Sorbent Samples Research Articles

Efficient carbonaceous sorbent based on the waste sludge of oil extraction industry for purifying wastewater from petroleum products

The opportunity to use the oil extraction industry waste kieselghur sludge as a raw stuff for carbonaceous sorbent for purifying wastewater from petroleum and petroleum products has been researched. It has been demonstrated that the thermal modification of the waste sludge results in oxidation of organic matter and the formation of a carbon layer on the surface of kieselghur (diatomite), as well as the formation of the obtained material’s porous structure. The maximum values of oil-absorption and petroleum-absorption of the carbonaceous sorbent samples, obtained at various temperatures of the initial waste product treatment, have been determined. The highest petroleum saturation (2 g/g) is observed in the first 5 minutes of the sorbent’s contact with the pollutant and is characteristic of the material, obtained at temperature 500°С. The highest oil saturation (3.6 g/g) is shown by the sorbent, obtained at temperature 450°С. This value was achieved after 30 minutes of the sorbent’s contact with oil. The efficiency of clarifying water-oil emulsion with the concentration 1.5 g/dm3 by using carbonaceous sorbents of various thermal pre-history has been determined. The highest degree of emulsion clarification – 91% was achieved at using the sorbent, obtained as a result of the waste sludge modification at temperature 450°С.

Сорбция ванилина сверхсшитым полистирольным сорбентом MN-202

Установлено, что изотерма сорбции ванилина сверхсшитым полистирольным сорбентом MN-202 относится к типу Ленгмюра. На основании изучения поглощения данного гидроксибензальдегида неионогенным полимером в статических условиях при различных температурах определено время достижения равновесия в системе и влияние температуры на емкость сорбента. С использованием метода низкотемпературной адсорбции/десорбции азота сравниваются поверхностные и объемные структурные характеристики MN-202 до и после поглощения ванилина

Characterization of calcium looping sorbents with a novel twin bed reactor

The experimental characterization of sorbents for Calcium Looping (Ca-L) processes is generally accomplished by thermogravimetric analysis or by using single fluidized bed bench scale reactors. These methods may present limitations, the most significant being the poor ability to reproduce the thermal history that sorbent particles experience in a real Ca-L plant. This limitation may severely affect the correct evaluation of the sorbent behavior in terms of CO2 capture capacity and attrition. In this study, a purposely developed experimental apparatus is applied for Ca-based sorbent testing under conditions that simulate a realistic thermal history of the sorbent. The apparatus consists of two identical lab-scale bubbling beds (Twin Beds - TB) operated batchwise as the calciner and the carbonator, respectively. The reactors are connected to each other via a rapid solids pneumatic transfer line, designed so as to enable rapid and selective transfer of the sorbent from one reactor to the other at the end of each calcination/carbonation stage. The two beds consist mostly of coarse-grained silica sand, acting as a thermal ballast, to which sorbent samples to be characterized are added.The TB apparatus has been used to investigate the effect of the thermal history on the performance of two limestones, in terms of CO2 capture capacity and attrition tendency, upon multiple calcination/carbonation cycles under the typical operating conditions of the Ca-L process. The results have been compared with those obtained for the same sorbents carried out in a single lab-scale fluidized bed reactor (SB) and under the same operating conditions. The comparison showed that the CO2 capture capacity in the TB system is larger than that found in SB tests for both sorbents. On the contrary, the absence of strong thermal shocks in the TB experiments leads in general to a decrease of the attrition tendency, with a reversal in terms of generated fines between calcination and carbonation stages. Indeed, the generation rate of fines measured in the TB tests during carbonation is smaller than that measured in the corresponding calcination stage, which is opposite to what was found during the tests in the SB device. These findings indicate that the sorbent thermal history plays a non-negligible role on its CO2 capture performance in Ca-L.

