Chemical Engineering Technology

The results of a set of experiments that were designed to integrate current knowledge on the major constituents of sugarcane bagasse lignin, specifically p-coumaric, ferulic, syringic acids, and vanillin are presented. These aromatic compounds have well-known antioxidant power and they are very important for the food, pharmaceutical, and nutraceutical industries. Following a study on the effect of pH upon the spectra of these monomers and the determination of their pK a values, their self-association properties in ethanol as a solvent, particularly at concentrations < 10 -4 M were investigated using UV spectrophotometry and their K ass values were determined. The results collected allowed to better understand the chemistry of sugarcane lignin and provide a contribution to the possible exploitation of this abundant straw material for the recovery of fine chemicals.

Information accessibility has changed the way that chemical process plants are being managed. The traditional pyramidal hierarchy that is usually the core of any management structure is being threatened by the potential of centralized decisionmaking covering more and more possibilities. But although present tools may have access to any significant piece of objective information, and can process it at growing speeds, they are still termed as ªdecision supportº systems. Sensible decision-making is not only the result of knowledge plus information; it is also important to consider the effects of the different factors that are usually embraced by the term ªhuman factorsº, probably because they are difficult to comprehend and include in a mathematical model. Current research in these areas, usually related to human and/or artificial intelligence, may provide significant advances in the near future.

The recent demand for nanoparticulate products such as viruses, plasmids, protein nanoparticles, and drug delivery systems have resulted in the requirement for predictable and controllable production processes. Protein nanoparticles are an attractive candidate for gene and molecular therapy due to their relatively easy production and manipulation. These particles combine the advantages of both viral and non-viral vectors while minimizing the disadvantages. However, their successful application depends on the availability of selective and scalable methodologies for product recovery and purification. Downstream processing of nanoparticles depends on the production process, producer system, culture media and on the structural nature of the assembled nanoparticle, i.e., mainly size, shape and architecture. In this paper, the most common processes currently used for the purification of nanoparticles, are reviewed.

It is said that oil and gas will be depleting soon. It is known that the conversion of coal produces the most CO 2. It is hoped that the use of alternative raw materials and energy sources is the salvation. Renewable raw materials are thought to be the most apparent alternative-at least if the number of publications and research funding is regarded.

Na-ZSM-5, synthesized using 1,6-hexanediol as the structure directing agent, has been found to have a suitable selectivity and adsorbing capacity for ethanol adsorption from aqueous solutions. In contrast to quaternary ammonium based Na-ZSM-5 zeolites, this Na-ZSM-5 did not show any catalytic interaction with ethanol during thermal desorption. The dynamics of the adsorption process were investigated using the finite volume ªuptake rateº route. The data predicted from the governing relations of the process were correlated with experimental results. The micro-diffusion coefficient was determined as a function of temperature.The macropore diffusional mass transfer contribution for biporous zeolite particles was found to be negligible.

Adsorption of Fe(III) from water was optimized using response surface methodology and artificial neural network. The initial concentration of Fe(III), contact time, and concentration of adsorbent were defined as input variables, while the percentage of adsorbed Fe(III) was labeled as output variable. Bentonite clay served as an adsorbent. The correlation coefficient, root mean square error, and mean absolute error were calculated after fitting the experimental data by the second-order polynomial model at the central composite design (CCD). The multilayer perceptron with architecture of 3-9-1 provided the best performance. A logistic sigmoid was applied as an activation function in the hidden layer, while in the output layer a linear function was used.

Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (ρ P) and particle diameter (d p) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations.

This study evaluates the suitability of using low-grade phosphate for Cu 2+ removal. The study also investigates the effects of the presence of ethylene-diamine-tetra-acetic acid (EDTA), citric acid, tartaric acid and sodium chloride in a solution containing Cu 2+ on the adsorption capacity of Cu 2+ onto low-grade phosphate. For aqueous solutions with 100 ppm Cu 2+ , the percentage removal of Cu 2+ at pH 4 onto 0.2 g of 0.063 mm low-grade phosphate was found to be 96.6 % after one hour. Using one mmol of either Cu 2+ , Cu-NaCl, Cu-tartaric acid, Cu-EDTA, or Cu-citric acid aqueous solutions, the present work shows trend of the percentage removal of Cu 2+ at equilibrium time: Cu 2+ > Cu-NaCl > Cu-tartaric acid > Cu-EDTA > Cu-citric acid. It is also found that increasing the concentration of ligand to copper ratio decreases the percentage removal of Cu 2+ significantly. This means that the adsorption capacity is ligand type and concentration dependent.

