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This paper presents the experimental research results, regarding the effect of hydromechanical parameters and based on the relative reduction of the starting hardness of geothermal water of Sijarinska Banja and Niska Banja as well as the water from the Medijana spring in Nis. The measurements were conducted on a laboratory pilot plant/ facility with glass pipes of diameter 2, 4, 6, 8 and 10 mm and with water flow controlled by a digital peristaltic pump with a flow interval from 2 to 5000 ml min-1. The effect of the hydrodynamic parameters on the change of input hardness of geothermal and other hard waters and the process of solid deposit creation were modelled by an empirical model based on simple linear regression analysis, multiple linear regression model and the neural network. The high accuracy of all applied models unequivocally proves that a synergism of hydrochemical and hydrodynamic parameters exists in the process of creation of solid deposit ? limescale, thanks to which the starting hypothesis is confirmed.

Pollution control and water purification are the main concerns associated with hazardous component eliminations from wastewaters which have inspired the research, among the others, on various clay minerals as useful adsorbents. The aim of this study was to examine morphological, structural, adsorption, and electrochemical characteristics of serpentinite in order to check its potential for removal of cadmium and textile dyes from synthetic waters. SEM technique has provided a detailed insight into the surface morphology of serpentinite indicating irregularly shaped particles and lamellar aggregates which are characteristic of lizardite mineral. Crystal phases detected in composition of serpentinite by using XRD technique are lizardite and tiny amount of periclase. Serpentinite adsorption characteristics were investigated towards Cd2+ and anionic textile dyes (Procion red MX-5B, Procion orange and Ramazol black) in aqueous solutions. The main goal of the study was the reliable removal of hazardous Cd2+ at low initial concentrations (up to 200 mu g/dm(3)). Textile dyes were taken as the models of anionic organic pollutants in water. All the adsorption experiments were carried out in batch conditions by varying initial parameters such as concentration of pollutant, contact time, mass of adsorbent and pH. Based on the obtained results, serpentinite has proven to be efficient adsorbent with removal efficiency over 98% for the selected pollutants. Native serpentinite was further modified in order to obtain forsterite. Electrochemical characteristics of serpentinite and forsterite were examined by using cyclic voltammetry of solution of 0.1 M H2SO4 as acidic supporting electrolyte and K-4[Fe(CN)(6)] which was chosen as a redox model compound. Due to its specific structure, surface groups, morphology, and non-stoichiometric composition, serpentinite and forsterite exhibited prominent electrocatalytic activity. (C) 2016 Elsevier B.V. All rights reserved.

An application of coatings composed of mixed (hydr)oxides over bentonite particles in aqueous suspension, in narrow range of pH, has been proven as a useful method for obtaining bentonite based composite with a developed, specific surface area and pronounced adsorption features toward cationic pollutants. This paper deals with detailed characterization of structure as well as textural and adsorption properties of bentonite based composite. The structure of the composite was examined by using XRD technique providing results that confirm changes in orientation of layered quasi-crystalline particles of montmorillonite, which is the most common component of bentonite clay. Surface area and pore volumes were determined by N-2 adsorption at -196 degrees C using BET, t-plot, alpha(s)-plot, Dubinin Radushkevich and Dolli-more Heal method. The results have revealed that the specific surface area for composite is about two times higher than for starting bentonite. Moreover, modification of bentonite leads to significant changes in the meso- and microporosity. Adsorption properties of the composite were studied by analyzing the adsorption of dye methylene blue which was used in this study as a model of cationic pollutant in water. The most prominent role in the mechanism of dye molecules retention on the surface, interlayers and in the pores of the adsorbent is ascribed to establishing of electrostatic, van der Waals and hydrogen bonds. The shape of adsorption isotherm indicates that methylene blue can be adsorbed onto composite in more than one layer. (C) 2014 Elsevier Inc. All rights reserved.

This paper deals with synchronised influences of hydromechanical and hidrochemical parameters on the formation of solid deposits in geothermal and other waters which compose complex heterogeneous and micro-heterogeneous system of liquid-solid. Constituents of these waters in ionic, colloidal and micro-heterogeneous suspended state of liquid-solid are responsible for the creation of the carbonates, sulphates and other solid matters. In these processes one cannot eliminate the influence of hydromechanical parameters with flow velocity and water flow criteria (laminar or turbulent flow) as vital factors. Experiments were conducted on the laboratory pilot installation with glass pipes diameter of 2, 4, 6, 8 and 10 mm respectively, and the flow was monitored by means of digital peristaltic pump with the flow rate of 2 ml/min to 5000 ml/min. The paper gives the results of the investigation of the impact of the linear flow velocity on the relative decrease of the initial water hardness in geothermal waters of Sijarinska Banja spa, Niska Banja spa and the estuary water of Medijana, Nis. From the obtained dependences, according to the linear regression model, for each diameter critical values for linear velocities as an important parameter for the understanding of the synergism of the hydromechanical and hydrochemical parameters were determined. [Projekat Ministarstva nauke Republike Srbije, br. 33046]

