Acid Sorbent Research Articles

Highly efficient catalytic direct air capture of CO2 using amphoyeric amino acid sorbent with acid‐base bi‐functional 3D graphene catalyst

Direct air capture (DAC) of CO2 is vital for combating global climate change, but DAC technologies have a low absorption efficiency due to the low concentration (∼400 ppm) of atmospheric CO2. A novel DAC technology was developed to solve this issue using lysine (an amino acid) as a sorbent and N-doped 3D graphene as an absorption/desorption-enhanced bifunctional catalyst. Introducing only 500 ppm N-3DG catalyst increased the working time (≥90% CO2 absorption efficiency) by 233% and its absorption capacity by 197%. The catalyst also significantly accelerated the CO2 working desorption capacity and rate by ∼280% and ∼338% at 70 °C, enabling regeneration of the sorbent by utilizing low-temperature waste heats. Furthermore, the excellent stability of the system was confirmed by 50 cyclic tests. The chemical mechanism driving catalytic CO2 capture was postulated and confirmed by density functional theory computations. This study provides a new strategy for developing next-generation DAC technologies.

Sintering resistant CO2 sorbents prepared by eggshell derived xerogels

• Sustainable and stable CO 2 sorbents were prepared from eggshells. • Lime sorbents were prepared by combustion of carboxylic acid derived xerogels. • Release of gas & heat during xerogel combustion modifies sorbents’ morphology. • Sorbents’ unimodal granulometric distribution minimizes particles coalescence. • Eco-friendly lactic acid sorbent showed the slowest carrying capacity decay. A sol–gel like method was used to prepare CaO sorbents from eggshells, and carboxylic acids, with improved sintering resistance. Sorbent materials obtained by calcination (900 °C) of the calcium xerogels presented different morphologies depending on the acid used as the complexing agent (citric, lactic, oxalic, maleic, acetic, and propionic). Sorbents were tested for cyclic carbonation (700 °C, 15% CO 2 in N 2 )/decarbonation (800 °C, in N 2 ) in a thermobalance. Sorbents had distinct specific areas and porosities resulting from the release of gaseous molecules, and heat, from the thermal decomposition of xerogels. The particle size distribution of sorbents was also a function of the acid. The acid carbon chain and the combustion enthalpy have opposite effects on the morphology of sorbents. The lactic acid-derived sorbent was the most performant showing the lowest carrying capacity decay. After 50 cycles the loss of CO 2 capture capacity was 45% for the lactic acid-modified sorbent, while the unmodified sorbent showed a sorption capacity decay of 74%. Scanning electron microscopy showed, after cyclic carbonation/decarbonation, a sintered morphology for the sorbent derived from raw eggshells. This sorbent presented non-porous large aggregates, while the lactic acid-derived sorbent showed a clear network of voids within the crystals agglomerates and a coral-like morphology that is known to confer sorbent stability. This sorbent was the only sorbent with a particle size distribution closer to the unimodal, while the other samples were bimodal. The absence of smaller particles reduces the contact between sorbent grain boundaries at high temperatures, which minimizes the sintering process.

Adenine-coated magnetic multiwalled carbon nanotubes for the selective extraction of aristolochic acids based on multiple interactions.

A method is described for the functionalization of magnetic carbon nanotubes to recognize aristolochic acid Ⅰ and Ⅱ. 3-Glycidyloxypropyltrimethoxysilane was used as a coupling agent to immobilize adenine on a solid support. The morphology and structure of adenine-coated magnetic carbon nanotubes was investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and a vibrating sample magnetometer (VSM). The adsorption performance of the adenine-coated magnetic carbon nanotubes was evaluated via adsorption isotherms, the kinetics and selectivity tests. The adsorption capacity of the adenine-functionalized sorbent for aristolochic acid Ⅰ was determined to be 24.5μg mg-1. By combining magnetic solid phase extraction with HPLC detection, a method was developed to enrich and detect aristolochic acids used in traditional Chinese medicine. A satisfactory recovery (92.7 - 97.5% for aristolochic acid Ⅰ and 92.6 - 99.4% for aristolochic acid Ⅱ) and an acceptable relative standard deviation (<4.0%) were obtained.

