Sorbent Research Articles

Facile synthesis of hollow carbon fiber/carbon quantum dots composite aerogels for oil sorption

Oil spill accidents are presented as a severe environmental problem because they cause ecological damage in the short and long term, especially in the aquatic environment. For this reason, the development of efficient materials to separate oil/water mixtures is fundamental. Studies have been performed using aerogels to fulfill this purpose because they are materials with a high porosity and high surface area, formed by solid particle networks and interconnected pores; these properties make them ideal for application as petroleum adsorbents. In this study, a simpler synthesis process using only renewable and environmentally friendly reagents for obtaining hollow carbon fiber/carbon quantum dots composite aerogels (CF-QD) is presented. Sorbent materials were prepared using an easy dip-coating technique and pyrolysis. Analyzing the effect of the concentration of carbon quantum dots (CQDs) in aerogels on the properties and adsorption capacity. CF-QD manifested remarkable characteristics, including a high surface area (up to 360.7 m2/g), hydrophobic surface, excellent buoyancy, and good adsorption capacity (up to 84.1 g/g). These features make them a viable option for application as sorbents for organic liquids, including oil.

Accurate descriptions of molecule-surface interactions for understanding CO2 capture by MgO-based sorbents in wet conditions

MgO shows promise as a CO2 sorbent material for the intermediate temperature range. Here, a hybrid computation scheme, xDH:GGA that combines the XYG3-type of doubly hybrid (xDH) and the generalized gradient approximation (GGA) functionals, is applied. It aims to provide an accurate description of molecular-surface interactions to reduce calculation uncertainties in exploring CO2 capture mechanisms for MgO-based systems. After validating the accuracy of the hybrid scheme by modeling CO adsorption on both MgO(100) and NaCl(100) surfaces against the experimental results, CO2 capture in wet conditions is examined. The results highlight the importance of competitive adsorption between CO2 and water, which undermines the significance of the conventionally identified active sites on MgO surfaces. In contrast, the intermediate Mg(OH)2 layer emerges as a more viable active phase, whose presence was experimentally observed, where the layered structure of Mg(OH)2 is found to kinetically retard water dissociative adsorption. In addition to surface areas and pore structures, our study emphasizes the pivotal role played by selective CO2 chemical adsorption in the development of effective CO2 sorbent materials.

Conocarpus lancifolius Leaves as Low-Cost, Green and Sustainable Sorbent Material for Simultaneous Removal of Cadmium, Chromium, and Lead Ions from Aqueous Samples

Conocarpus lancifolius Leaves as Low-Cost, Green and Sustainable Sorbent Material for Simultaneous Removal of Cadmium, Chromium, and Lead Ions from Aqueous Samples

Construction of N-Rich Aminal-Linked Porous Organic Polymers for Outstanding Precombustion CO2 Capture and H2 Purification: A Combined Experimental and Theoretical Study.

A large number of scientific investigations are needed for developing a sustainable solid sorbent material for precombustion CO2 capture in the integrated gasification combined cycle (IGCC) that is accountable for the industrial coproduction of hydrogen and electricity. Keeping in mind the industrially relevant conditions (high pressure, high temperature, and humidity) as well as good CO2/H2 selectivity, we explored a series of sorbent materials. An all-rounder player in this game is the porous organic polymers (POPs) that are thermally and chemically stable, easily scalable, and precisely tunable. In the present investigation, we successfully synthesized two nitrogen-rich POPs by extended Schiff-base condensation reactions. Among these two porous polymers, TBAL-POP-2 exhibits high CO2 uptake capacity at 30 bar pressure (57.2, 18.7, and 15.9 mmol g-1 at 273, 298, and 313 K temperatures, respectively). CO2/H2 selectivities of TBAL-POP-1 and 2 at 25 °C are 434.35 and 477.93, respectively. On the other hand, at 313 K the CO2/H2 selectivities of TBAL-POP-1 and 2 are 296.92 and 421.58, respectively. Another important feature to win the race in the search of good sorbents is CO2 capture capacity at room temperature, which is very high for TBAL-POP-2 (15.61 mmol g-1 at 298 K for 30 to 1 bar pressure swing). High BET surface area and good mesopore volume along with a large nitrogen content in the framework make TBAL-POP-2 an excellent sorbent material for precombustion CO2 capture and H2 purification.