The physicochemical modification of peat through thermal and oxidation processes was carried out, in order to obtain new, inexpensive and active material for purification of different types of waters. During the modification, surface chemical compounds of Shilov type were formed. Batch adsorption properties and suitability of physicochemically modified peat (PCMP) for odor removal were tested in aqueous solutions of H2S and colloidal sulphur. Additionally, PCMP was tested in the removal of As(V) which is hazardous ingredient in contaminated waters. Possible mechanisms of pollutants binding include interactions, which lead to formation of adducts and clathrates. All these processes are elucidated in detail. The results showed that the obtained material can be used for the removal of sulphide, colloidal sulphur and As(V) from different types of waters. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45012]

Sorption characteristics of three Lagenaria vulgaris-based biosorbents: raw biomass (rLVB), acid–base-activated biomass (aLVB) and sulfuric acid-treated biomass (ccLVB), were compared as a function of contact time, initial methylene blue concentration, and initial pH, in order to evaluate the effect of chemical modifications. The adsorption studies of raw and chemically modified L. vulgaris biomass were compared in batch mode. The Fourier transform Infrared spectroscopy (FTIR) results of biosorbents’ characterization showed presence of different functional groups which can be responsible for sorption of MB from aqueous solutions. Moreover, FTIR analysis reveals that acid–base activation of raw biomaterial resulted in hydrolysis of esters providing more reactive sites (–COO−), while sulfuric acid-treatment method introduced new functional groups such as –SO3−. Surface functional groups containing oxygen, such as carboxylic, lactonic, and phenolic, are quantified using the Boehm’s method. The kineti...

Samples of natural peat (NP) were hydrothermally treated at different temperatures in oxidative and acidic aqueous medium to tailor their acid-base, adsorption, morphological and other properties. The obtained materials were thoroughly characterized by SEM, XRD and FTIR techniques, followed by determination of pH(pzc), examination of adsorption characteristics and the extent of organic matter leaching in water. Acid-base characteristics of these materials were examined by potentiometric and conductometric titration of corresponding aqueous suspensions. Experimental potentiometric data were interpreted using ProtoFit software (NEM, non-electrostatic model) which provided pKa values and concentrations of surface sites which are compared with corresponding values obtained by conductometric titration method. There are two main types of surface groups (carboxylic and phenolic) that are dominant in the materials and determine their acid-base behavior in the aqueous medium. Temperature during oxidative hydrothermal treatment has no significant effect on the total number of surface groups, but influences the ratio of carboxylic and phenol-type groups. Hence, acid-base properties of peat can be tailored, which is useful in designing and improving adsorptive characteristics of peat for the preferential removal of certain pollutants from water.

The photochemical decolorization of C.I. Reactive Orange 16 (RO16), a reactive textile azo dye by the UV/H2O2 process using a batch photoreactor with UV lamps emitting at 253.7 nm, was studied. Complete decolorization of 50.0 mg dm-3 initial dye concentration was achieved in less than 6 min under optimal conditions (25 mM initial peroxide concentration, at pH 7.0 and with UV light intensity 1950 ?W cm-2). The effect of experimental variables, such as initial pH, initial concentration of H2O2, initial dye concentration, and the intensity of UV light was studied. The highest decolorization rates were performed at peroxide concentration in range from 20 mM up to 40 mM, above which decolorization was inhibited by a scavenging effect of peroxide. The decolorization was more efficient in neutral pHs. The efficiency of the process was improved in lower initial dye concentration and at higher intensity of UV light.

Distribution of chromium between soil and leachate was monitored. A natural process of percolating rainwater through the soil was simulated in the laboratory conditions and studied with column leaching extraction. Migration of chromium in the soil is conditioned by the level of chromium soil contamination, the soil organic matter content, and rainwater acidity. Chromium (III) and chromium(VI) were determined by spectrophotometric method with diphenilcarbazide in acidic media. Comparing the results of chromium speciation in leachate obtained by experimental model systems and geochemical modelling calculations using Visual MINTEQ model, a correlation was observed regarding the influence of the tested parameters. Leachate solutions showed that the concentration of Cr depended on the organic matter content. The influence of pH and soil organic matter content is in compliance after its definition through experimental and theoretical way. The computer model - Stockholm Humic Model used to evaluate the leaching results corresponded rather well with the measured values.

