Low Sorption Research Articles

Coupled effects of pH and kaolinite colloids on antibiotic transport in porous media

Antibiotics can interact with natural colloids and the surrounding media upon entry into soil and groundwater systems, which significantly alters their dynamic behavior and complicates our understanding of antibiotic fate and transport in porous media. In this study, co-transport of antibiotics and kaolinite colloids was systematically investigated using combined column experiments and numerical simulation under different pH conditions. Sulfadiazine (SDZ) transport was enhanced by kaolinite colloids under neutral and alkaline conditions, which was attributed to the higher mobility of colloids as SDZ carriers, as well as competitive sorption. However, most injected SDZ was transported in a dissolved form owing to the low sorption capacity of SDZ to kaolinite colloids and quartz sand. The colloid-facilitated transport model provided a good description of total SDZ transport, but underestimated colloidal SDZ transport using parameters from kinetic sorption experiments. Kaolinite colloids significantly promoted ciprofloxacin (CIP) transport at pH 4.0, but inhibited it at pH 7.0 and 9.0. Interestingly, enhanced CIP transport was due to the decreased number of effective sorption sites on quartz sand and the increased desorption of CIP from kaolinite colloids. Under neutral and alkaline conditions, deposited colloids provided additional sorption sites for CIP, which contributed to CIP retention. Moreover, CIP significantly inhibited the transport of kaolinite colloids owing to the increases in colloidal aggregate size and zeta potential. Overall, our results highlighted the different effects of mobile and immobile colloids on antibiotic transport, in addition to the implications of antibiotic speciation and clay colloids when predicting the transport behavior of these compounds.

Restriction of Re(VII) and Se(IV) diffusion by barite precipitation in compacted bentonite

The diffusion of anionic radionuclides in bentonite buffers for a high-level radioactive waste repository is only minimally retarded due to the anion exclusion effect and the low sorption onto the bentonite. In this study, barite precipitates in compacted barium-modified bentonite (Ba-bentonite) were used to study the restriction of the diffusion of Re(VII) and Se(IV). To this end, a synthetic porewater containing sulfate was placed in contact with compacted Ba-bentonite so that the sulfate ions could diffuse in the pores and produce barite precipitates. The Ba-bentonite and the bentonite with barium sulfate (BBS) retained the original interlayer structure based on X-ray diffractometer (XRD) analysis. Scanning electron microscopy (SEM) analysis revealed that the barite precipitates were formed in the inter-aggregate pores. A through-diffusion method was employed to measure the effective diffusion coefficient and the rock capacity factor of Re(VII) and Se(IV) in compacted Gaomiaozi (GMZ) bentonite, Ba-bentonite, and BBS. The effective diffusion coefficient decreased with increasing the compacted dry density of the three bentonites, and it decreased with increasing the amount barite precipitates in the BBS. The diffusive flux was completely stopped by the formation of high amounts of barite precipitates. The relationship between the effective diffusion coefficient and the accessible porosity could be described by Archie's law. The cementation factor of BBS was 2.9 for Re(VII) and 3.2 for Se(IV). Compared to the GMZ and Ba-bentonites, the high cementation factor of the BBS indicated a low connectedness and/or a high tortuosity. It had a better clogging effect on anion diffusion than the Ba- and GMZ bentonites.

Poly(β‐hydroxythioether)s as shape memory polymer foams for oil sorption in aquatic environments