Expanding the Library of Ions for Moisture-Swing Carbon Capture.

Developing materials that can more efficiently and cheaply capture carbon dioxide from ambient atmospheric conditions is essential for improving negative emission technologies. This study builds on the promising moisture-swing modality for direct air capture of carbon dioxide by investigating the use of several new anions─orthosilicate, borate, pyrophosphate, tripolyphosphate, and dibasic phosphate─that when introduced into ion-exchange resins allow for the cyclable capture of CO2 under dry conditions and its release under wet conditions. These ions, as well as many others that failed to show moisture-swing performance, are tested and directly compared thermodynamically and kinetically to understand their differences. This includes the use of analytical approaches new to the carbon capture field, such as the correlation of adsorption isotherms to moisture-swing performance, the use of phase lag kinetics, the examination of the humidity-carbon capture hysteresis of the sorbents, and the precise quantification of ion loading using inductively coupled plasma-optical emission spectroscopy. Phosphate dibasic was found to have the largest mass-normalized CO2 moisture-swing capacity, whereas phosphate tribasic had the best performance when factoring in kinetics, and pyrophosphate had the highest swing capacity when normalizing on a per-ion or per-unit-charge basis. This work not only sheds light on ways to improve DAC but also provides insights pertinent to the advancement of gas separation, negative emission technologies, and sorbent materials.

Growth/no-growth models of propionic and sorbic acid for bread and cake moulds

Propionic and sorbic acid are very effective weak-organic acid preservatives in bakery products. Their pH-dependent antifungal activity, the role of undissociated acid and the importance of the aqueous phase was studied. Besides looking for new natural preservation techniques the gain of further knowledge on their activity is still highly relevant to tackle the problem of food waste. In this study, the susceptibility of spoilage moulds for propionic (PA) and sorbic acid (SA) was tested in-vitro and in bread and cake. Aspergillus niger, Aspergillus montevidensis, Aspergillus ruber, Cladosporium ramotenellum, Penicillium brevicompactum and Penicillium roqueforti were subjected to PA and SA, both through macrodilution on malt extract agar (MEA) plates with adjusted aw (0.93, 0.95, 0.97), pH (5, 5.5, 6.0), acid (max. 2000 mg/L MEA), and through validation in wheat bread (max. 2901 mg PA/kg) and (lemon) cake (max. 1988 mg SA/kg). The undissociated acid concentrations (CHA) were estimated using either the Henderson-Hasselbalch (HH) equation or two modified HH equations. The influence of the food matrix (liquid oil, water, pH, aw), partitioning coefficient of the acids and spoilage fungi were evaluated and results were compared with in-vitro predictive models. In bread, the regular HH eq. proved to have good predictive power of CHA, whereas in cake a modified HH eq. (model 2) had better performance due to the inclusion of potential loss of CHA in the oil phase of complex food systems. The minimal inhibitory concentration (MIC) of PA in bread, after 30 days, was higher than 2901 mg/kg bread due to the strong resistance of P. brevicompactum, P. roqueforti and A. montevidensis. MIC of SA in lemon cake was 1429 mg SA/kg (pH 5.2), whereas in standard cake with pH 7.2, the max. level of 1988 mg SA/kg was insufficient for postponing mould growth to 30 days. The pH of cake had no influence on MIC of SA against A. niger and A. rubrum, whereas this effect was seen for C. ramotenellum, P. brevicompactum and P. roqueforti.

Carbon isotope effects in the sorption of chlorinated ethenes on biochar and activated carbon

