Sensitive spectrophotometric methods for determination of some organophosphorus pesticides in vegetable samples

Three rapid, simple, reproducible and sensitive spectrophotometric methods (A, B and C) are described for the determination of two organophosphorus pesticides, (malathion and dimethoate) in formulations and vegetable samples. The methods A and B involve the addition of an excess of Ce4+ into sulphuric acid medium and the determination of the unreacted oxidant by decreasing the red color of chromotrope 2R (C2R) at a suitable lmax = 528 nm for method A, or a decrease in the orange pink color of rhodamine 6G (Rh6G) at a suitable lmax = = 525 nm. The method C is based on the oxidation of malathion or dimethoate with the slight excess of N-bromosuccinimide (NBS) and the determination of unreacted oxidant by reacting it with amaranth dye (AM) in hydrochloric acid medium at a suitable lmax = 520 nm. A regression analysis of Beer-Lambert plots showed a good correlation in the concentration range of 0.1-4.2 μg mL−1. The apparent molar absorptivity, Sandell sensitivity, the detection and quantification limits were calculated. For more accurate analysis, Ringbom optimum concentration ranges are 0.25-4.0 μg mL−1. The developed methods were successfully applied to the determination of malathion, and dimethoate in their formulations and environmental vegetable samples

Fast extraction of vanadyl ion using grafted cotton fiber inserted with amidoxime moiety

393-400Egyptian cotton cellulose fibers have been adapted by graft copolymerization of polyacrylonitril (PAN) and then by ingestion of amidoxime moiety to finally generate C-AXO chelating fibers, which have been characterized by various instrumental techniques such as SEM, FTIR, EDX and XRD spectra. Using batch tests, the obtained C-AXO is used for removal and extraction of VO2 + from its aqueous solution. The kinetic studies have shown that the pseudo second-order model is the best fit for the experimental data

Polyvinyl chloride-based 18-crown-6, dibenzo18-crown-6 and calix-[6]-arene zinc(II)-potentiometric sensors

Polyvinyl chloride (PVC) based membranes of 18-crown-6 (18C6), dibenzo 18-crowen-6 (DB18C6) and calix[6]arene (CAX), as ionophores, with dioctylphenylphosphonate (DOPP), bis(ethylhexyl)sebacate (DOS) dioctyl phthalate (DOP), 2-nitrophenyloctylether (o-NPOE) and didecylphthalate (DDP) as plasticizing solvent mediators are prepared and constructed for the determination of Zn(II). Of the 15 membranes constructed, only the PVC based membranes of DB18C6 and 18C6 ionophores with DOPP, as plasticizer, in the ratio (w/w) PVC:ionophore:DOPP (60:2:120) give the best results in terms of working concentration range (1.0 × 10−5–1.0 × 10−1 M) with a Nernstian slope of 29.0 mV/decade of activity for membrane composed of DOPP + DB18C6(1a) and (1.0 × 10−5–1.0 × 10−1 M) with a Nernstian slope of 30.0 mV/decade of activity for membrane composed of DOPP + 18C6(1b). The usable pH range of the sensors is 3.0–8.0, beyond which a drift in potential is observed. The response time of the sensors is ⩽15 s with a lifetime of 2 months during which they can be used without any measurable divergence. The selectivity coefficient values indicate that the electrode is highly selective for Zn2+ over a number of other cations except Pb2+ and Ag+. The electrodes have successfully been used to determine Zn(II) in real alloys and standard samples with a precision as relative standard deviation (RSD) <2% for each of the cited electrodes. The results obtained by the proposed ISEs are in good agreement with the results obtained by direct flame AAS method

Superparamagnetic Core-Shell Polymeric Nanocomposites for Efficient Removal of Methylene Blue from Aqueous Solutions

Ultrafine well-dispersed Fe 3 O 4 magnetic nanoparticles (NPs) were directly prepared in an aqueous solution using controlled co-precipitation method. The Fe 3 O 4 -poly(acrylamide-co-sodium acrylate) core-shell magnetic nanogels are prepared by solution polymerization of acrylamide (AM) and sodium acrylate (AA-Na) monomers in the presence of Fe 3 O 4 NPs, N,N′-methylenebisacrylamide (MBA) as a cross-linker, N,N,N′,N′-tetramethylethylenediamine and potassium peroxydisulphate (KPS) as the redox initiator system. The novel Fe 3 O 4 -poly(acrylamide-co-sodium acrylate) core-shell magnetic nanocomposite hydrogels are prepared by in situ free radical co-polymerization of AM and AA-Na in an aqueous dispersion of nanogel particles using MBA as the cross-linker and KPS as the initiator. The as-prepared nanocomposite hydrogels are characterized by Fourier transform infrared spectroscopy spectra, X-ray powder diffraction and transmission electron microscopic measurements. The mean particle size of the synthesized magnetite (Fe 3 O 4 ) NPs was approximately 8 nm. The diameter of the stabilized polymer-coated Fe 3 O 4 nanogels is approximately 11 nm. The surface morphology of the nanocomposites has been studied by scanning electron microscopy and atomic force microscopy. The Fe 3 O 4 -poly(acrylamide-co-sodium acrylate) nanocomposites have been extensively investigated for the removal of basic dyes from aqueous solutions. Results of batch experiments showed that these adsorbents exhibited high sorption capacities towards methylene blue (MB). Experimental data were analyzed using first-order kinetics, pseudo-second-order kinetics and intra-particle diffusion models. The kinetics followed a pseudo-second-order equation. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich equations. The thermodynamic parameters for the adsorption of MB onto the nanocomposite hydrogels were also calculated. Regeneration of nanocomposite adsorbents can be easily achieved