Long-Term Uptake of Phenol-Water Vapor Follows Similar Sigmoid Kinetics on Prehydrated Organic Matter- and Clay-Rich Soil Sorbents

Typical experimental time frames allowed for equilibrating water-organic vapors with soil sorbents might lead to overlooking slow chemical reactions finally controlling a thermodynamically stable state. In this work, long-term gravimetric examination of kinetics covering about 4000 h was performed for phenol-water vapor interacting with four materials pre-equilibrated at three levels of air relative humidity (RHs 52, 73, and 92%). The four contrasting sorbents included an organic matter (OM)-rich peat soil, an OM-poor clay soil, a hydrophilic Aldrich humic acid salt, and water-insoluble leonardite. Monitoring phenol-water vapor interactions with the prehydrated sorbents, as compared with the sorbent samples in phenol-free atmosphere at the same RH, showed, for the first time, a sigmoid kinetics of phenol-induced mass uptake typical for second-order autocatalytic reactions. The apparent rate constants were similar for all the sorbents, RHs and phenol activities studied. A significant part of sorbed phenol resisted extraction, which was attributed to its abiotic oxidative coupling. Phenol uptake by peat and clay soils was also associated with a significant enhancement of water retention. The delayed development of the sigmoidal kinetics in phenol-water uptake demonstrates that long-run abiotic interactions of water-organic vapor with soil may be overlooked, based on short-term examination.

Lanthanides removal from mine water using banana peels nanosorbent

This study focuses on the performance of nanostructured banana peels in lanthanide-laden mine water treatment. Specifically, nanostructure formation via mechanical milling, characterization in detail and application of this sorbent media in rare earth elements (REEs) removal from synthetic and real mine water are thoroughly investigated. The sorbent samples were characterized by transmission electron microscopy, Brunauer–Emmett–Teller, X-ray diffraction and Fourier transform infrared analyses, while the amount of REEs adsorbed was analysed using inductively coupled plasma optical emission spectroscopy. Results revealed that the particle and crystallite sizes were reduced from <65,000 to <25 nm and 108 to 12 nm, respectively, as the milling progressed. Furthermore, the fracture of particles resulted in a surface area increment from 1.07 to 4.55 m2 g−1. Through Fourier transform infrared analysis, the functional groups responsible for the coordination and removal of metal ions were found to be carboxylic group (at absorption bands of 1730 cm−1) and amine groups (889 cm−1). The Langmuir maximum adsorption capacity was 47.8 mg g−1 for lanthanum and 52.6 mg g−1 for gadolinium. Meanwhile, results revealed that banana peels have a high affinity for Sm, Eu, Nd, Pr, Gd, Tb and Lu compared to other lanthanides present in the mine water samples. The results obtained so far indicate that nanostructured banana peel is a potential adsorbent for REEs removal from mine water. However, for any application, the water matrix to be treated substantially influences the choice of the sorbent material.

Synthesis and physicochemical properties of a biospecific carbon sorbent modified with lactic-acid oligomers

A method of lactic-acid (LA) polycondensation on a carbon sorbent, including sorbent impregnation and multistep thermal treatment with no catalysts or toxic solvents, is developed. This modification technique makes it possible to obtain materials with adjustable properties (molecular weight of the synthesized oligomer, amount of applied modifier, degree of screening of carbon-sorbent pores, etc.). The resulting sorbent samples were investigated using various physicochemical methods: 13С and 1Н NMR spectroscopy, low-temperature nitrogen adsorption, differential thermal analysis, etc. It is established that the modifier concentration has an impact on the physicochemical characteristics of the studied carbon-sorbent samples. Of greatest interest is the carbon-sorbent sample impregnated with a 50% lactic-acid solution with subsequent thermal treatment. Its composition includes a high content of the modifier (biologically active substance with biospecific properties) and exhibits durable action.

