Sorption Time Research Articles

Increased organic contaminant residence times in the urban riverbed due to the presence of highly sorbing sediments of the Anthropocene

This study evaluates the hypothesis that increased organic-contaminant sorption and hence residence time in urban riverbed deposits may occur due to the presence of highly sorbing sediment components of anthropogenic origin that contain thermally altered carbonaceous materials (TACM). The hypothesis was confirmed through laboratory-batch studies examining tetrachloroethene (PCE) sorption on riverbed sediment samples from the highly urbanised River Tame headwaters catchment (Birmingham, UK) and the River Tern (Shropshire) providing a nearby rural benchmark. Urban-riverbed sorption was elevated with observed organic-carbon partition coefficient (Koc) values over an order of magnitude greater than rural values. The latter compare to the widely used US EPA geometric-mean Koc and attributed to absorption-dominated partitioning into (recent) natural organic matter. Use of that mean is inappropriate for the urban riverbed, potentially underestimating retardation by an order of magnitude. Organic petrography confirmed the urban riverbed contained a high proportion of TACM-rich organic-matter particles to which significant adsorption might be expected; furthermore, elevated urban Koc values were consistent with TACM-rich sediment literature estimates. The TACM source appears to be riverine transport of particulate matter from historical industrial/urban or coal-mining/processing activities prevalent upstream since the Industrial Revolution. Consequences of the increased urban riverbed residence time on attenuation and bioavailability assumption sensitivities were modelled. Under the standard assumption of sorbed contaminant being non-bioavailable, rapid rates of aqueous-phase biodegradation are necessary for complete attenuation within a riverbed. Conversely, if adsorbed contaminant is bioavailable, then complete attenuation is probable where highly adsorbing (Anthropocene urban) riverbed sediments are present, even for long half-lives. Therefore, Anthropocene-sediment occurrence may significantly influence modern-day contaminant fate within the urban riverbed; the principal implication being greatly increased sorption and residence times may occur in urban riverbeds than conventionally assumed. Further research should focus upon whether adsorbed contaminants have any bioavailability causing increased contaminant flux attenuation and surface-water quality protection.

Poly(ionic liquid) embedded particles as efficient solid phase microextraction phases of polar and aromatic analytes

In this work, a facile preparation of SPME fibers with increased surface area is presented. The SPME fibers were prepared by grinding poly(ionic liquids) (PILs) to obtain particles of 1–16 µm and, with the aid of a silicon adhesive, attach these particles to a steel wire support. Three different PILs, poly(1-vinyl-3-benzylimidazolium-co-styrene bromide) [poly(ViBnIm-co-Sty Br)], poly(1-vinyl-3-benzylimidazolium-co-styrene bis(trifluoromethanesulfonyl)imide) [poly(ViBnIm-co-Sty TFSI)] and poly(diallyldimethylamine bis(trifluoromethanesulfonyl)imide) [poly(Pyrr11 TFSI)], were used. The first two PILs were obtained by reversible addition–fragmentation chain transfer polymerization followed by metathesis reactions. The thicknesses of the prepared fibers were found to be 19 ± 4 µm and 85% of the particles used have diameters between 2 and 10 µm. The prepared fibers were tested by performing the headspace extraction of two standard solutions, one containing a mixture of alcohols with different chain lengths, and the other a mixture of aromatic compounds, leading to sorption times of 10 – 15 min due the large surface area attained with this method. PILs with aromatic moieties containing the bromide anion showed high selectivity towards polar compounds, due to the hydrogen basicity of the anion, and also towards aromatic analytes, due to the aromatic nature of styrene moieties and the cation pendant groups. The limits of detection fall in the sub ppb level, while relative standard deviations and reproducibility from fiber-to-fiber found maximums of 16.2% and 22.5%, respectively. Furthermore, the PIL based fibers showed up to 90% higher extraction efficiencies compared to the commercial fibers of polydimethylsiloxane and polyacrylate.

