Sorption Sites Research Articles

Effects of humic acids on the adsorption of Pb(II) ions onto biofilm-developed microplastics in aqueous ecosystems

Microplastics (MPs), as emerging contaminants can behave as carriers for heavy metals in the water environments. Although the adsorption performance of heavy metals on MPs has been widely investigated, the effects of humic acids (HA) on the adsorption have seldom been explored. The authors were compared the Pb(II) adsorption onto biofilm-developed polyvinyl chloride (Bio-PVC) MPs with Pb(II) adsorption onto virgin PVC MPs (V-PVC), and explored the relationship between surface characteristics and the adsorption properties in the coexistence of HA. Our results showed that due to a larger specific surface area and more oxygen containing groups, Bio-PVC had a larger adsorption capability with a value of 3.57 mg/g than original ones (1.85 mg/g) due to its huge specific surface area and more oxygen containing groups. Microbial community analysis showed that the predominate bacteria in biofilms as Proteobacteria, Acidobacteria, Cyanobacteria, Firmicutes, and Bacteroidetes. Notably, the Pb(II) adsorption onto the V-PVC surfaces was increased, but the adsorption capacities of Pb(II) on Bio-PVC were suppressed with increasing HA. With the co-existence of HA, the increasing complexation and electrostatic attraction had attributed to the increased Pb(II) adsorption ability on V-PVC. Except for its competitive ability, HA has a shield effect which decreases the sorption sites on Bio-PVC. Overall, our findings provide a better understanding of the HA effect on the adsorption mechanism of heavy metals onto MPs in aquatic ecosystems.

A separation MOF with O/N active sites in nonpolar pore for One-step C2H4 purification from C2H6 or C3H6 mixtures

Here, a 2-fold interpenetrated metal–organic framework (MOF) was synthesized by imidazole derivative and carboxyl co-ligands, which features nonpolar pore environment with accessible N/O sorption sites, resulting in the suitable pore sizes (8.78 Å × 11.45 Å) to optimally interact with C2H6 and C3H6 compared to C2H4. The C3H6- and C2H6-selective phenomena were rigorously studied by combining pure-component sorption isotherms, ideal adsorbed solution theory (IAST) calculations, molecular simulations and breakthrough curves. The MOF exhibits high C3H6 uptake (53.6 cm3 g−1 at 10 kPa and 298 K) and benchmark C3H6/C2H4 selectivity (17.1), surpassing all of the reported porous materials for C3H6/C2H4 separation. Molecular simulations revealed both nonpolar pore environment and accessible O/N sites synergistically “match” better with C3H6 and C2H6 to provide stronger multiple interactions than C2H4. Experimental breakthrough curves and transient breakthrough simulations revealed that the MOF not only can realize one-step C2H4 purification (purity ≥ 99.9%) from various ratios of C2H6/C2H4 and C3H6/C2H4 mixtures with great recyclability, but also greatly increase the purity of C3H6 (such as from 28.5% to 87.7% for 2/5 C3H6/C2H4 mixture).

Sorption Characteristics and Site Energy Distribution Theory of Typical Estrogens on Microplastics

Microplastics (MPs) and estrogens are high-profile emerging contaminants at present, and MPs might become the carrier of estrogens in the environment and induce combined pollution. To study the adsorption behavior of polyethylene (PE) microplastics to typical estrogens, the adsorption isothermal properties of the six estrogens[estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (17β-E2), estriol (E3), diethylstilbestrol (DES), and ethinylestradiol (17α-EE2)] in single-solute and mixed-solute systems were studied through batch equilibrium adsorption experiments, in which the PE microplastics before and after adsorption were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Then, the site energy distribution theory of the adsorption of six estrogens on PE microplastics was further analyzed based on the Freundlich model. The results showed that the adsorption process of selected estrogens with two concentrations (100 μg·L-1 and 1000 μg·L-1) on PE were more consistent with the pseudo-second order kinetic model. The increase in initial concentration reduced the equilibrium time of adsorption and increased the adsorbing capacity of estrogens on PE. In the single system (one estrogen) or mixed system (six estrogens) with different concentrations (10 μg·L-1-2000 μg·L-1), the Freundlich model showed the best fitting effect for the adsorption isotherm data (R2>0.94). The results of isothermal adsorption experiments and XPS and FTIR spectra showed that the adsorption of estrogens on PE in the two systems was heterogeneous adsorption, and hydrophobic distribution and van der Waals forces were the principal factors in the process of adsorption. The occurrence of C-O-C (in only the DES and 17α-EE2 systems) and O-C[FY=,1]O (in only the 17α-EE2 system) indicated that the adsorption of synthetic estrogens on PE was affected slightly by chemical bonding function, but no obvious effects were observed for natural estrogens. The results of site energy distribution analysis showed that, compared with the single system, the adsorption site energy of each estrogen shifted to the high-energy region in its entirety in the mixed system, and the site energy increased by 2.15%-40.98%. The energy change in DES was the most significant among all of the estrogens, indicating its competitive advantage in the mixed system. The above results of this study can provide some reference for the study of adsorption behavior, mechanism of action, and environmental risks under the coexisting condition of organic pollutants and MPs.

