Flow-injection determination of total iron in freshwater samples with neutralisation chemiluminescence

A flow-injection chemiluminescence method has been established for the determination of total iron in freshwater samples. The enhanced chemiluminescence emission was caused by the iron(II) from the neutralisation reaction of hydrochloric acid and sodium hydroxide without the use of any chemiluminescent reagent. The calibration graph was linear in the concentration range of 2.8–560 µg L^?1 (r ² = 0.9983, n = 8), with relative standard deviation (RSD; n = 4) in the range of 0.8–2.6%. The limit of detection (S/N = 3) was 0.56 µg L^?1 with injection throughput of 180 h^?1. The effect of common anions and cations were studied over their environmentally relevant concentrations in freshwaters. The method was successfully applied to determine total iron in freshwater samples. Iron(III) was reduced to iron(II) by using hydroxylammonium chloride. The proposed method was compared with spectrophotometric method and there was no significant difference between the two methods at the 95% confidence level (t-test). Analysis of river water (certified reference material SLRS-4) for iron(II), after reduction of iron(III) with hydroxylammonium chloride, gave good results (2.17 ± 0.22 µM compared with the certificate value of 1.85 ± 0.1 µM).     

Determination of phosphate in freshwater samples by flow-injection with lucigenin chemiluminescence

Lucigenin chemiluminescence (CL) in conjunction with flow-injection analysis (FIA) is used for the determination of phosphate in freshwater samples. The procedure is based on the formation of molybdophosphoric heteropoly acid (MoP–HPA) by the reaction of phosphate and ammonium molybdate under acidic conditions. CL emission was observed as a result of oxidation of lucigenin in aqueous sodium hydroxide solution in the presence of MoP–HPA. Calibration was linear up to 500?µg?L^?1 (r ^2?=?0.9998; n?=?8), with a detection limit (S/N?=?3) of 0.95?µg?L^?1. An injection throughput of 120 h^?1, and relative standard deviation (RSD; n?=?4) of 1.3–3.2% were achieved in the concentration range studied. An on-line chelating column was used to remove interfering cations. The method was applied to freshwater samples, and the results (51?±?1.0 – 107?±?2.0?µg?L^?1) did not differ significantly from results obtained using a spectrophotometric method (52.5?±?1.0 – 102?±?2.0?µg?L^?1) at 95% confidence level (t-test).     

Conversion of biomass residual to acid-modified bio-chars for efficient adsorption of organic pollutants from industrial phosphoric acid: an experimental,kinetic and thermodynamic study

ABSTRACT

This study reports the removal of organic matters from phosphoric acid using waste-produced bio-charcoal structures. Particularly, the freshly made bio-char species via pyrolysis and two sub-driven acids activated charcoals were applied during the removal process. The treated charcoal with hydrochloric and nitric acids had attained a higher adsorption rate for organic matters than that of the non-treated one. Removal percentages of 70% and 60% were, respectively, attained by acid-modified chars. The kinetics of the adsorption process was fitted via pseudo-first/second-order and Morris–Weber models. The thermodynamic parameters of the presented sorption process indicate that organic matter removal has been endothermic, physical and spontaneous.     

Application of artificial neural networks for formulation and modeling of dye adsorption onto multiwalled carbon nanotubes

In this study, an artificial neural network (ANN) has been developed to predict the adsorption amount of dye (methylene blue) onto multiwalled carbon nanotubes. Batch experiments have been carried out to obtain experimental data. Important parameters in the adsorption system such as initial dye concentration, adsorbent dosage, temperature, pH and contact time have been used as the inputs of the network, while the output is the final concentration of dye in aqueous solution after adsorption. The neural network structure has been optimized by testing various training algorithms and different number of neurons in a hidden layer. An empirical equation for determination of final dye concentration in aqueous solutions after adsorption has been developed by using the weights of the optimized network. The results of the optimized ANN have been compared with conventional models in equilibrium and kinetic fields. According to error analysis and determination coefficient, the ANN was found to be the most appropriate model to describe this adsorption process. Sensitivity analysis showed that initial dye concentration, pH and contact time are the most effective parameters in this process. The influence percentages of these parameters on the output were 28, 24 and 24 %, respectively.     

Asymmetric aldol reactions catalyzed by the promiscuous aldo–ketoreductase enzyme

The promiscuous aldo–ketoreductase (AKR) enzyme is used as a sustainable biocatalyst for the first time to catalyze asymmetric aldol reactions in aqueous medium. The reactions between aromatic aldehydes and cyclic/acyclic ketones give the corresponding products in moderate yields and enantioselectivities in the presence of water. The influence of solvents, the mole ratio of substrates, and enzyme concentration are investigated. The mechanism of the AKR1A1-catalyzed aldol reaction is also discussed.     