Regeneration of Transformer Insulating Fluids Using Membrane Separation Technology

Oxidation of oil/paper insulation initiates premature aging and introduces carboxylic acids with eventual increase in oil acidity, which hampers the properties of the oil. In this paper, a membrane separation technology-based purification process for aged insulation oil has been evaluated and reported. The intent of the present study is to eliminate carboxylic acids, dissolved decay contents and other colloidal contamination present in aged oil and enhance the useful life of oil. The potential of the membrane treatment process has been demonstrated using Ultraviolet Visible Infrared Spectroscopy and Fourier Transform Infrared Spectroscopy diagnostic measurements for oil and membrane. Additionally, membrane retention properties like membrane flux, retention coefficient, sorption time and membrane mass have been analyzed to understand the treatment process. To further evaluate the performance of the membrane and effectiveness of the treatment process, acidity, dielectric dissipation factor, relative permittivity, and resistivity measurements of the oil before and after filtration have been also reported. The proposed membrane purification method has been tested for Algerian utility in-service oil samples. It is inferred that, membrane filtration method is a simple and effective method for treatment of aged oils and aids in extending the remnant life of the oil. The procedure is economically attractive because of increasing prices for transformer liquids, cost effective and environmentally sounds.

Кинетика сорбции нефти материалом на основе листового опада

Studies of leaf litter as a sorption material with respect to oil at various temperatures have been carried out. It has been revealed that with process temperature increasing, the samples sorption capacity decreases. The oil sorption mechanism has been studied. It has been shown that the active sorption time was in the interval from 60 to 600 seconds. It has been proved that at the time of oil and sorption material contact for more than 600 seconds, the desorption process began. Kinetic dependencies of oil absorption by the proposed sorption material have been constructed and analyzed. The reaction order determination by a graphic method has showed that obtained functions with a high degree of correlation can be attributed to first-order heterogeneous reactions. Have been calculated thermodynamic parameters confirming the absence of a chemical reaction between oil and leaf litter. The carried out researches determine the most acceptable parameters of oil sorption by material based on leaf litter.

Immobilization of layered double hydroxide in poly(vinylidene fluoride)/poly(vinyl alcohol) polymer matrices to synthesize bead-type adsorbents for phosphate removal from natural water

Layered double hydroxide (LDH) has been widely used as an adsorbent to remove contaminants from aqueous solutions. However, LDH in powder form might not be suitable in water and wastewater treatment systems due to low hydraulic conductivity and sludge production. Therefore, it is necessary to synthesize bead-type adsorbents for application in treatment systems. In this study, LDH beads were prepared through immobilization of powdered MgFe LDH in polymer matrices, composed of poly(vinylidene fluoride) and poly(vinyl alcohol). The LDH beads had an average size of 2.4 ± 0.6 mm with a Brunauer-Emmett-Teller (BET) specific surface area of 30.41 m2/g and total pore volume of 0.12 cm3/g. Batch experiments were conducted on the use of the LDH beads for phosphate sorption in stream water (pH = 6.9, ionic strength = 613 μS/cm) collected from the Seoho stream located in Suwon, Korea. Fourier-transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS) were used to analyze the chemical characteristics of the LDH beads before and after phosphate sorption. Phosphate sorption to the LDH beads remained relatively constant at initial pH values of 5–9. The LDH beads could be used repeatedly for phosphate sorption through desorption with a NaOH solution. The equilibrium time for the phosphate sorption was 3 h, whereas the maximum sorption capacity was 2.050 mgP/g. In addition, the phosphate sorption increased with a rise in temperature from 15 to 45 °C. Under dynamic flow conditions (flow rate = 4.9 and 9.8 mL/min; bed depth = 10, 20, and 30 cm; inner diameter of column = 2.5 cm), fixed-bed column experiments were performed to test the applicability of the LDH beads in the phosphate removal from the stream water. The phosphate sorption capacity of the column was quantified to be 1.175 mgP/g at given experimental conditions (bed depth = 30 cm; flow rate = 4.9 mL/min). The performance of fixed-bed columns was quantified by analyzing phosphate breakthrough curves with fixed-bed kinetic sorption models (Bohart-Adams and modified dose-response models). This study demonstrated that the LDH beads could be successfully applied as adsorbents for phosphate removal from natural water.

Graphene oxide chemically modified with 5-amino-1,10-phenanthroline as sorbent for separation and preconcentration of trace amount of lead(II).

