Insight into Equilibrium and Kinetics of the Binding of Cadmium Ions on Radiation-Modified Straw from <i>Oryza sativa</i>

The present study reports the chemical modification of agricultural waste (rice straw) with urea using microwave radiation and the efficiency evaluation of this modified rice straw for the adsorption of a toxic heavy metal, cadmium. The elemental analysis of urea modified rice straw affirmed urea grafting on rice straw, and FTIR spectra of chemically benign modified adsorbent showed the presence of hydroxyl, carbonyl, and amino functional groups. Effects of process parameters (adsorbent dosage, contact time, agitation speed, pH, and temperature) were studied in batch mode. Parameters were optimized for the equilibrium study, and adsorption mechanism was elucidated using five mathematical models (Langmuir, Freundlich, Temkin, Harkin-Jura, and Dubinin-Radushkevich). Binding of Cd(II) ions on modified adsorbent followed Langmuir model, and the maximum uptake capacity was found to be 20.70 mg g−1. Kinetic modeling was done using six different kinetic models. The process was considered physisorption according to the obtained activation energy value. Thermodynamic parameters confirmed the process to be favorable and feasible. Exothermic nature of adsorption of Cd(II) ions on urea modified rice straw was confirmed by the negative value of ΔH°.</jats:p

Stability-indicating HPLC-PDA assay for simultaneous determination of paracetamol, thiamine and pyridoxal phosphate in tablet formulations

With the increased number of multi-drug formulations, there is a need to develop new methods for simultaneous determinations of drugs. A precise, accurate and reliable liquid chromatographic method was developed for simultaneous determination of paracetamol, thiamine, and pyridoxal phosphate in pharmaceutical formulations. Separation of analytes was carried out with an Agilent Poroshell C18 column. A mixture of ammonium phosphate buffer (pH = 3.0), acetonitrile and methanol in the ratio of 86:7:7 (V/V/V) was used as the mobile phase pumped at a flow rate of 1.8 mL min-1. Detection of all three components, impurities and degradation products was performed at the selected wavelength of 270 nm. The developed method was validated in terms of linearity, specificity, precision, accuracy, LOD and LOQ as per ICH guidelines. Linearity of the developed method was found in the range 17.5-30 µg mL–1 for thiamine, 35-60 µg mL–1 for pyridoxal phosphate and 87.5-150 µg mL–1 for paracetamol. The coefficient of determination was ≥0.9981 for all three analytes. The proposed HPLC method was found to be simple and reliable for the routine simultaneous analysis of paracetamol, thiamine and pyridoxal phosphate in tablet formulations. Complete separation of analytes in the presence of degradation products indicated selectivity of the method

N-Phenyl-6-(1H-pyrazol-1-yl)pyridazin-3-amine

The mol­ecule of title compound, C13H11N5, is essentially planar (r.m.s. deviation = 0.0440 Å) and an intra­molecular C—H⋯N hydrogen bond generates an S(6) motif. In the crystal, mol­ecules are connected into chains by inter­molecular N—H⋯N and C—H⋯N hydrogen bonds. In addition, π–π stacking inter­actions are observed between the pyrazole and pyridazine rings [inter­planar distance = 3.6859 (10) Å]

3-Chloro-6-[(E)-2-(1-phenyl­ethyl­idene)hydrazin­yl]pyridazine

Two independent mol­ecules are present in the asymmetric unit of the title compound, C12H11ClN4, (Z′ = 2): the dihedral angles between the phenyl and pyridizine rings are 8.35 (10) and 37.64 (6)°. In the crystal, the two mol­ecules form inversion dimers with R 2 2(8) ring motifs through inter­molecular N—H⋯N hydrogen bonds. The crystal structure is stabilized by π–π inter­actions between the pyridazine rings of symmetry-related molecules. In one of the independent mol­ecules, the centroid–centroid separations are 3.6927 (13) and 3.7961 (13) Å, whereas in the other, the separations are 3.6909 (13) and 3.9059 (13) Å

3-Chloro-6-[2-(cyclo­pentyl­idene)hydrazin-1-yl]pyridazine

The asymmetric unit of the title compound, C9H11ClN4, contains two virtually planar mol­ecules that differ in conformation about the bond connecting the hydrazine and pyridazine units. The 3-chloro-6-hydrazinylpyridazine and cyclo­pentane groups are oriented at dihedral angles of 4.5 (3) and 8.8 (4)° in the two mol­ecules. In the crystal, the mol­ecules form a one dimensional polymeric structure extending along the a axis via N—H⋯N hydrogen bonds. The crystal stucired was an inversion twin [ratio of the twin domains = 0.73 (9):0.27 (9)]

3-[(2E)-2-(Butan-2-yl­idene)hydrazin­yl]-6-chloro­pyridazine

The asymmetric unit of the title compound, C8H11ClN4, contains two independent mol­ecules (A and B) with slightly different conformations: the dihedral angles between the 3-chloro-6-hydrazinylpyridazine units and butyl side chains are 4.5 (2) and 11.98 (16)°. In the crystal, the A and B mol­ecules are linked by a pair of N—H⋯N hydogen bonds, generating an R 2 2(8) loop

Phragmites karka as a Biosorbent for the Removal of Mercury Metal Ions from Aqueous Solution: Effect of Modification

Batch scale studies for the adsorption potential of novel biosorbent Phragmites karka (Trin), in its natural and treated forms, were performed for removal of mercury ions from aqueous solution. The study was carried out at different parameters to obtain optimum conditions of pH, biosorbent dose, agitation speed, time of contact, temperature, and initial metal ion concentration. To analyze the suitability of the process and maximum amount of metal uptake, Dubinin-Radushkevich (D-R) model, Freundlich isotherm, and Langmuir isotherm were applied. The values of max for natural and treated biosorbents were found at 1.79 and 2.27 mg/g, respectively. The optimum values of contact time and agitation speed were found at 50 min and 150 rpm for natural biosorbent whereas 40 min and 100 rpm for treated biosorbent, respectively. The optimum biosorption capacities were observed at pH 4 and temperature 313 K for both natural P. karka and treated P. karka. values indicate that comparatively treated P. karka was more feasible for mercury adsorption compared to natural P. karka. Both pseudo-first-order and pseudo-second-order kinetic models were applied and it was found that data fit best to the pseudo-second-order kinetic model. Thermodynamic studies indicate that adsorption process was spontaneous, feasible, and endothermic

3-Chloro-6-(1H-pyrazol-1-yl)pyridazine

The title compound, C7H5ClN4, is almost planar (r.m.s. deviation = 0.022 Å). The dihedral angle between the aromatic rings is 2.82 (5)°. The packing results in polymeric chains extending along the a axis. In the crystal, mol­ecules are connected to each other through inter­molecular C—H⋯N hydrogen bonds, resulting in R 2 2(10) ring motifs

N-(4-Methyl­phen­yl)-6-(pyrazol-1-yl)pyridazin-3-amine

In the title compound, C14H13N5, the pyrazole ring is disordered over two orientations in a 0.571 (10):0.429 (10) ratio and the dihedral angle between the pyridazine ring and the benzene ring is 28.07 (10)°. In the crystal, pairs of N—H⋯N and C—H⋯N hydrogen bonds link the mol­ecules into dimers, with the aid of a crystallographic twofold axis. The packing is consolidated by further C—H⋯N bonds and weak C—H⋯π inter­actions