The principles of the isochoric method are described, as well as the different variants of this method that can be considered according to the technique used to determine the amount of fluid inside the high pressure cell. An automated isochoric apparatus to measure the density of binary mixtures is presented. Accurate isochoric measurements of density of pure fluids, involving molecules like methanol, and mixtures, such as nitrogen plus methane and a multicomponent system with a composition representative of the U.S.A. commercial Gulf Coast natural gas, are analyzed. Moreover, the effect of the thermal degradation of fluids at high temperatures on the accuracy of the density measurements is also discussed.

The final product quality of crystallization and precipitation processes is often determined by the interplay between mixing and relevant phenomena such as, nucleation, molecular growth, aggregation and breakage. In this work the attention is focused on the aggregation and breakage processes and on the level of details needed to accurately describe them. Different modeling approaches are tested and compared for two different shear devices: a Taylor-Couette cell and a stirred tank. Results show that when aggregation and breakage processes are much slower than mixing a simplified homogeneous model can be used whereas when aggregation and breakage occur on a time-scale comparable with that of mixing then a detailed approach based on computational fluid dynamics (CFD) is needed. The very common lumped model, used to derive kinetic expressions for aggregation and breakage rates, can eventually lead to serious errors.

The powder-particle spouted bed process is one of the semi-dry processes that have been developed for flue gas desulfurization. In this study, which is designed for SO 2 removal by a powder-particle spouted bed, the reaction term is included in one-dimensional and streamtube models that were presented previously for spouted beds. Hydrated lime is used as the sorbent in this process. The predictions of the models are compared with some published experimental data and it is found that the developed models are valid. The results of two models are compared with each other and their various properties are evaluated. The effects of different operating conditions on SO 2 removal efficiency are also investigated and preferred operating conditions are discussed.

Different pyrolysis techniques for converting solid biomass material into liquid fuels that can be used in combustion motors are described and compared. The techniques include fast pyrolysis, pyrolysis in aqueous reaction media and a newly developed process based on a hydrogen donating solvent system and used for converting residual lignin after production of lignocellulosic ethanol production to liquids. New data from pyrolysis in liquid reaction media is presented and discussed. The quality of the oil as produced in the pyrolysis step is evaluated, and the range of different possible applications is emphasized.

Sulphur, one of the oldest inorganic fungicides, is mixed in different formulas with other organic or
inorganic products in order to increase its biological activity and to cover a larger area of different fruit
diseases treatment. In this paper, sulphur, as sulphides, polysulphides and thiosulphates, is one of the main
components in such a microemulsioned formulation, which include both overbasic potassium naphthenates and
oleates. Dilution and carbonation of the microemulsion results in a step-by-step gradual hydrolysis of all
initially stable entities. Organic hydrolysates may cover up any surface with an adherent layer incorporating
inorganic sulphur amorphous hydrolysates. After complete hydrolysis through carbonation most of the sulphur
compounds pass mainly to nanoparticulate elemental sulphur along with other of its neutral or acid salts.
Calcium and magnesium ions from hard dilution waters may contribute to micelle aggregation hydrolysate layer
adherence. This composite fungicide gather some of the most required properties of this class of products:
biological active entities generation as nanosized particulate hydrolysates straight on the surfaces subsequently
their application, amorphous elemental sulphur and sulphur compounds, mixed organic/inorganic micelle
aggregates ready to penetrate plasma cell membranes, etc. The experimental data encompass properties design
and commercial Frucol brand behavior as foliar product.

The selection functions and the breakage distribution functions are based on the experimentally-determined particle size distribution on the basis of comminution of one size fraction particles. Therefore, to obtain a clear picture of the product properties during comminution of the "real" polydisperse sample, a number of experiments are needed. This work introduces the tested methodology for the selection function determination based on the starting and maximal values of the selection function. The principle was tested on the planetary ball mill and the horizontal laboratory ball mill, and according to the results obtained, it can be concluded that the proposed methodology can be useful for the evaluation of the selection function during batch comminution in different mills.