Implementation of carbon nanomodification for sorption materials

The article addresses the urgent task of improving the adsorption capacity and expanding the scope of application for commonly used industrial sorbents – activated carbons and synthetic zeolites. Among a variety of methods for modifying these sorbents, more attention is now being given to techniques that employ carbon nanomaterials. This is due to the unique properties of nanostructures – developed surface, availability of active functional groups, etc. In the present work, the classic materials – NWC coconut shell activated carbon and synthetic NaX zeolite – were chosen as initial sorbent samples to be modified. The authors developed a process flowsheet for the carbon nanomodification, which contains the following main stages: preparation of a catalytic mixture solution under given temperature conditions, impregnation of porous materials using the obtained solution, and drying and synthesis of carbon nanotubes via chemical vapor deposition. The proposed technological line consists of a reactor for synthesis of carbon nanotubes, the patented design of which will allow for simultaneously modifying in an effective way different types of materials. As a result, the layer of carbon nanostructures, the quality of which can be varied by changing the conditions of the modification procedure, is formed on the substrate surface.

Investigation of the peculiarities of modification of carbon sorbent by lactic and glycolic acid with their subsequent polycondensation

A method of modification of carbon sorbents by copolymers of glycolic and lactic acids is developed. Control over the polycondensation process and adjustment of the synthesis conditions and parameters are done using the methods of NMR spectroscopy and thermogravimetric analysis. Optimal conditions for the modification of a carbon material are selected, allowing one to obtain predominantly the oligomers of glycolic and lactic acids. The surface shape and morphology, porous structure, elemental composition and composition of the functional groups, and mechanical strength of the carbon sorbent samples are investigated using a set of physicochemical methods. It is established that the adjusted conditions of polycondensation allow one to affix the modifying agent on the carbon sorbent.

High purity hydrogen production via sorption enhanced chemical looping reforming: Application of 22Fe2O3/MgAl2O4 and 22Fe2O3/Al2O3 as oxygen carriers and cerium promoted CaO as CO2 sorbent

High purity hydrogen can be produced using sorption enhanced chemical looping reforming (SE–CLR) in which an oxygen carrier and an in situ CO2 sorbent are involved. In this study, the effectiveness of alumina modification with Mg as the support of Fe2O3 based oxygen carriers is investigated in CLR and SE–CLR processes for clean hydrogen production. The 22Fe2O3/Al2O3 and 22Fe2O3/MgAl2O4 oxygen carriers are synthesized with impregnation and sequential impregnation methods, respectively. Prior to SE–CLR process, the performance of three different calcium based sorbents including industrial CaO, synthesized CaO and cerium promoted CaO are investigated for CO2 sorption in calcium loop. The characterization of the oxygen carriers and sorbent samples is performed by XRD, BET, FESEM and TEM. It is found that the addition of cerium to the calcium-based sorbent effectively improves its structural properties and CO2 sorption performance. The obtained results reveal that the sorbent surface area is a significant parameter affecting its CO2 removal efficiency at high temperatures. In addition, the presence of Mg in oxygen carrier structure successfully prevents the formation of Fe–Al spinel by MgAl2O4 formation. An excessive H2/CO molar ratio of 16.7 is also achieved using Fe2O3/MgAl2O4 oxygen carrier and synthesized Ce/Ca=0.2 sorbent at 600°C in SE–CLR process.

Desulfurization of coke oven gas using char-supported Fe-Zn-Mo catalysts: Mechanisms and thermodynamics

Sulfidation properties of char-supported Fe-Zn-Mo sorbents prepared by ultrasonic impregnation method were investigated during simultaneous removal of H2S and COS from coke oven gas (COG) using a fixed-bed quartz reactor. Sorbent samples before and after sulfidation were analyzed using X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that the addition of Mo significantly improved the desulfurization properties (i.e., breakthrough time, sulfur capacity and desulfurization efficiency) of Fe-Zn sorbents. Desulfurization reactions were exothermic and thermodynamically favorable in the temperature range of 200–400 °C. Thermodynamic analysis of the sorbents indicated that higher concentration of H2S and lower concentration of H2 favors the reaction of metal oxides with H2S to form metal sulfides.