The procedure for obtaining a bentonite based composite involves the application of mixed Fe and Mg hydroxides coatings onto bentonite particles in aqueous suspension and subsequent thermal treatment of the solid phase at 498K. Structural and textural modifications of montmorillonite which occurred during the synthesis of composite were confirmed by XRD technique and N-2 adsorption at 77K. The composite structure was found to be less ordered, while its specific surface area was about two times higher than the specific surface area of the starting/native bentonite. The effectiveness of the composite in Pb(II) removal from aqueous solutions at different initial concentrations, pH and ionic strengths of the solutions was examined. The equilibrium adsorption data were analyzed using three widely applied isotherms: Langmuir, Freundlich and Dubinin-Radushkevich. The composite effectively removes both ionic and colloidal forms of Pb(II) from water and the maximum adsorption capacity obtained from the Langmuir equation was 95.88 mg/g. The main mechanisms of Pb(II) removal at low pH values were ion-exchange and outer-sphere surface complexation. (C) 2011 Elsevier B.V. All rights reserved.

Adsorption of a cationic phenothyazine dye methylene blueonto activated carbon prepared from pine cones was investigated with the variation in parameters of contact time, dye concentration and pH. The kinetic data were found to follow the pseudo-second-order kinetic modelclosely. The equilibrium data were best represented by the Langmuir isotherm with maximum adsorption capacity of 233.1 mg g-1. Adsorption was favored by using a higher solution pH. Textural analysis by nitrogen adsorption was used to determine specific surface area and pore structure of the obtained carbon. Boehm titrations revealed that carboxylic groups are present in the highest degree on the carbon surface. The results indicate that the presented method for activation of pine cones could yield activated carbon with significant porosity, developed surface reactivity and considerable adsorption affinity toward cationic dye methylene blue.

Two series of zirconia based catalysts promoted with either sulfates or phosphates were prepared, calcined at different temperatures (600 and 700?C) and evaluated for the n-hexane isomerization reaction. The catalysts with different concentrations of sulfates or phosphates (4 or 10 wt. %) were characterized by BET, XRD, SEM methods, and total acidity was evaluated by using the Hammett indicators. Their final catalytic performances were correlated with their physical-chemical properties (surface, structural, textural and morphological). It was found that sulfated zirconia catalyst calcined at lower temperature showed the highest initial activity of all tested catalysts as the result of favorable total acidity, mesopore texture and structural properties. Somewhat lower activity of the sulfated catalyst calcined at higher temperature is related to the content of acid groups partially removed during thermal treatment, thus, lower total acidity, and also to less favorable textural and structural features. Negligible activity of phosphated zirconia catalysts is connected with low total acidity despite the positive status of particular property showing the complexity of the active phase/site formation in the catalyst.

A bentonite-based composite was synthesized by applying thin coatings of natural organic matter onto bentonite particles in aqueous suspension. Natural organic matter, mostly comprised of humic acids, was isolated from peat by alkaline extraction. It was insolubilized and immobilized on bentonite by heating at 350 °C in an inert nitrogen atmosphere. The composite obtained was then used to remove manganese from aqueous solutions. The results showed that manganese was removed significantly; the degree of removal was above 94% for initial concentrations of manganese from 0.250 to 10 mg/l. The effect of initial pH on manganese removal, dissolution of immobilized organic matter as well as the changes of pH and conductivity of water after treatment with composite were examined and explained.

This paper presents a procedure for the removal of manganese in ionic (Mn 2+ ) and colloidal (MnO 2 ) forms from synthetic waters, by reduction and adsorption processes on electrochemically active alumosilicate ceramics based composite material. Synthesis procedure of the composite material consists of two phases. Firstly, composite particles were synthesized by applying Al/Sn oxide coating on the bentonite particles in an aqueous suspension. In the second phase, aluminum powder was added to the previously obtained plastic mass and after shaping in the form of spheres 1 cm in diameter and drying, sintering was performed at 900 °C. Elemental tin, resulting from the reduction of Sn 2+ ion, comes into contact with liquid aluminum in the pores of the matrix performing aluminum microalloying and activation. Moreover, due to a low partial pressure of oxygen, nonstoichiometric oxides with metal excess are obtained, and they play an important role in the electrochemical activity of composite material. In accordance with this, a redox potential of water is changed in contact with composite. The detailed characterization of the composite was carried out by SEM, FTIR and XRD techniques and the influence of pH values on the removal of ionic form of manganese from water was investigated as well.