3D printed solid-phase extraction sorbents for removal of volatile organic compounds from water

A carbon black modified polylactic acid (PLA) sorbent was 3D printed from a commercially available conductive PLA filament on a personal 3D printer. The internal porosity of the sorbent was controlled through software-controlled infill print densities from 15 to 50%. The 3D printed sorbent was evaluated for its ability to remove model VOC contaminants (benzene, toluene, and ethyl benzene) from water where the pseudo-second order rate constants for VOC sorption were found to increase with a decrease of internal pore size of the sorbent infill density. The ability to 3D print carbon-based sorbents for on-demand, point-of-use water purification presents a potentially useful mechanism for in-home or emergency purification situations where consumption of clean water is not possible.

Development and validation of a rapid LC–MS/MS method for determination of methylated nucleosides and nucleobases in urine

Modified nucleosides and nucleobases serve as potential diagnostic and prognostic markers of various diseases, including cancer. These compounds are hydrophilic, but are determined mainly using columns with C18 stationary phase. Moreover, these compounds require purification due to the presence of high amounts of isotopomers in the sample matrix and risk of matrix interferences. The most commonly used method for analyte extraction (i.e. solid-phase extraction on phenylboronic acid sorbent) is not appropriate for all the analytes since compounds with cis-diol groups (e.g. 7-methylguanine) are not absorbed. Thus, the aim of this study was to develop and validate a simple and fast method for the simultaneous determination of the methylated nucleosides and nucleobases (derivatives of adenine and guanine including those with cis-diol groups) in urine. The method was based on hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC–MS/MS). The sample preparation involved only dilution with acetonitrile and centrifugation. The method was validated for selectivity, calibration curve, precision, accuracy, stability, matrix effect, dilution integrity, and carryover, according to the guidelines of the European Medicines Agency (EMA). All the analyzed validation criteria were fulfilled. The method was applied to the urine of rats and humans (adults and children). To our best knowledge, HILIC-MS/MS method established by our team is the first method that does not require the extraction step as well as this method enables simultaneously determination of 1-methylguanine, 2′-O-methylguanosine, 3-methyladenine, and N6-methyl-2′-deoxyadenosine in urine. The method is reliable and can be applied to determine the concentrations of the modified nucleosides and nucleobases in the urine of humans and rats. Because the method is cost-effective, fast, and easy to perform, it may be considered as a routine tool in clinical laboratories.

Synthesis of polyaminophosphonic acid-functionalized poly(glycidyl methacrylate) for the efficient sorption of La(III) and Y(III)

After synthesis of parent PGMA micro-particles by dispersion polymerization method, diethylenetriamine (DETA) is grafted on the polymer (DETA-PGMA). In the last step, methylene phosphonic groups are grafted on DETA-PGMA by reaction of phosphonic acid groups onto amine functions in the presence of formaldehyde to produce polyaminophosphonic acid sorbent (PPA-PGMA). The sorbent is characterized by elemental analysis, FTIR spectrometry, XPS, XRD, TG-TDA and SEM-EDX analyses. The sorption properties of the material are tested for the sorption of La(III) and Y(III): the effect of pH on sorption performance is investigated before studying uptake kinetics, sorption isotherms (and thermodynamics), metal desorption and sorbent recycling. Maximum sorption capacities reach up to 0.79 mmol La g−1 and 0.73 mmol Y g−1 at pH 5 (optimum initial pH value). Sorption isotherms are characterized by a saturation plateau: the Langmuir equation fits well data. The sorption on micron-sized particles is fast and equilibrium is reached within 3–4 h: the kinetic profiles are modelled by the Crank equation (resistance to intraparticle diffusion) though the pseudo-first order rate equation fits well experimental data. Nitric acid (0.5 M) solutions can be used for metal recovery and the sorbent is re-used for at least 6 cycles of sorption and desorption with limited decrease in performance (less than 7%). The sorbent has a preference at pH 5 for La(III) vs. Y(III) but the selectivity coefficient is not high enough for potentiating the selective separation of the two metals.