Effect of Experimental Variables on the Combustion Characteristics of Water-in-Diesel Emulsion Fuels

Water-in-diesel (W/D) emulsion fuels were prepared through an ultrasonic processor by using high energy emulsification method. Accordingly, the physical and chemical properties were analyzed. A decrease in viscosity was found in the emulsion fuel in contrast to the neat diesel which signifies the enhanced fluidity of the fuel. The emulsion fuel was then used to carry combustion tests in an internal combustion engine. A decrease in exhaust temperature was observed when a high surfactant to water ratio was used, which lead to minimal heat loss. As water is emulsified with diesel, effectiveness of combustion is improved rather than neat diesel fuel. It was also explored that the addition of water-in-diesel is influential in terms of reduction in exhaust gas emission such as carbon dioxide, carbon monoxide, ammonia from the internal combustion engine. Therefore, this type of emulsion fuel would be a useful contribution in the fuel economy, but also in making it environmentally friendly since diesel fuel is now considered one of the leading fuels causing ecological contamination.     

Radiosynthesis and biological evaluation of 166Ho labeled methoxylated porphyrins as possible therapeutic agents

¹⁶⁶Ho labeled 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin, and 5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl) porphyrin ([¹⁶⁶Ho]–TDMPP and [¹⁶⁶Ho]–TTMPP respectively) were prepared with acceptable radiochemical purity and specific activities. Stability and partition coefficient of the complexes were determined in the final formulations and biodistribution studies in mouse demonstrated high accumulation of [¹⁶⁶Ho]–TDMPP in the lung and liver and less excretion through the kidney. while [¹⁶⁶Ho]–TTMPP was mostly excreted into intestines and kidneys while lungs were a minor accumulation site. In contrast to other reported radiolanthanide labeled porphyrins these two complexes showed less liver accumulation. Further investigation of their potential therapeutic properties is of interest.     

1, 3-dipolar cycloaddition of C-phenyl carbamoyl-N-phenyl nitrone with some dialkyl-substituted 2-benzylidenecyclopropane-1,1-dicarboxylates: theoretical analysis of mechanism and regioselectivity

The regiochemistry of 1,3-dipolar cycloaddition reactions of C-phenyl carbamoyl-N-phenyl nitrone with some dialkyl-substituted 2-benzylidenecyclopropane-1,1-dicarboxylates as dipolarophile was investigated using density functional theory-based reactivity indexes and activation energy calculations at B3LYP/6-31G(d) level of theory. Analysis of the geometries and bond orders at the TS structures associated with the different reaction pathways shows that these 1,3-dipolar cycloaddition reactions occur via an asynchronous concerted mechanism. Analysis of the local electrophilicity and nucleophilicity indexes based on Parr functions only for reaction between 1 + 2a and based on Fukui functions only for 1 + 2b gives correct regioselectivity. The theoretical results obtained in the work clearly predict the regiochemistry of the isolated cycloadducts and agree to experimental results.     

Influence of polymeric coating on capillary electrophoresis of iron oxide nanoparticles

In this work, electrophoresis was successfully used to separate three different polymer-coated magnetic iron oxide nanoparticles with similar sizes (nominally 50 nm) using high-pH borate buffer system. The coating polymers were dextran, polyethylene glycol, or carboxymethyl dextran. The results showed that the migration time of carboxymethyl dextran coated nanoparticles is the longest due to relatively more negative surface charges. Investigation of the effects of buffer concentration, pH, electric field strength and the capillary temperature, on electrophoretic properties of samples was also carried out. The results showed that pH, electric field strength and the capillary temperature had indirect relations with both of the migration time and the separation resolution of three different polymer-coated nanoparticles while the buffer concentration had a direct relation.     

In vitro dielectrophoresis of HEK cell migration for stimulating chronic wound epithelialization

This article describes a dielectrophoresis (DEP)-based simulation and experimental study of human epidermal keratinocyte (HEK) cells for wounded skin cell migration toward rapid epithelialization. MyDEP is a standalone software designed specifically to study dielectric particles and cell response to an alternating current (AC) electric field. This method demonstrated that negative dielectrophoresis (N_DEP) occurs in HEK cells at a wide frequency range in highly conductive medium. The finite element method was used to characterize particle trajectory based on DEP and drag force. The performance of the system was assessed using HEK cells in a highly conductive EpiLife suspending medium. The DEP experiment was performed by applying sinusoidal wave AC potential at the peak-to-peak voltage of 10 V in a tapered aluminum microelectrode array from 100 kHz to 1 MHz. We experimentally observed the occurrence of NDEP, which attracted HEK cells toward the local electric field minima in the region of interest. The DIPP-MotionV software was used to track cell migration in the prerecorded video via an automatic marker and estimate the average speed and acceleration of the cells. The results showed that HEK cell migration was accomplished approximately at 6.43 μm/s at 100 kHz with 10 V, and F_DEP caused the cells to migrate and align at the target position, which resulted in faster wound closures because of the application of an electric field frequency to HEK cells in random locations.