Different Classes Of Water Research Articles

Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters.

The increase of the global population and shortage of renewable water resources urges the development of possible remedies to improve the quality and reusability of waste and contaminated water supplies. Different water pollutants, such as heavy metals, dyes, pesticides, endocrine disrupting compounds (EDCs), and pharmaceuticals, are produced through continuous technical and industrial developments that are emerging with the increasing population. Molecularly imprinted polymers (MIPs) represent a class of synthetic receptors that can be produced from different types of polymerization reactions between a target template and functional monomer(s), having functional groups specifically interacting with the template; such interactions can be tailored according to the purpose of designing the polymer and based on the nature of the target compounds. The removal of the template using suitable knocking out agents renders a recognition cavity that can specifically rebind to the target template which is the main mechanism of the applicability of MIPs in electrochemical sensors and as solid phase extraction sorbents. MIPs have unique properties in terms of stability, selectivity, and resistance to acids and bases besides being of low cost and simple to prepare; thus, they are excellent materials to be used for water analysis. The current review represents the different applications of MIPs in the past five years for the detection of different classes of water and wastewater contaminants and possible approaches for future applications.

A statistically coherent robust multidimensional classification scheme for water

Serious limitations of the existing water classification schemes prompted us to propose a new statistically coherent water nomenclature system. An extensive database of ionic charge-balanced concentrations of 8 elements (4 cations Ca, Mg, Na, and K; and 4 anions SO4, Cl, HCO3, and CO3), in 46,292 multivariate outlier-free simulated samples, was used for training the multidimensional classification system. The initial assignment for 16 classes was achieved from the greater molar concentration concept of each cation and anion, called the Greater molar conc model. Seven hybrid log-ratios (hlr) from 8 elemental concentrations were used for linear discriminant analysis (LDA) and canonical analysis to propose 16 multidimensional discriminant functions from the 7 hlr model. The LDA and canonical analysis were also performed on the initial molar concentrations of 7 elements, without any log-transformation, which was designated as the 7 M conc model. The robustness of these three classification systems (7 hlr, 7 M conc, and Greater molar conc) was tested against analytical uncertainty propagation and mineral-water interaction effects. The 7 hlr model, due to its higher robustness, was considered as the best option for the nomenclature of the 16 types of water. From the probability concept, it was possible to identify hybrid water types, along with the basic or primary types of water. Our water classification scheme (7 hlr model under the “basic+hybrid” option) can classify as many as 256 different classes of water. Due to the clearly high complexity of the proposed classification scheme, we developed a new online computer program WaterMClaSys_LDA (Water Molar Classification System from Linear Discriminant Analysis) available at our web portal http://tlaloc.ier.unam.mx, for use by anyone after registration and log-in. The usefulness of the new classification scheme is illustrated by applications to groundwater, lake water, and geothermal water samples from South India, Mongolia, and western Turkey, respectively.

Qualitative Assessment and Typology of the Water Resource Used for the Production of Drinking Water in Duékoué, Western Côte d’Ivoire

The objective of this study was to evaluate the typology of water through physicochemical and bacteriological characterization with the aim of highlighting its vulnerability as a drinking water resource. The methodology adopted was to evaluate the level of pollution by monitoring the spatiotemporal variation of the water pollution indicator levels of Lake Dohou. The sampling frequency is monthly for one year, from November 2017 to October 2018, in order to obtain a fairly representative image of water quality and its seasonal evolution in eight (8) well-defined stations. The parameters were determined using the standard methods defined by the French Association for Standardization (AFNOR). This study shows that the waters are acidic, with an average pH of 5.81 and a low electrical conductivity of between 42.67 ± 4.30 and 59.62 ± 21.84 μS.cm-1. At all stations, seasonal mean water transparencies are low (<1 m). It is also noted that 99.7% of the water samples collected had total nitrogen (TN) levels above the limit of 4 mg.L-1. All of the lake’s waters have non-compliant BOD5 (<3 mgO2.L-1) for raw water intended for the production of drinking water. Sites D6 and D7 have COD/BOD5 ratio greater than 3, which indicates the presence of non-biodegradable organic matter in these areas. Total coliforms, Escherichia coli and Enterococci were present in 100% (28/28) water samples at concentrations ranging from 2300 to 173,000 CFU/100 mL, from 100 to 1650 CFU/100 mL and from 20 to 1140 CFU 1/100 mL respectively. For Salmonella pathogens, they were detected in 50% of the dry season samples and in 100% of the rainy season samples. This almost permanent presence of this pathogenic germ denotes a poor quality of water with reference to this parameter. The presence of total coliform and other microbial contaminants suggests that supplied water is highly contaminated with pathogens and great reservoirs for them. Principal component analysis (PCA) of the physicochemical data set allowed defining three different classes of water on the Dohou Lake. Outside the upstream zone (D6 and D8), water could continue to be used for the production of drinking water.