Graphene oxide (GO) was chemically functionalized with 5-amino-1,10-phenanthroline. The resulting conjugate (phen-GO) was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The experiments show that phen-GO has a high affinity for extraction of Pb(II) ions. Isotherms and kinetics fit the Langmuir model and pseudo-second-order equations. By using phen-GO as a sorbent, Pb(II) ions can be quantitatively adsorbed at pH6.0. The adsorption capacity is 548mgg-1. Following desorption with 2molL-1 HNO3, Pb(II) was quantified by inductively coupled plasma optical emission spectrometry. The effects of pH value, eluent type, sorption time, sample volume, and matrix ions were optimized. The accuracy of the method was validated by analysis of the reference materials DOLT-3 (dogfish liver) and SRM 1640a (natural water). Under optimal conditions, the calibration plots cover the 0.25 to 500ngmL-1 Pb(II) concentration range. The method was successfully applied to the analysis of spiked water and biological samples. Other figures of merit include a preconcentration factor of 250, a detection limit of 46ngL-1, and a relative standard deviation of <5%. Graphical abstract Schematic presentation of the dispersive solid-phase extraction of lead(II) ions using graphene oxide modified with 5-amino-1,10-phenanthroline, followed by their determination by inductively coupled plasma optical emission spectrometry (ICP OES).

Synthesis, characterization and application of a new nano-structured samarium(III) ion-imprinted polymer

This work presents the synthesis of a new nano-structured samarium ion-imprinted polymer (Sm(III)-IIP) by precipitation polymerization. The Sm(III)-IIP nanoparticles were prepared by the copolymerization of Sm(III)–acrylic acid–4-vinylpyridine ternary complex with ethylene glycol dimethacrylate and methyl methacrylate, and then, Sm(III) was leached to obtain Sm(III)-IIP leached particles. Moreover, non-imprinted polymer particles were similarly prepared without Sm(III) ions. The characterization of polymers was carried out by Fourier transform IR spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) and surface analysis. The effect of several parameters such as solution’s pH, sorption and desorption time, type, concentration and volume of eluent on the extraction of the polymers was investigated and optimized by one variable at the time. Optimized parameters were as follows: pH 4; mass sorbent 0.1 g; sorption time, 120 min; desorption time, 120 min; aqueous phase volume, 10 mL. Moreover, it is found that 30 mL of HCl (3 M) provided the most effective elution of Sm3+ ion from IIP beads. The maximum sorbent capacity of the IIPs is 14.91 mg g−1. The sorbent was used for purification of samarium-152 stable isotope. The samarium-152 stable isotope recovery yield was % 99.67. The detection limit of the method was evaluated to be 0.27 ng mL−1. The precision of the method (%RSD, n = 6) was % 0.47.

Study of Acid Treated Mixed Sawdust as Natural Oil Sorbent for Oil Spill

Despite the presence of many techniques to clean up oil spills, sorbents are considered as one of the most attractive techniques due to the high rate of absorption or adsorption and ease of application. Organic-based sorbents have become the best type to use based on their abundance of resources and its biodegradability. Among the many natural organic sorbents available, sawdust has big potential to be used as oil absorbent due to its advantages of being low-cost source, low density and exhibiting hydrophobic-oleophillic characteristics. In this study, the utilization of mixed sawdust as oil sorbent was investigated. The mixed sawdust sorbent was treated using chemicals such as ethanol, sodium hydroxide and hydrochloric acid to further improve the efficiency for oil absorbency. The performance of as-prepared and acid-treated sorbent was characterized using sorption capacity (g/g). The effects of sorption time and surface condition (on seawater surface or on land) towards the performance of sorbent was then investigated. Besides that, the temperature, oil viscosities and reusability of treated sawdust were also studied. It has been proven that acid treated sawdust has higher sorption capacity of 4.82 g/g even after 90 minutes of sorption with four times reusability due to improved hydrophobic and oleophillic characteristics. It was also found that the viscosity of oil and temperature can also affect the sorption capacity. Crude oil, which poses lower viscosity (30.51cP) and at oil temperature of 27°C gave the highest sorption because of the migration of oil into the structure of sorbent was accelerated. This study indicated the possibility of using sawdust as sorbent for oil spill control.