Risk assessment is the tool for maintaining perfect safety management systems and aiding sustainable process design, with hazard identification as the critical step. This step can be executed by past accidents analysis (PAA) to achieve the mentioned objectives. Despite of available analyses, the recurring of accidents identifies the shortcomings in PAA and requires a detailed examination as reported in this review. The intensified exploration of accident information will strengthen both the safety management system at existing facilities and process designing in terms of sustainability. © 2019 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

The reuse of industrial wastes from a coal-fired power plant and a plasma electrolytic oxidation process was attempted to realize a zero discharge. The batch composition was adjusted by adding sodium hydroxide and sodium aluminate. A single-mode microwave oven equipped with reflux condenser was used for crystallization under atmospheric pressure. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, BET, thermogravimetric analysis, and cation-exchange capacity (CEC) measurement. Analytical results indicated that Na-A zeolite with a defined maximum crystallinity could be successfully synthesized by hydrothermal treatment of fly ash with wastewater. Due to the high CEC, the product can be applied for gas purification and soil remediation processes.

Three sorbents were compared in order to determine their potential for oil spill cleanup. Polypropylene nonwoven web, rice hull, and bagasse with two different particle sizes were evaluated in terms of oil sorption capacities and oil recovery efficiencies. Polypropylene can sorb almost 7 to 9 times its weight from different oils. Bagasse, 18 to 45 mesh size, follows polypropylene as the second sorbent in oil spill cleanup. Bagasse, 14 to 18 mesh size, and rice hull have comparable oil sorption capacities, which are lower than those of the two former sorbents. It was found that oil viscosity plays an important role in oil sorption by sorbents. All adsorbents used in this work could remove the oil from the surface of the water preferentially.

A 3-D two-fluid CFD model in the Eulerian-Eulerian framework was developed to predict the hydrodynamics and heat and mass transfer of sieve trays. Interaction between the two phases occurs via interphase momentum and heat and mass transfer. The tray geometries are ...

Rotary desiccant wheels are widely used in dehumidification and energy recovery applications. In this work, we have developed a 2D, steady state model of a rotary desiccant wheel. Mass and energy balance equations for the air streams and the desiccant wheels were developed. The hydraulic diameter and surface area for heat and mass transfer were calculated based on knowledge of the flute geometry. Appropriate correlations for the Sherwood number and Nusselt number were used to estimate heat and mass transfer coefficients. The model is capable of predicting steady state behavior of desiccant wheels having at the most three sections (process, purge, and regeneration). The mathematical model was validated using a real desiccant wheel, and the calculation results are in reasonable agreement with the experimental data. Based on this model, the temperature and humidity profiles in the wheel during both the dehumidification and the regeneration processes are analyzed. The simulated results were used to gain an insight into the operation of desiccant wheels. The model and the presented results will be useful for optimizing dehumidification and energy recovery applications.

A pilot-scale dual fluidized bed combustion system was used for CO 2 capture using limestone sorbent with CaO-CaCO 3 looping. The sorbent was regenerated at high temperature using an air-or oxygen-fired fluidized bed calciner with flue gas recycle firing hardwood pellets. Two limestones were evaluated for CaO-CaCO 3 looping. Changes in the sorbent morphology during the tests were identified by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). Changes in pore size distribution and sorbent surface area that occurred during reaction were determined by N 2 BET porosimetry. Thermogravimetric analysis (TGA) was used to determine the activity of the sorbent after processing in the dual fluidized bed combustion system. It was found that oxygenfired calcination with high CO 2 partial pressure reduced the effectiveness of the two limestone sorbents for CO 2 capture when compared to material calcined under oxygen-enhanced air combustion. A shell 1-2 lm thick, with reduced porosity, was formed around the sorbent particle and is believed to be responsible for reduced conversion of CaO to CaCO 3 . It is believed that ash deposition contributes to the formation of the shell.

catalyst activity was tested for methane steam reforming using two different reaction systems: a catalyst particle bed (0.42-0.5 mm catalyst particles diluted in SiC) with a surface area-to-volume ratio SA/V of 910 m -1 and a porosity e of 52 % and a catalyst-coated metal monolith with an SA/V of 3300 m -1 and an e of 86 %. Under a steam-to-carbon ratio of 2.5 and at a temperature of 700°C, the highest specific reaction rates were found for the catalyst-coated monolith. The high SA/V and e, together with the high rate of heat transfer of the metal monolith were found to be responsible of this optimum behavior. However, in both systems, the Ni-Al 2 O 3 catalyst suffered a catalyst deactivation during operation.

Alkanolamines are the most popular absorbents used to remove CO 2 from process gas streams. Therefore, the CO 2 reaction with alkanolamines is of considerable importance. The aim of this article is to provide an overview on the kinetics of the reaction of CO 2 with aqueous solutions of alkanolamines. The various reaction mechanisms that are used to interpret experimental kinetic data -zwitterion, termolecular and base-catalyzed hydration -are discussed in detail. Recently published data on reaction kinetics of individual amine systems and their mixtures are considered. In addition, the kinetic behavior of several novel aminebased solvents that have been proposed in the literature is analyzed. Generally, the reaction of CO 2 with primary, secondary and sterically hindered amines is governed by the zwitterion mechanism, whereas the reaction with tertiary amines is described by the base-catalyzed hydration of CO 2 .

