Jute Stick-Derived Cellulose-Based Hydrogel: Synthesis, Characterization, and Methylene Blue Removal from Aqueous Solution.

In this work, microcrystalline cellulose (MCC) was isolated from jute sticks and sodium carboxymethyl cellulose (Na-CMC) was synthesized from the isolated MCC. Na-CMC is an anionic derivative of microcrystalline cellulose. The microcrystalline cellulose-based hydrogel (MCCH) and Na-CMC-based hydrogel (Na-CMCH) were prepared by using epichlorohydrin (ECH) as a crosslinker by a chemical crosslinking method. The isolated MCC, synthesized Na-CMC, and corresponding hydrogels were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electronic microscopy (SEM), and energy dispersive spectroscopy (EDS) for functional groups, crystallinity, surface morphology, and composite elemental composition, respectively. Pseudo-first-order, pseudo-second-order, and Elovich models were used to investigate the adsorption kinetics. The pseudo-second-order one is favorable for both hydrogels. Freundlich, Langmuir, and Temkin adsorption isotherm models were investigated. MCCH follows the Freundlich model (R2 = 0.9967), and Na-CMCH follows the Langmuir isotherm model (R2 = 0.9974). The methylene blue (MB) dye adsorption capacities of ionic (Na-CMCH) and nonionic (MCCH) hydrogels in different contact times (up to 600 min), initial concentrations (10-50 ppm), and temperatures (298-318 K) were investigated and compared. The maximum adsorption capacity of MCCH and Na-CMCH was 23.73 and 196.46 mg/g, respectively, and the removal efficiency of MB was determined to be 26.93% for MCCH and 58.73% for Na-CMCH. The Na-CMCH efficiently removed the MB from aqueous solutions as well as spiked industrial wastewater. The Na-CMCH also remarkably efficiently reduced priority metal ions from an industrial effluent. An effort has been made to utilize inexpensive, readily available, and environmentally friendly waste materials (jute sticks) to synthesize valuable adsorbent materials.

Synthesis, characterization and application of a novel polyazo dye as a universal acid-base indicator.

A novel organic polyazo dye is synthesized by the diazotization of aromatic aniline, followed by coupling it with sulfanilic acid and N,N-dimethylaniline. Characterization was done by 1H-NMR, 13C-NMR, and FTIR spectroscopy. Differential scanning calorimetry (DSC) reveals that phase transition for this molecule is exothermic. The optical band gap is estimated from the absorption cutoff point using UV-Visible spectroscopy. Thermal gravimetric analysis (TGA) addresses the thermal stability of the molecule and is found to be at ∼250 °C. The structure of the synthesized molecule is analogous to that of methyl orange and contains three azo groups. These three azo groups help accept more than two protons and provide two pK a values when diprotic acid or a mixture of acids is used in different titrations. Specifically, when a polybasic acid is in strong base titration, the pK a values were found to be 3.5 and 9.1. Moreover, for strong base and (strong + weak) acid mixture titration, the pK a values are found to be 9.2 and 3.3. Furthermore, the pK a values are found to be 8.6 and 2.8 for (strong and weak) base mixture and (strong and weak) acid mixture titration, respectively. Owing to its increased proton accepting capacity, it can be found in the two pH ranges of 2.1-3.8 for orange color and 8.2-9.8 for yellow color, thus indicating a unique property as a universal indicator for acid-base titration. The dissociation constant of this dye is found to be 3.4 × 10-6, determined in a mixed aqueous solution of 10 wt% ethanol, and a linear relationship between pK a and pH is observed in this solvent system.

Pencil graphite as electrode platform for free chlorine sensors and energy storage devices.

Multifunctional and low-cost electrode materials are desirable for the next-generation sensors and energy storage applications. This paper reports the use of pencil graphite as an electrode for dual applications that include the detection of free residual chlorine using electro-oxidation process and as an electrochemical energy storage cathode. The pencil graphite is transferred to cellulose paper by drawing ten times and applied for the detection of free residual chlorine, which shows a sensitivity of 27 µA mM-1 cm-2 with a limit of detection of 88.9 µM and linearity up to 7 mM. The sample matrix effect study for the commonly interfering ions such as NO3-, SO42-, CO32-, Cl-, HCO3- shows minimal impact on free residual chlorine detection. Pencil graphite then used after cyclic voltammogram treatment as a cathode in the aqueous Zn/Al-ion battery, showing an average discharge potential plateau of ~1.1 V, with a specific cathode capacity of ~54.1 mAh g-1 at a current of 55 mA g-1. It maintains ~95.8% of its initial efficiency after 100 cycles. Results obtained from the density functional theory calculation is consistent with the electro-oxidation process involved in the detection of free residual chlorine, as well as intercalation and de-intercalation behavior of Al3+ into the graphite layers of Zn/Al-ion battery. Therefore, pencil graphite due to its excellent electro-oxidation and conducting properties, can be successfully implemented as low cost, disposable and green material for both sensor and energy-storage applications.

Acidochromic Behavior of Dibenzylidene Cyclohexanone-Based Bischalcone: Experimental and Theoretical Study.

Synthesis and characterization of substituted 2,6-dibenzylidene cyclohexanone-based bischalcone derivatives and their optimized geometries were investigated by density functional theory. The synthesized compounds were identified through ultraviolet-visible, Fourier transform infrared, and 1H nuclear magnetic resonance spectroscopies and elemental analysis. Significant acidochromic behavior was observed for 2,6-bis(4-dimethylamino-benzylidene)-cyclohexanone 1e. This result is owing to the preferential protonation of the chromophoric N,N-dimethylamino group, that is, quaternary salt formation and deactivation of the resonance system. The result was consistent with computational studies where the protonation was favored by 211 kcal/mol in the gas phase. The compounds also showed solvatochromic behavior. The geometries of the synthesized compounds were optimized with B3LYP/6-311G+(d,p) and APFD/6-311+G(d,p) basis sets. The single point energy indicated that APFD/6-311+G(d,p) basis set gave the lowest energy of 445-655 kcal/mol for the studied bischalcone derivatives. Quantum chemical parameters were also calculated.

Structural effect on the stability of acetophenone-B(OMe)2 complexes in the gas phase. The nature of the bond between the boron cation and neutral molecules.

The free energy changes (DeltaG, boron cation basicity; BCB) for the reaction [(MeO)2B]L+ = (MeO)2B+ + L (L = acetophenones) were determined in the gas phase by measuring ligand exchange equilibria using an FT-ICR mass spectrometer. On the basis of the correlation analysis by the Yukawa-Tsuno equation, DeltaG = rho(sigma degrees + r+DeltasigmaR+), the substituent effect on DeltaBCB of acetophenone was characterized by a rho value (in kJ mol(-1) sigma(-1) unit) of -43.2 and an r+ value of 0.89. Both the rho and r+ values were found to be similar to the corresponding values for protonation, indicating that the bond between (MeO)2B+ and the oxygen atom of the carbonyl group has a high covalent character similar to the H+-O=C bond. This conclusion was consistent with the geometrical features and the charge distribution calculated at DFT-B3LYP/6-311+G(d,p) level of theory. A comparison with the results for a series of Lewis cation basicity of the acetophenone system showed that the r+ value decreases in the order of H+ = (MeO)2B+ > Me3Si+ > Me3Ge+ > Cu+ > Li+. This decreasing order is related to increasing ionic (ion-dipole interaction) nature of the bonding interaction between Lewis cations and the carbonyl oxygen atom. This was also supported by the theoretical calculations.