AbstractOil spills in aquatic environments represent a significant ongoing threat to aquatic life due to the persistence of oil films or slick. While many methods are available for open ocean waterways, interior waterways represent a different set of challenges. To that end, we propose the use of poly(β‐hydroxythioether) (PBHTE) shape memory polymer foams as a highly porous, low density solid for environmental remediation through oil collection. PBHTE foams are produced through thiol‐epoxy “click” reactions in the presence of an organobase, with gas blown foaming producing the highly porous scaffold with tunable pore sizes and salt‐leaching yielding smaller pore sizes (~400 μm). The different porosities are used here for studying the oil sorption as functions of time and environmental temperature for different pore sizes and compositions. The PBHTE material demonstrated two different Tgs when dry versus wet to compare against environmental differences. While dry the foam showed a Tgof 51.5°C and conversely when wet the Tgwas at 25°C. The foams were compared to see how the pore size will affect the oil sorption of the material and how it can be optimized for oil spills in interior water ways. The pore sizes analyzed were 400 μm, 800 μm, and 1100 μm. The relationship of pore size, temperature of the oil system during sorption, and time in the oil system seemed to have the largest impact on the sorption of oil during this study. The peak conditions for maximum oil sorption yielded the best performer being the 800 μm foam at 10°C after 15 h of sorption yielding a 2250% sorption, comparable with graphene and other low density sorption materials. Ultimately, the role of density in scavenging, along with a literature review, is used to assemble a density vs sorption Ashby chart to provide insight into the different materials available for such environmental remediation. In this context, PBHTE foams represent a new, promising class of material capable of absorbing oil in aquatic environments.

Thermochemical sorption heat storage: Investigate the heat released from activated carbon beads used as porous host matrix for MgSO4 salt

For sustainable and cost-effective thermal management and energy storage, sorption-base thermal storage has received a lot of attention. However, the low sorption capacity of sorbents has long been a barrier to high energy-density sorption-based thermal storage. We present a new promising composite with high heat release and sorption capacity. The use of MgSO4/bead activated carbon composites in thermochemical sorption heat storage has been investigated. Because of the highly developed microporosity and high apparent specific surface area of about 1300 m2/g, bead activated carbon (BAC) is a potential candidate as support for salt/support composites for thermochemical heat storage. Also, the thermal conductivity of BAC has been measured and found to be 0.14 W/mK, which is higher than that of other materials like zeolites or alumina. This high thermal conductivity can influence the water sorption equilibrium, controlling the temperature of the solid, avoiding hot-spots, and thus preventing desorption during the hydration step. In stationary conditions (RH = 60 %, gas flow = 30 mL/min), the water sorption capacity of BAC was 0.138 g/g. This value was 2.32 times higher when the salt was dispersed into the BAC matrix, for the composite 7.6-MgSO4/BAC. A water adsorption capacity, higher than the theoretical value, was observed and attributed to the condensation of water molecules within the porous structure, resulting in a high thermal energy density. The 7.6-MgSO4/BAC composite achieved the highest heat of hydration of 920 J/g. The 10 hydration/dehydration cycles performed (dehydration at 150 °C and hydration at 30 °C with a RH of 60 %) confirmed the composite's excellent stability. This research provides a promising low-carbon pathway for the efficient capture, storage, and utilization of thermal energy.

Modelling atrazine sorption in carbon-rich substrates: a case study

Background The use of carbonaceous materials for environmental remediation is attractive due to low expense and high sorption capacity. However, their efficiency in contaminant removal is affected by substrate composition and sorption mechanism. Objective This study investigated atrazine sorption and desorption in three carbon-rich substrates. Data were evaluated considering isotherm models and sorbent chemical composition. Methods Sorption was performed by the batch equilibrium method with three substrates obtained from pig slurry composting with different proportions (w/w) of charcoal fines [...]

Metal ions doping effect on the physicochemical, antimicrobial, and wound healing profiles of alginate-based composite

The alginate (Alg) matrix with immobilized hydroxyapatite (HAp) and zinc oxide (ZnO), cross-linked by chitosan (CS) and metal ions (Men+) Ca2+, Zn2+, and Cu2+ was created as a wound dressing. The effect of Men+ and their concentrations on water vapor transition, fluid handling, dehydration, drug release, and healing are shown. Me-containing samples have a lower sorption capacity, than a commercial Kaltostat, however, a much lower degree of their dehydration provides a longer wound wet. The Men+ presence lowers the environmental pH to slightly acidic values promoting healing. Ca2+, Zn2+, and Cu2+ in complexes with CS increase antimicrobial effect against E. coli and S. aureus, slow down the Anaesthesine release, making it compatible with Fickian diffusion in the Zn2+ and Cu2+ presence, and non-Fickian transport under Ca2+ influence. The material promotes the proliferation of the fibroblasts, an increase of collagen fibres, and new arterial and venous capillaries, indicating the intensity of the healing process.