As an alternative to activated carbon, biochar is a promising, environmentally friendly sorbent that can be used to remove organic groundwater pollutants, such as chlorinated ethenes (CEs). Stable isotope fractionation in biofilters is used to quantify pollutant degradation and to distinguish degradation from pollutant sorption on e.g. biochar. However, the sorption of CEs on biochar, and the potential abiotic fractionation processes remain to be tested. The sorption process of CEs and ethene on activated carbon and biochar was investigated with regard to the isotope effects for the differentiation from microbial degradation processes. Results from physical and chemical characterization of biochar indicated that biochar feedstock and pyrolysis conditions determined sorption performance depending on the surface chemistry and the pore size distribution of the coarse sorbent particles. The sorption capacity of the activated carbon was significantly higher with highly chlorinated ethenes, but similar to the biochars with low chlorination. Apparent carbon isotope fractionation factors (ε) of +0.1 to −4.4 ‰ were found above measurement uncertainties of GC/IRMS. The extent of isotope enrichment of the 13C bearing isotopologues in the residual aqueous phase (ε < 0) was characteristic for individual pairs of pollutant and sorbent material and could be related to pore-filling processes limited by the micropore size distribution of sorbent materials and the chemical properties of sorbed pollutants. Especially the large isotope fractionation during the sorption of ethene led to the assumption that diffusion processes within the pore matrix of the sorbent particles contributed to the observed isotope effects, but should still be considered a property of sorption. Concluding on the results indicated that sorption processes can have a significant contribution to carbon isotope fractionation in CEs and ethene. These should not be neglected in the evaluation of biofilters for groundwater purification, in which CEs are simultaneously degraded by microbes.

Comparison of pesticide adsorption efficiencies of zeolites and zeolite-carbon composites and their regeneration possibilities

The presence of pesticides in our environment is a consequence of intensive industrial and civilizational development, necessitating the search for effective and safe methods to remove them. We suggest utilizing zeolite X and a zeolite-carbon composite, obtained through the chemical transformation of fly ash, as pesticide sorbents. To increase the sorption efficiency of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), carbendazim, and simazine, we functionalized the zeolite materials with cationic (hexadecyltrimethylammonium) and nonionic (Triton X-100) surfactants. We used transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric/differential thermal analysis (TG/DTA) and point of zero charge (pHpzc) analysis to characterize the functionalized sorbent materials. Our results indicate that cationic surfactants significantly enhance the adsorption of 2,4-D and MCPA. In contrast, carbendazim and simazine exhibit maximum sorption on the unmodified zeolite-carbon composite. The sorption mechanism is intricate, with physical sorption predominating, primarily due to electrostatic interactions between the protonated binding sites of the adsorbents and the negatively charged pesticide molecules. Regeneration tests demonstrated that ethanol is the most effective in regenerating zeolite-carbon composite with adsorbed MCPA and 2,4-D, while thermal regeneration was not possible. Adsorbents with simazine and carbendazim can be regenerated using both thermal and ethanol methods, but the thermal regeneration of zeolite with adsorbed simazine is more efficient. Utilizing functionalized zeolite materials obtained from industrial waste, such as fly ash, could provide an efficient way to remove pesticides from the environment.

The Effects of the Preparation Factors on the Properties of CO2 Capture Sorbent Derived from Local Waste Eggshell

In this study, the CaO adsorbent was prepared by using local waste eggshell as a raw material. The influence of preparation parameters including calcination temperature, calcination time and particle size of eggshell powder on the adsorption surface area were investigated. By means of statistically experiment design, the interesting parameters were investigated by a full 23 factorial design. The prepared sorbent material was characterized by X–ray diffraction (XRD), Scanning electron microscopy (SEM) and the Brunauer–Emmet–Teller (BET). The results showed the particle size of eggshell powder greatly affected the BET surface area. By applying the prepared condition of 149 μm in particle size, 6 h of calcination time and 1,000oC calcination temperature, the obtained CaO adsorbent yielded the highest in BET surface area of 5.023 m2 g-1. The CO2 performance test in the fluidized bed reactor with 12% V/V CO2 in N2 balance also revealed that the local waste eggshell can be used as CO2 adsorbent. The CO2 carrying capacity of the highest BET surface area sorbent was 0.011 g CO2 g-1 sorbent at 700°C carbonation temperature.