The stability of metal-humate complexes is an important factor determining and predicting speciation, mobility and bioavailability of heavy metals in the environment. A comparative investigation of the complexation of Cu(II) and Pb(II) with humic acid and humic-like ligands, such as benzoic and salicylic acid, was performed. The analysis was realized at pH 4.0, a temperature of 25°C and at an ionic strength of 0.01 (NaCl) using the Schubert ion-exchange method and its modified form. The stability constants were calculated from the experimental data by the Schubert method for complexes with benzoic and humic acid. A modified Schubert method was used for the determination of the stability constants of the complexes with salicylic acid. It was found that Cu(II) and Pb(II) form mononuclear complexes with benzoic and humic acid while with salicylic acid both metals form polynuclear complexes. The results indicate that Pb(II) has a higher binding ability than Cu(II) to all the investigated ligands. The Cu(II)-salicylate and Pb(II)-salicylate complexes showed noticeable higher stability constants compared with their complexes with humic acid, while the stabilities of the complexes with benzoic acid differed less. Salicylic and benzoic acids as humic-like ligands can be used for setting the range of stability constants of humic complexes with Cu(II) and Pb(II).

Activated carbon prepared from the cones of the European Black pine was used as adsorbent for the removal of lead(II) ions from aqueous solutions. The effect of pH, initial concentration of lead(II) ions, contact time, and adsorbent dosage on the adsorption was studied in a batch process mode. Equilibrium data were analyzed by the Langmuir, Freundlich and Temkin isotherm model. Langmuir isotherm provided the best fit to the equilibrium data with maximum adsorption capacity of 27.53 mg/g. The kinetic data were found to follow closely the pseudo-second-order model. The microstructures of the activated carbon before and after adsorption of lead(II) ions were observed by scanning electron microscope. Textural analysis was employed in order to determine specific surface area and pore size distribution of the prepared activated carbon. Surface structure was characterized by using Fourier transform infrared spectroscopy and Boehm titration.

Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface.

Horse chestnut kernel was used as the precursor for the preparation of powdered activated carbon using phosphoric acid as the activating agent. Batch adsorption experiments for the adsorption of cationic dye methylene blue from aqueous solutions were carried out using the obtained carbon as adsorbent. Equilibrium and kinetic experiments were conducted. The equilibrium data were fitted with the Langmuir, Freundlich and Temkin theoretical isotherm models. The best results was obtained in the case of Langmuir model, which indicates that monolayer adsorption occurs on finite number of the active adsorption sites on the carbon surface. The kinetic data were fitted with pseudo-first, pseudo-second, Elovich and interparticle diffusion model. Pseudo-second order model and Elovich model showed the best results of the kinetic data. The increasing of the solution pH led to a higher uptake of methylene blue due to the fact that competitive adsorption of methylene blue cation and proton exists in acidic solutions. The adsorption capacity for methylene blue in equilibrium study was significant (168.93 mg g-1). Comparison of the adsorption capacities of methylene blue onto activated carbons derived from various alternative precursors proves chestnut kernel to be efficient and low-cost material which could be substantially deployed in the future.

In this paper the influence of the formic and oxalic acids, as substances for dyebath pH adjusting, on the dyeability of polyester fabric dyed with disperse dye Disperse Yellow 23 was examined. The polyester undyed knitwear samples were dyed in baths containing the acids under the same dyeing conditions. Color differences of the samples were assessed using the reflectiometry technique and expressed in terms of CIELcoordinates. The influence of the tested acids on the surface structure of dyed polyester fibers was examined using the scanning electron microscopy (SEM). It was found that the differences in obtained dyeabilities, in the presence of both formic and oxalic acid, are acceptable according to both M&S 83A and CMC (2:1) standards which was not the case with acetic acid. Therefore, acetic acid can be replaced with either formic or oxalic acid as substances for dyebath pH adjusting in the dyeing process described in this paper. SEM micrographs showed small differences in the surface structure of dyed fibers, as well as differences in the shape of undyed samples? reflectance curves in presence of the acids. Since all of the color differences were quite small, it can be concluded that the influence of formic and oxalic acids on the polyester knitwear dyeability is not significantly different than that of acetic acid.

Low solubility of SiO2 and its occurrence in geothermal waters in the form of ionic, colloidal and suspended state are the main cause of the solid deposit occurrence. Certain chemical types of silica, under the influence of Fe2+, Al3+, F?, OH- ions and other micro-constituents, and due to significantly decreased solubility of SiO2, stimulate nucleation, particle growth and solid deposit formation. The aim of this paper is to inhibit the process of nucleation and solid deposit formation by adding originally designed inhibitor in the form of an emulsion, when the total concentration of the present and added colloidal SiO2 is beyond the solubility limit (120 mg/dm3). By turbidimetric, SEM, EDS and XRD analysis, the processes of solid deposit formation were investigated in Vranjska Banja (Serbia) spa geothermal water source (water hardness of 4?dH), and theoretical and practical conclusions were made.