Semicarbazide Functionalized Flax Fibers for Effective Adsorption of Cr(VI) from Wastewater Samples

Semicarbazid modified flax fiber (SC.MFF) was successfully synthesized for the removal of Cr(IV) from different wastewater samples. Preparation of the SC.MFF material occurred in two main steps, the first step is the oxidation of the flax fibers by potassium periodate and the next step is refluxing of the oxidized fibers with semicarbazide ligand. The results show that quaternary ammonium cations were grafted on the surface of SC.MFF successfully. Additionally, a series of characterization of the SC.MFF sorbent was carried out using scanning electron microscopy, FTIR, elemental analysis, and X-ray diffraction spectroscopy. The effects of pH and ionic strength on the adsorption capacity were also investigated, which showed the adsorption capacity of the adsorbent decreased significantly with the increase of ionic strength and pH. Under optimized extraction conditions, the sorption capacity of Cr(VI) is 97.4 mg. g-1. The kinetic studies show that the experimental data matches well with the pseudo-second-order kinetic model. Furthermore, the studied Cr(VI) adsorbed on the sorbent according to the Langmuir adsorption model. Finally, the SC.MFF sorbent was successfully applied for the selective and high-efficiency recovery of Cr(VI) ions from different water samples. </p

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Divalent transition metal complexes of nitrogen, oxygen and sulfur containing ligand: design, structural, spectral, pH-metric, theoretical molecular modeling, analytical and mechanism studies

Abstract In the present study, the 1-Nicotinoyl-4-phenyl thiosemicarbazide (H2NPT) multidentate nitrogen, oxygen and sulfur containing ligand is being synthesized in a simple single step reaction by condensing 1:1 molar ratio of ethanolic solutions of both phenyl isothiocyanate and nicotinoyl hydrazine. The prepared H2NPT and its complexes with Co2+, Ni2+ and Zn2+ and Cu2+ were characterized by pH-metric titrations, elemental analysis, FTIR, electronic spectra and thermogravimetric (TGA) analyses. The association constant of the ligand and the stability constants of its complexes were calculated by pH-metric measurements in 50% ethanol–water mixture. Also, DFT method was used to draw the geometry of all compounds and the parameters such as bond lengths, bond angles, dipole moment, Frontier orbitals (HOMO, LUMO), MEP and other energetic parameters (optical energy gap, softness, hardness, electronegativity) were evaluated. The prepared H2NPT reacted with Co2+, Ni2+ and Zn2+ and Cu2+ metal ions to form colored precipitates that were readily floated to the surface solution using oleic acid (HOL) surfactant with vigorous shaking of the flotation cell. The heavy metals' concentrations in the dissolved precipitates are determined by flame atomic absorption spectrometry (FAAS). The different parameters affecting the flotation process were thoroughly investigated, viz. pH of sample solution, concentration of ligand, metal ions and HOL, temperature and interfering ions. Nano-gram quantities of Cu2+, Co2+, Ni2+ and Zn2+in 1500-ml samples are quantitatively determined with 1-Nicotinoyl-4-phenyl thiosemicarbazide (H2NPT) at pH 3.0–6.5 for Cu2+ and at 7.0–7.5 for Co2+, Ni2+ and Zn2+. The concentrations of these heavy metals are increased 300-fold. Interferences, on the flotation process, from various foreign ions were avoided by adding excess H2NPT. The mode of chelation between H2NPT and the investigated metal ions is proposed to be through the S, N and/or O atoms of the ligand. The mechanism of flotation is proposed to be due to an electrostatic interaction between the HOL surfactant and the formed metal–ligand complexes through H-bond formation. The proposed multi-element flotation methodology has been utilized for the determination of the analytes in certified reference materials, alloys, synthetic mixtures and in water samples with a recovery % more than 90% and a relative standard deviation (RSD), as a precision < 2%