Sustainable bioactive pectin-based films to improve fruit safety via a circular economy approach

This work reports on the valorisation of persimmon (Diospyros kaki Thunb.) for the development of food-grade antiviral coatings against major viral foodborne pathogens, human noroviruses (NoVs) and hepatitis A virus (HAV). Initially, the antiviral activity of polyphenol-rich pectin extracts with abundant non-covalent interactions (PPN), pectin extracts enriched with intact pectin-polyphenol ester and O-glycosyl bonds (PPC) and hydro-ethanolic polyphenol-rich extracts (EPE) was compared. Higher viral reductions were found for the pectin extracts rich in polyphenols, mainly in those containing covalent pectin-polyphenol interactions. This specific extract was mixed with commercial citrus pectin (CP) to develop active edible films. Dry films were analysed in terms of their optical, morphological, mechanical and barrier properties. Addition of the bioactive pectin persimmon extract resulted in more coloured films with lower transparency. The presence of covalently-linked polyphenols gave rise to stiffer films, with lower sorption capacity and more hydrophobic nature. The infectivity of MNV and HAV on fresh blueberries after the coating treatments was reduced by approximately 4.28 and 2.38 log, respectively, after overnight incubation, as compared to the controls, when 10% PPC was incorporated into the film. Higher amounts of PPC did not significantly improve the antiviral activity and a complete inactivation for both viruses was observed after 4 days of storage at 25 °C. This paper highlights the potential of persimmon discards as a cheap source of food-grade antiviral coatings with improved physicochemical properties as compared to commercial citrus pectin.

Deriving parametric and probabilistic Kd values for fluoroquinolones in soils

The evaluation of the sorption affinity of fluoroquinolone antibiotics (FQs) in soils, by means of the derivation of solid-liquid distribution coefficients (Kd), is a valuable information for assessing their environmental mobility. Aiming to develop Kd (FQ) prediction tools in soils, in the first stage of this study we constructed a Kd (FQ) sorption dataset using current literature data. Furthermore, additional sorption and desorption data for norfloxacin were obtained in seven different soils of contrasting properties. Sorption isotherms of norfloxacin were linear under the experimental conditions tested and desorption percentages increased for scenarios in which low sorption was noted. Sorption tests in the same soils were then extended to ciprofloxacin, enrofloxacin and ofloxacin and pooled in the dataset, revealing comparable Kd (FQ) values among the FQ tested after analyzing the overall dataset consisting in 312 entries of Kd (FQ). A partial least square (PLS) regression model was then developed to predict values of Kd (FQ) based on specific relevant soil properties (i.e., pH, cation exchange capacity and organic carbon and texture information), and, for the first time, FQ properties (fraction of cationic FQ species) affecting sorption. Additionally, probabilistic, Kd (FQ) best estimates in soils were derived through cumulative distribution functions (CDFs) for the overall and for partial datasets created by grouping Kd (FQ) values according to key soil properties affecting FQ sorption (i.e., pH, organic carbon content and texture information). This latter approach permitted to derive more representative Kd (FQ) best estimates for the soils to be assessed, and with a lower related variability than that derived from the overall dataset. Best estimates Kd (FQ) values were > 1000 L kg−1 for most acidic to neutral soils, suggesting strong sorption, although lower sorption and thus higher environmental mobility may be expected in scenarios with soils with alkaline pH, low OC and high sand contents. SynopsisThis study aims to derive parametric and probabilistic Kd values for fluoroquinolone antibiotics in soils on the basis of a few relevant soil physicochemical properties.

