Amino-Functionalized Titanate Nanotubes: pH and Kinetic Study of a Promising Adsorbent for Acid Dye in Aqueous Solution.

This work reports the functionalization of sodium titanate nanotubes with amine groups obtained from the reaction of titanate nanotubes with [3-(2-Aminoethylamino)propyl]trimethoxysilane, NaTiNT-2NH, and 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane, NaTiNT-3NH. It was verified that the crystalline and morphological structures of NaTiNT were preserved after the functionalization, spectroscopies showed that aminosilane interacted covalently with the surface of NaTiNT, and the incorporation of the aminosilane groups on the surface of NaTiNT can be confirmed. The adsorbent matrices NaTiNT-2NH and NaTiNT-3NH were used to remove the anionic dye from remazol blue R (RB) in aqueous medium, and the highest adsorption capacity was around 365.84 mg g-1 (NaTiNT-2NH) and 440.70 mg g-1 (NaTiNT-3NH) in the range of pH 5.0 to 10.0 and the equilibrium time was reached in 210 min (NaTiNT-2NH) and 270 min (NaTiNT-3NH). Furthermore, the Elovich model, which reports the adsorption in heterogeneous sites and with different activation energies in the chemisorption process, was the most appropriate to describe the adsorption kinetics. Thus, these adsorbent matrices can be used as an alternative potential for dye removal RB in aqueous solution.

Study of interactions between organic contaminants and a new phosphated biopolymer derived from cellulose.

The extensive use of organic molecules (Rhodamine B and Amitriptyline) also has contributed to environmental pollution; adsorption is a relevant method for removal of these contaminants in aqueous media. In this context, the objective of this study was to modify the surface of cellulose (Cel) with phosphoric acid and sodium tripolyphosphate to obtain a biopolymer with incorporated phosphate groups (PCel). The modification was confirmed by X-ray dispersive energy spectroscopy, solid state nuclear magnetic resonance, X-ray diffraction, and thermal analysis. The obtained material (PCel) was used as a Rhodamine B (RhB) or Amitriptyline (AmTP) adsorbent, and the highest adsorption capacity of this material was obtained at pH 3.0 (RhB) and 7.0 (AmTP) and the equilibrium time was achieved at 65 (RhB) and 150 min (AmTP). Moreover, the pseudo-first-order model best describes the kinetics of this adsorption. The experimental adsorption isotherms were adjusted to the Langmuir model, indicating that monolayer adsorption occurred and the highest experimental adsorption capacity obtained was 47.58 (RhB) and 45.52 mg g-1 (AmTP) in PCel. The thermodynamic parameters showed that the adsorption process is exothermic and non-spontaneous, with increase of non-spontaneity with enhance of the temperature. However, PCel was efficient in removing the contaminant (RhB or AmTP) in an aqueous solution.

Understanding kinetics and thermodynamics of the interactions between amitriptyline or eosin yellow and aminosilane-modified cellulose.

A new adsorbent matrix (Cel-SiN) for the adsorption of the dye eosin yellow (EY) and the drug amitriptyline (AMI) from aqueous media has been synthesized. The Cel-SiN matrix was obtained via chemical modification of cellulose with (3-aminopropyl)trimethoxysilane. Successful modification was confirmed using Fourier transform infrared (FTIR) and 13C and 29Si solid state nuclear magnetic resonance (SSNMR) spectroscopies, thermal analysis (TG/DTG), X-ray diffraction (XRD), and elemental analysis. The effects of pH, contact time, concentration, and temperature were evaluated in batch adsorption tests. Cel-SiN efficiently adsorbed AMI and EY in aqueous media, with maximum adsorption capacities of 92.28 ±â€¯1.34 mg g-1 for AMI (pH = 7, time =240 min, and temperature = 318 K) and 61.0 ±â€¯0.36 mg g-1 for EY (pH = 5, time =80 min, and temperature = 298 K). The adsorption process occurs mainly via hydrogen bonding interactions for AMI and electrostatic interactions for EY.

Potential of amino-functionalized cellulose as an alternative sorbent intended to remove anionic dyes from aqueous solutions.

Adsorption has been explored to minimize the pollution caused by dyes. This work relates the preparation of diethylenetriamine-modified cellulose (DetaCel) by reacting phthalic anhydride-modified cellulose (PhCel) with diethylenetriamine (Deta). Materials were characterized by Elemental Analysis and results showed a degree of incorporation of 5.55 ±â€¯0.02 mmol of nitrogen per gram of modified material. The main bands observed for DetaCel by Fourier-Transform Infrared Spectroscospy (FTIR) were attributed to CN deformation (1330 cm-1) and NH stretching of amide (3400 cm-1), while Solid State Nuclear Magnetic Resonance of 13C (13C{1H}CP-MAS NMR) showed a signal at 164.6 ppm characteristic of amide group. Crystallinity index (CrI) obtained by X-Ray Diffraction (XRD) was 74.99 (Cel), 58.64 (PhCel) and 46.12% (DetaCel). Adsorbent matrices were employed to remove methyl orange (MO) and eosin (EY) dyes in aqueous medium. Data obtained experimentally from kinetic study had a better fit to the pseudo-first order, thus the adsorption process occurs in monolayer, with MO adsorption capacity by Cel and DetaCel of 2.19 and 65.45 mg g-1, respectively. For EY adsorption by Cel and DetaCel was 1.30 and 56.69 mg g-1, respectively. These results suggest that DetaCel can be used as an alternative potential for removal dyes in aqueous solution.