Volume 10 (2008): Issue 4 (December 2008)

The photocatalytic efficiency of alkali niobate-based compounds (Li, Na, K) for hydrogen generation has been investigated. The systematic study showed that the highest photocatalytic activity was observed in the case of Na/Nb₂O₅ catalyst which contained sodium niobate (NaNbO₃) phase and that the most efficient electron donor for hydrogen generation was formic acid. In addition, the effect of organic donor (HCOOH) concentration on the amount of the evolved hydrogen was studied.

Investigation was carried out on the optimal conditions of the synthesis of NaVO₃ and Cl₂ from NaCl and V₂O₅ in the presence of the atmospheric oxygen. The influence of the excess of NaCl relative to V₂O₅ was investigated. Also the effect of the quartz sand introduced into the reaction mixture on the yield of the NaVO₃ synthesis was determined. The obtained product of synthesis was isolated from the post-reaction mixture.

The results of the precipitation of calcium carbonate from waste distillation liquor (DS) from the Solvay method and sodium bicarbonate saturated solution in the presence of urea were presented. The investigation was carried out at 293K. The influence of the time of reagents dosage to the solution of urea on the physicochemical character of obtaining product was studied. The time of reagents dosage: 1, 5, 10, 20, 30 min and the concentration of the urea applied: 0.5, 1, 2 and 4 mol/dm³. The granulometric composition, the values of bulk and packing densities and the absorptiveness sorption of water and paraffin oil of the obtaining calcium carbonate were investigated.

The equilibrium research was performed for the NH₄NO₃ + NaVO₃ + NH₄VO₃ + NaNO₃ + H₂O system at 293 and 303 K. The location of the P₁ and P₂ triple points was determined on the equilibrium plots with the planar projection according to Jänecke method. The maximum yield of the conversion of ammonium nitrate(V) to ammonium vanadate(V) was calculated at P₁ points. The results constitute the basis to design further equilibrium experiments aimed to precisely determine the lines separating the areas of the co-crystallization of salts in the investigated system on the equilibrium plots in the oblique projection on a plane according to Jänecke method.

Pulp-mill waste is very noxious for the primary wood production. The problems of its manageability are correlated with its volume and a considerable degree of pollutions, mainly the organic ones, coming from wood processing. The other main components of waste material are aggressive reagents liberating the cellulose fibers, during washing, classification and the benediction processes. The results of environmental studies covering the superficial water of the pulp-mill impact were presented. The production process factors were assessed owing to the waste concentration and distribution in the water race.

In this paper the results of the investigation of magnesium removal, from zinc concentrate derived from zinc-lead ore enrichment plant, have been presented. The characteristics of the initial concentrate and the occurrence forms of dolomite in this material are estimated. It was found that magnesium is collected in the finest fraction of the initial material. The influence of chemical treatment and flotation on the quality improvement of zinc concentrate is determined. This method permits to obtain zinc concentrate containing below 0,3% Mg and about 0,7% Ca.

The influence of urea on the vanadium(V) and potassium ion concentrations in the K₂CO₃ + NH₄VO₃ + H₂O system was determined in the temperature range of 293 K to 313 K. Additionally, the solution density dependence versus the urea concentration was presented. These data are essential for the assessment of optimum operating conditions for the new production process of potassium carbonate.

High level of production and consumption in member-countries of the European Union is connected with generating a considerable amount of waste. In individual EU member-countries various methods aiming at decreasing the amount of generated waste are implemented. The current situation in Poland, and the best practical solutions introduced in some European regions have been presented in the paper. These solutions were put in place, mainly to fulfill the EU or country's regulations. The priority of municipal waste management measures is to prevent and minimize its generation. Decisions on preventing waste generation should be made as early as at the stage of product designing and manufacturing. The basic principle of proper municipal waste management is to create a system of regional solutions, which includes all the elements of waste management and relates them to the local conditions.