Biomass Modification Using Cationic Surfactant Cetyltrimethylammonium Bromide (CTAB) to Remove Palm-Based Cooking Oil

Adsorption based on natural fibre seems to widely used for oily wastewater recovery due to its low cost, simplicity, feasibility, easy handling, and effectiveness. However, oil sorbent based on natural fibre without modification has low adsorption capacity and selectivity. Thus, this paper proposes chemical modification of sago hampas to improve its adsorbent efficiency for the removal of palm-based cooking oil. The chemical modification was performed using a cationic surfactant, cetyltrimethylammonium bromide (CTAB). The chemical and surface properties of both unmodified and modified sago hampas were characterized by Fourier-Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). Parameters studied for the removal of cooking oil using modified sago hampas were sorption time, adsorbent dosage, and initial pH. The removal capacity was also compared using unmodified sago hampas. The results showed that additional functional groups were introduced on the surface of modified sago hampas. Modified sago hampas also showed a greater porosity than unmodified sago hampas. These properties enhanced the adsorption of palm-based cooking oil onto the surface of modified sago hampas. Modified sago hampas shows better removal of palm-based cooking oil than unmodified sago hampas, where 84.82% and 68.08% removal were achieved by modified and unmodified sago hampas, respectively. The optimum adsorption of palm-based cooking oil was identified at 45 min sorption time, pH 2, and 0.2 g adsorbent dosage.

Complex of polyphenols sorbed on buckwheat flour as a functional food ingredient

An innovative approach to creating a new generation of specialised foods for dietary therapy of type &#x0D; 2 diabetes can involve planned adding of plant polyphenols to their formulafions. The marked antioxidant properties of polyphenols largely determine their potential antidiabetic effects. However, the use of food polyphenols for prophylactic purposes is limited by their low bioavailability, which makes it expedient to search for technological approaches aimed at obtaining polyphenolic matrices with high biological activity, increased digestibility, and stability. This study objective was to purposely extract and concentrate the polyphenols by sorbing them from an aqueous solution of the bilberry leaf extract (BLE) on buckwheat flour and to assess their storage stability. A number of experiments on optimal parameters selection for sorbing polyphenols from the BLE on buckwheat flour were performed. The parameters included the concentration of the extract solution, the solution/sorbent ratio, the pH of the solution, the temperature and the time of sorption. The sorption on the polyphenol matrix was determined from the difference in their contents in the initial solution of the extract and in the supernatant after centrifugation by the Folin-Ciocalteu method. The effects of exposure to light, temperatures, and humidity on the polyphenol compounds in the dry BLE and in the food matrix contents during storage was analysed by the FTIR spectroscopy. The experiments determined the optimal conditions for the BLE polyphenol sorption on buckwheat flour by incubation of a 2% BLE solution pH = 3.6 with the portion of buckwheat flour at the ratio of 1g/50 cm3 solution for 45 minutes at 25°C. When storing the food matrix, there was no significant degradation of the polyphenolic compounds in the food matrix, which indicates an increase in the stability of the polyphenols sorbed on buckwheat flour. This paper presents the results that are scientifically and practically relevant for the nutritiology experts who devise promising technological approaches to expanding the range of functional food ingredients of the antidiabetic character.

A rotating cotton‐based disk packed with a cation-exchange resin: Separation of ofloxacin from biological fluids followed by chemiluminescence determination

A novel approach for green and simple solid-phase extraction of ionizable analytes using cation-exchange resin particles packed in a rotating cotton‐based disk has been developed and utilized for the chemiluminescence determination of ofloxacin in biological fluids (serum and urine). The use of highly-available cation-exchange resin provided effective separation of analyte from complex sample matrixes and its elution by aqueous electrolyte solution without any organic solvents. Ofloxacin ionization in acidic sample solution allowed to provide effective separation of the analyte for subsequent chemiluminescence detection. The cotton‐based disk was characterized by effective wettability. This feature promoted high mass transfer of the analyte to the cation-exchange resin surface at separation step and into elution solution at elution step. The sorption time was decreased to 10 min while the elution time was 5 min. Under the optimal conditions, the detector response for ofloxacin was linear in the concentration range from 9 × 10−8 to 3 × 10−5 mol L−1. The limit of detection, calculated from a blank test based on 3σ, was 3 × 10−8 mol L−1.

