Competitive Adsorption Experiments Research Articles

High selectivity and reusability of coordination polymer adsorbents: Synthesis, adsorption properties and activation energy

The effective treatment and recovery of Au(III) was a major challenge facing the world. In this study, a new type of coordination polymer adsorbent (Zr-DBMA) was synthesized and its ability to adsorb Au(III) was evaluated. Zr-DBMA shows an outstanding Au(III) removal effect in the solution pH 2–9, due to protonation. The adsorption reached equilibrium within 60 min and the maximum adsorption capacity was 570 mg g −1 at 298 K. The adsorption complied with pseudo-second-order and Langmuir models. Thermodynamic experiment illustrated that the reaction was a spontaneous endothermic behavior. The adsorption activation energy ( E a ) was 47.83 kJ mol −1 . These indicated that the adsorption behavior was a single-layer chemical adsorption. Competitive adsorption and adsorption-desorption experiments showed that Zr-DBMA had considerable selectivity and reusability for Au(III). N/O functional groups absorbed Au(III) on the surface of Zr-DBMA through electrostatic attraction, chelation and reduction. These results indicated that Zr-DBMA had broad prospects in removing Au(III) from solution. • A novel type of Zr-DBMA adsorbent was synthesized. • The adsorbent has a maximum adsorption capacity of 570 mg/g for Au(III) ions. • The activation energy ( E a ) is 47.83 kJ mol −1 . • The adsorbent has good selectivity and reusability. • The adsorption mechanism is electrostatic attraction, chelation and reduction.

Fabrication of in situ ZIF-67 grown on alginate hydrogels and its application for enhancing Cu (II) adsorption from aqueous solutions

Synthesizing high uniform metal-organic frameworks grown on natural biomass such as sodium alginate (ALG), which can efficiently remove metal ions from aqueous solution, is a challenging project. A simple and eco-friendly method of preparing ALG@ZIF-67 hydrogels by in situ synthesis of ZIF-67 onto ALG hydrogels was established. Combining the virtues of ALG with abundant hydroxyl and carboxyl groups and ZIF-67 with excellent porous structure, the obtained ALG@ZIF-67 hydrogels have excellent adsorption for Cu2+ (153.63 mg/g), which was much higher than that of pure ALG hydrogels (111.79 mg/g). The methodology showed that the adsorption process was in accord with the Langmuir isotherm adsorption model (R2 = 0.9972) and pseudo-second-order kinetic model (R2 = 0.9822). The thermodynamic experiments demonstrated that Cu (II) was absorbed by hydrogel with an endothermic and spontaneous process. The competitive adsorption experiment results of ALG@ZIF-67 hydrogel indicated that the absorption capacity of Cu (II) was higher than that of Cd (II), Ni (II), Zn (II) and Mn (II). Moreover, the ALG@ZIF-67 hydrogels still had excellent reusability after five adsorption-desorption cycles. The results indicated that the ALG@ZIF-67 hydrogels had the advantages of low cost, easy preparation, and environment friendly.

Bimetallic coordination polymer for highly selective removal of Pb(II): Activation energy, isosteric heat of adsorption and adsorption mechanism

The efficient removal of toxic Pb(II) from water was a serious problem for human. Herein, a bimetallic coordination polymer adsorbent (Ti/Zr-DBMD) was synthesized by 2,5-dimercaptoterephthalic acid ligand. The batch adsorption was performed and the relevant adsorption behavior was surveyed. Ti/Zr-DBMD had an outstanding adsorption performance in the range of pH = 3–7. The adsorption reached equilibrium at 120 min and the maximum adsorption capacity was 175 mg/g at 298 K. The adsorption of Pb(II) on Ti/Zr-DBMD conformed to pseudo-second order kinetic and Langmuir isotherm models. The activation energy (Ea) revealed a chemical adsorption in which the adsorption rate decreased with the increase of temperature. Thermodynamic analysis showed that the adsorption of Pb(II) by Ti/Zr-DBMD was a spontaneous exothermic behavior. Isosteric heat of adsorption (ΔHx) indicated that the energy heterogeneity of Ti/Zr-DBMD surface was low. The competitive adsorption experiment indicated that Ti/Zr-DBMD had the strongest affinity with Pb(II). Five adsorption–desorption cycles confirmed that Ti/Zr-DBMD had excellent regeneration performance. Furthermore, the adsorption mechanism is electrostatic attraction and chelation based on Zeta potential and XPS analysis. This study proved that Ti/Zr-DBMD had broad prospects in removing Pb(II).