The bacteriological quality of different brands of bottled water available to consumers in Ile-Ife, south-western Nigeria.

BackgroundThe upsurge in the demand for bottled water has prompted the interest of many manufacturers in the production of bottled water and very many water bottling companies are therefore involved in its production. These range from large scale multinational companies to medium scale business enterprises, institutional and government business investment companies as well as small scale entrepreneurs. There is however little information on the comparative quality of bottled water brands produced by different classes of water bottling companies in Nigeria. This study was undertaken to determine the bacteriological quality of brands of bottled water available to consumers in Ile-Ife.MethodsForty-three samples of bottled water comprising of three batches each of thirteen bottled water brands and two batches of two brands were purchased and analyzed for total bacterial count, presence of coliform and the presence of other bacterial indicators of drinking water quality.ResultsOnly 67.4% of the water samples representing the products of 10 companies or 66.7% of the brands had heterotrophic counts within the acceptable limits. Coliforms present in 100 ml of water were detected in 26.7% of the bottled water brands. Other indicator organisms detected included Staphylococci isolated from 27.9% of the samples (33.3% of the brands) and specifically Staphylococcus aureus found in four brands constituting 14% of the samples. Pseudomonas strains were consistently detected in consecutive batches of three brands of the water samples.ConclusionsBottled water samples produced by the large scale multinational producers were of acceptable bacteriological quality unlike those produced by most small companies. Significance and Impact of Study: There is need for a greater control of water bottling processes carried out by commercial bottled water producers in Nigeria.

Data mining for environmental analysis and diagnostic: a case study of upwelling ecosystem of Arraial do Cabo

The Brazilian coastal zone presents a large extension and a variety of environments. Nevertheless, little is known about biological diversity and ecosystem dynamics. Environmental changes always occur; however, it is important to distinguish natural from anthropic variability. Under these scenarios, the aim of this work is to present a Data Mining methodology able to access the quality and health levels of the environmental conditions through the biological integrity concept. A ten-year time series of physical, chemical and biological parameters from an influenced upwelling area of Arraial do Cabo-RJ were used to generate a classification model based on association rules. The model recognizes seven different classes of water based on biological diversity and a new trophic index (PLIX). Artificial neural networks were evolved and optimized by genetic algorithms to forecast these indices, enabling environmental diagnostic to be made taking into account control mechanisms of topology, stability and complex behavioral properties of food web.

Towards elucidation of the drug release mechanism from compressed hydrophilic matrices made of cellulose ethers. I. Pulse-field-gradient spin-echo NMR study of sodium salicylate diffusivity in swollen hydrogels with respect to polymer matrix physical structure

Cellulose ethers have been increasingly used in the formulation of controlled release dosage forms; among them, compressed hydrophilic matrices for the oral route of administration are of special importance. Much interest has also been expressed in the study of the drug release mechanism from such swellable systems, in particular, in trying to explain deviations from Fickian diffusion. Thus, swelling-controlled transport is often invoked without any rationale. It is the purpose of the present work to provide independently determined diffusivity data for elucidating the drug release mechanism from the water-soluble cellulose derivatives. In the first part of this work, pulsed-field-gradient spin-echo nuclear magnetic resonance (PFG-SE NMR) was used to investigate the self-diffusion of the model solute sodium salicylate and, incidentally, that of water, in hydrogels made of hydroxypropyl methylcellulose (HPMC), hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC) of varying polymer weight fraction and molecular weight in D 2O. In parallel, the extent of bound water in the gels was determined using differential scanning calorimetry (DSC), and the presence of liquid crystals in the gels was examined by polarized light microscopy, as these are the structural factors capable of affecting drug diffusion. Solute diffusivity was not significantly affected by the substitution type of the cellulose ether, and an exponential polymer weight fraction dependence of the solute's self-diffusion coefficient was observed, ascertaining the validity of the free-volume theory, with extrapolated self-diffusion coefficient values similar to those in pure solvent. This also indicates that diffusion also takes place in the so-called bound water (which represents about 40% of the hydrogel weight). This questions the existence of thermodynamically different classes of water. Slightly reduced solute diffusion was measured in the HPC hydrogel of the highest polymer concentration (45 wt.%) where a liquid crystalline mesophase was observed. This structural factor could be of importance, especially in consideration of hydrogels of higher polymer fractions. The polymer molar mass (viscosity grade) of the cellulose ethers also did not affect solute self-diffusivity. The polymer matrix displayed the same retarding effect at equal weight fraction. This confirms that solute molecules can only diffuse in the void space occupied by the solvent. Solute self-diffusivity is dictated by the microviscosity of the system, i.e., the solvent viscosity, with the polymeric matrix increasing only the diffusion pathlength. Overall, because of the similar retarding effects of the hydrated cellulose ether network, at least at the polymer concentrations tested, it would be unwise to ascribe observed differences in drug release kinetics from this type of swellable system to differences in solute diffusivity in the hydrated gel layer (see Part II of the work [J. Control. Release, to be submitted]).