Influence of non-equilibrium and nonlinear sorption of 137Cs in soils. Study with stirred flow-through reactor experiments and quantification with a nonlinear equilibrium-kinetic model

This paper addresses the modelling of cesium sorption in non-equilibrium and nonlinear conditions with a two-site model. Compared to the classical Kd approach, the proposed model better reproduced the breakthrough curves observed during continuous-flow stirred tank reactor experiments conducted on two contrasted soils. Fitted parameters suggested contrasted conditions of cesium sorption between 1) equilibrium sites, with low affinity and high sorption capacity comparable to CEC and 2) non-equilibrium sites, with a fast sorption rate (half-time of 0.2–0.3 h), a slow desorption rate (half-time of 3–9 days) and a very low sorption capacity (0.02–0.04% of CEC). Comparison of EK sites densities with sorption capacities derived from the literature suggests that the EK equilibrium and kinetic sites might correspond to ion exchange and surface complexation of soil clay minerals respectively. This work stresses the limits of the Kd model to predict 137Cs sorption in reactive transport conditions and supports an alternative non-equilibrium nonlinear approach.

Formation of pyromorphite by hydroxyapatite during lead migration in soil with different phosphorus sorption abilities

Chemical immobilization using hydroxyapatite is one of the promising approaches to handling soil with high-level lead contamination. To enhance the effectiveness of lead immobilization by hydroxyapatite, it is important to understand how lead reacts with hydroxyapatite and forms pyromorphite, insoluble lead phases. The up-flow suction percolation test was conducted in this study by the combined application of an X-ray diffraction analysis using fine-grained and sandy soils. The aim of the test was to understand how the availability of lead and phosphorus depends on the formation of pyromorphite in water-unsaturated soil. The results revealed that the available phosphorus derived from hydroxyapatite remained in the sandy soil after the percolation test, but it did not remain in the fine-grained soil. The X-ray diffraction analysis was able to quantify the amounts of lead as pyromorphite formed during the water percolation test. The presence of hydroxyapatite suppressed 48% and 76% of the lead leaching from the contaminated fine-grained and sandy soils, respectively. In the fine-grained soil, much of the pyromorphite formed in the soil near the inflow side; however, as the distance from the inflow side increased, the pyromorphite formation decreased, and lead, as water-soluble, remained. In contrast, in the sandy soil, phosphorus added as hydroxyapatite was extracted, as available. Therefore, pyromorphite homogeneously formed regardless of the distance from the inflow side, resulting in no lead as the water-soluble phases. Thus, hydroxyapatite application for lead immobilization is suitable for soil with a low phosphorus sorption ability.

A novel dental infiltration resin based on isosorbide-derived dimethacrylate with high biocompatibility, hydrolysis resistance, and antibacterial effect.

Objectives: The available infiltration resin has raised biosafety and treatment stability concerns because of the cytotoxicity of the main component, TEGDMA, and its susceptibility to hydrolysis in the oral environment. This study aimed to develop a TEGDMA-free infiltration resin to overcome these drawbacks. Methods: Using the synthetic bioderived monomer bis(methacrylate) isosorbide (IBM) and the zwitterionic compound 2-methacryloyloxyethyl phosphorylcholine (MPC), a novel infiltrant IBMA was developed and preferentially selected. We investigated the performance of the IBMA resin regarding cytotoxicity, antibiofilm adhesion, and hydrolysis resistance and further verified its ability to restore the demineralized enamel and stability of the infiltrated area under artificial aging conditions. Results: Compared with the commercial TEGDMA-based infiltration resin ICON, IBMA not only demonstrated similar enamel morphologic and esthetic restorative effects in chalky lesions but also exhibited favorable cell viability, durable Streptococcus mutans UA159 biofilm-repellent performance, and higher enamel microhardness (204.0 ± 5.12HV) of the infiltrated enamel. Specifically, because of the high crosslink density [(47.77 ± 5.76) ×103mol/mm3] and low water sorption [12.79 ± 2.56µg/mm3] of the polymer network, the IBMA resin was more resistant to hydrolysis than ICON, which prevents the disruption of the infiltrant's micropore-blocking effect after aging. Enamel lesions treated with IBMA demonstrated good color stability after the tea-staining challenge, which was significantly better than that in the ICON group. Conclusion: Based on these findings, the IBMA resin exhibits favorable cell viability, hydrolysis resistance, and biofilm-repellent properties, which alleviates the defects of traditional TEGDMA systems. Therefore, it is a better alternative for microinvasive treatment involving early caries and enamel whitish discoloration.

