Synthesis and Evaluation of Bis-quaternary-Based Surfactants as Additives for Water-Based Mud

Two series of cationic gemini surfactants, alkanediyl-α,ω-bis[N,N-dimethyl alkyl (octyl or dodecyl)ammonium] dibromide (R-s-R; s = 6, 10, 12 and R = 8 and 12) were prepared and evaluated as additives for water-based mud. The chemical structures of the prepared surfactants were confirmed using FTIR and mass spectroscopy. Surface activity of these compounds has been studied and their surface properties including surface tension, emulsification power, critical micelle concentration, effectiveness, maximum surface excess and minimum surface area were determined. The results showed that the prepared compounds have significant surface activity, especially those of longer hydrophobic chain length. The prepared cationic gemini surfactants were evaluated as viscosifiers and filter loss additives for water-based mud formulated from local Na-montmorillonite clay. XRD analysis was carried out to the Na-montmorillonite clay to determine the interaction of the surfactants with inter layers of the clay structure. Rheological properties, gel strength, thixotropy, filtration properties and the effect of temperature on rheological properties of the water-based mud were studied. The results indicated that the gemini surfactants have a positive effect on the rheological and filtration properties of the Na-montmorillonite clay according to American Petroleum Institute specifications.     

The energy intensity in Lithuania during 1995–2009: A LMDI approach

The measurement, assessment, and effective mitigation of energy intensity compose a foremost objective of contemporary energy policy. Although the European Union (EU) Member States have been experiencing the convergence in energy efficiency indicators, Lithuania, acceded to the EU in 2004, still remains peculiar with relatively high energy intensity. Our study, therefore, is aimed at analyzing the energy intensity trends in Lithuanian economy as a whole as well as in separate economic sectors. The investigation covers the period of 1995–2009. The Logarithmic Mean Divisia Index was applied for decomposition analysis. Our analysis has shown that energy efficiency falls during economic downturn. In order to facilitate these challenges the Lithuanian Government as well as business should opt for increasing energy efficiency in the most problematic sectors of transport and services. In addition, the analysis of legal acts, namely National Energy Efficiency Programme for 2006–2010 and Energy Efficiency Action plan for 2010–2016, was taken into consideration. Some suggestions, thus, were offered for successful implementation of strategic goals outlined in the aforementioned strategic documents.     

External cost of electricity generation in Baltic States

This article deals with external cost of electricity generation in Baltic States. The costs of electricity generation and distribution are the most important criteria shaping decisions within the electricity system. However, the external cost due to air pollution should also be adequately taken into account seeking to promote new and clean technologies for electricity generation. External costs of electricity generation in the main power plants burning fossil fuel were calculated based on ExternE methodology for Baltic States during EU Framework 6 project CASES. The article presents the first results of external cost of electricity generation in Baltic States.     

A stable quicksort

A sorting algorithm, called Stable Quicksort, is presented. the algorithm is comparable in speed with the Quicksort algorithm, but is stable. The experimental evidence presented support the theoretical evaluation of the performance of Stable Quicksort.     

Novel Imidazolium-Based Gemini Surfactants: Synthesis, Surface Properties, Corrosion Inhibition and Biocidal Activity Against Sulfate-Reducing Bacteria

Three novel imidazolium-based gemini surfactants had been synthesized and characterized using different spectroscopic techniques. The surface properties of the synthesized surfactants were determined using surface tension measurements at 20 °C. The surface parameters including critical micelle concentration (CMC), π _CMC, Pc₂₀, Γ_max and A _min were determined. The synthesized compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution using the weight loss and polarization techniques. The biological activity of these surfactants was evaluated against sulfate reducing bacteria using most probable number method. The results indicate that the synthesized compounds have good surface properties and are proper corrosion inhibitors for low carbon steel, with a high inhibition efficiency observed around their CMC. These compounds exhibit a significant biocidal activity against sulfate reducing bacteria.     

Influence of different reactor types on Nannochloropsis oculata microalgae culture for lipids and fatty acid production

Greenhouse gases emitted into the atmosphere by burning of fossil fuels cause global warming. One option is obtaining biodiesel. Nannochloropsis oculata was cultured under different light intensities and reactors at 25°C for 21 days with f/2 medium to assess their effects on cell density, lipid, and fatty acids (FAs). N. oculata improved cell density on fed-batch glass tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, yielding 3.5 × 10⁸ cells ml⁻¹, followed by fed-batch Erlenmeyer flask (1 L) at 650 μmol E m⁻² s⁻¹ with 1.7 × 10⁸ cells ml⁻¹. The highest total lipid contents (% g lipid × g dry biomass⁻¹) were 44.4 ± 0.8% for the reactor (1 L) at 650 μmol E m⁻² s⁻¹ and 35.2 ± 0.2% for the tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, until twice as high compared with the control culture (Erlenmeyer flask 1 L, 80 μmol E m⁻² s⁻¹) with 21.2 ± 1%. Comparing the total lipid content at 200 μmol E m⁻² s⁻¹, tubular reactor (7 L) and reactor 1 L achieved 35.2 ± 0.2% and 28.3 ± 1%, respectively, indicating the effect of shape reactor. The FAs were affected by high light intensity, decreasing SFAs to 2.5%, and increased monounsaturated fatty acids + polyunsaturated fatty acids to 2.5%. PUFAs (20:5n-3) and (20:4n-3) were affected by reactor shape, decreasing by half in the tubular reactor. In the best culture, fed-batch tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹ contains major FAs (16:0; 38.06 ± 0.16%), (16:1n-7; 30.74 ± 0.58%), and (18:1n-9; 17.15 ± 0.91%).     

Multivariate analysis of a biologically activated carbon (BAC) system and its efficiency for removing PAHs and aliphatic hydrocarbons from wastewater polluted with petroleum products

The efficiency of a biologically activated carbon system for treating wastewater polluted with petroleum products was examined and the effects of process parameters on its efficacy were evaluated. In each experiment 17 alkylated and 19 non-alkylated polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs, C₁₀–C₄₀) were extracted using semipermeable membrane devices from wastewater before and after treatment. The acquired data during experiments were analyzed using principal component analysis (PCA). The treatment system robustly removed dissolved PAHs across the studied ranges of the process parameters, providing overall removal efficiencies of 96.9–99.7% for the sum of 36 PAHs. However, the major contributor to their removal was sorption rather than biodegradation, and despite the general efficiency of the process there was up to a 9-fold range in the sums of quantified PAHs in the effluents between experiments. Combinations of long process contact time (24 h) with high temperature (24 °C) and moderate oxygen concentration (6–7 mg O₂ L⁻¹) resulted in good removal of bioavailable PAHs. The removal of TPHs was more dependent on biological activities during the wastewater treatment, and consequently more dependent on the process parameters. In addition, small but significant proportions of PAHs were volatilized and released during the wastewater treatment.     

GHG emission trading implications on energy sector in Baltic States

The article deals with the issues related to the implementation of EU greenhouse gas (GHG) emission trading scheme in Baltic States. The main objectives of the article are to analyse the main features and requirements of EU emission trading scheme and to assess the results of the first trading GHG trading period based on verified GHG emissions in Baltic States. The main aim of the article is to compare GHG emission trading results among Baltic States and provide with some insights for the next GHG trading period and assess possible implications on energy sector of Lithuania, Latvia and Estonia.