A New Sensitive Fluorescence Sensor and Photocatalyst for Determination and Degradation of Sodium Valproate Using g-C3N4@Fe3O4@CuWO4 Nanocomposite and FCCD Optimization

In this research, carbon nitride nanocomposite coupled with Fe3O4 and CuWO4 was thermally synthesized and characterized by different techniques, including SEM, TEM, XRD, EDX, and FTIR. Due to sodium valproate's luminescence quenching of this nanocomposite, a reliable, accurate, sensitive, selective, and fast-acting sodium valproate assay was proposed. Optimization of this fluorescent sensor was carried out by the FCCD approach. In the optimum conditions, the plot of sodium valproate concentration versus nanocomposite fluorescence emission showed a linear response (R2 = 0.9918), with a range of 0-0.55 µM, the limit of detection (S/N = 3) equal to 0.85 nM and limit of qualification equal to 2.82 nM. Photocatalytic activity of g-C3N4@Fe3O4@CuWO4 (40%) nanocomposite exhibited a good potency to sodium valproate degradation. Active species of degradation including superoxide radicals, holes, and hydroxyl radicals were investigated using ammonium oxalate, benzoquinone, and 2-propanol to identify the mechanism of photodegradation action. The activity of benzoquinone in the photocatalytic process led to a reduction in the rate of analyte degradation, which indicates the prominent role of superoxide radicals compared to other species in the degradation process. The degradation rate of the analyte using the Fenton reagent was found to be around two times more than in the Fenton reagent-free process. The possible mechanism for the fluorescence sensor and photocatalytic degradation reaction was also discussed.

Application of a new metal-organic framework of [Ni2F2(4,4'-bipy)2(H2O)2](VO3)2.8H2O as an efficient adsorbent for removal of Congo red dye using experimental design optimization

The new metal-organic framework of [Ni₂F₂(4,4'-bipy)₂(H₂O)₂](VO₃)₂.8H₂O was synthesized by a sonochemical method for the adsorptive removal of Congo red (CR) in a batch system. It was characterized by infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), thermogravimetric (TGA), and elemental analyses. Box-Behnken design (BBD) was applied to obtain an appropriate regression model for removal percent (R%) of CR dye. The optimized conditions for three effective factors: adsorbent dosage, temperature, and CR concentration were m = 0.0107 g, T = 45 °C, and C_d = 50 mg.L^-1, respectively, while maximum removal percent is 96%. Langmuir isotherm shows that the maximum monolayer adsorption capacity (q_max) is 242.1 mg.g^-1. The pseudo-second-order kinetic model better describes the adsorption kinetics behavior. Thermodynamic parameters illustrate that the adsorption process is endothermic and spontaneous chemisorption. The aim of this study is the introduction of a new metal-organic framework that can adsorb Congo red with high adsorption capacity. Therefore, due to synthesis of the new metal-organic framework as a high efficient adsorbent for Congo red removal, and also multivariate optimization of removal conditions, this study outright is novel.

Simultaneous removal of binary mixture of Brilliant Green and Crystal Violet using derivative spectrophotometric determination, multivariate optimization and adsorption characterization of dyes on surfactant modified nano-γ-alumina

The present study deals with the simultaneous removal of Brilliant Green (BG) and Crystal Violet (CV) by surfactant-modified alumina. The utilization of alumina nanoparticles with an anionic surfactant (sodium dodecyl sulfate (SDS)) as a novel and efficient adsorbent is successfully carried out to remove two cationic dyes from aqueous solutions in binary batch systems. A first-order derivative spectrophotometric method is developed for the simultaneous determination of BG and CV in binary solutions. The linear concentration range and limits of detection for the simultaneous determination of BG and CV were found to be: 1-20, 1-15 mg/L, 0.3 and 0.5 mg/L, respectively. The influence of various parameters, such as contact time, initial concentration of dyes and sorbent mass on the dye adsorption is investigated. A response surface methodology achieved through performing the Box-Behnken design is utilized to optimize the removal of dyes by surfactant-modified nanoparticle alumina through a batch adsorption process. The proposed quadratic model resulting from the Box-Behnken design approach fitted very well with the experimental data. The optimal conditions for dye removal were contact time t=50 min, sorbent dose=0.036 g, CBG (Initial BG concentration)=215 mg/L and CCV (Initial CV concentration)=170 mg/L. Furthermore, FT-IR analysis, the isotherms and kinetics of adsorption were also explored.