Biochar-bacteria partnership based on microbially induced calcite precipitation improves Cd immobilization and soil function

Microbially induced calcite precipitation (MICP) technique utilizes ureolytic bacteria to decompose urea and generate carbonate ions for metal combination. MICP can remediate heavy metal (e.g., Cd) contaminated soils while maintaining or even improving soil functions, but its efficiency in agricultural soil practical application still needs to be enhanced. Here, we constructed a biochar-bacteria (2B) partnership in which biochar provides high nutrition and diverse sorption sites. Using the 2B system, Cd immobilization effectiveness and the underlying mechanism were examined along with the soil properties and soil functions. Results showed that compared to the single biochar and ureolytic bacteria systems, soil Cd mobility was reduced by 23.6% and 45.8% through co-precipitating with CaCO3 as otavite (CdCO3) in the 2B system, whereas soil fertility, bacterial diversity, and richness increased by 11.7–90.2%, 5.4–16.1%, and 6.8–54.7%, respectively. Moreover, the abundances of Proteobacteria and Firmicutes were enhanced in the 2B system. Notably, Sporosarcina and Bacillus (Firmicutes genus) that carry the ureC gene were boosted in the system, further implicating the microbiological mechanism in reducing Cd migration and its bioavailability in soil. Overall, the constructed 2B system was efficient in soil Cd immobilization by strengthening the ureolytic bacteria growth and their nutrient supply in the bacteria-rich soil ecosystem.

Removal of different vat dyes by Aspergillus niger: A comparative study focusing on the molecular structure

Vat dyes are the most commonly used dyes in the denim industry. Since the pollution of the textile industry is a worldwide problem, Aspergillus niger was used in this study, to treat vat dye wastewater by pre-culture and simultaneous-culture methods. A comparison between the two biosorption techniques used showed that pre-culture was about 30% more efficient than simultaneous culture. The adsorption capacity was determined using the Langmuir and Freundlich adsorption models, with Langmuir proving to be the most suitable model. The high saturation capacity of 121.35 mg/g for C.I. Vat Brown 1 calculated with the Langmuir adsorption model indicated that A.niger is a suitable sorbent for vat dye wastewater.To investigate the influence of dye structure on biosorption efficiency, eight vat dyes with different chemical characteristics were used. The results showed that the complete decolorization time was reduced by 200 and 150 min for planar and non-planar structures, respectively, due to the reduction of molecular mass, indicating that molecular mass is probably the dominant factor in vat dye removal. In addition, planar structures resulted in a 50-min reduction in biosorption time. The possible adsorption sites were analyzed by Fourier transfer infrared analysis. The results showed that the amino and carboxyl groups of the fungus could serve as sorption sites for vat dyes through hydrogen bonding.”