Green nanosilica@folic Acid (VB9) nanocomposite for engineered adsorptive water remediation of bivalent lead, cadmium and copper

Folic acid (VB9) was used as an eco-friendly sequestering chemical compound to modify and develop a novel nanocomposite via surface immobilization and chemical bonding with nanosilica (Nano-SiO2) in the chloride form to generate Nano-SiO2@VB9. The synthesized materials were investigated and characterized by several means of SEM, HR-TEM, TGA, FT-IR, XRD and surface area determination. The tendency of Nano-SiO2@VB9 nanocomposite to extract and remove bivalent lead, cadmium and copper ions was studied and optimized under various variables including pH of contact medium, nanocomposite dose, contact time, effect of metal ion concentration and interfering cations-anions. The highest determined capacity values were 562.1, 973.8 and 152.1 mg g−1 for Cd(II), Pb(ІІ) and Cu(II), respectively. The optimum contact time for sorption of metal ions was identified as 25 min, while 10.0 mg of Nano-SiO2@VB9 nanocomposite was the optimum dosage to establish the maximum capacity values. The adsorbed ions were arranged in a multilayer surface and the equilibrium up-take of metal ions by Nano-SiO2@VB9 nanocomposite was favorably characterized by the Freundlich adsorption isotherm model. The potential applications of Nano-SiO2@VB9 for removal and preconcentration of Cu(II), Pb(II) and Cd(II) from real water samples using multistage microcolumn were also studied to confirm excellent percentage extraction values 94–100%, 100% and 57–81%, respectively.

Effect of liming on hexazinone sorption and desorption behavior in various soils

ABSTRACTLiming is a practice commonly used to modify soil acidity, neutralize aluminum, and increase calcium and magnesium in the soil. Liming can change herbicide retention processes and consequently weed control and potential environmental contamination. The effects of liming on the sorption and desorption of hexazinone in different soils were evaluated. Samples from seven Brazilian soils were collected and separated into two subsamples, with and without limestone incubation. Hexazinone was quantified using ultra high-performance liquid chromatography. The sorption and desorption coefficients were determined in soils using Freundlich isotherms. Increasing the pH did not alter the sorption kinetics of hexazinone in the same soil class. The shortest sorption time of hexazinone occurred in soils with higher organic matter (OM) and clay content. Liming reduced the sorption and increased the desorption of hexazinone in the soils, which was caused by the increase in pH and reduction of OM content. Although the application of limestone increased desorption, the rate at which this process occurred was less than the sorption rate of hexazinone in most cases. In alkaline soils, the recommended dose of hexazinone for pre-emergence application should be low to avoid leaching and reduce the contamination of groundwater resources.

Sorption of 3,6-dibromocarbazole and 1,3,6,8-tetrabromocarbazole by microplastics

Microplastics and organic pollutants are typical contaminants in the marine environment. However, little is known about their interactions. In this study, the sorption of 3,6-Dibromocarbazole(3,6-BCZ) and 1,3,6,8-Tetrabromocarbazole (1,3,6,8-BCZ) by Polypropylene microplastic in simulated seawater was studied. Factors, including particle size, salinity and concentration, were investigated, and the experimental results were simulated using a mathematical model. Results showed that the pseudo-second-order kinetic model was more suitable to describe the sorption of polyhalogenated carbazole by microplastics, with equilibrium sorption times of 6 h and 8 h for 3,6-BCZ and 1,3,6,8-BCZ, respectively. Sorption capacity increased with decreasing particle size and the adsorption capacity increased initially and then decreased with increasing salinity, with a maximum sorption occurring at salinity of 14%. Moreover, the sorption amount increased with the increasing concentration of polyhalogenated carbazole. The sorption isotherms were confirmed as the extended Langmuir model and the extended Freundlich model, both of which were S-type.