Single and ternary competitive adsorption-desorption and degradation of amphenicol antibiotics in three agricultural soils

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the Kf value was in the range of 0.15–3.59 μg1-1/nL1/n kg−1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

Zeolitic Octahedral Metal Oxides with Ultra‐Small Micropores for C2 Hydrocarbon Separation

AbstractSeparation of C2 hydrocarbons, C2H6, C2H4, and C2H2, remains significant challenges in chemical industry. However, there are only few adsorbents that can effectively isolate C2 hydrocarbons from their mixtures particularly at a high temperature. Herein, we design a zeolitic octahedral metal oxide based on ϵ‐Keggin polyoxometalates with metal ion linkers. Single gas adsorption of the material shows the different adsorption performances for the C2 hydrocarbons and the strong interaction of the material with the C2 hydrocarbons. Dynamic competitive adsorption experiments show that the material efficiently separates each of the binary C2 hydrocarbon mixtures and even the ternary C2 hydrocarbon mixtures with high selectivity. The material keeps high separation performance even the temperature was increased to 85 °C. The material is stable and is able to be reused without loss of the separation performance.

Zeolitic Octahedral Metal Oxides with Ultra-Small Micropores for C2 Hydrocarbon Separation.

Separation of C2 hydrocarbons, C2 H6 , C2 H4 , and C2 H2 , remains significant challenges in chemical industry. However, there are only few adsorbents that can effectively isolate C2 hydrocarbons from their mixtures particularly at a high temperature. Herein, we design a zeolitic octahedral metal oxide based on ϵ-Keggin polyoxometalates with metal ion linkers. Single gas adsorption of the material shows the different adsorption performances for the C2 hydrocarbons and the strong interaction of the material with the C2 hydrocarbons. Dynamic competitive adsorption experiments show that the material efficiently separates each of the binary C2 hydrocarbon mixtures and even the ternary C2 hydrocarbon mixtures with high selectivity. The material keeps high separation performance even the temperature was increased to 85 °C. The material is stable and is able to be reused without loss of the separation performance.

A novel method for the functionalization of graphene oxide with polyimidazole for highly efficient adsorptive removal of organic dyes

Graphene oxide (GO) and its related composites have been extensively studied for various applications due to their unique two-dimensional structure and promising performance. In this study, we reported for the first time that polyimidazole-modified GO composites (abbreviated as PILGO) could be successfully fabricated through the combination of thiol-ene click and Radziszewski reactions. Functionalized GO composites were characterized by a series of techniques, such as nuclear magnetic resonance hydrogen spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis, and the adsorption behaviour of these PILGO composites towards Congo red (CR, an anionic dye) was investigated in detail. We demonstrated that the adsorption capacity of PILGO was significantly improved as compared with that of pristine GO. The maximum uptake performance of PILGO was up to 191.9 mg g−1 with a near-saturation state achieved in the first 5 min. The adsorption equilibrium data were better fitted through the pseudo-second-order model, while the adsorption isotherm data were better correlated with the Freundlich and Tempkin models. The adsorption affinity between CR and PILGO was positively related to the solution pH. The adsorption mechanism between CR molecules and composite material was further put forward, and it included electrostatic attraction, π-π stacking and hydrogen bond interactions. Competitive adsorption and cycling experiments further demonstrated that PILGO composites can be used as clean, efficient and novel adsorbents in wastewater treatment.

Xylem Inc, USA

The widespread usage of veterinary antibiotics results in antibiotic contamination and increases environmental risks. This study was evaluated the single and ternary competitive adsorption-desorption and degradation of three amphenicol antibiotics (AMs): chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in three agricultural soils. The adsorption capacity of amphenicol antibiotics in the soil was weak, and the Kf value was in the range of 0.15–3.59 μg1-1/nL1/n kg−1. In the single adsorption-desorption experiment, the ranked order of adsorption capacity was TAP > FF > CAP. However, in the ternary competitive adsorption experiment, the order was changed to be CAP > FF > TAP. The degradation of AMs in soils was performed at various conditions. All AMs were vulnerable to microbial degradation in soils. A higher initial concentration would reduce the degradation rate and enhance the persistence of AMs in soil. The degradation of AMs was positively influenced by changes in soil moisture content and culture temperatures up to 30 °C and decreased at higher temperatures. An equation was used to predict the leachability of AMs in soils and assess their risk to the water environment. The weak adsorption capacity and poor persistence of FF indicated that it may have a strong effect on groundwater based on the equation. It is imperative to further assess the biological impacts of FF at environmentally relevant concentrations given its mobility and extensive use in the livestock industry.