A new approach to obtain chitosan films – Characteristics of films prepared with tea and coffee kombucha as natural chitosan solvents

The environmental degradation that is currently taking place makes it important to develop new natural and biodegradable packaging for various branches of industry. Therefore, the aim of the research was to characterize films prepared from chitosan and kombucha solutions obtained from coffee and three types of tea (black, green, and white). Kombucha solutions were used as a natural solvent for the preparation of chitosan films which is a new approach in the production of chitosan films and has not been used so far. Both the kombucha and chitosan-kombucha solutions were characterized by high antioxidant activity in the DPPH test. This could be connected with the presence of phenolic compounds in kombucha solutions, which were determined by ultra-high performance liquid chromatography. In turn, chitosan-kombucha films had different physical, mechanical and biological properties depending on the type of kombucha solutions used. The highest oxygen barrier was determined for the film obtained from chitosan and green tea kombucha solution. The film consisting of chitosan and white tea kombucha solution was characterized by the highest tensile strength. In turn, microbiological studies showed that films based on chitosan and tea kombucha solutions showed higher activity against Salmonella eneterica than kombucha solutions, while film that consisted of a chitosan and black tea kombucha solution additionaly exhibited greater activity against Escherichia coli. Moreover, the analysis of sorption showed that kombucha solutions limited the accessibility of primary sorption sites. The results indicated that the type of kombucha used to prepared chitosan-kombucha films affects the properties of the obtained films. In addition, kombucha solutions can be used as a natural chitosan solvent instead of inorganic acids. The results of the study confirmed that chitosan films produced using kombucha as a solvent are better than the chitosan films commonly produced with acetic acid, so they can be a viable alternative material for food packaging.

Microbial biosorbent for remediation of dyes and heavy metals pollution: A green strategy for sustainable environment.

Toxic wastes like heavy metals and dyes are released into the environment as a direct result of industrialization and technological progress. The biosorption of contaminants utilizes a variety of biomaterials. Biosorbents can adsorb toxic pollutants on their surface through various mechanisms like complexation, precipitation, etc. The quantity of sorption sites that are accessible on the surface of the biosorbent affects its effectiveness. Biosorption's low cost, high efficiency, lack of nutrient requirements, and ability to regenerate the biosorbent are its main advantages over other treatment methods. Optimization of environmental conditions like temperature, pH, nutrient availability, and other factors is a prerequisite to achieving optimal biosorbent performance. Recent strategies include nanomaterials, genetic engineering, and biofilm-based remediation for various types of pollutants. The removal of hazardous dyes and heavy metals from wastewater using biosorbents is a strategy that is both efficient and sustainable. This review provides a perspective on the existing literature and brings it up-to-date by including the latest research and findings in the field.

Moisture Sorption Isotherms and Thermodynamic Properties of Biodegradable Polymers for Application in Food Packaging Industry.

This work aims to evaluate the influence of two starch-based materials (B16 and B20) on the moisture sorption isotherms, determined at 30, 40, and 50 °C, where B16 contains 5% (w/w) more starch than B20. Thermodynamic functions (differential enthalpy (∆Hdif), differential entropy (∆Sdif), integral enthalpy (Δhint), integral entropy (ΔSint), free Gibbs energy (∆G), and spreading pressure (φ)) were used to understand the water-binding behaviors and the energy requirements to remove the moisture content from the surface of these materials. The moisture sorption isotherms exhibited type III behavior, and the Guggenheim-Anderson-de Boer (GAB) model was the most suitable to fit the experimental moisture adsorption data. The adsorption isotherms of microparticles were enthalpy-controlled, with isokinetic temperature values of 221.45 and 279.77 K for B16 and B20, respectively, being higher than the harmonic mean temperature (312.94 K). The values of ∆G were positive (45.274 and 44.307 kJmol-1 for B16 and B20, respectively), indicating a non-spontaneous process. The spreading pressure values increased with increasing water activity (aw) for all isotherms. Higher values of ∆Hdif and ∆Sdif obtained from B16 confirmed its higher number of sorption sites available for binding with water molecules when compared to B20, making it less suitable for application in the food packaging industry.

