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Open access

J. Burlakovs, M. Klavins and A. Karklina

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Soil remediation at contaminated sites very often needs customized approach, because of the different content of pollutants. Various technologies from simple soil excavation and transporting to hazardous waste landfills to different kinds of remediation by vitrification and the use of additives can be used for the treatment of soil. A series of remediation experiments using zeolites and humic acids were applied to soil contaminated with copper. Remediation can be performed with easily available additive materials of natural origin found near the place of application, in order to diminish the leaching of contaminants. Soils contaminated and spiked with copper were mixed with additives, and ion selective electrode potentiometry was used in order to establish the stability constants of humic-metal complexes. Thus the study provides an opportunity to gain information on the fate of copper variously mixed with potential remediation agents zeolites and humic acids - as additives to contaminated soils.

Open access

M. Klavins and O. Purmalis

Abstract

Humic substances form most of the organic component of soil, peat and natural waters, but their structure and properties are very much dependent on the source. The aim of this study was to characterize humic acids from raised bog peat to evaluate the homogeneity of humic acids isolated from the bog bodies and to study peat humification impact on the properties of humic acids. Peat humic acids (HA) have an intermediate position between the living organic matter and coal organic matter, with their structure formed in a process where the relatively labile moieties (carbohydrates, amino acids, etc.) are destroyed, and thermodynamically more stable aromatic and polycyclic structures emerge. Comparatively, the studied peat HAs were at the start of this transformation process. Concentrations of carboxyl and phenolic hydroxyl groups changed depending on the source depth of peat from which HAs were isolated. The carboxylic acidity of peat HAs increased with depth of the source and the extent of peat humification

Open access

M. Klavins, L. Ansone and A. Zicmanis

Behaviour of Nanomaterials in the Environment: A Study of Interaction between Humic Acids and Fullerene C60

Interaction between buckminsterfullerene and humic substances of different origin was investigated using fluorescence spectrometry as function of concentration of humic substances, pH and ionic strength. Binding constants of humic substances and buckminsterfullerene were calculated. It can be suggested that the complexation was driven by hydrophobic interaction depending on properties of the interacting compounds. Hydrophobic interaction model was indicated by linear Stern-Volmer plot, and high Kd values characterized interaction between buckminsterfullerene and humic acids. The results of this study support the development of understanding of fate of nanomaterials in environment as well as development of analytical techniques for nanomaterials in water and wastewater treatment approaches.

Open access

A. Robalds, M. Klavins and A. Zicmanis

Peat as Sorbent for Cu2+ and Cr3+ Ions

Heavy metals as trace elements can often be found in industrial waste waters, and their discharge to the environment is a significant threat due to their acute toxicity to the aquatic and terrestrial life. The common methods used for removal of toxic metals and trace elements from the municipal and industrial waste waters are based on their adsorption onto insoluble compounds - sorbents. Synthetic sorbents usually are quite expensive; therefore, as a prospective approach to the metal removal, the use of a natural sorbent - peat - was tested. Peat as sorbent was proved to have a relatively high sorption capacity in respect to the studied metal ions, it can be used batchwise and in a dynamic regime and is a relatively robust and reliable sorbent regarding pH, the ionic strength, and the amounts of sorbed metal.

Open access

D. Dudare and M. Klavins

The aim of this study is to determine the Cu(II) complexing capacity and stability constants of Cu(II) complexes of humic acids isolated from two well-characterized raised bog peat profiles in respect to the basic properties and humification characteristics of the studied peats and their humic acids. The complex stability constants significantly change within the studied bog profiles and are well correlated with the age and decomposition degree of the peat layer from which the humic acids have been isolated. Among factors that influence this complexation process, molecular mass and ability to form micellar structures (supramolecules) of humic substances are of key importance.

Open access

A. Zicmanis, S. Pavlovica, E. Gzibovska, P. Mekss and M. Klavins

2-Hydroxyethylammonium Carboxylates - Highly Biodegradable and Slightly Toxic Ionic Liquids

Highly hydrophilic ionic liquids easily form in reactions between 2-hydroxyethyl amines and carboxylic acids. They have low toxicity and high biodegradability, serve both as reaction solvents and catalysts in condensation reactions, and they may be reused several times without any purification.

Open access

S. Pavlovica, E. Gzibovska, A. Zicmanis, P. Mekss and M. Klavins

Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester

Hantzsch ester synthesis was investigated using (2-hydroxyethyl)-ammonium carboxylates, polar and hydrophilic ionic liquids possessing low toxicity and high biodegradability. The reaction rates and yields of the products in ionic liquids were greater than those in common organic solvents. The relationship between the structure of the ionic liquid used and the structure of the heterocyclic compound was investigated.

Open access

L. Ansone, M. Klavins, A. Robalds and A. Viksna

Water contamination with arsenic compounds is a serious problem. One of the solutions is to develop new sorbents based on natural materials that would be cost-effective and environmentally friendly. New sorbents based on biomaterial impregnation with iron oxyhydroxides have been developed. Raw peat material, iron modified-peat, sand, iron modifiedbiomass (shingles, straw) were used for removal of arsenic compounds. The highest sorption capacity was observed for iron modified-peat. Kinetic studies indicated that most of arsenates were removed within 2 hours, and arsenate sorption on iron modified-peat was characterized by the pseudo-second order rate law.

Open access

J. Klavins, G. Mozolevskis, A. Ozols A., E. Nitiss and M. Rutkis

Abstract

We report on a screen printing fabrication process for large-area SU-8 layers utilised for the preparation of microstructures in display devices such as microelectronic, electrowetting or bistable devices. The screen printing method has been selected for its effectiveness and simplicity over traditionally used spin-coating ones. Layers and microstructures produced thereof have shown proper homogeneity. Relationships between screen parameters to coating thickness have been established. Coating on an ITO (indium tin oxide) hydrophobic surface is possible when surface has been treated by UV/Ozone to increase its aqueous ability. To this end, the hydrophilic microstructure grids have been successfully built on a hydrophobic layer by screen printing and traditional lithography processes. Compared to conventional spin-coating methods, the screen printing method offers the advantages of simple, cheap and fast fabrication, and is especially suitable for large-area display fabrication

Open access

A. Abramenkovs, M. Klavins, J. Rudzitis and A. Popelis

Organic sorbents like peat can be successfully used for the purification of radioactive waste waters and are favoured by economical and technical considerations. The peat filters are also friendlier to the environment, since the manufacturing of such filters is a low emission process. This study examined the sorption of radionuclides 137Cs, 55Fe, 63Ni and 14C on peat samples. The initial radioactivity of the peat samples was studied before the experiments. Peat samples were taken from different bogs. Radionuclide solutions were prepared using deionised water and appropriate radionuclide composition from the Salaspils research reactor stock water. It was found that in all cases of peat samples, the main natural radionuclides were 210Pb, 40K and 214Bi. The artificial radionuclides 152Eu, 137Cs and 60Co were also found in the peat samples. Radionuclide sorption studies indicated that the initial radioactivity of the solution decreased in the case of radionuclides 63Ni, 14C, 55Fe and 137Cs. This confirmed that peat samples can effectively remove the radionuclides from radioactive water solutions.