Development of a method of carbon sorbent modification with polyglicolic acid to create new carbon materials for medical application

The surface of the VNIITU-1 carbon mesoporous sorbent was modified with polyglicolic acid characterized by antibacterial and antifungal properties. Synthesis was carried out in three stages: 1) carbon sorbent impregnation with 50% aqueous glycolic acid solution for 8 h, 2) sorbent drying for 1 h at a temperature of 105 ± 2°C; 3) and thermal treatment of the carbon sorbent impregnated by glycolic acid during the first hour at a temperature of 195 ± 5°C with further heating for 5 h at the temperature of 225 ± 5°C. Carbon sorbent samples were studied using a complex of physico-chemical methods: scanning electron microscopy; IR spectroscopy; X-ray photoelectron spectroscopy; low-temperature adsorption of nitrogen; nuclear magnetic resonance; thermogravimetry; X-ray microanalysis; and C, H, S, O analysis. It is found that the modifier is strongly fixed in the carbon sorbent surface predominantly in the form of glycolic acid oligomers (hexamers). As a result of modification, the amount of oxygen-containing moieties increases considerably as compared to the initial sorbent. The synthesized samples are of great interest as materials for sorption medicine.

Sorption-active matrix based on titanium hydroxide for concentration and joint immobilization of caesium and strontium radionuclides

The possibility of using ferrocyanide sorbent based on hydrated titanium dioxide as a matrix for concentration and joint immobilization of caesium and strontium radionuclides is studied in the article. Chemical stability of sorbent samples saturated by radionuclides is determined via long-term leaching method and thermal behaviour of samples is studied. High chemical stability of sorption-active matrix with respect to leaching of caesium and strontium radionuclides by various types of water (distilled, tap, mineral and sea water) as well as thermal stability within the range of 20–100 °C are shown. Distilled water is the most aggressive leachant sorption-active matrix; for distilled water leaching rates ranged from (3.7 ± 0.2) × 10−10 to (8.2 ± 0.2) × 10−12 g cm−2 day−1 for caesium and from (1.8 ± 0.1) × 10−10 to (1.2 ± 0.1) × 10−12 g cm−2 day−1. Burial or storage of saturated sorption-active matrices dried at temperature of up to 100 °C is recommended.

Removal of Acidic and Basic Dyes from Water using Crosslinked Polystyrene Based Quaternary Ethyl Piperazine Resin

In this study, a beaded polymer with quaternary amine functions was prepared in two steps, starting from poly (vinyl benzyl chloride-ethylene glycol dimethacrylate) (PVBC) based beads, according to the synthetic protocol; modification of ethyl piperazine with PVBC (EP-PS), and quaternization of ethylpiperazine modified beads with chloroacetic acid (QEP-PS). The QEP-PS resin was used for the removal of reactive red 120 as an acidic dye and malachite green chloride as a basic dye. Dye extraction experiments were carried out simply by contacting wetted sorbent samples with aqueous dye solutions at room temperature. Capacities were determined by colorimetric analysis of the residual dye contents. The resin showed that reasonable high dye sorption capacity (0.34-0.41 g per gram of dry resin) was achieved. The adsorption conditions (initial dye concentration and pH) were varied to evaluate the mechanism of adsorption of both basic dyes and acidic dyes on the prepared resin. This material is also able to remove both the anionic dye and cationic dyes completely even from highly diluted aqueous dye solutions.

The behavior of the AV-17(Cr) sorbent in various media

A stability study of a strongly basic anion exchanger modified with Cr3+-containing compounds was conducted. The AV-17(Cr) sorbent described in this paper was prepared by reacting commercial gel-type AV-17 resin bearing N(CH3)3Cl groups with Cr2(SO4)3 solution. The results show that the material is unstable in HNO3 and H2SO4 solutions with a concentration of 1–5N, while in HCl solutions with a concentration higher than 2N, the sorbent becomes more stable due to the transformation of jarosite type compounds into R4N[Cr3(OH)6Cl6] and R4N[Cr3(Cl)6Cl6]2−. Sorbent samples were investigated using FT-IR, SEM spectroscopy, TG-DTG and TG-MS-FTIR. The obtained results reveal a complex degradation mechanism, depending on the chemical structure of the compounds, and on the atmosphere in which the degradation process was conducted. The first degradation stages consist in water removal, followed by trimethylamine (N(CH3)3), ethane (C2H6), sulphur dioxide (SO2), and oxygen (O2) release at temperatures higher than 300°C and by release of an additional amount of water (H2O) resulted from the dehydoxylation process.