The metal organic framework CPM-5 (crystalline porous materials) was successfully synthesized and characterized for the first time using microwave irradiation as a rapid and facile synthesis method in about 10 min compared to several days crystallization time required for the conventional solvothermal approaches. Furthermore, CPM-5 produced by microwave-assisted synthesis exhibited a very high surface area of 2187 m 2 g-1 compared to, e.g., 580 m 2 g-1 of the conventionally synthesized samples. Moreover, the as-synthesized CPM-5 showed high carbon dioxide uptake.

The degree of NO x conversion over the SCR catalyst is given as the quotient of gas-chromatographic N 2 peak areas from outlet and converted inlet gas analysis. There is no necessity to transform peak areas into concentrations by additional calibration.

Absorption of SO2, diluted with nitrogen up to concentrations of 500 Pa, was performed at 20 °C and 1 atm, with water and sulfuric acid solutions containing hydrogen peroxide in two different contactors: a packed column and a cable scrubber. The absorption rate was determined for various SO2 partial pressures, as well as different concentrations of sulfuric acid (up to 40 wt %) and of hydrogen peroxide in the scrubbing liquid. It was found that the SO2 absorption rate increases with the hydrogen peroxide concentration, and decreases as the acidity of the scrubbing liquid increases. Taking into account hydrodynamic and mass transfer characteristics of the packing for both scrubbers, a practical enhancement factor depending on the liquid phase H2SO4 and H2O2 contents, was deduced from semi-continuous tests. As a good concordance was observed between results determined for both contactors, a single correlation is proposed, allowing the computation of this kinetic factor for quite simple simulation or design of SO2 scrubbers, provided the gas and liquid phase mass transfer coefficients kGa and kLa are known.

Microfiltrations of Saccharomyces cerevisiae yeast particles of various deformabilities were conducted to examine the blocking mechanism due to particle deposition during the initial stage of the microfiltration process. The S. cerevisiae particles were treated with glutaraldehyde to form particles of various deformabilities. To compare differences in the blocking mechanisms among the different particles during microfiltration, a blocking model was adopted to estimate the filtrate flux, which accounts for initial blocking due to pore obstruction and subsequent blocking due to the growth of a cake over these initially blocked regions. The surface morphology of the cake layer on the membrane surface and the blockage by particles in membrane pores was examined by scanning electron microscopy (SEM). Analysis of the blocking mechanism of particles of varying deformability during microfiltration based on the blocking model indicated that softer particles resulted in more severe pore blocking problems and greater flux decline. A comparison of the theoretical results with experimental observations by SEM showed good qualitative agreement.

The design and construction of a prototype of a dividing-wall distillation column was possible by integrating previous knowledge in process intensification, energy savings, theoretical control properties, and closed-loop dynamics of thermally coupled distillation sequences. In order to achieve the predicted energy savings for this class of complex distillation column, a dividing wall and a side tank were implemented in order to manipulate the internal flows associated with energy consumption. The reaction between ethanol and acetic acid was conducted within the prototype, and the experimental results indicate that a heterogeneous mixture of ethyl acetate and water is obtained as the top product. The temperature profile measured during the experimental run can be used for controlling the batch distillation column in cyclic operation mode.

An aerobic membrane bioreactor (MBR) at complete biomass retention was studied over a period of time under starvation conditions. Kinetic parameters were determined in a no-feed batch test. The decay rate of activated sludge, k d = 0.05 d -1 , was determined by tracking the decrease of MLSS. The ratio of MLVSS/MLSS was in the range 0.76-0.85. The pH values were between 7.02 and 8.23. As a function of different initial concentrations of MLSS, specific nitrification rates q N, decreased from 4.23 to 0.02 mg-N/(g MLVSS d) and specific biodegradation rates q b increased from 0.23 to 1.90 mg-COD/(g MLVSS d).

The calcium carbonate precipitation in a single feed semi-batch precipitator has been
investigated, aiming a kinetic analysis of the process. The feed rate, concentration of
reactants and the feed location point influence the particle size distribution (PSD) as well as
kinetic parameters. The values of the transient kinetic parameters suggest a nucleation process
accompanied by the dissolution and recrystallization of the CaCO3 polymorphs.

