Bifunctional Sorbent Research Articles

Alternating adsorption of gaseous Hg0 in smelting flue gas and aqueous Hg2+ in waste acid using FeSx/Fe2TiO5: Full utilization of active S resource and centralized control of Hg pollution

Gaseous Hg0 adsorption by metal sulfides is considered as a surface reaction, and most active S species may not be fully utilized during this process, causing the wastage of these valuable resources. To maximize the utilization of active S resource in FeSx/Fe2TiO5 after gaseous Hg0 adsorption, FeSx/Fe2TiO5 was exploited as a bifunctional sorbent to alternately adsorb gaseous Hg0in smelting flue gas and aqueous Hg2+in waste acid. FeSx/Fe2TiO5 demonstrated exceptional performance in adsorbing both gaseous Hg0 and aqueous Hg2+. The utilization of active S resource in FeSx/Fe2TiO5 was significantly improved after the alternating adsorption of gaseous Hg0 and aqueous Hg2+. FeSx/Fe2TiO5 showed strong super-paramagnetism, enabling it to be recovered via magnetic separation for recycle and regeneration. The spent FeSx/Fe2TiO5 can be effectively regenerated by re-reacting it with gaseous H2S for recycle. Hg species adsorbed on FeSx/Fe2TiO5 were primarily desorbed as extremely high levels of gaseous Hg0, which was afterwards recovered via a condensing unit as liquid Hg0 for centralized control. Therefore, the alternating adsorption of gaseous Hg0 in smelting flue gas and aqueous Hg2+ in waste acid using FeSx/Fe2TiO5 offered significant advantages in the centralized control of Hg pollution in smelters, double as fully utilizing its active S resource.

Imidazolium functionalized polysulfone/DTPA-chitosan composite beads for simultaneous removal of Cr(VI) and Cu(II) from aqueous solutions

Simultaneous removal of chromium(VI) oxyanions and heavy metal cations from contaminated water body is of great significance. In this work, a novel and bifunctional sorbent, imidazolium functionalized polysulfone/DTPA-chitosan composite bead (IMPSF/DACS) was successfully constructed by phase inversion method and applied for co-removal of Cr(VI) and Cu(II) from aqueous solutions. The maximum adsorption capacities for Cr(VI) and Cu(II) on IMPSF/DACS in single system at pH 5 were 56.72 and 43.05 mg g−1, respectively. In binary system, the removal of Cr(VI) could be further enhanced by the presence of Cu(II) due to the electrostatic shielding effect, while Cu(II) sorption was not significantly affected by the coexistence of Cr(VI). Moreover, IMPSF/DACS could simultaneously reduce low concentrations of Cu(II) and Cr(VI) in simulated contaminated lake water below the limit, while also showing good reusability in co-removal of Cr(VI) and Cu(II). The order of inhibitory effect of competing anions on Cr(VI) removal was as follows: H2PO4− < Cl− < NO3− < SO42−, while the competing hardness cations had a little effects on the adsorption of Cu(II), implying that the Cr(VI) removal was mainly depended on the electrostatic attraction between Cr(VI) and imidazolium ions modified on IMPSF/DACS, and Cu(II) uptake was associated with chelation of DACS encapsulated in IMPSF/DACS beads. These assumptions were confirmed by XPS, FTIR and EDS-mapping techniques.

Effect of bi-functionalization of algal/polyethyleneimine composite beads on the enhancement of tungstate sorption: Application to metal recovery from ore leachate