Hard-to-remove water in cellulose fibers characterized by thermal analysis: A model for the drying of wood-based fibers

A new parameter, hard-to-remove (HR) water content, was recently defined as the moisture ratio at the onset point between the constant and falling rate zones in an isothermal cellulose drying process and was further investigated with differential scanning calorimeter (DSC) characterization in this study. The linear relationship between the HR water content and the water retention value (WRV) was explained by the combined results of thermogravimetric analysis (TGA) and DSC. The drying order of different classes of water was quantitatively verified. We found that free water was evaporated first, followed by trapped water, freezing-bound water, and then nonfreezingbound water, with some overlap. This was found for bleached, unbleached, and mechanical pulp. It was also found that the HR water mass is a combination of trapped water, freezing-bound water, and nonfreezing-bound water. Trapped water could be described as water that is not bound to the fibers, but is difficult to evaporate. For the pilot paper machine samples, all the water in the wet web after pressing and entering the dryer section, was found to be entirely HR water with no free water detected. Based on the results, a qualitative drying model of cellulose fibers is proposed with regard to decreasing moisture ratio. This model is valid for different types of wood-based cellulose fibers.

An Investigation of the Discrete and Continuum Models of Water Behavior in Hydrogel Contact Lenses

To investigate the water behavior in hydrogels of differing equilibrium water content (EWC) and to use these results to investigate the opposing discrete model (thermodynamically different classes of water exist in hydrogels) and continuum model (water behaves as a consequence of nonequilibrium conditions) of nonfreezing water in swollen hydrogels. Differential scanning calorimetry (DSC) was used to obtain melting thermograms for five lenses of each of 12 hydrogel lens types. The gravimetric content of the nonfreezing water was subsequently determined from an integrated endotherm for water. The effect of anneal time on the amount of nonfreezing water obtained in samples was investigated before undertaking these measurements. The glass transition temperature (Tg) of each of the lens types was obtained with DSC to investigate how the Tg was related to the amount of nonfreezing water found in the hydrogels. Melting enthalpy increased with increasing anneal time and leveled off at 6 hours. Low-EWC lenses showed endotherms with a single melting peak at 0 degrees C. Materials with a higher EWC showed more complicated melting endotherms, with a broad shoulder occurring at temperatures below 0 degrees C. There was a statistically significant positive correlation between EWC and freezing water (R=0.95, P<0.0001), but the amount of nonfreezing water was similar for all lens materials. There was a statistically significant positive correlation between the Tg of the hydrogels and the theoretically derived weight fraction of nonfreezing water in the hydrogels required to bring the Tg of the gels down to 0 degrees C (R=0.99, P<0.0001) but not with the experimentally derived values (R=0.29, P=0.07). Low-EWC hydrogels have the lowest free-to-bound water ratios. That the experimentally derived values of nonfreezing water are different from the theoretically derived values creates doubt with the continuum model theory. The best model probably employs a combination of the discrete and continuum theories.

Sorption isotherms, GAB parameters and isosteric heat of sorption

AbstractThe diffusion–sorption drying model has been developed as a physics‐based way to model the decreasing drying rate at low moisture contents. This new model is founded on the existence of different classes of water: free and bound water. The transition between these classes and the corresponding thermodynamics form distinct components of the drying model. This paper shows that the characteristics of the different classes of water and of the transition between them can be deduced from the GAB sorption isotherm. The parameters in the GAB sorption isotherm support the theory of localised sorption, establishing the existence of different classes of water. Moreover, the sorption mechanism retrieved from the GAB parameters is in accordance with the sorption mechanism, which is obtained from the moisture dependence of the net isosteric heat of sorption. This holds for experimental sorption data of corn and starch as well as for literature data on five vegetables and four fortified cassava products. An extremum in the net isosteric heat of sorption coincides with the transition between bound and free water, and the partition moisture content corresponds with the monolayer value derived from the GAB equation. This confirms that the GAB monolayer value can be chosen as model boundary between bound and free water. Moreover, it reveals that this method can be developed into a technique to estimate the bound water content in foods. Copyright © 2005 Society of Chemical Industry

Effect of kappa-carrageenan on the properties of poly(N-vinyl pyrrolidone)/kappa-carrageenan blend hydrogel synthesized by γ-radiation technology

A series of hydrogels in the form of rods were prepared from kappa-carrageenan (KC) and poly (N-vinyl pyrrolidone) (PVP) by gamma radiation with 60Co γ source at room temperature. The properties of the prepared hydrogels, such as the gel strength, gel fraction and swelling behavior were investigated. Incorporation of KC into the PVP/water system increased obviously the gel strength and equilibrium degree of swelling (EDS) of PVP hydrogel. The experimental analyses showed that the crosslinking reaction of PVP was quicker than the degradation of KC at a low dose (less than 30 kGy), and the degradation of KC was inhibited in the PVP/KC mixture system. So an interpenetrating polymer network (IPN) hydrogel composed of PVP (a chemical crosslinking network) and KC (a physical crosslinking network) was proposed here. The existence of different classes of water in this IPN system was shown by water melting curves using DCS.