In this study the influence of the different fluorescent brightener Periblanc BA concentrations on the degree of knitted cotton fabric whiteness was investigated. Two consecutive experimental runs were performed. The first was the bleaching of the knitted cotton fabric with hydrogen peroxide using the methods of two and single bath exhaustion while the second was the optical bleaching with fluorescent brightener Periblanc BA using the exhaustion method. CIE Whiteness Index and Tint value were measured on the Color-Eye 3000 spectrophotometer at the standard illuminant D65 (Ice-Texicon, d/8, D65/10?) while K/S values were determined using the Kubelka Munk equation. The results show that cotton fabric bleached with fluorescent brightener Periblanc BA after bleaching with hydrogen peroxide using two bath exhaustion method has higher degree of whiteness (118.8) with a reddish tint in comparison to the one bleached with hydrogen peroxide using single bath method (106.1).

Cones of the European Black pine and Horse chestnut kernel, regarded as brown municipal waste, was utilized in this work as a precursor for powdered activated carbons. Chemical activation was employed at 500?C in inert atmosphere of nitrogen. Standard physico-chemical analyses were performed to examine obtained products. FTIR method was employed to determine fuctional groups which were found to be typical for activated carbons. Acidic oxygen groups were quantitatively determined using Boehm titrations. It was established that carboxylic groups on pine cone activated carbon, and phenolic groups on chestnut kernel activated carbon were dominant from all acidic oxygen groups. Since both contact pH and pHPZC were determined to be fairly acidic, it could be concluded that obtained activated carbons belong to L-type. Shape and layout of micrometer dimensioned particles were observed by scanning electron microscopy. Particles of different shapes and dimensions along with small cracks and wide crevices and voids were noticed. Textural analysis was used to determine specific surface area and pore distribution of obtained activated carbons. Obtained products possess highly developed surface area and wide pore distribution.

Kaolinite and bentonite clay powders mixed with active additives, based on Mg(NO3)2 and Al(NO3)2, sintered at high temperatures produce very porous ceramics with microcrystalline and amorphous regions and highly developed metalized surfaces (mainly with magnesium surplus). Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. The ceramics samples were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction analysis (XRD) and IR spectroscopy analysis, prior and after treatment in ?synthetic water?, i.e. in aqueous solution of arsenic-salt. Grain size distribution for untreated and treated samples was done with software SemAfore 4. It has shown great variety in size distribution of grains from clay powders to sintered samples.

Manganese is frequently present at elevated concentrations in both surface and groundwater. In addition, manganese is a health hazard, highly soluble over a wide pH range and difficult to remove from the contaminated waters. It was observed that during the interaction of Mg-enriched kaolinite-bentonite ceramics (2 wt% of Mg and Al surplus each) prepared in this work, with manganese aqueous solutions (530 μg L−1–530 mg L−1 of Mn(II)) the manganese concentration decreases. It appears that these changes of metal concentration are on account of manganese deposition on the ceramics surface. The interaction of the ceramic samples prepared at 800°C with the manganese aqueous solutions for 24 h reduced manganese concentration up to 80%.

Arsenic is a naturally occurring element in water, food and air. It is known as a poison, but in very small quantities it is showed to be an essential element. Actual problem in the world is arsenic removal from drinking water using modern and alternative technology, especially because EPA's and other international standards have reduced MCL from 50 to 10 ug/1. Because of rivers and lakes pollution, in a number of plants for natural water purification, average concentrations of arsenic in water are up to 100 ug/1. According to MCL, present technologies are unadjusted for safely arsenic removal for concentrations below of 10 ug/1. This fact has inspired many companies to solve this problem adequately, by using an alternative technologies and new process able materials. In this paper the observation of conventional and the alternative technologies will be given, bearing in mind complex chemistry and electrochemistry of arsenic, formation of colloidal arsenic, which causes the biggest problems in water purification technologies. In this paper many results will be presented, which are obtained using the alternative technologies, as well as the newest results of original author's investigations. Using new nanomaterials, on Pilot plant "VALETA H2O-92", concentration of arsenic was removed far below MLC value.

The present paper describes the assessment of colour parameters of industrial paints for horizontal signalization (designed as POM S1 and POM S2 / ZEB 1 and ZEB 2) of white colour hue, coming from two different producers ("Pomoravlje" and "Zorka") with reference to an independent sample (IND 0) and some physical properties of each sample. Colorimetric characterization of samples was performed using a reflectance spectrophotometer "Update Colour Eye 3000". Standard and modified test methods (ASTM) were performed to establish physical properties of the paints. The industrial paints show better values for the investigated parameters and properties and satisfy standards prescribed by law. POM S2 sample with dry film thickness, similar to the same of other samples, provides the best physical features maximizing quality and minimizing protection cost.

