Physical entrapment of chitosan in fixed-down-flow column bed enhances triclosan removal from water

Triclosan (TCS) is an emergent pollutant with wide-ranging deleterious effects on aquatic organisms and humans. There is a growing concern about the development of low-cost and efficient treatment systems for the removal of TCS from water. This report describes the performance of a prototype of a continuous flow, fixed bed column device with physically entrapped industrial by-product chitosan. The effects of initial TCS concentration, adsorbent dose in the column matrix, and flow rate were investigated with regard to removal efficiency (%), adsorption capacity and breakthrough time. To understand the thermodynamic properties of the adsorption process, three kinetic models – Thomas, Yoon–Nelson and Adams–Bohart – were applied to the experimental data for the prediction of characteristic parameters of the adsorption process. The Yoon–Nelson model showed the best agreement between the experimental and calculated values. The column showed a near saturation state (Ct/C0 = 0.92; C0 and Ct are the concentration of TCS before and after treatment.) at 90 mg L−1 TCS concentration after 60 minutes. In view of non-availability of a treatment process for the emergent pollutant TCS, the data of the present investigation will facilitate the development of novel prototypes of column bed reactors for the removal of TCS.

99Mo/99mTc radioisotope generator based on adsorption of 99Mo (VI) on cerium (IV) molybdate column matrix

Based on neutron activated 99Mo, a procedure for preparation of 99Mo/99mTc radioisotope generator was developed. Batch equilibration method was used to investigate the sorption behavior of Mo (VI) (10−4 M) in chloride and nitrate solutions on cerium (IV) molybdate gel matrix using 99Mo radiotracer. The breakthrough sorption capacity of cerium molybdate gel matrix for 99Mo (VI) (3×10−2 M) were found to be 0.54 mmol/g of the sorbent [1 g column (0.6 cm i.d.)]. Elution performance of the generated 99mTc from cerium molybdate-99Mo chromatographic column was investigated as a function of inside diameter of the column, amount of the bed matrix and flow rate of the eluent. Based on the obtained results, 99Mo/99mTc radioisotope generator was prepared based on adsorption of neutron activated 99Mo (VI) of low specific activity onto chromatographic columns packed with 5 g cerium molybdate gel matrix. The radioactivity of 99mTc is periodically eluted with 10 mL 0.9% NaCl solution at a flow rate of 1 mL/min. Elution yield of 78±5% was obtained with high chemical, radionuclidic (99Mo breakthrough 1×10−3±0.3×10−3%) and radiochemical purity (97±2%).

Accurate evaluation of the conditions for generation of quantum effects in relativistic interactions between laser and electron beams

The quantum behavior of the system composed of an electron in an electromagnetic field is described by the Dirac equation, whose solution is a wave function represented by a column matrix with four components. We prove, without using any approximation, that these components can be put in a form which reveals directly the values of the electron energy, laser beam intensity, or amplitude of the electric field intensity, for which the quantum electrodynamics effects are generated. Our results are in good agreement with the experimental data reported in the literature. We prove that the four components of the wave function verify the continuity equation of quantum electrodynamics. Our treatment is in good agreement with the Compton relation. We show that the interaction of electrons with laser beams could be modeled using classical approaches regardless of the laser beam intensity as long as the electrons are non-relativistic, in agreement with published experimental data.

Multiresidue Analysis of Five Neonicotinoid Insecticides and Their Primary Metabolite in Cucumbers and Soil Using High-Performance Liquid Chromatography with Diode-Array Detection

A sensitive, selective, and validated HPLC–diode-array detection method was developed for the simultaneous determination of five neonicotinoid insecticides—acetamiprid, imidacloprid, nitenpyram, flonicamid, and thiacloprid—and their primary metabolite, 6-chloronicotinic acid, incucumbers and soil based on the quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique as a pretreatment procedure. In the QuEChERS procedure, cucumber samples were extracted with acetonitrile and cleaned using C18, whereas soil samples were extracted with an acetonitrile–dichloromethane mixture (1 + 2). The HPLC conditions were optimized by separating neonicotinoids using an acetonitrile–water mixture (25 + 75) and a Synergi Hydro RP C18 column. Matrix-matched calibrationstandards were prepared in cucumber and soil to eliminate any matrix interference. RSDs were ≤9% in all recovery tests. LODs and LOQs for the five neonicotinoids were in the ranges of 0.006–0.122 and 0.018–0.366 μg/g, respectively. This method was successfully applied to determine residues, the rate of disappearance of the five neonicotinoids from cucumber and soil, and the half-lives of the neonicotinoids.

Assessment of the natural variability of B, Cd, Cu, Fe, Pb, Sr, Tl and Zn concentrations and isotopic compositions in leaves, needles and mushrooms using single sample digestion and two-column matrix separation

Over 240 samples are analyzed for concentration and isotopic composition of eight elements.

Application of the partitioning method to specific Toeplitz matrices

We propose an adaptation of the partitioning method for determination of theMoore-Penrose inverse of a matrix augmented by a block-column matrix. A simplified implementation of the partitioning method on specific Toeplitz matrices is obtained. The idea for observing this type of Toeplitz matrices lies in the fact that they appear in the linear motion blur models in which blurring matrices (representing the convolution kernels) are known in advance. The advantage of the introduced method is a significant reduction in the computational time required to calculate the Moore-Penrose inverse of specific Toeplitz matrices of an arbitrary size. The method is implemented in MATLAB, and illustrative examples are presented.