Studies of the effect of surface modification of carbon sorbents by poly-N-vinylpyrrolidone using a complex of physicochemical and microbiological methods

The surface of the VNIITU-1 carbon mesoporous sorbent was modified with poly-N-vinylpyrrolidone characterized by antibacterial activity. Synthesis was carried out in two stages: (1) impregnation of the carbon sorbent by an aqueous solution of poly-N-vinylpyrrolidone with the molecular mass of 10000 g/mol; and (2) impregnation of the carbon sorbent by an aqueous solution of the (N-vinylpyrrolidone) monomer and initiator with their further polymerization in an inert atmosphere. Carbon sorbent samples were studied using a complex of physicochemical methods: scanning electron microscopy, infrared spectroscopy, low-temperature nitrogen adsorption, nuclear magnetic resonance, and thermogravimetry. It was found that the polymer obtained on the carbon surface is free of the initial toxic VP monomer. Microbiological tests of modified sorbents with respect to pathogenic and opportunistic microflora were carried out.

Role of Looping-Calcination Conditions on Self-Reactivation of Thermally Pretreated CO2 Sorbents Based on CaO

The conversion of thermally pretreated CaO along successive carbonation/calcination cycles has been investigated, as affected by looping-calcination conditions, by means of Thermogravimetric Analysis (TGA). Sorbent samples have been subjected in situ to a thermal preheating program based on Constant Rate Thermal Analysis (CRTA) by virtue of which decarbonation is carried out at a low controlled rate, which is able to promote self-reactivation in the first carbonation/calcination cycles. Our observations support a pore-skeleton model according to which solid-state diffusion in the first carbonation stages, which is enhanced by thermal pretreatment, gives rise to a soft skeleton with increased surface area. Yet, the results show that self-reactivation is hindered as looping-calcination conditions are harshened. Increasing the looping-calcination temperature and/or the looping calcination time period favors sintering of the soft skeleton and eventually self-reactivation is precluded. A model is developed that retrieves the main features of multicyclic conversion of thermally pretreated sorbents in the first cycles based on the balance between surface area gain due to promoted solid-state diffusion carbonation and surface area loss due to sintering of the soft skeleton in the looping-calcination stage, which can be useful to investigate the critical looping-calcination conditions that nullify self-reactivation. The proposed model allows envisaging the behavior of the sorbent performance as a function of the pretreatment conditions.

Professional ski waxers' exposure to PFAS and aerosol concentrations in gas phase and different particle size fractions

Previous reports show that professional ski waxers have elevated blood levels of perfluorinated substances (PFAS) such as perfluorooctanoate (PFOA) and are exposed to very high concentrations of PFAS in air during ski waxing. Aerosol exposure increases the risk of cardiovascular disease, and PFOA is a potential hormonal disruptor and carcinogen, and can affect the fatty acid metabolism. Animal studies have shown that 8:2 FTOH can undergo biotransformation to PFOA. For the first time, this study presents an occupational scenario of professional ski waxers who are exposed to extremely high dust levels as well as per- and polyfluorinated compounds. Personal and fixed measurements of total aerosol, inhalable and respirable fractions were performed during World Cup events 2007-2010. The occupational exposure limit (OEL) is exceeded in 37% of the personal measurements with concentrations up to 15 mg m(-3) in air. There are differences between personal and area total aerosol concentrations with levels from personal measurements twice as high as those from the area measurements. The personal levels for FTOH ranged up to 996 μg m(-3) (mean = 114 μg m(-3)) and for PFOA up to 4.89 μg m(-3) (mean = 0.53 μg m(-3)) in ENV+ sorbent samples as compared to the general exposure levels from air reaching only low ng m(-3) (<30 ng m(-3)) levels. FTOHs were not detected in aerosols but PFOA showed an average level of 12 μg m(-3) (range = 1.2-47 μg m(-3)). The ski waxers' exposure to paraffin fumes and PFAS is not in compliance with the occupational exposure standards and by far exceed the general populations' exposure. Preventive measures must be taken to minimize the exposure in this occupational group.