Algal/polyethyleneimine composite beads (ALPEI) have been successfully functionalized by grafting phosphonate (ALPEI-P), quaternary ammonium groups (ALPEI-Q), and by dual moieties (ALPEI-PQ). The materials are characterized by a wide diversity of analytical methods: SEM and SEM-EDX, TGA, BET, FTIR and XPS, elemental analysis and titration (detailed discussion in Supplementary Information). FTIR and XPS analyses show contributions of quaternary ammonium, hydroxyl, and phosphonate groups in tungstate binding (which may involve polynuclear species, depending on the pH). The synergistic effects of phosphonate and quaternary ammonium moieties contribute to strongly increase W(VI) sorption capacity up to 1.8 mmol W g−1 (i.e., 4-times compared with pristine beads), at pH 5. The strong increase of sorption properties with temperature (2.45 mmol W g−1 at T: 50 °C) demonstrates the endothermic nature of metal binding, which is spontaneous (and characterized by positive entropy change). The Langmuir Dual Site equation successfully fits sorption isotherm for functionalized sorbents (bearing phosphonate and phosphonate/quaternary ammonium groups in addition to proper reactive groups of pristine beads) contrary to the isotherms for raw beads (fitted by Langmuir equation). The pseudo-first order rate equation fits kinetics (equilibrium reached within ≈60 min). The bi-functional sorbent shows marked preference for W(VI) against base and alkali-earth metals (especially at pH close to 3.5). These properties are confirmed in the treatment of raffinate solutions (after ore leaching and solvent extraction): despite the complexity of the effluent, ALPEI-PQ reveals highly efficient for W(VI) recovery and separation. The sorbent can be used as a polishing treatment for enhancing the recovery of strategic metals. Sorbed tungstate is readily desorbed from the sorbent using 0.2 M NH4Cl solution. The sorbent is efficiently recycled for at least 5 cycles (complete desorption, loss in sorption performance less than 4% at the fifth cycle).

Highly efficient, bioactive, and bifunctional sorbent p-n-p visible light heterogeneous photocatalyst utilizing ultra-fine ZnS nanoparticles embedded in a polymeric nanocomposite.

This study reports the successful synthesis of a ZnS@GO@Pani polymeric nanocomposite (NC) via chemical polymerization. The product was used for simultaneous photocatalytic degradation–adsorption of malachite green (MG), a carcinogenic and widely used dye. The physicochemical properties of the prepared NC were characterized by various techniques. Morphological and XRD results confirmed the fine size of ZnS nanoparticles (NPs) with an approximate mean size of 5 nm, uniformly distributed within the polymeric matrix. For comparative purposes, photocatalytic dye degradation–adsorption of this nanohybrid was explored both in the dark and under natural light. It was observed that 0.1 g of the ternary NC in MG aqueous solution (20 ppm) leads to dye adsorption within 15 minutes with an efficiency of 70% under dark conditions. Also, MG removal efficiency of up to 90% was achieved in 15 minutes under natural light owing to integrated photocatalytic degradation–adsorption mechanisms. Adsorption isotherm studies were performed considering Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) models. The results showed that the Freundlich isotherm with R2 = 0.988 is well consistent with the experimental data. Integrated photocatalytic degradation–adsorption kinetics were modeled with pseudo-first-order (PFO) and pseudo-second-order (PSO) models where PSO with R2 = 0.999 best fitted the data, implying the predominant role of chemical adsorption in the dye removal process. Antibacterial tests revealed superior antibacterial activity of the prepared ZnS@GO@Pani NC against both Gram-negative and Gram-positive bacteria, demonstrating the remarkable synergistic effect of ZnS NPs embedded in the GO@Pani matrix. Accordingly, the prepared NC could be regarded as a promising candidate for wastewater treatment applications. The leaching and regeneration studies also confirmed that the prepared NC is a non-toxic dye removal agent with good reusability.

Numerical Simulation of Enrichment of the Air-Helium Mixture with a Bifunctional Sorbent Based on Glass Microspheres

Numerical Simulation of Enrichment of the Air-Helium Mixture with a Bifunctional Sorbent Based on Glass Microspheres

Efficient oxidation and sorption of arsenite using a novel titanium(IV)-manganese(IV) binary oxide sorbent

Owing to the high toxicity and mobility, the removal of arsenite (As(III)) is significantly more difficult than arsenate (As(V)), thus representing a major challenge in arsenite-contaminated water treatment. For efficient elimination of As(III), we successfully fabricated a novel Ti-Mn binary oxide via a simultaneous oxidation and coprecipitation process. The amorphous oxide was aggregated from nanosized particles with a high specific surface area of 349.5 m2/g. It could effectively oxidize As(III) to As(V) and had a high As(III) sorption capacity of 107.0 mg/g. As(III) sorption occurred rapidly and equilibrium was achieved within 24 h. The kinetic data was well fitted by the pseudo-second-order equation, indicating a chemical sorption process. The material was almost independent upon the presence of competitive ions. The As(III) removal by the sorbent is a combined process coupled oxidation with sorption, where the MnO2 content is mainly responsible for oxidizing As(III) to As(V) and the formed As(V) is then adsorbed onto the surface of amorphous TiO2 content, through replacing the surface hydroxyl group or the adsorbed As(III) and forming inner-sphere surface complexes. Furthermore, the arsenic-containing oxide could be effectively regenerated and reused. The bi-functional sorbent could be used as a potentially attractive sorbent for As(III) removal in drinking water treatment and environmental remediation.