Scanning electronic microscope JSM-5300 (JEOL, Japan) has been used to investigate the structure of the PES fibers upper layers. Preparation of samples was performed by placing them on an aluminium support, with a glue or double-sided adhesive tape. The tool for spreading the conductive layer on the sample's surface, used in this work, was JFC-1100E ION SPUTTER (JEOL Co., Japan). Potential difference of electron acceleration was 30 kV, and multiplication of the samples was 3500 times. ORWO NP 20 DIN films were used for taking the photos. The samples were dyed with C.I.D. Yellow 23, in concentration of l%, at pH = 4.5, with the following acids added: acetic formic and oxalic. The results show absence of any internal damage in fiber structure. On the surface however, groups of particles have been observed varying in shape, magnitude and spacing density. Organic (acetic, formic and oxalic) acids used in the experiments caused differences in upper layers structures of dyed PES fibers. This is the main reason to induce differences in color (DE), chromaticity (DH) and lightness (DL), among the samples (with the all acids included) and a standard (addition of acetic acid only).

The aggregation of soil humic acid (HA) after addition of cations was investigated by nephelometric measurements of HA solution turbidity. Here we show that aggregation is promoted by the presence of positive ions in the solution and that the order of increasing effectiveness in turbidity follows Schulze-Hardy rule. Also, the obtained results indicate that the cation with the largest ionic radius within a common valence is the most effective coagulant. Influence of unions follows the sequence: chloride < nitrate < sulphate, but it is insignificant comparing the influence of cation. This confirms that HA molecules are of negative charge.

Microalloyed and alloyed aluminium-silicate ceramics represents multiphase and multifunctional solid-solid system. The microstructure of aluminium-silicate ceramics matrix is arranged with favorable relationship between crystallinity and amorphousness. Numbered physical processes and interactions take place in very complex intergranular and interphase areas, making new boundaries and regions with fractal nature. Fractal nature of grains contours, macro, mezzo and micro pores and nanostructure phases at grain boundaries make this ceramics an active dielectric material. The synergistic effect of additives, dislocations and impurities leads to dislocations movement at grain boundaries and fragmentation of existing grains in a large number of micrograins with distinct fractal nature. Hence, permanent change of micromorphology occurs in intergranular area. Fractal analysis of intergranular microstructure has included application of Minkowski layer, correlated with fractal dimension. It represents convex layer of grains contour roughness and irregularity, determined in accordance with grain contours fractality. The introduction of fractal microstructure analysis allows better interpretation of many physical and physico-chemical processes, bearing in mind that Minkowski layer defines grains contact probability. (C) 2015 Elsevier B.V. All rights reserved.

In this paper, the steel active-passive anticorrosive protection was done. Steel plates samples with dimensions 40 ?100 ?2 millimeters were used. Samples surfaces preparation was done by degreasing, then by sandblasting by pneumatic pistol. The metallising by molten metal was done by hand pistol which worked with metal vein "Protector" (? 3,18 millimeters) of electrochemical active anode material on the basis of microalloyed aluminum. The mentioned application was done twice and obtained layer thickness was 150-200 micrometers. After this operation, organic coating "Vinilpom", the product of Coatings Industry "Pomoravlje", was applied. Coating quality was followed by measuring of coating thickness, of dried film hardness, level of connecting with a base and of gloss. Whole composition steel - "Protector", organic coating electrochemical study was done by measuring of galvanic team electrochemical potential change in 20% NaCl solution, during the time.

Carbon cryogel (CC) has been prepared through sol gel polycondensation of resorcinol with formaldehyde in basic aqueous solution followed by freeze-drying and carbonization. Porous properties of CC analyzed by gravimetric McBain method confirmed the expected surface area and degree of mesoporosity. Obtained powdered material was used for the removal of pesticide imidacloprid from aqueous solutions under regular batch adsorption procedure. A set of several isotherm models including Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Brouers-Sotolongo, Redlich-Peterson, Sips, Toth, Jovanovic, Hurkins-Jura, Halsey and Radke-Prausnitz model was used for nonlinear fitting of equilibrium data. Several models fitted with quite high correlation coefficients. Bangham and Elovich model fitted suitably for kinetic study indicating that pesticide diffusion into carbons pores is important step which dictates the process rate. Suitability of kinetic models decreased with the increase in adsorbent dosage. Imidacloprid uptake was not influenced by the solution pH.

