs, which was favorable for enhancing the adsorption efficiency. This work provides an efficient adsorbent for pollutant removal and contributes a feasible idea for constructing the potential adsorbents using natural minerals with abundant hydroxyl groups.
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