Efficient extraction and analysis of precious metals with a conducting polymer modified magnetic sorbent material

Polymerization of pyrrole-1-carbodithioic acid on silica coated Fe3O4 nanoparticles created the magnetic sorbent, PPy-CS2@SiO2@Fe3O4, for extraction and analysis of precious metals. PPy-CS2@SiO2@Fe3O4 is an air stable, granular composite readily dispersible in water and suitable for magnetic solid-phase extraction of Ru, Rh, Ir, Pd, Pt and Au. Maximum sorption and recovery was achieved at pH 6, 15 mg of sorbent and a 15 min extraction time, and a 4 mL desorption solution consisting of 2 M HNO3 and 0.5 M thiourea. Limits of detection (0.02 to 0.08 µg L−1), linear dynamic ranges (0.5 to 1000 µg L−1) and relative standard deviations (1.3 to 5.2%) were determined. Extraction with PPy-CS2@SiO2@Fe3O4 was not affected by a 400-fold excess of co-existing metals, allowing extraction from a complex chemical reaction mixture and produced water. Bulk sorption capacities for Pd2+ and Au3+ were 163.0 and 132.7 mg g−1, respectively, indicating larger scale extractions are possible.

Synthesis and characterization of seed-based Carbon Black Agglomerates: Application as sorbent material using a novel microextraction technique for dexamethasone in urine sample determination

The growing development of Nanotechnology has allowed the synthesis and characterization of nanomaterials with peculiar physicochemical properties. These nanomaterials have been applied in various scientific and industrial sectors. The present study established the synthesis of carbon black agglomerates (CBA) from waste vegetal materials as a source of renewable raw materials using a simple, fast, and effective procedure. Once this nanostructured material was obtained, several analytical techniques were applied to establish its main characteristics, including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller (BET) theory analysis, and SEM imaging. The results of this characterization have made it possible to establish that these materials have properties that make them suitable for application as extracting sorbents in microextraction sample treatment techniques under the green analytical chemistry approach. In this study, we applied Pipette-tip SPE microextraction for pharmaceutical compound extraction studies, preparing extraction devices with less than five milligrams of the sorbent. The results showed high extraction percentages for compounds such as paracetamol, caffeine, diazepam, and dexamethasone. Finally, an application example of the last compound is presented, developing a procedure for its determination in urine samples by high-performance liquid chromatography with diode array detection (HPLC-DAD) chromatographic analysis with high merit figures in terms of simplicity, high extraction efficiency, and environmental friendliness. Keywords: carbon black; nanostructured material; olive seed; microextraction; biological samples

Polydimethylsiloxane-carbon nanotubes-based hydrophobic sponge for treatment of palm oil mill effluents with enhanced reusability

Improper treatment and discharge of palm oil mill effluents (POME) into the water bodies have become one of the leading causes of aqueous contamination due to the release of a large volume of POME into the environment. This study reports the development of poly(dimethylsiloxane) (PDMS) and carbon nanotubes (CNTs) supported sorbent material to reduce the oil and grease (O&G) content of POME. The morphology and chemical properties of the prepared material were characterized using SEM-EDX, FTIR, Raman spectroscopy, XRD, TGA, water contact angle, and pH point of zero charge (pHPZC) analysis. CNT-PDMS optimal O&G removal capacity has been determined using batch experiments with varying parameters, including CNT wt%, contact time, pH, and initial POME concentration. The introduction of CNT significantly improves the oil sorption capacity almost three times as compared to pure PDMS. The maximum sorption capacity achieved was 658.09 ± 7.21 mg/g with the O&G removal of 84% within 8 min using initial POME concentration (1:20) and at room temperature. The study shows that the O&G sorption process using PDMS and CNT-PDMS-0.8 followed the pseudo-second-order kinetic model. Moreover, the adsorption isotherms study revealed that the adsorption process can be described by the Freundlich isotherm model based on the R2 values of 0.98075 and 0.99981 for PDMS and CNT-PDMS-0.8, respectively. Furthermore, the composites also show excellent reusability, retaining high O&G sorption and removal even after the tenth cycle.