Novel Optimized Process for Utilization of CaO-Based Sorbent for Capturing CO2 and SO2 Sequentially

Calcium oxide (CaO) based sorbents, used for CO2 capture in calcination/carbonation cycles, reduce in activity with increasing numbers of cycles, thus reducing the economic benefits of this capture process, generating a significant amount of spent sorbent and raising the potential for pollution from its disposal. This paper presents research into the use of this spent sorbent for the prior capture of sulfur oxides (SOx), as required when the cycle is used with coal-derived flue gases. Using a thermogravimetric analyzer (TGA), the sulfation behaviors of two limestones from Hebei Province (named LA and LB) were examined after different numbers of calcination/carbonation cycles. The results show that the sulfation conversions for spent sorbent of the LA and LB after 40 cycles were, respectively, about 4% and 14% less than that of the original sorbent, indicating that spent sorbents from CO2 capture cycles remain active for SO2 retention. As the number of cycles increased, there was a difference in the sulfation conversions between LA and LB, probably due to the difference in pore structure development for the two limestones as the sulfation reaction progressed. The surface morphology and pore structure of sorbents after different numbers of cycles were examined by scanning electron microscopy (SEM) and nitrogen adsorption/desorption spectroscopy. It was found that the pore size distributions show two peaks in all cases, and as the number of cycles increased, the larger pores fuse together while the number of small pores was not markedly diminished, which is not consistent with the existing sintering model. The observed sintered pore structure provides greater product growing space for reactions to occur in the pore inner surface, which benefits sulfation more than carbonation due to their different product molar volumes, helping to explain why cycled sorbent samples remain active in sulfation.

Characterization and lead(II), cadmium(II), nickel(II) biosorption of dried marine brown macro algae Cystoseira barbata.

The objectives of this research are to identify the functional groups and determine corresponding pK (a) values of the acidic sites on dried brown algae Cystoseira barbata using FTIR and potentiometric titrations, and to investigate the biosorption ability of biomass towards divalent nickel, cadmium, and lead ions. Adsorption was studied as a function of solution pH and contact time, and experimental data were evaluated by the Langmuir isotherm model. CaCl(2) pretreatment was applied to the sorbent for enhancing the metal uptake capacity. The effect of solution pH on biosorption equilibrium was investigated in the pH range of 1.5-5.0. Individual as well as competitive adsorption capacity of the sorbent were studied for metal cations and mixtures. The retention of the tested metal ions was mostly influenced from pH in the range of 1.5-2.5, then stayed almost constant up to 5.0, while Ni(II) uptake showed the highest variation with pH. Potentiometric titrations were performed to find the number of strong and weak acidic groups and their acidity constants. The density of strong and weak acidic functional groups in the biomass were found to be 0.9 and 2.26 mmol/g, respectively. The FTIR spectra of the sorbent samples indicated various functionalities on the biomass surface including carboxyl, hydroxyl, and amino and sulphonate groups which are responsible for the binding of metal ions. The capacity of the biomass for single metal ions (around 1 mmol/g) was increased to 1.3 mmol/g in competitive adsorption, Pb(II) showing the highest Langmuir intensity constant. Considering its extremely high abundance and low cost, C. barbata may be potentially important in metal ion removal from contaminated water and industrial effluents.

Nuclear analytical techniques for quantification of uranium for its recovery from seawater

Nuclear analytical techniques namely fission track technique using solid state nuclear track detector (SSNTD) and instrumental neutron activation analysis (INAA) have been standardized and applied for quantification of low uranium concentrations in liquid samples such as feed, elute and brine and solid sorbent samples respectively. The quantification of uranium is required for its recovery study from seawater, which is one of the potential sources of uranium. The uranium concentration of a liquid sample obtained by SSNTD method was compared with the other well established conventional techniques like ICP-MS, ICP-AES, adsorptive stripping voltametry and alpha spectrometry. INAA was applied for uranium concentration determination in the radiation grafted polyamidoxime sorbent samples.