DMAEMA-grafted cellulose as an imprinted adsorbent for the selective adsorption of 4-nitrophenol

4-Nitrophenol is a highly toxic environmental pollutant. It is a challenge to selectively remove it from a mixture of various pollutants. Herein, we report a study on the selective adsorption of 4-nitrophenol by using molecularly imprinted polymers (MIPs). The imprinted polymer was synthesized using cellulose as a framework, onto which, the complex of the imprinting molecule (i.e., 4-nitrophenol) and a candidate material [namely, 2-(dimethylamino)ethyl methacrylate. DMAEMA] was grafted. The obtained MIP showed an excellent adsorption capacity with good selectivity. Also, the adsorption of 4-nitrophenol by the obtained MIP was fast and the adsorbent exhibited good recyclability. The thermodynamics and kinetics of the adsorption process of 4-nitrophenol by MIP was thoroughly studied, where an otherwise-equivalent non-imprinted polymer was used as a control in the experiments. The selectivity of the MIP adsorbent for 4-niteophenol was evaluated by two types of experiments: (1) adsorption experiments in single-component adsorbate systems (containing 4-nitrophenol, 3-nitrophenol, catechol, or hydroquinone), and (2) competitive adsorption experiments in binary adsorbate systems (containing 4-nitrophenol plus either 3-nitrophenol, catechol or hydroquinone). The selectivity coefficient for 4-nitrophenols was twice of those of other phenols (that were all around 2), indicative of the extent of the affinity of MIPs to these phenolic compounds. The recyclability of the adsorbent was evaluated for 5 adsorption–desorption cycles, where the adsorption capacity of the last cycle remained over 90.2% of that of the first cycle.Graphic

Synthesis of boric acid-functionalized microspheres and their adsorption properties for flavonoids

Poly(styrene–divinylbenzene)-based adsorption resin has the advantages of high specific surface area, adjustable pore size and other advantages, and has been widely used in the separation and purification of natural products and sewage treatment. However, its adsorption selectivity for specific compounds is poor. Therefore, to improve the selectivity of poly(styrene–divinylbenzene), the boric acid–functionalized monodisperse poly(styrene–divinylbenzene) was synthesized by seed swelling method by adding boric acid–functionalized polymerized monomer in the swelling stage. The static adsorption results showed that this polymer was pH–responsive. When pH> 9.5, the adsorption reached the maximum, and it could be desorbed with a pH< 3.5 60% ethanol aqueous solution. The microspheres were stable in the organic solvent and pH range of 1.0–14.0. Furthermore, adsorption isotherms of baicalein on these materials were fitted better to the Langmuir model and adsorption kinetics followed the pseudo–first–order equation. Competitive adsorption experiments showed that the polymers had a higher adsorption selectivity for flavonoids with a planar molecular structure. As the concentration of the flavonoids increased, the adsorption capacity of the microspheres also increased. The synthesis processes of P(S-DVB-BA) and its adsorption/desorption processes.

Dendrimer-assisted boronate affinity cellulose foams for the efficient and selective separation of glycoproteins

Surfaces engineered to identify and enrich glycoproteins are of considerable interest in the diagnostic and detection fields. A boronate affinity (BA) material was proposed as a potential candidate for the isolation of glycoproteins. However, this material has the disadvantages of low efficiency and non-degradability. Herein, a novel dendrimer-amplified BA cellulose foam (PEI-PBA-CF) was fabricated via a mild two-step approach. The as-prepared PEI-PBA-CF exhibited a rapid adsorption equilibrium rate (within 60 min) and outstanding adsorption capacity for horseradish peroxidase (537.4 mg g−1) and ovalbumin (495.5 mg g−1). Furthermore, competitive adsorption experiments demonstrated that PEI-PBA-CF could achieve selective separation and purification of glycoproteins from complex biological samples due to the synergistic effect of the improved BA capacity by the dendrimer and the well-interconnected porous structure of the biomass matrix. Consequently, these cellulose foams might present new application opportunities in analytical and biomedical fields.

Enhanced Sorption of Supercritical CO2 and CH4 in the Hydrated Interlayer Pores of Smectite.