Surfactant supported chitosan for efficient removal of Cr(VI) and anionic food stuff dyes from aquatic solutions

Abstract In order to develop a novel and cost-effective adsorbent with outstanding adsorption capacity and excellent recyclability for anionic pollutants, the chitosan-modified cetyltrimethylammonium bromide sorbent (CS@CTAB) was fabricated. Fourier-transform infrared spectroscopy, N2 adsorption–desorption isotherm, elemental analysis, Thermogravimetric analysis, X-ray diffraction, and Scanning electron microscopy have been applied to evaluate both raw and surfactant modified chitosan (CS@CTAB). Azorubine, Sunset Yellow, and hexavalent chromium were used to study the adsorption behavior of CS@CTAB under various parameters such as adsorbent dose, initial dye and metal ion concentration, contact time, and temperature. Adsorption equilibrium, kinetics models and thermodynamic parameters were investigated. The adsorption isotherm fitted well with the Langmuir isotherm model, with a maximum adsorption capacity of 492.6 mg/g, 492.6 mg/g, and 490.196 mg/g for Azorubine, Sunset Yellow, and Hexavalent Chromium, respectively. The kinetic studies showed that the pseudo-second-order model provided a better correlation between experimental data. Furthermore, the calculated thermodynamic parameters confirmed that the adsorption of Cr(VI), E110, and E122 by CS@CTAB material is a spontaneous and exothermic process. The fabricated CS@CTAB adsorbent was employed for the efficient elimination of Azorubine, Sunset Yellow, and hexavalent chromium from real water samples, synthetic mixtures, and colored soft drinks, with a percentage of recovery of ~ 96%. The plausible adsorption mechanisms of Azorubine, Sunset Yellow, and hexavalent chromium on the surface of CS@CTAB are elucidated. The adsorption anticipated to be due to electrostatic interaction and hydrogen bond formation for hexavalent chromium; while the adsorption of Azorubine and Sunset Yellow, was assumed to be due to electrostatic interaction, hydrogen bonding, and n-π interaction. Finally, the study demonstrates the efficiency of CS@CTAB for the removal of anionic species from several samples, including natural water and colored beverages

Additional file 1 of Novel diaminoguanidine functionalized cellulose: synthesis, characterization, adsorption characteristics and application for ICP-AES determination of copper(II), mercury(II), lead(II) and cadmium(II) from aqueous solutions

Additional file 1: Fig. S1. FTIR of (a)Native cellulose, (b)DAC, (c) DiGu.MC. (d) DiGu.MC-Cu(II). Fig. S2 TGA curves of (a) DiGu-MC, (b) Cu-DiGu-MC, (c) Hg-DiGu-MC, (d) Pb-DiGu-MC (e) Cd-DiGu-MC. Fig. S3. Effect of initial concentration on adsorption of heavy metals by DiGu-MC. Table S1: Specific Surface areas of native cellulose and DiGu-MC fibers

Smart guanyl thiosemicarbazide functionalized dialdehyde cellulose for removal of heavy metal ions from aquatic solutions: adsorption characteristics and mechanism study

Abstract In recent years, facing the problem of improving environmental quality, cellulose and cellulose-based (nano) composites have received great attention as adsorbents. In this work, we report the modification and functionalization of cellulose by nitrogen- and sulfur-containing moieties through a three-steps process; native cellulose is first oxidized by potassium periodate (KIO4) to form dialdehyde cellulose (DAC), which then condenses with aminoguanidine and react with phenyl isothiocyanate to form 4-phenyl guanyl thiosemicarbazide dialdehyde cellulose (DAC@GuTSC). The prepared DAC@GuTSC is characterized by a number of techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental analysis (EA), Brunauer–Emmett–Teller (BET) and thermogravimetric analysis (TGA). The prepared DAC@GuTSC adsorbent was used to remove Cu2+ Hg2+ and Pb2+ from aqueous solution and environmental water samples. The influence of various factors on the adsorption efficiency including pH, initial metal concentration, contact time, adsorbent dosage, temperature, and ions interfering with adsorption was investigated. Under optimal adsorption conditions, the adsorption capacity of Cu2+, Hg2+ and Pb2+ was 50, 94 and 55 mg g−1, respectively. The adsorption process is well described by the Langmuir model, and it was found to follow the pseudo-second-order kinetics model. The spontaneous and endothermic adsorption of Cu2+, Hg2+ and Pb2+ was confirmed by the calculated thermodynamic functions. The prepared DAC@GuTSC composite has been successfully applied to remove Cu2+, Hg2+ and Pb2+ from real water samples with recovery greater than 90% and relative standard deviation (RSD) less than 3%. The reasonable Cu2+, Hg2+ and Pb2+adsorption mechanism on the prepared DAC@GuTSC composite has been elucidated