Water compatible functionalized chitosan-based 4-HBA mimic imprinted polymer as a potential sorbent for salicylic acid

ABSTRACT An efficient acrylamide grafted chitosan (AGCTS)-based polymer (AGCTS-based mimic 4-hydroxy benzoic acid imprinted polymer [AGMIP]) was synthesized using 4-hydroxy benzoic acid as a mimic template for the recognition of salicylic acid (SA) in aqueous solution. The influence of grafting parameters on grafting percentage of AGCTS was studied. AGMIP was characterized by scanning electron microscopy, Fourier transform infrared spectrometer, and Brunauer–Emmett–Teller surface area analysis. Adsorption process could be well described by Langmuir and Temkin adsorption isotherm model and the maximum adsorption capacity calculated for SA was 62 mg/g. The adsorption kinetic data was fitted with pseudo-second order equation. The experimental results suggest that AGMIP is a promising adsorbent for SA. Abbreviations AGMIP: Acrylamide grafted chitosan-based mimic 4-hydroxy benzoic acid imprinted polymer; SA: salicylic acid; 4-HBA: 4-hydroxy benzoic acid; GA: gallic acid; 2,5-DBA: 2,5-dihydroxy benzoic acid; 4-HBACTSMIP: chitosan-based 4-hydroxy benzoic acid molecularly imprinted polymer; SACTSMIP: chitosan-based salicylic acid molecularly imprinted polymer; AGCTS: acrylamide grafted chitosan; AGMIPAE: acrylamide grafted chitosan-based mimic 4-hydroxy benzoic acid imprinted polymer after extraction; AGMIPBE: acrylamide grafted chitosan-based mimic 4-hydroxy benzoic acid imprinted polymer before extraction; COD: Chemical oxygen demand; PCA: Protocatechuic acid; APS: Ammonium persulphate.

Sustainable carbon microtube derived from cotton waste for environmental applications

Given its natural state and cost-effectiveness, cotton can be an ideal material for the fabrication of high performance catalyst and pollutant removal from the environment. In this study, novel carbon microtube derived from cotton waste were successfully prepared by thermal treatment of cotton in an argon atmosphere and used as a tannic acid sorbent. Carbon microtube (CMT) properties were investigated by electron microscopy (SEM, TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), zeta potentiometer and N2 adsorption − desorption. The most stable solutions in water were established using CMT treated at 900 and 1300 °C and in tannic acid (TA) at 1100 and 1300 °C, respectively. Maximum TA sorption capacity, 596.5 mg g−1, was found for CMT treated at 1100 °C. The suitability of Langmuir model with simultaneously good fitting of other tested models of sorption implied that monolayer sorption was the first step of TA sorption onto CMT via π–π interactions and hydrogen bonds. Given the repeatability, high removal performance and cost effectiveness of the cotton based carbon microtubes when compared to other well-known sorbent such as carbon nanotubes, the carbon microtubes demonstrated great potential as low-cost and effective tannic acid (and dissolved organic matter) adsorbent.

Kinetic Studies on the Removal of Some Lanthanide Ions from Aqueous Solutions Using Amidoxime-Hydroxamic Acid Polymer.

Lanthanide metal ions make distinctive and essential contributions to recent global proficiency. Extraction and reuse of these ions is of immense significance especially when the supply is restricted. In light of sorption technology, poly(amidoxime-hydroxamic) acid sorbents are synthesized and utilized for the removal of various lanthanide ions (La3+, Nd3+, Sm3+, Gd3+, and Tb3+) from aqueous solutions. The sorption speed of trivalent lanthanides (Ln3+) depending on the contact period is studied by a batch equilibrium method. The results reveal fast rates of metal ion uptake with highest percentage being achieved after 15–30 min. The interaction of poly(amidoxime-hydroxamic) acid sorbent with Ln3+ ions follows the pseudo-second-order kinetic model with a correlation coefficient R2 extremely high and close to unity. Intraparticle diffusion data provide three linear plots indicating that the sorption process is affected by two or more steps, and the intraparticle diffusion rate constants are raised among reduction of ionic radius of the studied lanthanides.