Modification of Natural Minerals with Technogenic Raw Materials

The presence of uranium-containing wastes from large provinces in the Republic of Kazakhstan significantly complicates the ecological situation, causing damage to the soil and hydrosphere due to the uncontrolled spread of large volumes of natural waters contaminated with radionuclides. They are usually utilized by the sorption method; however, the use of synthesized sorption materials is limited by their high price, and natural minerals are limited by low sorption characteristics. Many modification options are used in order to improve the sorption characteristics, but only a few methods have been found applied in industry. The main disadvantages include the complexity in the application and modification of reagents rarely used in industrial practice, which increases their cost, and is an obstacle to their widespread use. The authors of this research have studied the possibility of using technogenic raw materials—slags of phosphorus production—as a modifier of natural minerals. The methods of slag activation are investigated, the optimal conditions for the modification of the natural minerals zeolite and shungite by activated slag are determined, and the sorption properties of modified sorbents are studied.

High efficient pre-combustion CO2 capture by using porous slurry formed with ZIF-8 and isoparaffin C16

Integrated gasification combined cycle (IGCC) power generation has drawn more and more attention because of the increasing demand for zero CO2 emission. H2/CO2 mixture with middle/higher pressure like IGCC gas is usually separated by using low energy consumption physical absorption approach. Here, for upgrading traditional physical absorbents, we report a new porous slurry formed with ZIF-8 and isoparaffin C16 to raise CO2 capture capacity and selectivity. The properties and sorption behaviors of this slurry have been experimentally investigated, and the content of ZIF-8 is optimized as 20 wt%. The optimized slurry exhibits low viscosity (11.02–2.75 mPa·s when temperature ranges from 273.15 to 303.15 K), sufficiently high sorption speed, low CO2 sorption heat (9.39–18.47 kJ/mol, decreasing with increasing CO2 loading). More importantly, the slurry exhibits much higher CO2 sorption capacity (e.g., 3.39 mol/L/MPa at 0.1 MPa and 273.15 K, vs. 2.48 mol/L/MPa for dimethyl ethers of polyethylene glycol (DEPG) and 2.22 mol/L/MPa for propylene carbonate (PC)) and selectivity over H2 (17.4–205, which could be one time higher than DEPG and three times higher than PC). The recyclability of this slurry system is also excellent. The 98% sorption capacity is recovered by vacuuming for 5 min without heating, showing that the easy sorption-desorption cycle can be completed only via pressure swing. We believe ZIF-8/isoparaffin C16 slurry would be a promising alternative to existing commercial CO2 absorbent for separating IGCC gas with higher efficiency and lower energy cost.

Identification of Phosphate Sorption-Desorption and Accumulation Characteristics to Reduce Environmental Consequences