Understanding the long-term confinement of supercritical fluids in the clay pores of subsurface rocks is important for many geo-energy technologies, including geological CO2 storage. However, the adsorption properties of hydrated clay minerals remain largely uncertain because competitive adsorption experiments of supercritical fluids in the presence of water are difficult. Here, we report on the sorption properties of four source clay minerals-Ca-rich montmorillonite (STx-1b), Na-rich montmorillonite (SWy-2), illite-smectite mixed layer (ISCz-1), and illite (IMt-2)-for water at 20 °C up to relative humidity of 0.9. The measurements unveil the unsuitability of physisorption analysis by N2 (at 77 K) and Ar (at 87 K) gases to quantify the textural properties of clays because of their inability to probe the interlayers. We further measure the sorption of CO2 and CH4 on swelling STx-1b and nonswelling IMt-2, both in the absence (dehydrated at 200 °C) and the presence of sub-1W preadsorbed water (following dehydration) up to 170 bar at 50 °C. We observe enhanced sorption of CO2 and CH4 in STx-1b (50 and 65% increase at 30 bar relative to dry STx-1b, respectively), while their adsorption on IMt-2 remains unchanged, indicating the absence of competition with water. By describing the supercritical adsorption isotherms on hydrated STx-1b with the lattice density functional theory model, we estimate that the pore volume has expanded by approximately 6% through the formation of sub-nanometer pore space. By presenting a systematic approach of quantifying the smectite clay mineral's hydrated state, this study provides an explanation for the conflicting literature observations of gas uptake capacities in the presence of water.

Selective recovery of rare earth elements with ligand-functionalized polymers in fixed-bed adsorption columns

Rare earth elements (REE) are a group of valuable metals with growing demand and broad applications. Mineral ores, the traditional sources of REE, require significant capital investment and their refinement has been a source of environmental contamination. Industrial fluids and natural REE-bearing liquids are potential alternative sources for these metals. This work investigated the performance and REE selectivity of polymer resin beads functionalized with N,N-bis(phosponomethyl)glycine (BPG) for extraction of REE from saline solutions in fixed-bed adsorption columns. Competitive batch adsorption experiments were conducted with various metals (Nd, Gd, Ho, Al, Fe, Co, Ni, Ba, Pb, Th, and U) and the BPG-functionalized resins were up to 137 times more selective for REE than aminated resins. In column experiments, the BPG-functionalized resins preferentially adsorbed heavier metals and REE were strongly retained in the functionalized column, taking 270 times longer than the amine column to reach 10% breakthrough and 128 times longer to reach 50% breakthrough. REE bound to the BPG-functionalized resins were recovered with a dilute HNO3 solution, yielding REE concentrations up to 236 times higher than the influent feedstock. This work provides new insight into the operational performance of novel functionalized adsorbents for recovery of REE from saline fluids.

Selective solid phase extraction and preconcentration of Cd(II) in the solution using microwave-assisted inverse emulsion-suspension Cd(II) ion imprinted polymer

Microwave-assisted inverse emulsion-suspension polymerization was to synthesize Cd(II) ion imprinted polymer (MW@Cd(II)-IIP) using salicylic aldehyde ethylene diamine Schiff Base and methyl methacrylate as functional monomers, Ethylene glycol dimethacrylate as crosslinking agent and Azodiisobutyronitrile as initiator. SEM and FTIR were used to characterize the structure of MW@Cd(II)-IIP. The influences of initial concentration, pH value, temperature and competitive ions on adsorption capacity of MW@Cd(II)-IIP were studied by the static adsorption experiments and competitive adsorption experiments. Under the optimum conditions, the adsorption capacity of MW@Cd(II)-IIP was 179.04 mg·g−1. The relative selectivity coefficient k′ for Cd2+/Pb2+, Cd2+/Cu2+ and Cd2+/Zn2+ were 2.1061, 4.7306 and 4.5602, showing the good selectivity of MW@Cd(II)-IIP. The pseudo-second-order kinetic model and Langmuir isotherm (R2 > 0.99) could describe the adsorption process of MW@Cd(II)-IIP. The thermodynamic parameters showed that the adsorption process was a spontaneous and endothermic process. MW@Cd(II)-IIP was used as the packing of solid phase extraction column. The extraction efficiency decreased by 9.9% after adsorption and elution. The relative standard deviation (RSD) and the detection limit (3σ) of this method were 2.699% and 0.288 μg·L−1 (n = 11). Under the optimum conditions of solid phase extraction, the recovery rate of Cd(II) in waste water samples was 95.22%–104%.

