Materials Science and Applied Chemistry

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Authors: Anna Timofejeva, Dagnija Loca
Abstract: Composite hydrogels on the basis of hydroxyapatite (HAp) and polyvinyl alcohol (PVA) has been proposed as a promising materials for bone and cartilage tissue engineering. HAp/PVA composite hydrogels with phase ratio 50:50wt% and 70:30wt% were obtained via in situ wet chemical precipitation technique in combination with the freeze-thawing approach. The XRD studies of sintered products revealed that HAp/PVA composite hydrogels synthesized from PVA with degree of hydrolysis (DH) 98% and molecular weights (MW) 25 kDa and 78 kDa are more suitable for biomedical purposes due to the formation of stoichiometric HAp. Swelling studies indicated that HAp/PVA 50:50 (78 kDa, 88% and 98%) hydrogels after 24h of immersion swell ~4.25-6.5 times less than identical samples with phase composition of 70:30wt%, which is accounted to different number of intermolecular hydrogen bonds formed. After 16 subsequent freeze-thawing cycles (FTC), HAp/PVA 50:50 (78 kDa, 88% and 98%) hydrogels contain ~1.2 times higher content of crosslinked PVA than HAp/PVA 70:30 (78 kDa, 88% and 98%) hydrogel samples.
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Authors: Elvis Klaucans, Karlis Sams
Abstract: Food production industry is the main producer of wastewaters with high fat, oil, and grease (FOG) content. FOG waste can be recovered from the wastewater stream by using physicochemical methods and reused considering their high methane potential. Popular method of FOG reuse is anaerobic co-digestion (AcoD) with wastewater treatment sludge and scum from the primary wastewater sedimentation tanks. This short review focuses on understanding the efficiency of FOG reuse possibilities by AcoD and takes a closer look at problems connected to degradation issues, gives an understanding on microbial changes during FOG degradation, and reviews enzymes involved in the degradation process.
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Authors: Andrejs Bērziņš, Olga Mutere, Ruta Švinka, Visvaldis Švinka
Abstract: Oily water was treated with porous ceramic granules and immobilized microorganisms. Floating granules with bulk density of 0.63-0.66 g cm-3 were used. The sorption of motor oil was investigated for dry and wetted granules. Respiration experiments showed that microorganisms immobilized on floating ceramic carrier and treated with oily water were influenced by agitation of liquid. The treatment of oily water with low salinity (1-9 g L-1) showed that oil removal efficiency decreased after increasing water salinity. Likewise, oil removal efficiency decreased from 12 to 9% per gram of ceramic carrier after increasing the spill of oil from 9 to 35 g per square meter. Porous granules with immobilized microorganisms can be used in cases with insignificant oil pollution or for pretreatment of wastewater before feeding it into a wastewater treatment plant.
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Authors: Tjaša Birsa, Kristīne Kalneniece, Mārtiņš Jansons, Mārtiņš Kalniņš, Inga Ozoliņa, Andrejs Bērziņš, Visvaldis Švinka, Ruta Švinka, Vadims Bartkevičs, Olga Muter
Abstract: Glyphosate (G) is a broad-spectrum systemic organophosphate herbicide being widely used to control weeds in agricultural fields and urban areas. Its safety for both human health and aquatic biomes is a subject of wide debate. This study was aimed at evaluating the removal efficiency and ecotoxicity of G based herbicide (GBH) Klinik® (Nufarm, Austria) added to the raw municipal wastewater (WW) in a lab-scale model column system. The effect of oxide ceramics as a filtering medium (treatment „B”), as well as activated sludge and nutrients (treatment „C”) was compared with the control columns, which contained only WW (treatment „A”). After 72h treatment of WW spiked with 100 mg/L G, the lowest G concentration was detected in the treatment „B”, i.e., 79.4±0.6 mg/L. Treatments „A” and „C” resulted in the remaining G concentrations of 83.3±3.8 and 89.6±3.7 mg/l, respectively. The second addition of 100 mg/L G to the columns followed by 72h incubation also showed the advantage of oxide ceramics. Most probably, this effect could be explained by coupled sorption and biodegradation processes. Experiments were accompanied by microbiological (colony forming units; biological oxygen demand) and ecotoxicological (Daphtoxkit F magna, MicroBioTests) testing. The results indicated that WW-derived microorganisms resist the presence of GBH in the tested concentration range of G, i.e., up to 300 mg/L. As for Daphnia magna, the 24-h EC50 for the GBH Klinik® under standard conditions and in raw WW was found to be 22 mg/L and 6 mg/L G, respectively.
