Fabrication of attapulgite/magnetic aminated chitosan composite as efficient and reusable adsorbent for Cr (VI) ions

An efficient composite was constructed based on aminated chitosan (NH2Cs), attapulgite (ATP) clay and magnetic Fe3O4 for adsorptive removal of Cr(VI) ions. The as-fabricated ATP@Fe3O4-NH2Cs composite was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Scanning Electron Microscope (SEM), Zeta potential (ZP), Vibrating Sample Magnetometer (VSM), Brunauer–Emmett–Teller method (BET) and X-ray photoelectron spectroscope (XPS). A significant improve in the adsorption profile was established at pH 2 in the order of ATP@Fe3O4-NH2Cs(1:3) > ATP@Fe3O4-NH2Cs(1:1) > ATP@Fe3O4-NH2Cs(3:1) > Fe3O4-NH2Cs > ATP. The maximum removal (%) of Cr(VI) exceeded 94% within a short equilibrium time of 60 min. The adsorption process obeyed the pseudo 2nd order and followed the Langmuir isotherm model with a maximum monolayer adsorption capacity of 294.12 mg/g. In addition, thermodynamics studies elucidated that the adsorption process was spontaneous, randomness and endothermic process. Interestingly, the developed adsorbent retained respectable adsorption properties with acceptable removal efficiency exceeded 58% after ten sequential cycles of reuse. Besides, the results hypothesize that the adsorption process occurs via electrostatic interactions, reduction of Cr(VI) to Cr(III) and ion-exchanging. These findings substantiate that the ATP@Fe3O4-NH2Cs composite could be effectively applied as a reusable adsorbent for removing of Cr(VI) ions from aqueous solutions.

Recuperative Amino Acids Separation through Cellulose Derivative Membranes with Microporous Polypropylene Fiber Matrix

The separation, concentration and transport of the amino acids through membranes have been continuously developed due to the multitude of interest amino acids of interest and the sources from which they must be recovered. At the same time, the types of membranes used in the sepa-ration of the amino acids are the most diverse: liquids, ion exchangers, inorganic, polymeric or composites. This paper addresses the recuperative separation of three amino acids (alanine, phe-nylalanine, and methionine) using membranes from cellulosic derivatives in polypropylene ma-trix. The microfiltration membranes (polypropylene hollow fibers) were impregnated with solu-tions of some cellulosic derivatives: cellulose acetate, 2-hydroxyethyl-cellulose, methyl 2-hydroxyethyl-celluloseand sodium carboxymethyl-cellulose. The obtained membranes were characterized in terms of the separation performance of the amino acids considered (retention, flux, and selectivity) and from a morphological and structural point of view: scanning electron microscopy (SEM), high resolution SEM (HR-SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and thermal gravimetric analyzer (TGA). The re-sults obtained show that phenylalanine has the highest fluxes through all four types of mem-branes, followed by methionine and alanine. Of the four kinds of membrane, the most suitable for recuperative separation of the considered amino acids are those based on cellulose acetate and methyl 2-hydroxyethyl-cellulose.

Evaluation of properties of sulfur-based polymers obtained by inverse vulcanization: Techniques and challenges

Sulfur-based polymers are unique renewable materials that are receiving a growing attention. The utilization of elemental sulfur with a variety of monomers in their preparation in the absence of solvents using the inverse vulcanization are granting them green nature and unique properties. Several characterization techniques have been used to evaluate the properties of sulfur-based polymers. However, the complex structure and lack of solubility undermine the applicability of some standard characterization techniques in the usual manners. This article reviews the characterization methods used for the evaluation of various properties of sulfur-based polymers such as chemical, morphological, structural, thermal, rheological and mechanical properties, all of which vary depending on the type of comonomer involved in the reaction and heat treatment conditions. The successful applications of different characterization techniques including Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, nuclear magnetic resonance (NMR), scanning electron microscopy/X-ray energy dispersion (SEM-EDX), X-ray diffraction (XRD), mechanical tester, rheometer, thermal gravimetric analyzer (TGA) and differential scanning calorimetry (DSC) are discussed. The challenges to the evaluation of the properties of sulfur-based polymers and the innovative applications of the conventional techniques to overcome them are also deliberated.

Preparation and characterization of lignin-containing nanofibrillated cellulose

Lignin-containing nanofibrillated cellulose (LNFC) were prepared from p-toluenesulfonic acid (p-TsOH) pretreated sugarcane bagasse (SCB) using either formic acid (FA) or hydrochloric acid (HCl) and high-pressure homogenization. The composition, morphology, dispersity, crystallinity, particle size, thermal stability, and hydrophobicity of LNFC treated with FA (F- LNFC) and HCl (H- LNFC) were compared via electron microscopy, an X-ray diffractometer (XRD), a thermal gravimetric analyzer (TGA), a Fourier transform infrared spectroscope (FTIR), and water contact angle (WCA) analysis. The results of morphology and dispersity testing showed that LNFC with uniform dispersion were successfully prepared using a homogeneous pressure of 30 MPa and the F- LNFC particles were more stable in an aqueous solution. The crystallinity of the LNFC was well maintained after homogenization. The TGA, FTIR, and WCA data indicated that F-LNFC had better thermal stability and were more hydrophobic than H-LNFC because FA could esterify cellulose. Improved dispersity and thermal stability and increased crystallinity and hydrophobicity of cellulose nanofibrils would enhance the performance of nanocomposite materials.

Graphene/Thermoplastic Polyurethane Composites

Thermoplastic polyurethane/graphene nanocomposites were successfully prepared by mixing masterbatches with neat polymers using the melt compounding process. Graphene was obtained from graphite by the chemical mean. Graphite was initially converted into graphite oxide which was then converted to graphene oxide. Graphene oxide was then reduced by L-ascorbic acid to obtain graphene. The effects of graphene addition on thermal and morphological properties of nanocomposite were studied by a differential scanning calorimeter, a thermal gravimetric analyzer and a scanning electron microscope. TPU/graphene nanocomposites showed higher melting temperature compared to TPU. On the other hand, heat of fusion of nanocomposites was lowered. TPU and TPU/graphene nanocomposites have two steps of decomposition. The first degradation of TPU occurred at higher temperature compared with nanocomposites but the second degradation showed the opposite results. The percentage of residue after thermal degradation of nanocomposites was lower than that of TPU. For surface morphology, nanocomposite exhibited the rougher surface comparing with TPU and well graphene dispersion in TPU phase was achieved. Nevertheless, there were some agglomeration of graphene.