Synthesis of 3D iron and carbon-based composite as a bifunctional sorbent and catalyst for remediation of organic pollutants

We prepared a 3D monolith by integrating graphite nanosheet encapsulated iron nanoparticles (Fe@GNS) into graphite felt (GF) supports. The structural properties of the resulting Fe@GNS/GF monolith are characterized by x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and N2 adsorption–desorption isotherms. The Fe@GNS/GF monoliths are utilized as a bifunctional sorbent and catalyst for water remediation. Using Congo red and methyl violet 2B as model pollutants, the sorption and catalytic performance of the Fe@GNS/GF composite are examined. The Fe@GNS/GF monolith possesses maximum sorption capacities of 177 and 142 mg g−1 for the sorption of CR and MV-2B, respectively. It also exhibits rate constants of 0.0563 and 0.0464 min−1 for the catalytic degradation of CR and MV-2B, respectively. As a proof of concept, the Fe@GNS/GF is successfully utilized to decontaminate simulated organic waste water via a combination of sorption and catalytic degradation processes.

Modified Sorbents of Sapropel for Wastewater Treatment

There was demonstrated that using that by heat treatment sapropel under air temperature 300 – 350 °C can be obtained bifunctional sorbent capable of removing organic substances and metal ions from aqueous solutions. Sorbent capacity for copper ions is 29,3 ± 2,1 mg/g, for petroleum derivatives – 33,1 ± 2,7 mg/g. There was found that modifying polyhexamethylenguanimidin and humic acids allows expanding possibilities and improving the sorption capacity characteristics of carbon-mineral sorbent.

CO2 Sorption-Enhanced Processes by Hydrotalcite-Like Compounds at Different Temperature Levels

Abstract The aim of this work is to identify solid sorbents for CO2 capture for coal and biomass syngas conditioning and cleaning by means of a sorption-enhanced reaction process. Hydrotalcite-like compounds (HTlcs) were synthesized with and without K2CO3 impregnation. Samples were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) porosimetry after synthesis and after capture tests, respectively. Sorption and desorption tests were performed in a fluidized bed reactor, under cyclic conditions, at two different temperature levels: 350/450°C and 600/700°C. At low temperature only the Mg–Al HTlcs K promoted samples showed stability and sorption capacity comparable with literature values. On the other hand, results at high temperature indicate that the mixed Mg-Ca-Al HTlcs samples exhibit the best behavior with the highest sorption capacity (1.7 mmolCO2/g) almost stable over 5 sorption/regeneration cycles; furthermore, addition of steam allowed increasing their reactivity by 70% compared to the dry value. This type of sorbent could be a promising candidate to prepare a bifunctional sorbent–catalyst for sorption-enhanced processes, taking place directly in the fluidized bed gasifier, or downstream the reactor for adjustment of gas composition before further conversion in gaseous energy carriers.

Hydrogen production by sorption-enhanced steam methane reforming process using CaO-Zr/Ni bifunctional sorbent–catalyst

A bifunctional CaO-Zr/Ni (13, 18, and 20.5wt% NiO) sorbent–catalyst was developed using the wet-mixing/sonication technique and applied for hydrogen production by sorption-enhanced steam methane reforming (SESMR), an intensified process that integrates hydrogen production with CO2 capture. The material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and N2 physisorption (BET). CO2 sorption efficiency of the developed materials was evaluated during 25 CO2 sorption/regeneration cycles. The prepared sorbent–catalysts were then applied in the SESMR during 10 reaction cycles. The results showed that the bifunctional sorbent–catalyst with 20.5wt% NiO loading presented the most suitable activity. The H2 yield of ∼91% at the end of the 10th SESMR cycle is considerably higher than equilibrium H2 yield that could be obtained by traditional steam methane reforming.