CO2 adsorption the numerical simulations and the controlling factors to low rank coal

Carbon Capture Sequestration (CCS) in unmineable coal seams questionably gives benefits for the commercial success through potential release of additional methane during the injection of CO2 adsorbs into the coal seams, the process known as enhanced coalbed methane (ECBM) recovery. However, a significant concern lies in the loss of injectivity due to reduction in permeability by coal matrix swelling occurences with CO2 adsorption although this effect can be partially be offset with ‘huff and puff’ scheme of cyclic CO2 injection followed by extraction of the released methane. The paper discusses the results of a numerical simulation study carried out with GEM compositional reservoir simulator to evaluate the effects of uncertainties in various reservoir parameters on the overall volume of CO2 storage and additional methane recovery of low rank coalfield. A 12-15m thick seam at shallow depth, 50-75 m was considered for fluid flow simulation study. While some information on the reservoir setting was obtained through literature and personal communication with the CBM operators, the rest of the information was derived through laboratory studies. The reservoir parameters considered for the study are injection pressure, adsorption capacity, cleat permeability and porosity, and initial gas saturation. A 100-acre drainage area with 5-spot vertical well pattern was considered with one central injector and four producers on four corners of the study area. The maximum allowable injection pressure was estimated to be 7500 kPa at the reservoir setting. The injection pressure was varied from 1000 kPa to 7500 kPa in the simulation. A number of adsorption isotherms were established in the laboratory. The variations in the adsorption parameters observed through the isotherms were considered as uncertainty in the storage capacities. Significant variations were observed due to the variation in adsorption isotherms both for CO2 storage and additional methane recovery. Fracture permeability was varied from 3 md to 200 md, which is the range of permeability observed in the coalfield is around 100-200 mD. The results of simulation indicate a strong influence of porosity on the CO2 storage and ECBM recovery. Fluid flow simulation study shows that variation in sorption time has no significant effect for a low permeability situation while some marginal effect in high permeability situation. Cleat porosity was varied from 1 % to 10 %. Within this range of porosities, enhanced methane recovery varied from 1 % to 10 % relative to the primary recovery but the volume of stored CO2 did not vary significantly. Lastly, the pore pressure, adsorption and gas saturation of CO2 sequestered volume and additional methane recovery were found to increase substantially.

Synthesis of functionalized magnetic nanoparticles as a nanocarrier for targeted drug delivery

AbstractIn this research, iron oxide magnetic nanoparticles (NPs) were synthesized by chemical co‐precipitation method. The surface of particles was grafted with β‐cyclodextrin/N,N‐dimethylacrylamide (β‐CD/DMAA) copolymer. Potency of NPs as carrier of antibiotic ofloxacin (OFL) was evaluated. They were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The effect of the adsorption parameters such as pH, contact time, and temperature for sorption of drug onto NPs was evaluated and optimized. The drug release profile showed that approximately 60% of the adsorbed drug was released in the first 10 min at pH of 1.2 (simulated gastric fluid) and 55% was released within 30 hr in pH of 7.4 (simulated intestinal fluid). Findings of study suggested the suitability of β‐CD/DMAA grafted magnetic NPs for OFL delivery.

Comparison of the sorption capacities of 1,10-phenanthroline and 2,2-bipyridyl complexes with cadmium on activated carbon and graphene oxide

In this study adsorption potential of oxidation activated carbon (ox-AC) and graphene oxide (GO) was investigated. Cd(II) was bound to cationic complexes with 1,10-phenanthroline or 2,2-bipyridyl. The sorbents have been used for the dispersive solid-phase extraction of Cd(II) prior to its inductively coupled plasma optical emission spectrometric or electrothermal atomic absorption spectrometric determination. The influences of the various analytical parameters including pH, eluent type, ligand amount, sample volume and sorption time on the recovery efficiencies of Cd(II) were investigated. The limit of detection for activated carbon - 1,10-phenanthroline and activated carbon - 2,2-bipyridyl were 0.006 and 0.016 ng mL−1, respectively. For graphene oxide with 1,10-phenanthroline and graphene oxide with 2,2-bipyridyl obtained limit of detection were 0.046 and 0.091 ng mL−1, respectively. Maximum adsorption capacities and preconcentration factors were compared. The equilibrium sorption fitted better to the Langmuir isotherm. The method was validated with the certified reference materials ERM-BB186 and SRM 1640a.