Oil spills removal from seawater surface by magnetic biochar composite derived from Heglig tree bark and cobalt ferrite

Purpose This study aims to explore the possibility of using magnetic biochar composite (MBCC) derived from Heglig tree bark (HTB) powder (agricultural solid waste) and cobalt ferrite (CoFe2O4, CFO) for oil spill removal from seawater surface. Design/methodology/approach One-pot co-precipitation route was used to synthesize MBCC. The prepared materials were characterized by X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy. The densities of the prepared materials were also estimated. Crude, diesel engine and gasoline engine oils were used as seawater pollutant models. The gravimetric oil removal (GOR) method was used for removing oil spills from seawater using MBCC as a sorbent material. Findings The obtained results revealed that the prepared materials (CFO and MBCC) were able to remove the crude oil and its derivatives from the seawater surface. Besides, when the absorbent amount was 0.01 g, the highest GOR values for crude oil (31.96 ± 1.02 g/g) and diesel engine oil (14.83 ± 0.83 g/g) were obtained using MBCC as an absorbent. For gasoline engine oil, the highest GOR (27.84 ± 0.46 g/g) was attained when CFO was used as an absorbent. Originality/value Oil spill removal using MBCC derived from cobalt ferrite and HTB. Using tree bark as biomass (eco-friendly, readily available and low-cost) for magnetic biochar preparation also is a promising method for minimizing agricultural solid wastes (e.g. HTB) and obtaining value-added-products.

Qualitative and quantitative analysis for the content of benzoic, salicylic, sorbic and glycyrrhizic acids in an aqueous extract of alfalfa

The article presents the results of experimental studies on the assessment of the content of benzoic, salicylic, sorbic and glycyrrhizic acids in the aqueous-alcoholic extract of alfalfa (Medicago sativa L.) and in its condensed extract (BAA «Erakond»), belonging to the class of preservatives of natural origin. Qualitative and quantitative analysis was carried out by high performance liquid chromatography (HPLC) on a Waters Breeze chromatograph (Waters, USA). The content of acids endowed with antiseptic and fungicidal properties in the air-dry raw material of alfalfa was, mg/g: benzoic – 3.2 ± 0.3; salicylic – 1.8 ± 0.2; sorbic – 0.15 ± 0.11; glycyrrhizin – 2.0 ± 0.3. The technology of hydrobaric extraction, used in the industrial production of the dietary supplement «Erakond» from alfalfa, ensured the concentration of the analyzed acids in the finished product: the content of benzoic acid in the dietary supplement «Erakond» was 26.0 ± 3.0 mg/g, salicylic acid – 2.9 ± 0.3 mg/g, sorbic – 0.22 ± 0.03 mg/g, glycyrrhizin – 5.2 ± 0.6 mg/g. The mechanisms of implementation of the antioxidant properties of polyphenolic compounds of alfalfa, which exhibit a synergistic preservative effect together with identified organic acids, are disclosed. Relatively high concentration of polyphenolic compounds in Erakond dietary supplement (naringenin – 0.05 ± 0.0006; rutin – 8 ± 3; licuraside – 3.5 ± 0.4; quercetin – 0.04 ± 0.001; fisetin – 0.35 ± 0.01; naringin – 0.5 ± 0.0006; dihydroquercetin – 0.20 ± 0.002) provides high stability of Eracond-containing food products during long-term storage with preservation of nutritional, taste and biological properties. The combined antiseptic and antioxidant action in vitro of organic acids, polyphenolic compounds, essential oils, coumarins and plant saponins ensures the effectiveness of the use of natural preservatives in food industry technologies.

Modification of cotton fibers with functional silane and application for emergency treatment of spilled oil or other organic pollutants

Water contamination issues caused by spilled oil or other organic pollutants are urgently requiring the development of new oil sorbent materials that may desirably have the functionalities of reusability and efficiency. To further improve hydrophobicity, sorption capacity and oil retention rate, in this study, cotton modified with vinyl triethoxysilane (VTES, KH-151) to improve them. The introduction of KH-151 onto the surface of cotton was verified by SEM, FT-IR, XPS and EDS. The oil-water selectivity, sorption and retention capacities and cycling performance were tested. Compared with the raw cotton, modified cottons surface enhanced the rate and capacity of oil separation from oily water, the sorption capacity for soybean oil was increased from 9.83 g g–1 to 27.26 g g–1 and for dimethylsilicone oil from 7.92 g g–1 to 25.09 g g–1 after 10 cycles. The oil retention rates of modified cottons exceed 95 % for soybean oil within 10 min at low specific volumes. It gradually decreased by specific volume increasing but still maintained over 75 % at the 14 cm3 g–1. These indicated the hydrophobic and superoleophilic properties, and good recyclability. The developed method and sorbent hold promise for easy storage, environmentally friendly, reusable and relatively cost-effective oil cleanup in emergency treatment of spilled oil or other organic pollutants.