ABSTRACT Phosphorus (P) enrichment of soil due to the intensification of P fertilizer usage in crop production has resulted in eutrophication and serious economic consequences. Further, rapidly decreasing P reserves have renewed interest in improving more sustainable soil P management through monitoring diverse soil P reactions in contrasting soils. Therefore, the study was conducted to (i) characterize P sorption and desorption capacities related to soil properties and (ii) determine the added P availability and distribution among the different pools of P over the period concerning P sorption capacity of the soils. Three soils, namely Ultisols, Entisols, and Inceptisols, were equilibrated with a series of P concentrations to study P sorption–desorption using Langmuir isotherms. These soils were subjected to a sequential extraction procedure to study fractions in different pools after incubating with added P for 120 days. Maximum P sorption for Ultisols, Entisols, and Inceptisols were 1,428.6, 1,666.7, and 3,333.3 mg kg−1 soil, respectively. Phosphorus desorption by Ultisol was about 1.7- and 4.2-fold higher than Entisols and Inceptisols. The maximum P sorption showed a negative and significant correlation with soil pH (r = −0.88), whereas P des % has a significant and positive correlation (r = 0.98). Exchangeable Al, Al-ox, Al-cD, and Fe-ox showed a significant positive correlation with maximum P sorption and a negative correlation with P des %. During incubation, 93.3% of added P became non-extractable in Inceptisols, and in contrast only 64.3% for Ultisols. A greater increase in labile NaHCO3-P fraction was found in Ultisols from 66.96 to 135.6 mg/kg at the end of the incubation. Accordingly, the soils with lower sorption capacity consist of more labile P pools, which indicates a higher risk of the loss of P from the soil.

Improved Stability of Platinum Oxygen Reduction Reaction Catalysts by Implementation of Thermally Treated Carbon Supports with High Biomass Content

To improve the lifetime of polymer electrolyte membrane fuel cells (PEMFCs), optimization of the fuel cell components is necessary wherein one research focus is the stability of the platinum catalyst support. Due to the harsh conditions in PEMFCs, e.g. high potentials (≥ 0.85 VRHE) and low pH (≤ 2), the catalyst support, which commonly consists of a high surface area carbon, degrades.[1] This is mainly caused by carbon corrosion, which becomes significant at potentials above 1.1 VRHE.[2] Typically, commercially available and chemically derived raw oil based carbons are used as catalyst supports. The use of multi-walled carbon nanotubes (MWCNTs) as a more stable, graphitic catalyst support with high electrical conductivity is well known in literature.[3, 4] The production of MWCNTs is expensive, which makes upscaling difficult. However, a previous study of our group Schonvogel et al. showed low stability of biomass-based supports, which requires further optimization.[5] Therefore, an approach to increase the stability of the biomass-based carbon support is thermal graphitization to generate a stable and ordered carbon structure. This leads to an increased amount of sp2-hybridized carbon with increased crystallinity and increased graphitic degree. At this point, the use of activated biomasses as carbon support is a cheap and sustainable alternative to MWCNTs and commercially available carbon blacks, for example Vulcan XC-72®.[5, 6] In this work, novel composite supports using thermally treated activated sawdust and MWCNTs will be investigated as Pt-nanoparticle support towards their physical properties and electrochemical ORR activity and stability. Sawdust was steam activated at 750 °C for 1 h in nitrogen atmosphere to create a defined pore system. Afterwards, the activated sawdust (aSD) was mechanically mixed with 20 wt.% MWCNTs. The mixture was treated at high temperatures (1500, 1800 and 2100 °C, under Ar atmosphere) in a furnace. For comparison, MWCNTs only were thermally treated under the same conditions. Physical characterization of the supports was performed using low temperature nitrogen sorption for determination of surface properties and crystallinity powder x-ray diffractometry (PXRD) for analysis of the degree of graphitization. Next, these novel carbon materials were used as support for 40 wt.% platinum nanoparticles. The platinum content was determined using inductive coupled plasma with mass spectrometry (ICP-MS) and the platinum nanoparticle diameter was analyzed with transmission electron microcopy (TEM) resulting in mean diameters ≤ 2 nm. In order to evaluate the activity and stability of the synthesized platinum catalysts, electrochemical characterization was performed for most promising catalysts before and after an accelerated stress test (AST, 0.6 – 1.5 VRHE, 500 mV s-1, 5000 cycles). For electrochemical characterization a three-electrode setup with a rotating ring disc electrode (RRDE) was used. The electrochemical active surface area was obtained by hydrogen underpotential deposition (HUPD) and CO stripping method. In Figure 1 the ORR curves, mass activities (MA) determined at 0.9 VRHE and MA loss of Pt/gaSD_gMWCNTs_2100 and Pt/gMWCNTs_2100 before and after AST are shown.Our study reveals that the mixture of 20 wt.% MWCNTs with sustainable aSD and subsequent thermal treatment results in a catalyst with comparable MA and stability to Pt/MWCNTs_2100. Thus, the use of activated biomass as the main component in catalyst supports constitute a more sustainable and cheaper alternative to MWCNTs. Based on these results, thermal treatment at higher temperatures of ≥ 2500 °C and higher biomass content will be further investigated to increase the stability.[1] F. Ettingshausen, J. Kleemann, A. Marcu, G. Toth, H. Fuess, C. Roth, Fuel Cells 2011, 11, 238-245.[2] V. Bandlamudi, P. Bujlo, C. Sita, S. Pasupathi, Materials Today: Proceedings 2018, 5, 10602-10610.[3] V. N. Popov, Materials Science and Engineering: R: Reports 2004, 43, 61-102.[4] D. Schonvogel, J. Hülstede, P. Wagner, I. Kruusenberg, K. Tammeveski, A. Dyck, C. Agert, M. Wark, J. Electrochem. Soc. 2017, 164, F995-F1004.[5] D. Schonvogel, M. Nowotny, T. Woriescheck, H. Multhaupt, P. Wagner, A. Dyck, C. Agert, M. Wark, Energy Technology 2019, 7, 1900344.[6] M. Iwanow, T. Gartner, V. Sieber, B. Konig, Beilstein J Org Chem 2020, 16, 1188-1202. Figure 1