Utilization of extracellular fungal melanin as an eco-friendly biosorbent for treatment of metal-contaminated effluents

Fungal melanins have been considered as potential biosorbents due to their metal-binding properties, stability, and scalability. Previous studies established scalable fungal melanin production methods with promising strains, however, their applicability for metal-contaminated effluents treatment has not been sufficiently reported. Herein, melanin pigment derived from Amorphotheca resinae was produced and characterized using microscopy and spectroscopy techniques. Adsorptive properties towards Cu(II), Pb(II), Cd(II), and Zn(II) were evaluated using batch tests. Melanin pigment was composed of aggregates of nanosized particles with indole-based constituents. Adsorption capacities increased with the pH of solution, especially at pH > 4.0. Maximum binding capacities of Cu(II), Pb(II), Cd(II), and Zn(II) on melanin were 69.18, 103.23, 24.31, and 13.57 mg/g, respectively. The competitive adsorption experiments elucidated affinity as Cu(II)>Pb(II)≫Cd(II)>Zn(II). Adsorption time generally required <2.5 h to reach equilibrium; the pseudo-second-order kinetic model well described the kinetics. Chelating ability of free radicals in pigment was considered as a possible mechanism for adsorption. Initial adsorption capacities remained almost intact even after 5 consecutive adsorption–desorption cycles. Complete removal of Cu(II), Pb(II), and Cd(II) from metal-contaminated effluent was confirmed. Consequently, melanin pigment derived from A. resinae can be used as a biosorbent suitable for the treatment of metal-contaminated aqueous solutions.

Electron-Scale Insights into the Single and Coadsorption Cd(II) Behaviors of a Metal-Nonmetal-Modified Titanium Dioxide

Metal (Fe) and nonmetal (P) were used to modify TiO2, and then, several functional groups such as P-O, P=O, Fe-O, and -OH were introduced on its surface to enhance the adsorption capacity for Cd(II), which could reach 121 mg/g. According to the experimental analysis of adsorption performance, chemical adsorption dominates the adsorption process, and the adsorption capacity increases with increasing temperature within a certain range. The results of competitive adsorption experiments showed that both Pb(II) and Cu(II) affect the adsorption of Cd(II) and that the adsorption order of P-Fe-TiO2 for heavy metal ions is [Formula: see text]. We further investigated the adsorption mechanism of P-Fe-TiO2 for Cd(II) and the reasons for the difference in competitive adsorption and used DFT calculations to confirm the experimental results. In the analysis of binding energy and frontier molecular orbitals (FMOs), we confirmed that charge transfer occurred during the adsorption process, so chemical reactions occurred. The binding energy of P-Fe-TiO2 and Pb(II) is the largest. The results of the competitive adsorption experiment also confirmed that the adsorbent has the greatest effect on Pb. Mulliken analysis was used to identify the best binding site on the adsorbent. The results of electrostatic potential, total potential, and differential charge analysis further prove the conclusions described above.

A Coupling Technology of Capacitive Deionization and Carbon-Supported Petal-Like VS2 Composite for Effective and Selective Adsorption of Lead (II) Ions

The existing separation technologies, including chemical precipitation and adsorption process, cannot quickly and selectively separate and recycle heavy metal ions of lead (II) from battery waste liquid. Due to its rich sulfur content and excellent electrical conductivity, vanadium disulfide is a potential material for effectively removing lead from wastewater. The vanadium disulfide material with selective adsorption ability was introduced into CDI technology to construct a coupling technology with both advantages. The n-doped ZIF@vanadium disulfide (ZAC@VS 2 ) composites were successfully synthesized by hydrothermal method. Electrosorption experiments show that ZAC@VS 2 material presents the remarkable saturated adsorption capacity to lead(II) ions (239.52mg/g) in the 500mg/L PbCl 2 solution. In the triplex blend system (Fe 3+ /Pb 2+ /Na + ) with each solute density of 100 mg/L, the saturated adsorption efficiency of 85.4% to Pb 2+ can still be maintained. In addition, compared with the Langmuir(R 2 =0.873) adsorption isotherm model, the Freundlich model (R 2 =0.922) can be better used to fit the adsorption process, which proves that the adsorption process is multilayered and heterogeneous. XPS tests and competitive adsorption experiments show that the electric double layer (EDL) and complexation together promote the selective adsorption of heavy metal ions by ZAC@VS 2 . ZAC@VS 2 composite electrode shows excellent performance in the removal of lead ions in battery waste liquid, indicating the potential of introducing ZAC@VS 2 into CDI to remove heavy metal ions.

