Andrei Shishkin

Ferromagnetic Sorbents for Collection and Utilization of Oil Products

This Current paper reports the research conducted at Riga Technical University and Rezekne Higher Education Institution on the development of sorbent material, which is made of closed hollow microspheres possesses ferromagnetic properties, with a large specific surface. A review and comparison of existing sorbents for oil products collection are presented. The manufacturing process of proposed sorbent are described. The structure and morphology of obtained composite sorbent are discussed. It was found that proposed sorbent allows an efficient and safe way for surface water cleaning contaminated by spilled oil products. In particular, it shows a storing effect on a thin oil film (1-2 mm). Adsorption capacity to motor oil is investigated and compared with other magnetic sorbents on metal powders base. Newly proposed sorbent demonstrates a significantly higher adsorption capacity comparing to iron powders. Sorbent saturated by spilled oil can be evacuated by means of magnetic (or electromagnetic) captures.

Pore Distribution and Water Uptake in a Cenosphere-Cement Paste Composite Material

Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore size distribution by using the mercury porosimetry was determined. In a cold climate where the temperature often falls below 0 °C, it is important to avoid the amount of micrometer sized pores in the final structure and to decrease water absorption capacity of material. In winter conditions, water fills such pores and causes additional stresses to their walls by expansion while freezing. It was found that generally water uptake capacity for cement paste samples decreased up to 20% by increasing the concentration of CS up to 40 volume %, at the same time, the volume of micrometer sized opened pores increases.

Improvement of the Sorption Characteristics of Diatomite by Heat Treatment

In this paper, the adsorption of Orange Bezaktiv (SRL-150), onto Diatomite treated at 100°C (Dt-100) and at 300°C (Dt-300) was investigated in aqueous solution. The crystalline phases and surface study of Dt-100 and Dt-300 was investigated using respectively XRD, SEM, FTIR, and BET. The effect of operational parameters such as pH, contact time and, initial dye concentration was studied. From the obtained results there is not drastic difference in the crystalline phases between the obtained materials Dt-100 and Dt-300. The treatment at 300°C increases slightly the specific surface area from 11.09 to 16.12 m2/g, and pores volume. The results of adsorption tests show, that the most suitable pH and equilibrium time were respectively 2 and 30 min, at an adsorbent dosage of 2 g/L. The kinetic studies revealed that the adsorption results fitted very well with pseudo-second order model (R2 = 0.99 for both adsorbents). Adsorption isotherms results were in accordance with Freundlich.

Effect of Fly-Ash Cenospheres on Properties of Clay-Ceramic Syntactic Foams

A low-density clay ceramic syntactic foam (CSF) composite material was successfully synthesized from illitic clay added by fly ash cenospheres (CS) using the semi-dry formation method. The content of CS varied in the range of 10, 30, 50 and 60 vol %. Furthermore, reference samples without cenospheres were produced for property comparison. The materials comprising different amount of the additives were fired at temperatures of 600, 950, 1000, 1050, 1100, 1150 and 1200 °C. Firing times were kept constant at 30 min. Processing characteristics of the materials were evaluated in terms of density achieved and shrinkage observed as functions of both the CS content and the sintering temperature. The compressive strength and water uptake were determined as application-oriented properties. Except for the reference and the low CS level samples, the materials show an increase in strength with the increase in firing temperature, and a decrease of mechanical reliability with a decrease in density, which is typical for porous materials. Exceptions are the samples with no or low (10 vol %) content of cenospheres. In this case, the maximum strength is obtained at an intermediate sintering temperature of 1100 °C. At a low density (1.10 and 1.25 g/cm3), the highest levels of strength are obtained after sintering at 1200 °C. For nominal porosity levels of 50 and 60 vol %, 41 and 26 MPa peak stresses, respectively, are recorded under compressive load.

Intermediate and low radiofrequency electromagnetic field transmission properties in case of common building materials

Controlling exposure to the electromagnetic fields (EMFs) may serve many causes: to protect sensitive electronic equipment from outside interference; to protect the environment from the high radiation generating equipment; to protect humans from excess radiation etc. Strong EMFs may be encountered in public domain but especially in occupational settings, where the process and technology of work requires the EMFs. Technical measures to manage risks may include using construction materials. In this study the intermediate and low radiofrequency transmission characteristics in case of building materials were investigated. The measurements are called for to determine the amplitude of the electric and magnetic field at the close proximity to the material. A set of common building materials was selected, widely used in modern constructions. The included materials can broadly be divided into three groups: load bearing materials, thermal insulation materials and cover materials. Altogether 17 building materials were tested, forming an overview of some most common materials in construction of houses. The testing was done at 2, 20 and 200 kHz frequencies. The measurement point was in close proximity (10mm) to the material under testing. The electromagnetic irradiator point was on the other side of the material, 150 mm from the measurement sensor. Somewhat frequency dependent variation in the amplification could be observed only in few cases: gypsum panel, aerated concrete, LECA, gypsum board and solid wood. The highest electric field amplification was measured for some materials, up to 5.6 dB increase: custom made gypsum panel, aerated concrete, LECA, gypsum board, high performance concrete plate, solid wood. The results show for the selected samples that semiconductive materials which cannot be grounded due to the high resistance, electric fields may be amplified several folds in close proximity to the material.