Use of Reduced Graphene Oxide to Modify Melamine and Polyurethane for the Removal of Organic and Oil Wastes

Methods for obtaining efficient sorption materials based on highly porous melamine and polyurethane matrices modified with reduced graphene oxide were developed. These materials are promising for solving environmental problems such as water pollution with organic products by sorption treatment. Reduced graphene oxides (rGOs) were synthesized from graphene oxide suspensions using potassium hydroxide, ascorbic acid or hydrazine hydrate. Composites with obtained rGO and melamine and polyurethane foam were produced for further characterization. The composites demonstrate high sorption of organic pollutants (oil, diesel fuel and gasoline) and low sorption of water. The composites were comprehensively analyzed by physicochemical techniques (SEM, XPS, Raman spectroscopy, UV–Vis) to elucidate the mechanism of sorption.

Refuse-derived Fuel Based Cobalt Catalysts for Hydrogen Production

Refuse-derived fuel (RDF) is a mixed industrial waste, which often contains combustible materials (cellulose, polymers, rubber, biomass, etc.). The RDF waste precursor is subjected to thermo-oxidation treatment at 300℃, followed by carbonizations at 600℃, and high temperature hydropyrolysis at 800℃. The obtained nanoporous carbon material was subjected to detailed characterization by low temperature nitrogen sorption, elemental analysis, etc. Carbon derived from RDF is distinguished by micro/mesoporous texture and moderately high surface area (650 m2 g-1). The catalyst obtained is tested in the process of methanol decomposition, leading to production of hydrogen as a fuel. The influence of the physico-chemical characteristics of the synthesized carbon on the catalytic activity of carbon-based cobalt catalyst is studied.

Hybrid PET Track-Etched Membranes Grafted by Well-Defined Poly(2-(dimethylamino)ethyl methacrylate) Brushes and Loaded with Silver Nanoparticles for the Removal of As(III).