Direct air capture of CO2 via aqueous-phase absorption and crystalline-phase release using concentrated solar power

Using negative emissions technologies for the net removal of greenhouse gases from the atmosphere could provide a pathway to limit global temperature rises. Direct air capture of carbon dioxide offers the prospect of permanently lowering the atmospheric CO2 concentration, providing that economical and energy-efficient technologies can be developed and deployed on a large scale. Here, we report an approach to direct air capture, at the laboratory scale, using mostly off-the-shelf materials and equipment. First, CO2 absorption is achieved with readily available and environmentally friendly aqueous amino acid solutions (glycine and sarcosine) using a household humidifier. The CO2-loaded solutions are then reacted with a simple guanidine compound, which crystallizes as a very insoluble carbonate salt and regenerates the amino acid sorbent. Finally, effective CO2 release and near-quantitative regeneration of the guanidine compound are achieved by relatively mild heating of the carbonate crystals using concentrated solar power.

Polyhydroxamic acid functionalized sorbent for effective removal of chromium from ground water and chromic acid cleaning bath

Polyhydroxamic acid sorbent was synthesized by polymerization of acrylamide using N, N′-methylene-bis-acrylamide as crosslinker and ammonium per sulphate as a thermal initiator. The sorbent was characterized for composition, thermal stability, functional group and morphology by elemental analysis, thermal analysis, infrared spectroscopy and secondary electron microscopy respectively. The synthesized sorbent was evaluated for the removal of trivalent and hexavalent chromium ion from aqueous solution. Experimental parameters such as pH, equilibration time, solute concentration and temperature were optimized. It showed a sorption capacity of 322mgg−1 for Cr (III) and 176mgg−1 for Cr (VI) at pH 4. The sorbent reduces the more toxic Cr (VI) to relatively less toxic Cr (III) during the sorption process as confirmed by X-ray photoelectron spectroscopy. The sorption phenomena followed Langmuir model and the sorption reaction was found to be pseudo–second order confirming chemisorption.

Mixed silica-alumina oxide as sorbent for dyes and metal ions removal from aqueous solutions and wastewaters

Wastewaters containing organic and inorganic contaminants such as dyes, heavy metal ions, salts, and surfactants are considered to be a serious environmental problem in human society. Adsorption is the most popular technique for wastewater treatment. In this paper, a new mesoporous silica-alumina oxide (97% SiO2, 3% Al2O3) synthesized by pyrogenic method was proposed as a sorbent for acid (C.I. Acid Orange 7), reactive (C.I. Reactive Black 5) and direct (C.I. Direct Blue 71) dyes as well as for heavy metal (Co(II), Cu(II), Ni(II), Zn(II)) ions removal from the aqueous solutions and wastewaters. The batch method was employed. The parameters such as phases contact time (1–360 min), initial metal and dyes concentrations (10, 20, 30 mg/L), effect of hydrochloric acid concentration (0.1–6.0 M), anionic surfactant (0.1–1.0 g/L) and salt (5–20 g NaCl/L) as well as wastewater decolorization were studied. The kinetic and equilibrium studies were also performed. An equilibrium time of 1 min and >240 min was required for the adsorption of heavy metal ions and dyes onto mixed oxide, respectively. The experimental data were better fitted to the Freundlich equation than to the Langmuir one. The potentiometric titrations indicated that dyes and heavy metal ions adsorption influence the structure of electrical double layer at the mixed oxide - liquid interface which was evidenced by changes in the solid surface charge density. The results showed that the mixed oxide could be an effective adsorbent especially for heavy metal ions removal from aqueous and industrial wastewaters.