This work reports the results of experimental and theoretical investigations of NO decomposition in a catalytic monolith reactor. Monolithic catalysts are composed of a commercial cordierite substrate (Corning Inc.) and copper containing ZSM-5 zeolite (Si/Al = 40; 1.92 % Cu). Laboratory scale activity tests were carried out in the integral monolith reactor, operating under atmospheric pressure at different temperatures (573-773 K) and at various space times. The reactor performance was modeled using several mathematical models. The kinetics of NO decomposition was described by a LHHW type rate equation. The parameters of the monolith reactor models were estimated from experimental data using a modified differential method and Nelder-Mead method of non-linear optimization. It was found that the behavior of the experimental monolithic reactor was mainly limited by interphase mass transfer. The 2D heterogeneous model with distributed parameters was determined to be the most suitable mathematical model for detailed consideration of physico-chemical processes occurring in the catalytic monolith reactor.

Ion-exchange (IEX) chromatography steps are widely applied in protein purification processes because of their high capacity, selectivity, robust operation, and wellunderstood principles. Optimization of IEX steps typically involves resin screening and selection of the pH and counterion concentrations of the load, wash, and elution steps. Time and material constraints associated with operating laboratory columns often preclude evaluating more than 20-50 conditions during early stages of process development. To overcome this limitation, a high-throughput screening (HTS) system employing a robotic liquid handling system and 96-well filterplates was used to evaluate various operating conditions for IEX steps for monoclonal antibody (mAb) purification. A screening study for an adsorptive cation-exchange step evaluated eight different resins. Sodium chloride concentrations defining the operating boundaries of product binding and elution were established at four different pH levels for each resin. Adsorption isotherms were measured for 24 different pH and salt combinations for a single resin. An anion-exchange flowthrough step was then examined, generating data on mAb adsorption for 48 different combinations of pH and counterion concentration for three different resins. The mAb partition coefficients were calculated and used to estimate the characteristic charge of the resinprotein interaction. Host cell protein and residual Protein A impurity levels were also measured, providing information on selectivity within this operating window. The HTS system shows promise for accelerating process development of IEX steps, enabling rapid acquisition of large datasets addressing the performance of the chromatography step under many different operating conditions.

The role that water vapor plays in atmospheric phenomena is extremely important. Saturation of moist air at a given temperature and pressure occurs if its mixing ratio is such that the moist air can coexist in a stable condition with an associated condensed phase at the same temperature and pressure. The saturation mixing ratio is useful to calculate the relative humidity which is a ratio, expressed in percent, of the amount of water vapor in the air (actual mixing ratio) compared to the amount of water vapor the air can hold (saturation mixing ratio). In this work, an attempt has been made to develop a simple-to-use Arrhenius-type function to estimate the mixing ratio for saturated air over water as a function of pressure and temperature. Estimations have been found to be in excellent agreement with the data reported in the literature, with the average absolute deviation being around 0.4 %.

The powder-particle spouted bed process is one of the semi-dry processes that have been developed for flue gas desulfurization. In this study, which is designed for SO 2 removal by a powder-particle spouted bed, the reaction term is included in one-dimensional and streamtube models that were presented previously for spouted beds. Hydrated lime is used as the sorbent in this process. The predictions of the models are compared with some published experimental data and it is found that the developed models are valid. The results of two models are compared with each other and their various properties are evaluated. The effects of different operating conditions on SO 2 removal efficiency are also investigated and preferred operating conditions are discussed.

The kinetic parameters of the selective isothermal adsorption of ethanol from an aqueous solution onto a hydrophobic zeolite type NaZSM-5 were determined using a series of the so-called standard methods (the initial rate, the saturation rate and the maximum rate methods). The kinetic model of ethanol adsorption was determined by the "model fitting" method. The dependence of the kinetic parameters on the degree of adsorption and the presence of a compensation effect were determined by the isoconversional method. The complex changes of the activation energy and pre-exponential factor with the degree of adsorption were explained by the model of the activation energy distribution of elemental adsorption processes.

Reserves of fossil primary energy carriers are limited. Consequently liquid secondary energy carriers especially for mobile applications made from fossil reserves will not carry on forever but need to be replaced in a not-to-far future. Two substitution strategies are currently under investigation -the use of oil from plant seeds either directly or after chemical modification (biodiesel) or the gasification of complete plants, use of the product gases (mainly CO and H 2 ) in a Fischer-Tropsch process with subsequent refining. A third possible pathway would be the so-called direct liquefaction, i.e., the conversion of complete plants into liquid fuels without gasification. This process is discussed and various technical implementations are critically evaluated in the present paper.