Nanoporous track-etched membranes (TeM) are promising materials as adsorbents to remove toxic pollutants, but control over the pore diameter and density in addition to precise functionalization of nanochannels is crucial for controlling the surface area and efficiency of TeMs. This study reported the synthesis of functionalized PET TeMs as high-capacity sorbents for the removal of trivalent arsenic, As(III), which is more mobile and about 60 times more toxic than As(V). Nanochannels of PET-TeMs were functionalized by UV-initiated reversible addition fragmentation chain transfer (RAFT)-mediated grafting of 2-(dimethyamino)ethyl methacrylate (DMAEMA), allowing precise control of the degree of grafting and graft lengths within the nanochannels. Ag NPs were then loaded onto PDMAEMA-g-PET to provide a hybrid sorbent for As(III) removal. The As(III) removal efficiency of Ag@PDMAEMA-g-PET, PDMAEMA-g-PET, and pristine PET TeM was compared by adsorption kinetics studies at various pH and sorption times. The adsorption of As(III) by Ag@DMAEMA-g-PET and DMAEMA-g-PET TeMs was found to follow the Freundlich mechanism and a pseudo-second-order kinetic model. After 10 h, As(III) removal efficiencies were 85.6% and 56% for Ag@PDMAEMA-g-PET and PDMAEMA-g-PET, respectively, while PET template had a very low arsenic sorption capacity of 17.5% at optimal pH of 4.0, indicating that both PDMAEMA grafting and Ag-NPs loading significantly increased the As(III) removal capacity of PET-TeMs.

A novel alternative to free oil remediation and recovery: Foamy absorbents designed from low molecular paraffinic waste

This study focuses on preparing porous, hydrophobic, and oleophilic hydrocarbon-based foams applicable for removing free oils from water surfaces. Paraffinic waste material generated during industrial production of low-density polyethylene (Qatar Petrochemical Company) was used for the preparation of foamy, elastic structures through crosslinking of short aliphatic chains by dicumyl peroxide and foaming by 1,1′-azobiscarbamide. The porosity of the foam determined by computer microtomography was 58.9%, and the bulk density was 0.42 g.cm−3. The sorption ability of the foam was tested using diesel oil, motor oil, and heavy crude oil. The absorption capacity of foam was characterized as the ratio between the mass of oil absorbed by the foam and the mass of a neat foam (Sw) and as the ratio between the volume of oil absorbed by the foam and the volume of a neat foam (Sv). The absorption capacities of the new foam reported in this study (referred to here as Qwax foam) are 6.6 ± 0.3 g/g, or 3.3 ± 0.2 cm3/cm3 for diesel oil, 3.9 ± 0.4 g/g or 1.9 ± 0.3 cm3/cm3 for motor oil, and 3.4 ± 0.2 g/g or 1.4 ± 0.4 cm3/cm3 for crude oil. To compare the sorption ability of Qwax foam with some standard foams, the absorption capacities of highly porous commercial polyurethane (PU) and melamine (MA) foams were investigated under the same conditions. These foams showed much higher sorption capacity considering the Sw parameter as a reference; however, there was a lower sorption capacity compared to parameter Sv. In the last paragraph, the suitability and the relevancy of parameters Sw and Sv for a comparison of the absorption capacity of foams were theoretically analyzed.

Experimental analysis of a high-performance open sorption thermal storage system with absorption-crystallization-adsorption processes

Sorption thermal energy storage is one of the promising solar thermal energy storage considering its long-term storage ability. Since the common sorption thermal storage suffers from low sorption capacity, a high energy storage density enhancement mechanism is always essential for a cost-effective and compact storage system. With three-phase sorption thermal storage, high energy storage density from the crystallization sorption process can be achieved. However, such a sorption process brings significant challenges, including crystal blockage issues in absorption system or solution leakage handling problems in adsorption system, which need to be resolved. Here, we showed a high-performance sorption thermal storage that can attain high energy storage density via a full liquid-to-solid state sorption process. Such a process is achieved by adopting moist air as heat and mass transfer media, which enables liquid absorption, crystallization, and solid adsorption in a simple configuration simultaneously. The lab-scale model achieved high energy storage density in the range of 333–405 kWh/m3 resulting from the heat of absorption and crystallization of LiCl, which is the record value for liquid absorption systems. The energy storage density obtained from the dual liquid and solid sorption processes is enhanced by 278 % compared with that of the conventional cycle at 70 % RH (relative humidity) and temperature lift of 10 °C. With simple construction and high energy storage density, the proposed system has great potential in real applications.