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Authors: Hakim Aguedal, Abdelkader Iddou, Janis Locs
Abstract: A design of experiments based on the Taguchi method was used to evaluate the main parameters affecting the removal of textile dyes from aqueous solution. By using the adsorption capacity of textile dye as target response, several experiments were carried out using L27 orthogonal array, and the higher-the-better as quality characteristics was applied. The controlling factors, including initial dye concentration, contact time and pH of solution were assessed. Analysis of variance (ANOVA) was used to determine the effects of each factor on the adsorption capacity. The optimum adsorption conditions giving higher adsorption capacity were selected as initial dye concentration of 500 mg.L-1, contact time of 180 min and pH of solution of 2. The analysis results revealed that the most relevant factors affecting the adsorption process of textile dye are the initial dye concentration and pH of solution. After 3 cycles of thermal regeneration, the diatomite behavior did not change and more than 60 % of dye was eliminated from solution after regeneration at 600°C. From the obtained results, the Taguchi method was very successful to optimize of the adsorption parameters for maximum removal rate, and gives more credibility for industrial application.
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Authors: Farhat Bensalah, Abdelkader Iddou, Hafida Hentit, Abdallah Aziz, Andrei Shishkin
Abstract: 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.
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Authors: Habib Khodja, Abdelkader Iddou, Hakim Aguedal, Abdallah Aziz, Andrei Shishkin
Abstract: 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.
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Authors: Ance Plavniece, Aivars Zhurinsh, Galina Dobele, Aleksandrs Volperts
Abstract: Carbon compounds with large surface area can be used as electrocatalytic cathodes for fuel cells. Nitrogen atoms largely determine the properties of doped activated carbon, such as hardness, wear resistance, electrical resistance etc., and therefore there is a need for new scientific information on the properties and structure of modified carbon matrix. Wood char and activated carbons based on wood char, cellulose, black liquor, and fine cellulose sludge were obtained in different activation conditions and doped with dicyandiamide. The obtained N-doped carbon materials porous structures were compared taking into account preparation conditions and raw material.
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Authors: Ance Eglīte, Linda Pudnika, Marta Anda Balode, Anda Prikšāne
Abstract: A series of monocationic and dicationic -SO3H functionalized Brønsted acidic ionic liquids (BAILs) are synthesized using different amines int.al., N,N,N′,N′-tetramethylethylenediamine, 1-methylimidazole, pyridine and alkylating agents 1,3-propane- and 1,4-butanesultones. The Hammett acidity (H0) and thermal properties by TG-DSC techniques are investigated. These ionic liquids have been applied to catalyze the dehydration reaction of aliphatic long chain alcohols (1-heptanol, 1-octanol, 1-decanol) at 195 °C. The optimization of reaction conditions and use of dicationic ionic liquids allow to reach rather high yields of symmetric diheptyl ether and dioctyl ether. The reusability of ionic liquids is evaluated using monocationic [PyPS][HSO4], dicationic [TMEDAPS][HSO4] ionic liquids and 1-heptanol.
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Authors: Hassiba Benchekor, Abdelkader Iddou, Hafida Hentit, Abdallah Aziz, Jeferson Steffanello Piccin
Abstract: In this work, chitin-based material has been proposed for removing the purple NR5 dye in aqueous solution. The material chosen is from shrimp shell: Aristeus antennautus. This biomaterial is used as a raw form. The adsorption isotherms obtained showed a behavior of L3a indicating the passage of monolayer to multilayer adsorption. The results are well correlated with the BET model, (R²>0.99). And the maximum monolayer adsorption capacity was found to be 667.33 mg/g. The kinetic data were evaluated using pseudo first order, pseudo second order and the intraparticle diffusion models. The chemical nature of the biomaterial is confirmed by Fourier Transform infrared spectroscopy (FTIR).
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