High-pressure hydrogen adsorption in clay minerals: Insights on natural hydrogen exploration

Natural hydrogen has been widely detected in many environments. However, up to date, the knowledge about the occurrence of hydrogen in the geological formation is very limited. Clay minerals with large adsorption capacities due to their huge specific surface area are widely distributed in the subsurface. In order to find whether the hydrogen can be adsorbed on the clay minerals, 6 types of clay minerals (montmorillonite, chlorite, sepiolite, palygorskite, kaolinite and illite) were used for the hydrogen adsorption analysis at various temperatures (0, 25, 45, and 75 °C) and pressures (up to 18 MPa). In addition, multi-scale simulations via density functional theory (DFT) and grand canonical Monte Carlo (GCMC) were carried out to further explore the hydrogen adsorption mechanism of clay minerals in bulk phase. The results show that the excess adsorption capacities of sepiolite and palygorskite are much higher than those of montmorillonite and chlorite, and the excess adsorption capacities of illite and kaolinite are very low, nearly reaching the detection limit. The variation of hydrogen adsorption capacity (HAC) in different clays is attributed to the difference in their pore structures (i.e., specific surface area). A more complex pore structure and a larger specific surface area could provide more sorption sites for hydrogen molecules. HAC increases with pressure and decreases with temperature irrespective of the clay mineral types. This study highlights the features of hydrogen adsorption in clay minerals, contributes to a better understanding of natural hydrogen occurrence and storage in the subsurface, providing the potential application for geological hydrogen exploration.

Revealing the Pore Size-Dependent Sorption Mechanism of Toluene and Cetane in Porous Carbon by Nuclear Magnetic Resonance.

The adsorption of contaminants by porous carbon has been extensively studied by conventional isotherm and kinetic methods. However, the co-adsorption behavior and sorption sites of multiple contaminants in different-sized pores remain unclear. Herein, the nuclear magnetic resonance (NMR) approach is performed to investigate the adsorption mechanism of toluene and cetane in the confined space of carbon at the molecular level. The ring current effect induces the variation in the NMR chemical shifts of in-pore adsorbed toluene and cetane, realizing the identification of pore-dependent adsorption sites for contaminant removal. Cetane has a slower adsorption kinetic but a higher binding energy than toluene, which could squeeze toluene from micropores to larger pores with increasing adsorption quantity. This leads to a stronger competitive adsorption effect in small micropores than in mesopores. Accordingly, hierarchical porous carbons are determined to be the most effective adsorbents for the adsorption of coexisting contaminants. This study not only provides an effective NMR method to reveal the adsorption mechanism in the confined space of porous carbon at the molecular level but also offers new insights into the pore size-dependent adsorption of activated carbon for petroleum contaminant treatment.

Benchmarking biochar with activated carbon for immobilizing leachable PAH and heterocyclic PAH in contaminated soils

Remediation of residually contaminated soils remains a widespread problem. Biochar can immobilize polycyclic aromatic hydrocarbons (PAH). However, studies on its ability to immobilize PAH and N, S, and O substituted PAH (hetero-PAH) in real soils, and benchmarking with commercial activated carbon are missing. Here, we compared the ability of pristine biochar (BC), steam-activated biochar (SABC), and commercial activated carbon (AC) to immobilize PAH and hetero-PAH. The three carbons were tested on soils from four different contaminated sites in Austria. Different amendment rates (w/w) of the carbons were investigated (BC: 1.0, 2.5, and 5%; SABC: 0.5, 1.0, and 2.0%; AC: 1%) in batch experiments to cover meaningful ranges in relation to their performance. SABC performed better than AC, removing at least 80% PAH with the lowest application rate of 0.5%, and achieving a complete removal at an application rate of 1.0%. BC performed slightly worse but still acceptable in residually contaminated soils (40 and 100% removal at 1 and 5% amendment, respectively). The ability of BC and SABC to immobilize PAH decreased as the PAH-molar volume increased. PAH with three or more rings were preferentially removed by AC compared to SABC or BC. This can be explained by the difference in pore size distribution of the carbons which could limit the accessibility of PAH and hetero-PAH to reach sorption sites for π- π electron donor-acceptor interactions, which drive PAH and hetero-PAH sorption to carbons. Column percolation tests confirmed the results obtained in batch tests, indicating, that decisions for soil remediation can be derived from simpler batch experiments. In soil samples with 1% BC, a reduction of over 90% in the total concentration of PAH in the leached water was observed. Overall, BC and SABC were demonstrated to be valid substitutes for AC for stabilizing residually contaminated soils.