Illite Clay Ceramic Hollow Sphere - Obtaining and Properties

This work focuses on clay ceramic hollow spheres (CCHS) preparation using Liepa clay and sacrificial template method in a lab scale device and testing of their properties. Water retention and compression strength were investigated in order to found out if obtained CCHS can be used as an additive for improving soil resilience.The synthesis and characterization of CCHS using expanded polystyrene spheres (EPS) as sacrificial template is presented. CCHS were fired at five different temperatures and their compressive strength, water retention, bulk density, material density, water absorption, phase composition, surface morphology, porosity using hydrostaticweighing and BET nitrogen adsorption methods, were determined.Study of clay ceramic hollow sphere structure and surface morphology revealed that all samples have spherical shape. These spheres have several pronounced protrusions from the granulation process. Clay ceramic hollow spheres have porosity rate of 21 - 36% and a water absorption rate of 15 -33%. The highest rate of porosity and water absorption was observed for hollow spheres fired at 1050°C.The increase of clayceramic hollow spheresfiringtemperature led to decrease of specific surface area-thehighestvaluewas observed at950°C and the lowest at 1150°C. The bulk density increased at 1150°C.Mechanicalstrength test of ceramic hollowspheres(HS)revealedthat with the increase of scorchingtemperature the compression strength of the spheres increasedas well.The sphere hollowshadpractically globular shape with the averagewallthickness of0,6 mm, whichcomprises10-13% ofthe outer diameter.The obtained clay ceramic hollow spheres are proposed as water retention agent.

Bioremoval of Lead (II) and Cadmium (II) in Single and Multicomponent Systems Using Penicillium sp.

The biosorption of cadmium and lead by Penicillium sp. isolated from an uncontaminated soil was studied at different initial metal ions concentrations. The maximum removal yields were obtained at 5 mg/L initial metal concentration. The highest removal yields were 35.67% and 81.99% for cadmium and lead respectively in the single system. In the binary system, the removal yield increased to 90.99% and 97.48% for both metal ions at the same initial concentration. This study has also confirmed that Penicillium sp was able to grow in the presence of both metal ions at different concentrations. In addition, this study showed that Penicillium sp was more tolerant to cadmium than lead. Fungi have also shown a tolerance to high concentrations of toxic heavy metals.This study can provide useful information on the bioremoval of heavy metals such as Cd(II) and Pb(II) from wastewaters.

Activated Carbon Design from Sludge to Remove Red Scarlet Nylosan “F3GL” in Aqueous Solution

Activated carbon prepared from industrial wastewater treatment plant dry sludge was proven to be efficient for the removal of refractory dye red scarlet nylosan (F3GL). Mixed treatment (chemical followed by thermal) considerably improved the adsorption capacity of the sludge. Batch tests at 40 °C gave maximal adsorption capacity. Application of Langmuir model gave 434.78 mg/g for treated material (SNHC) and 169.49 mg/g for the unmodified material (S). Thermodynamic parameters indicated that the adsorption is favored by an increase of temperature. The values of the enthalpy revealed physic-sorption. The results clearly showed that the mixed treatment of the adsorbent is the most adequate for the removal of toxic substances such as dyes present in industrial wastewaters.

Characterization and Recycling of a Low-Coast Derivative Iron Hydroxide Adsorbent

This work presents the possible recovery and reuse, after treatment, of an iron-based sludge from wastewater treatment station in the removal of cadmium in aqueous solution. The sludge sustained a heat treatment (100 and 500°C) and was characterized by XRD, FTIR, BET and SEM witch shown an evolution in the morphology and the structure of the materials indicating the effect of the heat temperature. The material was then applied to remove cadmium in aqueous solution. The results show that the raw material gives the best results with a maximal adsorption capacity of 70.92 mg/g at pH=5.This study has shown us that it is possible to recover and reuse effectively sludge, from wastewater treatment plant, considered as a solid waste, in the removal of a pollutant such as cadmium in aqueous solution.

Bio-Waste Recovery for the Removal of Cr (VI) in Aqueous Solution: Case of the Green Alga Ulva lactuca

This work is in addition to the various works undertaken by the researchers, using biomass as adsorbent. However, the aim of this study is the recovery of a marine material alga: Ulva lactuca) that we were able to transform into adsorbent with treatment under physical carbonization and chemical activation. The ability of treated and untreated Ulvala ctuca, to remove hexavalent chromium Cr (VI) ions in aqueous solutions was investigated. The influence of pH, sorbent dose, initial concentration, temperature, and contact time has been studied in batch process. The materials are characterized by FTIR and SEM analysis. The highest Cr (VI) removals (100%) were achieved at pH of 3, particle size of less than 250μm, dose of 1 g/L, and equilibrium time of 180 minutes. Thermodynamic results indicated that the Cr (VI) adsorption process was spontaneous and exothermic. The adsorption data fit well with Langmuir isotherm model with a maximum adsorption capacities (qmax) of untreated and treated Ulva lactuca were between 0.6 and 2 mg/g. Higher Cr (VI) removal revealed the practical applicability of Ulva lactuca in water and wastewater treatment systems.