Multi-response optimization using Taguchi design and principle component analysis for removing binary mixture of alizarin red and alizarin yellow from aqueous solution by nano γ-alumina

The nanostructure of γ-alumina was used as an effective adsorbent for simultaneous removing of a mixture of alizarin red and alizarin yellow from aqueous solutions. The Taguchi design and principle component analysis were applied to explore effective parameters for achieving a higher adsorption capacity and removal percentage of the binary mixture containing alizarin red and alizarin yellow. Seven factors including temperature, contact time, initial pH value, the shaker rate, the sorbent dose, and initial concentrations of alizarin red and alizarin yellow in three levels were considered through the Taguchi technique. A L27 orthogonal array was used to determine the signal-to-noise ratio. Then, the removal percentage (R%) and adsorption capacity (q) of the above-mentioned dyes were transformed into an accurate S/N ratio. The Taguchi method indicates that the solution pH has the most contribution in controlling the removal percentage of alizarin red and alizarin yellow. Under optimal condition, the maximum removal percentages of 99% and 78.5%, and the capacity uptake of 54.4 and 39.0mg g(-1) were obtained for both alizarin red and alizarin yellow, respectively. Isotherm modeling and kinetic investigations showed that Langmuir, modified Langmuir, and pseudo-second-order models describe both the adsorption equilibrium and kinetic behavior well. The Fourier transform infrared analysis also firmly confirmed the involving active sites of nano γ-alumina in the adsorption process.

Spectrophotometric determination of trace amounts of fluoride using an Al-xylenol orange complex as a colored reagent

A new spectrophotometric reagent for the determination of trace amounts of fluoride has been introduced. This method is based on the decolorization of a complex of Al(III) with xylenol orange (XO) as an ultra-sensitive colored reagent. Since the Al-XO complex plays an important role in this method, the protonation and complexation of XO with Al(III) at an ionic strength of 0.1 mol L(-1) at 25 degrees C has been studied by a spectrophotometric global analysis method. The EQUISPEC program was used to evaluate the protonation constants of XO and the stability constants of the formed complexes with Al(III). The protonation and the stability constants of the major complex species such as ML, MLH and MLH2, were determined. Finally, a spectrophotometric method for the assay of fluoride based on a decrease of the color intensity of the Al-XO complex, in an aqueous solution has been designed. The effects of some important variables on the determination of fluoride based on the proposed method were investigated. The method was applied to the determination of fluoride under the optimum conditions (pH 5.2, ionic strength 0.1 mol L(-1), 25 degrees C). The determination of fluoride in the range of 0.08-1.4 microg mL(-1) (SD = 1.2%) was successfully performed. Interferences of Fe(III) were easily eliminated by using ascorbic acid. The proposed method was applied to the determination of trace amounts of fluoride content of some real water samples.

Spectrophotometric determination of acidity constant of some indicators in various micellar media solutions by rank annihilation factor analysis

Rank annihilation factor analysis (RAFA) was used to the spectrophotometric studies of the acidity constant of methyl orange, methyl red and methyl violet in water and different micellar solutions at 25 degrees C and an ionic strength of 0.1M. When the acidity constants (surfactant concentration dependent acidity constant) acts as an optimizing object, and simply combined with the pure spectrum of acidic and basic forms, the rank of original data matrix can be reduced. The residual standard deviation (R.S.D.) of the residual matrix after bi-linearization of the background matrix is regarded as the evaluation function. Results show that the acidity constant of these indicators are influenced as the percentages of neutral, cationic and anionic surfactant such as Triton X-100 (poly(oxyethylene)(9.5)p-(1,1,3,3-tetramethyl), sodiumdodecylsulfate (SDS) and cethyltrimethylammonium (CTAB), respectively, added to the solution of these reagents. Also, RAFA is an efficient chemometrics algorithm for completely analysis of acid-base equilibrium systems by spectrophotometric method. Effects of surfactant on acidity constant and absorption spectra are also discussed.

Highly selective and efficient membrane transport of silver as AgBr2- ion using K+-decyl-18-crown-6 as carrier

Potassium-decyl-18-crown-6 was used as a highly selective and efficient carrier for uphill transport of silver as AgBr2-complex ion through a chloroform bulk liquid membrane. When thiosulfate anion was used as a metal ion acceptor in the receiving phase the amounts of silver transported across the liquid membrane after 120 and 180 min were 87.0 +/- 1.8% and 96.0 +/- 1.9%, respectively. The selectivity and efficiency of silver transport from aqueous solution containing Cu2+, Zn2+, Ni2+, Cd2+, Pb2+ and Fe3+ ions were investigated. In the presence of EDTA at pH = 4 as suitable masking agent in the source phase, the interfering effects of Pb2+ and Fe3+ ions were diminished drastically.