Ibuprofen and acetylsalicylic acid biosorption on the leaves of the knotweed Fallopia x bohemica

Knotweed is proposed as a cheap, renewable and efficient sorbent for ibuprofen (IBU) and acetylsalicylic acid (ASA) removal from water.

Synthesis of mesoporous silica-tethered phosphonic acid sorbents for uranium species from aqueous solutions

Abstract One-pot synthesis of highly ordered SBA-15 type silica-tethered phosphonic acid at weakly acidic pH (3.75) allows for higher loading of phosphonic functionality (up to 33%) without significant deterioration of the mesostructure. In this synthesis sodium metasilicate was used instead of tetraethylorthosilicate. The resulting samples featured high specific surface areas (362–533 m2/g) and well-developed mesoporosity. The hexagonal structure and high concentration of phosphonic acid groups (1.0–3.0 mmol/g) in the synthesized samples were established by XRD, TEM, EDS and elemental analysis methods. Since inexpensive sodium metasilicate was used as a source of silica, these materials can be of interest for large-scale applications. Experimental studies of the synthesized materials showed that they are effective for extraction of trace uranium species under weak basic conditions (pH 8.3), which are relevant for practical use such as uranium extraction from seawater.

Humic acid adsorption onto cationic cellulose nanofibers for bioinspired removal of copper(II) and a positively charged dye.

Waste pulp residues are herein exploited for the synthesis of a sorbent for humic acid (HA), which is a major water pollutant. Cellulose pulp was etherified with a quaternary ammonium salt in water thereby introducing positive charges onto the surface of the pulp fibers, and subsequently mechanically disintegrated into high surface area cellulose nanofibers (CNF). CNF with three different charge contents were produced and their adsorption capacity towards HA was investigated with UV-spectrophotometry, quartz crystal microbalance with dissipation, and ζ-potential measurements. Substantial coverage of the CNF surface with HA in a wide pH range led to a reversal of the positive ζ-potentials of CNF suspensions. The HA adsorption capacity and the kinetics of HA uptake were found to be promoted by both acidic pH conditions and the surface charge content of CNF. It is suggested that HA adsorption onto CNF depends on electrostatic interactions between the two components, as well as on the conformation of HA. At pH ∼ 6, up to 310 mg g(-1) of HA were adsorbed by the functionalized CNF, a substantially higher capacity than that of previously reported HA sorbents in the literature. It is further shown that CNF-HA complexes could be freeze-dried into "soil-mimicking" porous foams having good capacity to capture Cu(II) ions and positive dyes from contaminated water. Thus, the most abundant natural polymer, i.e., cellulose could effectively bind the most abundant natural organic matter for environmental remediation purpose.

Composites of Multiwalled Carbon Nanotubes and Molecularly Imprinted Polymers for Enantioselective Recognition of D-Mandelic Acid

A novel chiral sorbent for D-mandelic acid (D-MA) has been fabricated on vinyl functionalized multiwalled carbon nanotube (MWCNT) by molecular imprinting technology. Molecular imprinted polymers (MIPs) were formed by D-MA as a template molecule on the surface of the vinyl functionalized MWCNT with 4-vinyl pyridine (functional monomer) and ethylene glycol dimethacrylate (crosslinking agent) with a thermal polymerization technique. FTIR, X-ray diffraction technique (XRD) and transmission electron microscopy (TEM) were used to characterize the composite structure, morphology and determine the grafted MIP quantities in the composite. Properties like adsorption dynamics, specific binding and selective recognition capacity were evaluated. The resulting MWCNT-MIP demonstrated favorable selectivity, good stability and a higher adsorption capacity for the template molecule compared to products created by bulk polymerization. For comparison, blank polymer (MWCNT-NIP) was prepared by the same procedure, only without using the template molecule in the polymerization process. To get an insight into the role of MWCNT on chiral recognition, D-MA imprinted and non-imprinted polymers without MWCNT were also prepared.