In this paper, electrophysical properties of porous alumo-silicate ceramics, modified by alloying with magnesium and microalloying with aluminum, were investigated. Complex multiphase system, as active microalloyed ceramics, has specific behavior under influence of external electrical field, which involves changes of dielectric losses and impedance, depending on frequency and temperature. Dielectric properties were measured in the frequency range 20 Hz - 1 MHz. Values for permittivity (er) ranged between 140 - 430. Order of magnitude for electrical resistivity was about 106 Ωm, for impedance 104 - 108 Ω, and loss tangent had values about and greater than 0.05. Current flow through active dielectric takes place through dielectric barrier and throughout conduction bands of thin aluminum and magnesium metal films. Permittivity has nonlinear distribution and complex functional dependences because of significant nonhomogeneity of active microalloyed ceramics. Lower values of electrical resistivity are the result of complex electron and ion transfer of charge through solid phase and pores, with decreased potential barriers height, due to the influence of additives, ingredients and defects. [Projekat Ministarstva nauke Republike Srbije, br. III 45012 i br. ON 172057]

© 2012 Ranđelovic et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. New Composite Materials in the Technology for Drinking Water Purification from Ionic and Colloidal Pollutants

The purpose of this paper was to determine the unknown concentration of dichlortriazinyl reactive dyes, namely Reactive Yellow 22 and Reactive Blue 163, in dyed cotton fabric. The samples of cotton fabric were dyed individually with each dye as well as with a mixture of two dyes. The unknown concentrations of dyes were determined by measuring the corresponding reflectance values of dyed fabric samples and then using the relation between the concentration and reflectance values of the samples. The method set by Kubelka and Munk was used. The accuracy and repeatability of the concentrations determination were calculated by the statistical processing of the data obtained by measurements. Relative errors of individual determination of Reactive Yellow 22 and Reactive Blue 163 were 3.66% and 5.94% respectively. Relative errors in determination of Reactive Yellow 22 and Reactive Blue 163 in a mixture were 3.47% and 3.19% respectively. The results showed that reflectance spectrophotometry can be successfully used as the method for concentration determination of Reactive Yellow 22 and Reactive Blue 163 in dyed cotton fabric and can therefore be applied as the shade control method in dyeing.

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0-7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. + 1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25-44.20 mu g mL(-1) (1.77 x 10(-4)-5.05 x 10(-6) mol L-1), showing-for the first time-the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination. V tomto sdělení jsou shromážděny výsledky z voltammetrických studií s herbicidem Linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methyl-močovina] získané na uhlíkové pastové elektrodě obsahující trikresyl-fosfát (TCP-CPE) jako kapalné pojivo. Byly optimalizovány zásadní experimentální podmínky, jako vliv pH ověřovaný v Britton-Robinsonových pufrech (pH 2 až 7), charakteristiky píků sledovaného analytu, nebo přístrojové parametry pro použitý měřící mód diferenčně pulsní voltammetrie. Jak bylo zjištěno, nejlepší elektroanalytická výkonnost elektrody TCP-CPE byla dosažena při pH 2, kdy byl oxidační pík Linuronu zaznamenán při cca +1,3 V vs. SKE. Vyvinutý analytický postup nabízí dobrou linearitu v koncentračním rozsahu 1.25–44.20 μg mL−1 (tj. 1.77×10−4–5.05×10−6 mol l−1), což dokládá vůbec poprvé využitelnost elektrody TCP-CPE pro anodické oxidace v přímých voltametrických měřeních (bez nahromadění). Metoda byla poté ověřována na stanovení Linuronu v modelovém vzorku říční vody (s přidaným analytem) a v komerčním preparátu, kdy získané výsledky souhlasily s referenčním stanovením pomocí HPLC/UV.

Lagenaria vulgaris (LV) shell was used as a biosorbent for the removal of heavy metal ions, Pb2+, Cd2+ and Zn2+, from aqueous solutions. Experiments were carried out under batch conditions. The effects of contact time, initial pH, temperature and stirring speed on removal efficiency are presented. Sorption of the investigated metals was fast, reaching equilibrium after about 5 to 10 min, depending on the metal. Biosorption was highly pH-dependent, and the optimal pH for investigated metals was in the range of 4.5 to 6.0. The effects of temperature demonstrated that biosorption of the metals is a chemical process. SEM analysis revealed interesting morphological changes after acid refinement of the raw biosorbent and metal uptake that is related to the chemical nature of the biosorption process. EDX analysis of Lagenaria vulgaris biosorbent (LVB) before and after metal sorption revealed that the ion exchange mechanism was the principal sorption process. Fourier transform infrared spectroscopy (FTIR) analysis has shown that major functional groups (carboxyl and hydroxyl) on the biosorbent surface took part in the metal ion uptake process as active sites. The results obtained showed that Lagenaria vulgaris based biosorbent could be used as an effective and low-cost pre-treatment step for removal of toxic metals from wastewaters .