Speciation of Hexavalent Chromium in Aqueous Solutions Using a Magnetic Silica-Coated Amino-Modified Glycidyl Methacrylate Polymer Nanocomposite

A new magnetic amino-functionalized polymeric sorbent based on glycidyl methacrylate was synthesized and used in the separation of chromium Cr(VI) oxyanions sorption from aqueous solutions in a static batch system. The kinetic and isothermal parameters of the sorption process were determined. The experimental data were best fitted by a pseudo-second-order model with R2 = 0.994 and χ2 = 0.004. The sorption process of Cr(VI) removal by amino-functionalized sorbent was controlled by both intraparticle diffusion and liquid film diffusion. The equilibrium results showed that the sorption process is best described by the Freundlich model, followed closely by the Sips isotherm model, with a maximum sorption capacity of 64 mg/g. Quantum chemical modeling revealed that the sorption sites on the sorbent surface are fragments with diethylenetriamine and aminopropyl silane groups that coated the magnetic nanoparticles. The calculations showed that Cr(VI) oxyanions (Cr2O72-, CrO42- and HCrO4-) bind to both sorption sites, with diethylenetriamine centers slightly favored. The X-ray photoelectron spectroscopy (XPS) spectra demonstrate that the chromium bound to the sorbent in the form of Cr(III), indicating that the Cr(VI) can be converted on the surface of the sorbent to a less harmful form Cr(III) due to the sorbent's chemical composition.

Adsorption of hexavalent chromium from aqueous solution using cationic modified rice husk: Parametric optimization via Taguchi design approach

The current work study the adsorption capacity of modified rice husk for the removal of Cr(VI) from aqueous solution. The rice husk was prepared and modified cationicaly. The cationic modified risk husk (cRH) was characterized by scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy. Also, point-of-zero pH (pHzero), specific surface area (m2/g) and bulk density (g/cm3) of the cRH were determined. The adsorption process was optimized by considering four independent process parameter at three variation levels using Taguchi design approach. The results showed the bulk density (0.392 g/cm3) and surface area (192 m2/g) which revealed the presence of numerous sorption sites on the cRH. Also the SEM micrograph showed the pores of different sizes which favoured the adsorption of Cr(VI). Taguchi experimental design predicted initial Cr (VI) concentration of 25 mg/L, contact time of 90 min, 2 g cRH dosage and pH of 2 as the optimum conditions to achieve 91.48% removal efficiency. The optimized condition was verified and 91.13% removal efficiency was achieved. The experiment data fitted well to Langmuir model indicating anion species monolayer adsorption on the cRH homogeneous surface. Also, the process is in better agreement with pseudo-second-order kinetic model, indicating a chemisorption controlled process. Thus, the study revealed that cationic modified rice-husk is suitable for the removal of Cr(VI) from aqueous solution.

Experimental and numerical investigations of biochar-facilitated Cd2+ transport in saturated porous media: role of solution pH and ionic strength

The nanoscale biochar (N-BC) generated during the production and weathering of bulk biochar has caused significant concerns for its cotransport with contaminants spreading the contamination. In this study, the cotransport behaviors of N-BC with Cd2+ under variable solution chemistry were investigated for the first time, which can pose environmental contamination risks but have received little attention. The column experiment results showed that increasing ionic strength (IS) or decreasing pH retarded the transport of N-BC but promoted the transport of Cd2+ in their individual transport. In cotransport scenarios, Cd2+ facilitated the deposition of N-BC on the quartz sand with increasing IS or decreasing pH by providing additional sorption sites and led to the ripening of N-BC via cation bridging. N-BC retarded the transport of Cd2+ under all conditions. However, lower pH and higher IS could facilitate the release of Cd2+ from the immobile N-BC. The cotransport modeling results demonstrated that the Cd2+ adsorption on and desorption from the immobile N-BC controlled the retention and release of Cd2+ under variable pH and IS, while the influence of mobile N-BC on Cd2+ transport was minor. This study provided new insight for evaluating the potential contamination-spreading risks and suggested that rational use of biochar with great caution is necessary.Graphical

Highly efficient sorption of U(VI) on TiO2 nanosheets supported by amidoxime polyacrylonitrile in a variety of multi-carbonate solutions