SYNTHESIS AND APPLICATION OF A BI-FUNCTIONAL SORBENT DERIVED FROM ETHYLACRYLATE-DIVINYLBENZENE COPOLYMER FOR THE SOLID-PHASE EXTRACTION OF PESTICIDES FROM WATER

A bi-functional sorbent derived from ethylacrylate-divinylbenzene copolymer was synthesized in beaded form by a suspension polymerization technique. Unlike conventional alkaline hydrolysis of the copolymer, a novel hydrolysis technique was used in this study and the copolymer was treated with concentrated sulfuric acid. More than 70% of the ester groups were converted into –COOH groups and about 60% of the aromatic rings in the copolymer were introduced by –SO3H groups. The synthesized copolymer was used as a solid-phase material for extraction of pesticides from water samples. Recoveries of five pesticides, namely, chlorfenvinfos, endosulfan sulfate, chlorpyrifos, fenvalerate, and diuron, were compared to those using commercially available silica-based C-18 sorbent. The recoveries obtained with the synthesized sorbent were low compared to commercial C18 cartridge. However, the synthesized polymer is cost effective and can be reused. Three extraction cycles did not affect the % recoveries of the studied pesticides. The % recoveries, obtained for chlorfenvinphos, diuron, endosulfan sulfate, chlropyrifos, and fenvelerate, ranged from 28 to 62%; linear range, 0.035 to 22 mg L−1; LOD, 37 to118 µg L−1; and LOQ, 123 to395 µg L−1.

Synthesis, characterization and application of a novel mercapto- and amine-bifunctionalized silica for speciation/sorption of inorganic arsenic prior to inductively coupled plasma mass spectrometric determination

A bifunctional sorbent, (NH2+SH)silica, containing both amine and mercapto functionalities was prepared by modification of silica gel with 3-(triethoxysilyl)propylamine and (3-mercaptopropyl)trimethoxysilane. In addition to the bifunctional sorbent, silica gel was modified individually with the functional mercapto- and amino-silanes, and the mono-functional sorbents, namely (SH)silica and (NH2)silica, were also mechanically mixed ((NH2)silica+(SH)silica) for the sake of comparison of sorption performances. It has been demonstrated that (SH)silica shows quantitative sorption only to As(III) at two pH values, 1.0 and 9.0, while (NH2)silica displays selectivity only towards As(V) at pH 3.0. On the other hand, the bifunctional (NH2+SH)silica possesses the efficient features of the two mono-functionalized sorbents; for example, it retains As(III) at a wider pH range, from 1.0 to at least 9.0 with the exception at pH 2.0, and it also shows quantitative sorption to As(V) at pH 3.0. This property gives the bifunctional (NH2+SH)silica a better flexibility in terms of sorption performance as a function of solution pH. The mechanically mixed (NH2)silica+(SH)silica exhibits a similar but less efficient sorption behavior compared to the bifunctional sorbent. Desorption of both As(III) and As(V) species can be realized using 0.5M NaOH. The validity of the proposed method was checked through the analysis of a standard reference material and a good correlation was obtained between the certified (26.67μgL−1) and determined (27.53±0.37μgL−1) values. Spike recovery tests realized with ultrapure water (93.0±2.3%) and drinking water (86.9±1.2%) also confirmed the applicability of the method.

Alkyl diol silica: restricted access pre-column packings for fast liquid chromatography-integrated sample preparation of biological fluids

A silica-based pre-column packed with a ‘restricted access material’ was used for fully automated solid-phase extraction of drugs and metabolites from untreated biological fluids via a simple valve-switching method. The bifunctional sorbent employed, alkyl diol silica, is characterised by a different chemical modification of the outer surface (diol groups) and the pore surface of the particles (alkyl chains: C 4, C 8 or C 18). This allows for a fast and efficient clean-up of complex biological samples, such as blood, serum, urine or milk, with exclusion of the macromolecular matrix (proteins, nucleic acids) in less than 1.5 min.