The addition of Mg2(NO)3 and some active additives, composed of Al salts, to the mixtures of kaolinite and bentonite can provide clay compositions which, after sintering at high temperatures, produce very porous ceramics with microcrystalline and amorphous regions and highly developed metalized surfaces (mainly with magnesium surplus). Characterization of sintered samples was done before and after treatment in ?synthetic water?, i.e. in aqueous solution of arsenic-salt. Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. Electrical characterization was estimated by determining dielectric constant and electrical resistivity in function of active additives amount and sintering temperature. Fractal analysis has included determination of grain contour fractal dimension.

This paper analyzes the conditions for membrane extraction of pesticides using ACD / LABS 12 program. The program contains a large database of more than 2000 compounds and their ionized species, for determining the pKa, further analysis includes 600 new compounds confirmed by Hammett?s equation, which gives more precise values for logD and solubility. The 16 pesticides of different classes (organophosphates, carbamates, carbamidas, neonicotinoids etc.) and polarities commonly used in Serbia were examined. The program is used to calculate logD, pKa and solubility at different pH values for the mixture of pesticides. Based on the calculated values, the conditions for the extraction of pesticides in water using two-phase liquid-liquid membrane extraction were optimized.

Mg-enriched kaolinite–bentonite ceramics prepared in this work exhibited very porous and non-uniform structures, with grain sizes ranging from 1 to 20 µm. During the interaction of this ceramics with aqueous solutions of Na 2 HAsO 4 ·7H 2 O, it was observed that the concentrations of Na, K, Ca and Mg in the ceramics and arsenic concentration in the solution decrease. These changes of metals concentrations in the ceramics and arsenic concentrations in water solutions appear to be on the account of arsenic deposition into the ceramics surface. The interaction of the ceramic samples prepared at 600 °C and 800 °C with used arsenic aqueous solutions reduced their arsenic concentration about 70–90%.

Isolated soil humic acid (HA) and commercial Aldrich HA were derivatized by esterification with methanol-thionyl and acetylation with acetic anhidride, in order to obtain derivatives with selectively blocked carboxyl and phenol groups, respectively. Results obtained by FT-IR spectroscopy and potentiometry show that the methanol-thionyl procedure is a selective, specific and efficient route for blocking carboxyl groups. The good correlation between results obtained by direct potentiometry after HA esterification and by classical calcium-acetate and baryta exchange methods suggests that esterification followed by direct acid-base potentiometric titration can be used as a method for the estimation of carboxyl and phenol group contents. Phenol groups can not be specifically identified by the acetylation method, due to the low selectivity of the acetylation method. The average values of apparent and intrinsic pK of underivatized and derivatized HAs confirm decrease in ionizable groups content due to derivatization and their values are related to the different chemical structures of the acids.

A direct potentiometric titration method was applied to commercial and soil humic acids in order to determine their carboxyl and phenol group concentrations and apparent and intrinsic pK. In that context, acid-base properties of humic acids are interpreted by selective blocking of carboxylic and phenolic groups by esterification and acetylation. Differences in underivatized and derivatized HA's acid-base properties are ascribed to carboxyl and phenol groups influence on total humic acidity. Potentiometric data were treated with the modified Henderson-Hasselbalch equation. Infra red results, the acidic group contents and the average values of apparent and intrinsic pK for underivatized and derivatized HAs confirmed the selectivity of esterification derivatization method. After blocking of the functional groups, the values of acidic group contents decreased, while the value of apparent pK increased after derivatization. Phenol groups cannot be specifically identified by the acetylation method, due to low selectivity of the acetylation method.

This paper deals with Cr(VI) ion removal from water, by micro-alloyed aluminium composite (MAlC), under flow conditions. In a water environment the MAlC acts as a strong reducing agent. Dissolving it in water is accompanied by the generation of Al(III) ions and reduction of water to H2, with OH- ions. The final product is insoluble Al(OH) 3. A series of Cr(VI) model solutions, with initial pH ranging between 1 and 5, were treated in the original semi-flow system (SFS), which simulated flow conditions well. The results demonstrate a high MAlC efficacy, considering that at the end of the treatment, concentrations of Cr(VI) were below the maximal allowed concentrations for drinking water, in all model solutions. The MAlC mechanism of action is based mainly on processes of reduction and co-precipitation by Al(OH) 3, because Cr(VI) is removed from the water phase as metal chromium and insoluble Cr(OH) 3. Behaviour of the composite in water is under significant influence of pH, which affects its efficacy and mechanism of action. Therefore, the rate of Cr(VI) removal is greater at the beginning, decreasing towards the end of the treatment. Additionally, the ratio of [metal chromium]/[Cr(OH) 3] in precipitate, at the end of the treatment, decreases with increasing initial pH of the model solution. Application of the SFS significantly enlarges efficacy of the MAlC, compared to work under stationary conditions. WaterSA Vol.30 (3) 2004: 353-359