Continuous production of O2-free enriched CO2 from ambient air using moisture swing sorbents

Herein, we report the production of O2-free CO2 from a CO2/O2/N2 mixture using moisture swing sorbents in two parallel reactors under isothermal conditions, wherein CO2/O2/N2 and H2O/N2 are alternately fed into the reactors. The CO2/O2/N2 mixture was fed into the reactor containing the water-pre-adsorbed metal oxide sorbent to capture CO2. After changing to an H2O/N2 gas mixture, moisture-promoted CO2 desorption took place. Sorbent-screening tests showed that Rb-loaded Al2O3 (Rb/Al2O3) was the most effective sorbent material for this process. Thus, Rb/Al2O3 sorbents with different Rb loadings were tested for continuous CO2 separation using two parallel reactors. Various structural analyses revealed that the highly dispersed Rb(I) species were responsible for CO2 capture/desorption. The formation and desorption of surface carbonates on Rb/Al2O3 under working conditions were then studied using in situ Fourier transform infrared spectroscopy (FTIR) with online gas composition analysis (operando FTIR). Finally, we demonstrate the continuous production of O2-free and ca. 5 times enriched CO2 from ambient air.

Using 19F NMR to Investigate Cationic Carbon Dot Association with Per- and Polyfluoroalkyl Substances (PFAS).

There is much concern about per- and polyfluoroalkyl substances (PFAS) based on their environmental persistence and toxicity, resulting in an urgent need for remediation technologies. This study focused on determining if nanoscale polymeric carbon dots are a viable sorbent material for PFAS and developing fluorine nuclear magnetic resonance spectroscopy (19F NMR) methods to probe interactions between carbon dots and PFAS at the molecular scale. Positively charged carbon dots (PEI-CDs) were synthesized using branched polyethyleneimine to target anionic PFAS by promoting electrostatic interactions. PEI-CDs were exposed to perfluorooctanoic acid (PFOA) to assess their potential as a PFAS sorbent material. After exposure to PFOA, the average size of the PEI-CDs increased (1.6 ± 0.5 to 7.8 ± 1.8 nm) and the surface charge decreased (+38.6 ± 1.1 to +26.4 ± 0.8 mV), both of which are consistent with contaminant sorption. 19F NMR methods were developed to gain further insight into PEI-CD affinity toward PFAS without any complex sample preparation. Changes in PFOA peak intensity and chemical shift were monitored at various PEI-CD concentrations to establish binding curves and determine the chemical exchange regime. 19F NMR spectral analysis indicates slow-intermediate chemical exchange between PFOA and CDs, demonstrating a high-affinity interaction. The α-fluorine had the greatest change in chemical shift and highest affinity, suggesting electrostatic interactions are the dominant sorption mechanism. PEI-CDs demonstrated affinity for a wide range of analytes when exposed to a mixture of 24-PFAS, with a slight preference toward perfluoroalkyl sulfonates. Overall, this study shows that PEI-CDs are an effective PFAS sorbent material and establishes 19F NMR as a suitable method to screen for novel sorbent materials and elucidate interaction mechanisms.

Double step heating synthesis of MIL-101(Cr) composites for water harvesting applications