Natural carbonate-rich uranium-containing water contributes to the formation of multi-carbonate solutions, including U(VI)–CO3, Mg/Ca–U(VI)–CO3, U(VI)–P–CO3, and U(VI)–X–CO3 (X = F, Cl, Br, I) systems. Herein, a novel composite of TiO2 nanosheets supported by amidoxime polyacrylonitrile (TNSs-PAN-AO) was newly prepared to study the U(VI) sorption in various multi-carbonate solutions. The results showed that the composite achieved the maximum sorption capacity (qe) of 108.4 mg·g−1 in U(VI)–CO3 solution, which was monolayer chemisorption. The competitive complexation of CO32– with U(VI) and the enhanced electrostatic repulsion caused by the transformation of (UO2)2CO3(OH)3– to UO2(CO3)34– species resulted in the relatively low qe values at high pH and [CO3]Total. The U(VI) sorption was suppressed in Mg/Ca–U(VI)–CO3, U(VI)–P–CO3, and U(VI)–X–CO3 solutions, especially in U(VI)–F–CO3, possibly due to the formation of dominant ternary complexes that can preempt the sorption sites of U(VI) on the composite. The desorption experiments showed that the highest desorption rate was 93.78% obtained by 0.1 mol∙L−1 HNO3. The XPS test and DFT calculations indicated that the –C(NH2)=N–OH and Ti–OH groups were the main sorption sites, which can scramble for U(VI) from the formed uranyl complex anions in multi-carbonate solutions. This work presented new insights into the understanding of uranium extraction from multi-carbonate solutions based on the practical U(VI) species, which may be of great significance for the recovery of uranium from natural water.

Anisotropic wood–water interactions determined by gravimetric vapor sorption experiments

Gravimetric vapor sorption experiments were performed on beech wood samples to determine the directional permeability, diffusion and sorption coefficients in the three orthotropic wood directions. Dynamic Vapor Sorption (DVS) experiments allowed for the direct evaluation of the diffusion coefficient from the analysis of the kinetic sorption profile using a double stretched exponential model with values ranging from 0.10 × 10−10 to 1.52 × 10−10 m2/s and depending on the wood direction of the sample and the RH-values. Moisture sorption isotherms (MSIs) were constructed and fitted to a modified Guggenheim-Anderson-de Boer and a Sorption Site Occupancy model, which allowed for the calculation of the sorption coefficient which was found to be between 2.4 and 3.0 mol/(m3 Pa). Dynamic Vapor Transport (DVT) experiments were performed to calculate the permeability coefficient from the vapor flow rate and it ranges between 0.56 × 10−10 and 4.38 × 10−10 mol/(m s Pa) as a function of the flow direction and RH conditions. These results indicate that such an experimental approach is suitable for determining wood–moisture interactions.

Modelling the reaction of uranium with carboxylic groups on surfaces through mono- and multi- dentate surface complexes on the basis of pH and redox potential

An analytical expression is proposed to simulate effects of pH and redox potential (E) on the sorption of uranium onto bioorganic model particles in saline or other aquatic environments. The elaborated expression is intended to avoid use of the classical approach of sorption which relies on experimental data and empirical models. The goal is to produce an expression that provides a distribution coefficient (Kd e.g. mL g−1) as function of pH, E and ligand concentration (through complex formation in solution) by applying a surface complexation model on one type of mono-dentate surface sites> (SuOH) as well as utilizing multi-dentate surface sites> (SuOH)c. The formulation of the worked out expression makes use of correlations between the surface complexation and hydrolysis constants for all species and sorption sites. The model was applied to the sorption of uranium onto bioorganic sites with and without carbonates in solution e.g. Log Kd: + 2.75 at pH 8 for 2 sites per nm2. The calculated distribution coefficients were found very sensitive to the presence of carbonates, e.g. Log Kd: − 7.0 at pH 8 for 2 × 10−3 M total carbonate. The potential reduction of uranium U(VI) and its complexes (carbonates) which are the primary stable species in surface waters, to U(IV) during sorption was simulated in association with a decrease in the redox potential and was found generally below the redox stability limits of water. The calculated distribution coefficient values were validated by the values reported in literature for the sorption of uranium onto specific adsorbents. The investigated simulations are also applicable to the sorption of other redox sensitive elements.

