Adsorption of acid blue on synthesized polymeric nanocomposites, PPy/MCM-41 and PAni/MCM-41: Isotherm, thermodynamic and kinetic studies

Enhanced adsorption and removal of Cd(II) from aqueous solution by amino-functionalized ZIF-8

Zeolite imidazolate framework-8 (ZIF-8), which is a special subgroup of metal-organic frameworks (MOFs), was synthesized and modified by ethylenediamine (ZIF-8-EDA) to prepare an efficient adsorbent for the high sorption of Cd2+ ions from solution. The synthesized and modified ZIF-8 (ZIF-8-EDA) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. The optimum conditions for dosage of adsorbent, initial ion concentration, pH, and contact time were 0.05 g/l, 50 mg/l, 6, and 60 min, respectively, for cadmium ion sorption from aqueous solutions with a removal efficiency of 89.7% for ZIF-8 and 93.5% for ZIF-8-EDA. Adsorption kinetics and equilibrium data were analyzed using the Langmuir and Freundlich equations. The Langmuir model fitted the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for the cadmium ions was 294.11(mg/g). The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was feasible, spontaneous, and endothermic at 20-50 °C. Based on the results, the amino functionalized ZIF-8 had improved adsorption performance due to the replacing of the starting linker with organic ligands that had effective functional groups, leading to chemical coordination due to the interaction of metal ions with the non-bonding pair of electrons on the N atoms of the amino functional group. The selectivity toward metal ion adsorption by ZIF-8-EDA was Cd2+ > Pb2+ > Ni2+‏.

Removal of Cr(VI) from Aqueous Solution by Polypyrrole/Hollow Mesoporous Silica Particles

The removal of Cr(VI) in wastewater plays an important role in human health and environment. In this work, polypyrrole/hollow mesoporous silica particle (PPy/HMSNs) adsorbents have been newly synthesized by in-situ polymerization, which prevent the aggregation of pyrrole in the process of polymerization and exhibit highly selective and powerful adsorption ability for Cr(VI). The adsorption process was in good agreement with the quasi-second-order kinetic model and the Langmuir isotherm model. And the maximum adsorption capacity of Cr(VI) was 322 mg/g at 25 °C. Moreover, the removal rate of Cr(VI) by PPy/HMSNs was ~100% in a number of binary systems, such as Cl⁻/Cr(VI), NO₃⁻/Cr(VI), SO₄²⁻/Cr(VI), Zn²⁺/Cr(VI), Fe³⁺/Cr(VI), Sn⁴⁺/Cr(VI), and Cu²⁺/Cr(VI). Thus, the PPy/HMSNs adsorbents have great potential for the removal of Cr(VI) in wastewater.

Construction of an Aminated MIL-53(Al)-Functionalized Carbon Nanotube for the Efficient Removal of Bisphenol AF and Metribuzin

A versatile organic-inorganic hybrid structure makes a metal-organic framework (MOF) an outstanding host for different kinds of guests; in addition, its easy pyrolysis nature has been proven to be useful as precursors in the construction of carbon-based materials with a special porous structure. Herein, a novel porous composite nanostructure of an aminated MIL-53(Al)@carbon nanotube (CNT) has been successfully constructed for the first time based on in situ synthesis combining the pyrolysis of ZIF-67. The resulting composite nanostructure was performed by the means of scanning electron microscopy, Brunauer-Emmett-Teller analysis, typical and high-resolution transmission electronic microscopy, X-ray photoelectron spectroscopy, etc. The results showed that a compact heterostructure has been formed between an aminated MIL-53(Al) and a CNT. The resulting composites, named N-MIL@CNT, represent distinct promoted activities in the removal of Bisphenol AF (BPAF) and Metribuzin from wastewater, and the maximum adsorption values were 274 mg/g (BPAF) and 213 mg/g (Metribuzin), which are larger than the results obtained by other MOF-based nanomaterials. The adsorption isotherm, kinetics, and thermodynamics were studied in detail, and the selective adsorption mechanism was also suggested. The excellent selectivity, reusability, and structure stability suggest the potential application of this composite nanostructure in the selective removal of BPAF or Metribuzin from the practical wastewater.