A 3-D two-fluid CFD model in the Eulerian-Eulerian framework was developed to predict the hydrodynamics and heat and mass transfer of sieve trays. Interaction between the two phases occurs via interphase momentum and heat and mass transfer. The tray geometries are based on the large rectangular tray of Dribika and Biddulph and FRI commercial-scale sieve tray of Yanagi and Sakata. In this work a CFD simulation is developed to give predictions of the fluid flow patterns, hydraulics, and mass transfer efficiency of distillation sieve trays including a downcomer. The main objective has been to find the extent to which CFD can be used as a design and prediction tool for real behavior, concentration and temperature distributions, and efficiencies of industrial trays. Despite the use of simple correlations for closure models, the efficiencies obtained are very close to experimental data. The results show that values of point efficiency vary with position on the tray because of variation of affecting parameters, such as velocities, temperature and concentration gradients, and interfacial area. The simulation results show that CFD can be used as a powerful tool in tray design and analysis, and can be considered as a new approach for efficiency calculations and as a new tool for testing mixing models in both phases. CFD can be used as a "virtual experiment" to simulate tray behavior under operating conditions.

Direct contact evaporators are nonisothermal bubble columns where a hot gas, usually obtained by combustion, is used to heat and vaporize the solvent of a given solution that needs to be concentrated. The design of such equipment has been relied on experimental data or on a simplified method that assumes that the gas leaves the evaporator at equilibrium with the liquid phase, giving no information about the necessary bubbling height to attain such equilibrium conditions. Recent advances in the heat and mass transfer processes during the formation and ascension of superheated bubbles together with simple mass and energy balances in the liquid phase and gas distributor system were used to develop a more detailed design procedure. The accuracy of both design procedures are compared to available experimental data in a direct contact evaporator operating in semibatch mode. The new design method agreed well with the experimental data.

The chemical process involves the once through precipitation of adsorbing compounds from the low solubility classes of phosphates and hydroxides, accompanied by the total chromium adsorption and bonding.

The approach subsumes the addition of phosphate ions as phosphoric acid into waste water to induce Cr3+ ion complexation, as well as the significant growth in chromium phosphate super saturation of liquid phase before mass precipitation of the adsorbents.

From the distribution of the ionic molar concentrations between liquid phase and precipitated phase, ionic balance, solubility products and literature data, there was figured out formulas of the hypothetical precipitated compounds.
Chromium and aluminium are completely removed from chromate solutions completely and found integrally in the solid phase as Cr(OH)3, Cr(OH)2Cl, Cr(OH)Cl2, CrPO4, AlPO4  and Al(OH)3.

The PO43- ion is just partially precipitated as calcium, magnesium and aluminum insoluble phosphates. Thus, the lowest concentration of PO43- ion in the mother liquors has to be considered as a criterion in appoint the best reactant combination and the appropriate reaction pH.

It was demonstrated the advanced chromium removal from tannery is possible and the resulted precipitated material could be easily converted to a safe disposable waste.

Lucrarea prezintă evoluţia principalilor poluanţi evacuaţi din halda - mal stâng de
zgură şi cenuşă de la termocentrala Işalniţa pentru o perioadă de 8 ani. Se evidenţiază
fluxurile de ape descărcate din acest tip de haldă şi se prezintă valoarea indicatorilor
specifici şi impactul asupra receptorului.

The layered sodium silicates are valuable co-builders minded to substitute tripolyphosphates
in detergent formulations. The sodium disilicate polymorphs are fairly characterized, but the
recrystallization procedures of the metastable phases from the amorphous are not well known.
Some attempts to obtain a single enriched ,  or  phase have been carried out . The
properties of these materials related to their use as builders have been evaluated.
As a result of the ecological pressure, many detergent manufacturers started incentiving
researches to find suitable alternatives for tripolyphosphates, which are main responsible for
the so called “eutrophication” process. A wide range of sodium silicates , with general
formula (Na2O)x(SiO2)y(H2O)z , have already been tested and developed to full commercial
scale as multifunctional builders [14].All these products perform the following functions in
detergency: soften the water, provide alkalinity, suspend the soil and buffer the washing
liquors, adsorb surfactants onto the particle porous surface, stabilize the bleaching agents, do
not cake and support any kind of processing. Beyond the optimal detergency, crystalline
silicates bring about less pollution and environmental friendliness