Water in Wool

The polymer absorption model developed by Vrentas and Vrentas is applied to the wool/water isotherm. In principle, all parameters in this model can be determined independently of sorption behavior so that a genuine prediction can be made. This model emphasizes the role of the glass transition in generating the sigmoidal shape of the absorption isotherm. By applying an extended version of the model and thermo dynamic data obtained from the literature to the wool/water isotherm, a reasonable fit to experimental data is achieved. Sorption behavior at higher temperatures is also rea sonably well predicted. The influence of the glass transition in restricting the rate of water crystallization during cooling is used to reinterpret the results of a previous study using differential scanning calorimetry (DSC). This study concluded that three different states of water may exist in wool, cotton, and silk, i.e., free water, freezing bound water, and nonfreezing bound water. However, an alternative and more plausible in terpretation for the Dsc behavior recognizes the influence of the glass transition, and the appearance of freezing bound water coincides with the depression of the glass transition to just below O°C. Thus, the DSC data do not support the presence of different classes of water in wool.

Modification of the dynamic swelling behaviour of poly(2-hydroxyethyl methacrylate) hydrogels in water through interpenetrating polymer networks (IPNs)

Interpenetrating hydrogel networks based on poly(vinyl alcohol) (PVA) and 2-hydroxyethyl methacrylate have been synthesized. Water absorption and desorption properties of these hydrogels were analysed extensively. The influence of solutes (urea, potassium iodide, d-glucose, sodium chloride) on equilibrium water content (EWC) of these gels was also studied. Incorporation of PVA into poly(2-hydroxyethyl methacrylate) in the form of an interpenetrating polymer network (IPN) increases the EWC. The existence of different classes of water in this IPN system is shown by water melting curves using differential scanning calorimetry. The morphological features of these films were studied by scanning electron microscopy.

Do hydrogels contain different classes of water?

In the first part of this article calorimetric studies on poly (hydroxy ethyl methacrylate) (PHEMA) are presented. In the past the irregular melting curves in this type of experiment have been interpreted as evidence for the existence of different types of water in these gels. The studies presented here demonstrate that the occurrence of a glass transition in the freezing hydrogels may be responsible for this irregular melting behavior, and that this behavior is not (necessarily) an indication for the existence of different types of water. In the second part results are shown of measurements of the mobility of water in hydrogels, made by relaxation NMR. These results indicate that very rapid interchange occurs between the water molecules, and they support the conclusion that the calorimetric data mentioned above are not indicative for the existence of different classes of water in hydrogels. These results are compared with data from other fields of science, especially from fundamental freeze drying studies, which support the alternative interpretation of the calorimetric measurements.

Thermal analysis of water in p(HEMA) hydrogels

Hydrogels composed of poly(hydroxyethyl methacrylate) (pHEMA) and water were investigated using differential thermal analysis (DTA) and adiabatic calorimetry (AC). The results show that the crystallization of water in the gels is a very gradual process, leading to the development of a metastable, non-equilibrium state. They are not in agreement with models that assume the actual presence of thermodynamically different classes of water in the gels, based on the abnormal melting behaviour of this water. The results indicate that the internal structure of these gels can be described as that of an elastic solution, in which the water molecules are distributed continuously over all possible orientations to and interactions with the polymer.

Relation between Germination, Trehalose and the Status of Water in Phycomyces blakesleeanus Spores as Measured by Proton-NMR

The distribution and properties of the cellular water in sporangiospores of Phycomyces blakesleeanus were investigated using proton-NMR. In dormant spores different classes of water were characterized by a difference in their transverse relaxation times (T 2). The amount of cytoplasmic water was estimated to be as low as about 700 mg (g dry wt)−1 and its small T 2 (18·2 ms) indicated a very limited mobility. About 10 min after induction of germination (by a heat shockor by addition of 0·1 m-acetate), both the content and the mobility of the cytoplasmic water increased sharply. These changes coincided with a rapid breakdown of most of the cellular trehalose and with the production (and leakage from the spores) of large amounts of glycerol. The role of these biochemical changes is discussed in relation to the water status of the spores.