Energy storage is a valuable mechanism for managing fluctuations in energy demand by allowing the distribution of energy production needed during peak demand over a more extended period. Thermal energy storage is among the most valuable categories of energy storage. The optimal sorbent material must satisfy thermal, physical, chemical, and environmental requirements for designing sorption heat storage systems. MIL-101(Cr) is a Metal-Organic Framework (MOF) with remarkable properties such as a high surface area, hydrothermal stability and good water sorbent capacity that make it a potential candidate as a working sorbent. Their physicochemical properties can be modulated by functionalizing the organic linker or by modifying its structure, improving the interaction with the target sorbate, mainly environmentally friendly and non-toxic sorbates such as water. However, good water sorption capacity is not the only characteristic to be considered when selecting the sorbent material for sorption heat storage systems. Here, we propose an alternative method to obtain a sorbent material with the objective of reducing the reaction time and achieving a good balance between the physical properties of the material, such as the density and the thermal conductivity, without substantially decreasing its water uptake capacity. For this aim, we show that structural modification of MIL-101(Cr) induced by CaCl2 and graphene oxide (GO) can improve the water sorption capacity and optical properties compared to the pristine sorbent. The MIL-101(Cr)/GO/CaCl2 composite had a higher water uptake capacity of 1.08 gwater g−1composite-1, even compared with MIL-101(Cr)/CaCl2 composite with a water uptake capacity of 0.68 gwater g−1composite. Additionally, MIL-101(Cr)/GO and MIL-101(Cr)/GO/CaCl2 sorbents tend to absorb light toward the near-infrared region and increase the temperature around twice as much compared to sorbents without GO when illuminated with a flash lamp. These results demonstrate that GO added at the MIL-101(Cr) structure allows a better distribution of CaCl2 in the MIL-101(Cr) pores and it may be advantageous in the water desorption process making use of renewable infrared radiation sources such as solar energy.

Yerba mate waste: Transformation to magnetic composites for the adsorption of chemically diverse pollutants

Biochar (BC) from yerba mate waste was produced as sorbent material contributing to the circular economy. The BC was magnetized through the nucleation of Fe oxides. Three different magnetic composites were synthesized: BC2.5-Fe (2.5 g of BC), BC1.25-Fe (1.25 g of BC), and BC0.625-Fe (0.625 g of BC). The resulting BC consisted of carbon (C) and oxygen (O), with a BET surface area of 2 m2/g. It exhibited various functional groups and whewellite was identified. Comparing with BC, the BET surface area of the composites increased whereas the number of functional groups decreased. Meanwhile, whewellite was chemically destroyed. Magnetite/maghemite were the main magnetic iron oxides, which imparted a magnetic response. The saturation magnetization for BC0.625-Fe was 30.3 Am2/kg. The BC and the composites were tested against various types of pollutants found in wastewater, including emerging pollutants, oxyanions and dyes. The increases of the BET area and the change of surface properties lead to a higher adsorption efficiency of the composites, when compared to the BC. The magnetic properties of the composites and the magnetic force studies revealed that these materials can be used in water treatment systems based on magnetic recuperation of the sorbent materials. The finding highlights the need to design adequate geometries for the indirect manipulation of these types of sorbent materials when using them in practical applications. This study makes a significant contribution to the circular economy by providing an efficient method for recycling the yerba mate waste and a sustainable solution for water remediation processes. Besides, the developed materials allow their indirect manipulation by means of magnetic fields, which decrease the health risk of operators by reducing their exposure to pollutants such as drugs, oxyanions, and dyes.

α-Zirconium(IV) Phosphate: Static Study of 225Ac Sorption in an Acidic Environment and Its Kinetic Sorption Study Using natEu as a Model System for 225Ac.

Zirconium phosphate (ZrP), especially its alpha allotropic modification, appears to be a very promising sorbent material for the sorption and separation of various radionuclides due to its properties such as an extremely high ion exchange capacity and good radiation stability. Actinium-225 and its daughter nuclide 213Bi are alpha emitting radioisotopes of high interest for application in targeted alpha therapy of cancer. Thus, the main aim of this paper is to study the sorption of 225Ac on the α-ZrP surface and its kinetics, while the kinetics of the sorption is studied using natEu as a non-radioactive homologue of 225Ac. The sorption properties of α-ZrP were tested in an acidic environment (hydrochloric and nitric acid) using batch sorption experiments and characterized using equilibrium weight distribution coefficients Dw (mL/g). The modeling of the experimental data shows that the kinetics of 225Ac sorption on the surface of α-ZrP can be described using a film diffusion model (FD). The equilibrium weight distribution coefficient Dw for 225Ac in both hydrochloric and nitric acid reached the highest values in the concentration range 5.0-7.5 mM (14,303 ± 153 and 65,272 ± 612 mL/g, respectively). Considering the results obtained in radioactive static sorption experiments with 225Ac and in non-radioactive kinetic experiments with natEu, α-ZrP seems to be a very promising material for further construction of a 225Ac/213Bi generator.