Accessibility of adsorption sites for superfine powdered activated carbons incorporated into electrospun polystyrene fibers

Superfine powdered activated carbon (SPAC) is sub-micron sized activated carbon with superior adsorption kinetics compared to regular powdered activated carbon (PAC) due to the short intraparticle diffusion times. SPAC has recently been demonstrated as an excellent adsorbent; however, subsequent removal of spent SPAC in suspended reactors may be challenging due to its fine size. Thus, SPAC may benefit from immobilization into a macroscopic scaffolding if its adsorptive properties can be preserved. Composition of non-woven electrospun polystyrene (PS) fibers consisting of SPAC is a novel approach to immobilize SPAC; however, the potential losses of adsorption capacity due to polymer-SPAC interactions is still mostly unknown. In this study, SPAC-laden electrospun PS with intentionally tuned SPAC sizes were fabricated for the first time. The centrifugal separation of SPAC generated two different particle sizes with median diameters of 0.30 ± 0.15 µm (SPAC-Fine) and 0.62 ± 0.25 µm (SPAC-Coarse). Both SPAC-Fine and SPAC-Coarse were added to the spinning solution and compared against the PS-only control fibers. Phenanthrene was used as a probe molecule to investigate the accessibility of adsorption sites on PS/SPAC composite fibers. This study showed that most SPAC adsorption sites are still accessible when incorporated into electrospun polymer fibers, regardless of whether the carbon particle size is larger or smaller than the fiber diameter. It can be speculated that the disposition of fine particles on the external surface of PS fibers as well as partial incorporation of large SPAC particles in the fiber allow diffusion of probe molecules onto the ultimate sorption sites of SPAC particles.

Exploring the use of sodium caseinate-assisted responsive separation for the treatment of washing effluents in shoreline oil spill response

The produced effluents after shoreline washing contain a certain number of oil droplets and further treatment is necessary. In this study, the innocuous, widely available, and biodegradable sodium caseinate (NaCas) was deployed to capture oil pollutants from oily wastewater. Oil droplets can be effectively and rapidly captured by NaCas and subsequently removed after pH-triggered separation, producing a clean supernatant with low turbidity. The removal efficiency was enhanced by increasing NaCas concentration and separation time. The salinity inhibited the oil removal by increasing the interfacial tension of NaCas and reducing their sorption sites caused by the large particle size. Humic acid negatively influenced the oil separation performance of NaCas because of the competitive sorption and enhanced repulsion force between oil and NaCas. In addition, the increasing temperature was found to augment the oil removal. Factorial analysis revealed the individual factors and two-factor interactions that had significant effects on oil removal. Biotoxicity experiments proved that NaCas can fully offset the inhibitory effect of oil on the photosynthesis of algae and thus promote algae growth. Two post-treatment methods, namely thermal treatment, and biodegradation, can be used for the post-treatment of NaCas/oil precipitation residues. The use of NaCas-assisted responsive separation in the treatment of washing effluents can help achieve a sustainable shoreline oil spill response.

Rational design of the nanocomposite by in-situ sub-10 nm La(OH)3 formation for selective phosphorus removal in waters

Phosphate removal by nanocomposite is a promising approach in water remediation. But it is still challenged by the small size nanoparticles formation and kinetic diffusion under the nanopore confinement. Herein, we report a different strategy, which relies on the deposition of nano-La(OH)3 particles inside the porous biomass Artemia Cyst-shells matrix. The charged amino acid components of matrix drivers for the in-situ growth of rod-like nano-La(OH)3 with size below 10 nm, while the broad-porous skeleton structures enable and accelerate the accessibility of trace phosphate to nano-La(OH)3 sorption sites available, resulting in the efficient and fast phosphate removal performance. This nanocomposite exhibited excellent adsorption capacity as high as 180.5 mg/g, which is beyond of most adsorbents by recent-ten-year survey. It also revealed superior selectivity against various competing ions with a distribution coefficient (Kd) up to ∼ 34000 mL/g, exceeding commercial ion-exchange resin by 15 times and outdoing 10 times the performance of well-known Fe based nanocomposites Lewatit FO36. An outstanding treatment capacity of 10980 L/kg under the continuous operation and the satisfactory regeneration property (> 95 %) further proves its applicability. This technology provides a new perspective approach for nanocomposite design and wastewater determination. It is also promising alleviating problems of trace phosphate deep purification in drinking water and wastewater medium.