High efficiency removal of heavy metals using tire-derived activated carbon vs commercial activated carbon: Insights into the adsorption mechanisms

In this study, activated carbon was derived from pulverized waste tires using carbonization and chemical activation techniques. Single and competitive batch adsorption experiments for the removal of three synthetic heavy metal ions (Pb2+, Cu2+ and Zn2+) from an aqueous solution were performed to benchmark the efficiency of the Tire-derived Activated Carbon (TAC) in comparison to that of commercial activated carbon (CAC), which was used as the reference material. The sorbents physicochemical properties with corresponding adsorption mechanisms were evaluated by different experimental techniques. TAC exhibited great potential to adsorb heavy metals, with monolayer adsorption capacities as high as 322.5, 185.2, and 71.9 mg g−1 for Pb2+, Cu2+ and Zn2+, respectively, which were significantly higher than the adsorption capacities exhibited by CAC, which were 42.5, 15.0, and 14.0 mg∙g-1 for Pb2+, Cu2+ and Zn2+, respectively. Competitive adsorption results demonstrated the adsorption ability of sorbents is restricted by presence of other ions, and was decreased compared to the single sorption. Sorption kinetics data, with better fit to the pseudo-second order kinetics model, revealed that TAC had faster sorption rate in comparison to CAC. The adsorption capacities of TAC and CAC were reduced to half of their initial capacities after three successive adsorption-desorption cycles. Zeta potential, FT-IR, and XPS analyses revealed that electrostatic attraction and surface complexation mechanisms, as two metal-adsorbing mechanisms, were more influential for TAC. For CAC, a higher cation exchange capacity (CEC) value indicated that the removal of heavy metals by ion exchange was the predominant mechanism.

Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate

AbstractMolybdenum (Mo) adsorption by acidic yellow-brown soil was investigated as a function of a pH (1–13) and the equilibrium of P solution (0, 3.1, and 31 mg L−1) concentration. Mo adsorption by acidic yellow-brown soil increased within the pH range from 1 to 4. Above pH 4, Mo adsorption decreases with an increase in pH. The maximum adsorption was found between pH 2 and 4. Competitive adsorption experiments showed that the equilibrium sorption data fitted into Langmuir and Freundlich isotherms. The sorption data of Mo on the acidic yellow-brown soil fitted well with the Langmuir isotherm model due to the higher R2 value. A reduction in Mo adsorption by the acidic yellow-brown soil was noticed at higher addition levels of P (3.1 and 31 mg L−1). Therefore, P increasing the bioavailability of Mo and enhancing Mo uptake by plants might be related to the inhibition of Mo absorption by the acidic yellow-brown soil.

Magnetic surface molecularly imprinted polymer for selective adsorption of quinoline from coking wastewater

Quinoline, a refractory organic pollutant in coking wastewater, will harm human health and the environment if discharged directly. However, if recycled, it has considerable economic value. To realise the efficient and selective adsorption of quinoline from coking wastewater, a novel magnetic surface molecularly imprinted polymer (SMIP/MCNSs) was prepared for the specific removal and recycling of quinoline, using magnetic carbon nanospheres (MCNSs) as a carrier, quinoline as a template molecule, and acrylamide (AAm) as a functional monomer. The key preparation conditions were systematically optimised. The structure, morphology, and adsorption behaviours of SMIP/MCNSs were investigated in detail. With an imprinted layer thickness of approximately 9 nm, SMIP/MCNSs exhibits favourable magnetic responsivity, good adsorption performance, and reusability. Owing to the existence of imprinted cavities, for an initial quinoline concentration of 50 mg L-1, a high adsorption capacity qe (76.63 mg g−1) and high partition coefficient PC (0.847 mg g−1 μM−1) for SMIP/MCNSs are obtained. Competitive adsorption experiments revealed that SMIP/MCNSs possesses a greater affinity towards quinoline than towards other analogues, indicating its high quinoline selectivity. Moreover, SMIP/MCNSs shows a particular binding property for quinoline in real coking wastewater. Therefore, SMIP/MCNSs shows promise for the selective removal and enrichment recovery of quinoline in wastewater.