Reactivity of rice husk-derived lithium silicates followed by in situ Raman spectroscopy

Lithium silicates were synthesized using rice husk ash as a precursor of silica to be used in CO2 capture. Two different treatment steps, with water (SiO2-W) or HCl 3 M (SiO2-A), were carried out prior to the rice husk burning. Silica with a high surface area of 303 m2g-1, a yield of 16.9% and a purity of 96.8% was obtained for the acid treatment. Subsequently, silica was impregnated with LiNO3 employing different Li/Si molar ratios and two different methods, successive incipient wetness impregnation and wet impregnation. SEM images showed agglomerates of nanometric spheres (70–100 nm) for the silica, and polyhedral particles for the silicate samples. The presence of three silicate phases, Li2Si2O5, Li2SiO3, and Li4SiO4, with different proportions was found by XRD and Raman spectroscopy measurements. In addition, the effect of particle size, temperature and sorption time over the CO2 capture capacity was analyzed. The best performance was found in the Li/Si = 4.1-HW sample with a particle diameter of 0.3 mm and 2 h of isothermal capture at 863 K. In situ Raman experiments were carried out to follow the phase transformations during the capture/regeneration steps. All samples remained in a stable value of capture capacity after several sorption/desorption cycles.

Modification of magnetized MCM-41 by pyridine groups for ultrasonic-assisted dispersive micro-solid-phase extraction of nickel ions

Nickel is one of the heavy metals, which is discharged to ecosystem by normal process and human actions. Nickel is regarded as crucial ion in the living creature and is a component of protein structure at very low level. Dispersive micro-solid-phase extraction assisted by ultrasonic waves with a new magnetic material using pyridine-functionalized magnetic nanoporous sorbent was utilized for detection of nickel ions at trace levels in real matrices. Magnetized nanoporous silica (MCM-41) was modified with pyridine groups, and the structure of prepared magnetic nanoporous sorbent was confirmed by instrumental techniques. The applied techniques were Fourier-transformed infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy and thermogravimetry–differential thermal analysis. Preconcentrated nickel using the mentioned sample preparation procedure was monitored by GFAAS at ng L−1 concentrations. To optimize the effect of significant parameters on sorption and desorption of nickel ions using the applied sample preparation procedure, Box–Behnken design was utilized. The influencing parameters in the sorption step are: sorption amount (mg), pH of solution and sonication time (min), and these parameters for desorption step are: volume of eluent (mL), concentration of eluent (mol L−1) and sonication time (min). Optimized data for parameters that obtained by Box–Behnken design were: sample’s pH: 7.5, sonication time for sorption: 8 min, sorbent amount: 24 mg, desorption solvent: HCl 1.2 mol L−1, eluent volume: 420 μL and time of sonication for desorption, 8 min. Relative standard deviation and method detection limit for nickel monitoring under optimized conditions by UA-d-μSPE were observed to be < 6% and 0.008 μg L−1, respectively.

Synthesis of porous biomass fly ash-based geopolymer spheres for efficient removal of methylene blue from wastewaters

In this work, and for the first time, fly ash (FA)-based geopolymer (d = 2.6 mm) spheres were used to extract methylene blue from synthetic wastewaters. The influence of sorption time, dye initial concentration and adsorbent amount on the dye removal efficiency and uptake by the porous spheres was evaluated. The adsorbents' recyclability and their dye fixation efficiency were also considered. The initial dye concentration strongly affected the uptake and removal efficiency by the porous bodies, the former rising from 1.1 to 30.1 mg/g when the dye initial concentration jumped from 10 to 250 ppm, and the latter increasing from 82.3% to 94.3% when the dye initial concentration varied from 10 to 125 ppm. Results showed a much faster (24 h) and higher (30.1 mg/g) methylene blue uptake in comparison with the other bulk-type geopolymers reported to date (30 h; 15.4 mg/g). The cumulative methylene blue uptake shown by these innovative spheres (79.7 mg/g) surpasses all other powdered geopolymer adsorbents, being among the highest values ever reported for geopolymers. The adsorbent was successfully regenerated and reused eight times. Regeneration was found to negatively affect the MB uptake, but nevertheless, even after eight regeneration cycles a very high MB removal efficiency (83%) was maintained. The use of these bulk-type waste-based geopolymer adsorbents is a low-cost, more eco-friendly, safer and easier alternative to the use of powdered adsorbents in wastewater treatment systems, since these ∼3 mm spheres may be used directly in packed beds, and were produced using significant amounts of waste material.