The research was conducted to determine the influence of the pH of the leaching solutions and hydrogen peroxide addition on the efficiency of the recovery of vanadium, potassium and iron compounds from the used vanadium catalyst from the node of oxidation of sulfur dioxide to sulfur trioxide.

In this work obtaining of magnesium hydroxide from the solutions obtained during magnesium removal from zinc concentrates is presented. The received product was used for the winning of composites from polyethylene (PE) using extrusion and injection methods. The obtained composites were tested in terms of thermal stability (TG, DTG) as well as combustibility (LOI and thermovision camera). The preliminary results indicate the beneficial effect of the decrease of PE quality by magnesium hydroxide obtained by means of solution purification and precipitation of Mg(OH)₂ by means of soda lye.

This study presents the use of fluidised bed combustion to produce thermal energy, aluminium recovery and the reduction of the Tetra Pak and Combibloc packaging waste stream. Fluidisation and the pneumatic transport, which take place in the same apparatus, allow recovering bits of the aluminium foil from the combustion zone. The limited time spent in the high temperature zone leads to a high content of free metal in the solids separated in the ash trap and cyclone. Other solid products are practically chemically inert and may be disposed in a landfill of municipal or inert wastes.

The paper discusses the possibility of using the reversible reaction CaCO₃ ↔ CaO + CO₂ for the cyclic capture and release of CO₂ directly inside a fluidised bed combustor. This could lead to the lowering of CO₂ emissions into the atmosphere, as part of an effort to mitigate the greenhouse effect associated with the rising atmospheric CO₂ concentrations resulting from obtaining energy from burning fossil fuels.

An enrichment coefficient E has been introduced and defined as a measure of the production of CO₂ (on calcining CaCO₃) or its removal (on carbonation of CaO) with respect to the level associated with fuel combustion alone. The observations made on the effect of introducing an additional external stream of CO₂ on the efficiency of the chemical capture process have been described. Through an appropriate control of the temperature inside the reactor it is possible to change the value of E over the range [-0.8; 0.8]. This implies that up to about 80% of the CO₂ derived from the fuel can be temporarily retained within the bed and released later, at a higher concentration. The proposed method of burning fuel in a chemically active fluidised bed could be an available method leading to CO₂ isolation from the flue gases and leading to its eventual sequestration.

A terrestrial disposal of the fly ash has been regarded as a potential source of contamination due to the enrichment and surface association of trace elements in ash particles. In laboratory conditions the leaching of soluble components existing in ashes proceeds in a different way than in land deposits.

On the landfill site coal combustion by-products are under the pressure of atmosphere agents, especially water, sun and rain activity (drying and wetting alternately), freeze/thaw (in cold climate) and gases included in the air. Also the time of exposition is an important parameter.

In the presented experiment the observed dynamics of ash solubility over a long period of time provides the evidence that in the ash-water system, a variety of precipitation processes dominate the solubility of solid mass. Simulating the weathering by the freeze/thaw test approximates the effectuated changes in ash particles structure.

The leaching of a particular ash component depends on reactions in the ash-water systems.

Solidification by compaction of the material is often favoured because of the cementitious properties of ashes being in contact with water. Secondary hydrated minerals such as ettringite, portlandite and calcite are formed during a contact with water. Calcium -silicate hydrates, aluminate-hydrates and gypsum can occur as secondary minerals. The solubility of such new phases and the solidification process determine the leaching characteristics of the ash mass.

FTIR analysis was used to study the hydrogen bonding in 4,4'-diaminodiphenylmethane-based segmented poly(urethane-urea)s varying in the length of the poly(tetramethylene oxide) (PTMO)-based soft segments. Experiments were designed to follow the IR absorption of both the NH and carbonyl regions as a function of temperature in order to directly investigate the extent and strength of the hydrogen bonds, and thereby to gain some information about the possible alteration of the initial phase-segregated morphology as a result of the applied thermal treatment.