Sorption Kinetics of Cd(II) Species on Humic Acid‐Based Sorbent

A new sorption kinetic model has been developed and applied to quantify the sorption rate constant (ks) of cadmium(II) (Cd(II)) and humic acid–complexed Cd(II) (dissolved HA–Cd(II)) sorbed on solid humic acid (HA) sorbent. In a medium containing both Cd(II) and dissolved HA–Cd(II) at a relatively comparable initial concentration, the ks value of Cd(II) was half of that of dissolved HA–Cd(II). This lower ks value for Cd(II) may be attributed to the presence of competition between the solid HA sorbent and the dissolved HA fraction in attracting Cd(II). Under these conditions, the developed sorption kinetic model provided better correlation to the experimental data than the pseudo‐first order kinetic known as Lagergren model. The developed model, in comparison to the Lagergren and Ho pseudo‐second order sorption models, was also used to treat the data of Cd(II) sorption on a sorbent of HA and chitin (HA–chitin) hybrid at a wide range of ratios of the initial moles of Cd(II) to the weight of the HA–chitin sorbent from 8.90 to 154.12 × 10−6 mol/g. At this ratio range, the developed model satisfactorily gave constant values of ks, but the Lagergren and Ho models yielded inconstant β (the pseudo‐first order sorption rate constant) and k (the pseudo‐second order sorption rate constant), respectively. While the correlation of the developed model to the experimental data at that ratio range was satisfactory, the correlation of the Lagergren model to the experimental data decreased as the ratio decreased and that of the Ho model improved.

Solutochromic Molecular Spectroscopy with a Reference Hydrogen-Bond Acid Dendrimer

A zeroth order dendritic carbosilane structure, SiFA4H with four hexafluoroisopropanol (HFIP) functional groups attached via propyl ligand arms to a central silicon atom, has been developed as a model hydrogen-bond (HB) acid sorbent coating and candidate reference HB acid. The HB donor interaction, through the hydroxyl of the HFIP moiety, with a solute HB base can be monitored by observing the hydroxyl stretching frequency through measurements of SiFA4H FTIR spectra before and during vapor exposure. HFIP hydroxyl stretch shifts, upwards of 700 cm-1 have been observed depending on the HB base. For a range of HB bases, the resulting hydroxyl stretch shifts correlate directly with the solute HB basicity scale, “B”, developed by Abraham et al [1]. A variety of techniques exist to measure solute HB basicity, however, the applicability to examine HB bases delivered as vapors or gases and the simplicity of the measurements described herein, with a reusable reference HB acid sorbent coating and standard FTIR spectrophotometer techniques is attractive for some applications including those with hazardous chemicals. Moreover, as an extension of this work we propose employing SiFA4H or related sorbents as molecular sensing coatings, where the semi-selective sorbent is examined by various infrared (IR) spectroscopic techniques to monitor and identify hazardous chemicals, taking advantage of molecular binding phenomena which occur in the sorbent [2].

Preparation of A Spherical Cellulose Adsorbent as Amino Acid Sorbent

The spherical cellulose adsorbent was prepared by grafting acrylic acid onto the spherical cellulose beads prepared by NMMO method. The effecting factors, e.g., monomer concentration, initiator concentration, reaction temperature and reaction time were optimized by the orthogonal and signal-factor experiments and the structure of the adsorbent was characterized by FTIR and SEM. The graft mechanism was also discussed. Moreover, the spherical cellulose adsorbents were shown to behave as good sorbents for basic amino acids L-Arg, L-Lys and L-His.

Synthesis of nanoporous iminodiacetic acid sorbents for binding transition metals

Iminodiacetic acid (IDAA) forms strong complexes with a wide variety of metal ions. Using self-assembled monolayers in mesoporous supports (SAMMS) to present the IDAA ligand potentially allows for multiple metal–ligand interactions to enhance the metal binding affinity relative to that of randomly oriented polymer-based supports. This manuscript describes the synthesis of a novel nanostructured sorbent material built using self-assembly of a IDAA ligand inside a nanoporous silica, and demonstrates its use for capturing transition metal cations, and anionic metal complexes, such as PdCl 4 - 2 .