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Transition-metal dichalcogenides (TMDCs) present great potential in the area of noble metals recovery and separation. Herein, a one-pot solvothermal method was carried out to fabricate CuS nanoparticles (CuS NPs). The morphology structure and physical properties of the CuS NPs were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, and thermogravimetric analysis. Successful attempts to apply CuS NPs to the noble metal capture were firstly made. CuS NPs demonstrated highly selective binding and extremely efficient capture of Au3+, Pd2+ and Pt4+. The selectivity and capture capacity order were Au3+ > Pd2+ > Pt4+ > other metal ions. The enormous capacities for Au3+ (2.92 mmol g−1, 574.7 mg g−1), Pd2+ (1.13 mmol g−1, 222.2 mg g−1), and Pt4+ (0.72 mmol g−1, 142.9 mg g−1), and high distribution coefficients (Kd) of Au3+ (3.12 × 106 mL g−1), Pd2+ (2.24 × 106 mL g−1), and Pt4+ (6.220 × 103 mL g−1) placed the CuS NPs at the top known for such capture. Sorption isotherm of Au3+, Pd2+ and Pt4+ accorded with the Langmuir model suggesting homogeneous adsorption sites. The sorption kinetics for Au3+, Pd2+ and Pt4+ followed a pseudo-second-order model and the capture process was endothermic driven. The adsorption may occur by the reduction reaction of Au3+ and Pd2+ with CuS NPs as a captor in the hydrochloric systems, while it may occur by electrostatic interaction and electron-mediated coordination interaction for Pt4+. After the capture of noble metals, the crystallites of the CuS NPs retained the original shape, suggesting good stability and reversibility. This work proposes a new strategy to capture and recover noble metals and further expands the applications of TMDCs in pollution control.

A multi-functional, self-regenerating material was designed to adsorb and biodegrade formaldehyde from water in a simple, one-step process. The material is based on montmorillonite clay, polyethyleneimine and formaldehyde-degrading Pseudomonas putida, and has three unique functions which facilitate bioremediation: a. selectively adsorbs formaldehyde to reduce cytotoxicity, b. buffers the solution to allow efficient biodegradation, and c. self-cleans through slow release of formaldehyde and subsequent degradation by the attached bacteria, allowing regeneration and long-term use of the material. A polyethyleneimine-clay composite was optimized to carry positive surface charges and a high concentration of functional amine groups, which facilitated formaldehyde adsorption and bacterial adhesion. Formaldehyde binding was specific, yet reversible and pH dependent; binding fitted the Langmuir model and had a qmax of 62 mg·g−1 composite. A formaldehyde-degrading Pseudomonas putida strain was then immobilized on the positively charged composite through electrostatic interactions. The efficiency of the resulting bio-composite was demonstrated for multiple successive treatment cycles, with degradation rates as high as 1600 mg·L−1·FA·h−1. This self-regenerating one-step process is a promising solution to the challenging drawbacks of formaldehyde remediation and could also help design other adsorption-degradation platforms for wastewaters that demand complicated treatment strategies.

A novel robust metal sulfide (NaTS) was synthesized via a simple one-step hydrothermal reaction for the first time. SEM, TEM, EDS, and XPS analyses indicated that NaTS has a sheet-like structure stacked by hexagonal thin flakes with the formula Na2Sn3S7. PXRD and TG results indicated that NaTS was chemically and thermally stable. The rapid kinetic studies showed that NaTS can rapidly remove Sr2+, with a rate of 98.71% in the first minute, and can reach adsorption equilibrium within 5 min. A pseudo-second-order model and intraparticle diffusion model were found to be good fits for the NaTS adsorption data. The adsorption isotherms were well described by the Langmuir model and NaTS exhibited high adsorption capacity for Sr2+ (80.0 mg/g at 298 K). They also displayed a high distribution coefficient (Kd = 3.43 × 107 mL/g) and excellent removal efficiency of 99.98% with 0.5 g/L dosage in 5 mg/L Sr2+ solutions. In particular, NaTS exhibited outstanding affinity (Kd ≥ 1.31 × 105 mL/g) for Sr2+ over a broad pH range of 3–13. In addition, the adsorption mechanism of NaTS towards Sr2+ was ion exchange and Sr⋯S binding, as confirmed by EDS, XPS and ICP-OES. Furthermore, NaTS had significant advantages for Sr2+ removal compared with other adsorbents. In general, these adsorption advantages combined with facile synthesis, as well as structural stability, make NaTS promising for removal of radioactive Sr2+ from strongly acidic or alkaline radioactive wastewaters easily and efficiently.

The triazine-based porous organic polymers were synthesized by a one-pot amidation polycondensation reaction and they were applied for Hg2+ removal from aqueous solution. The results showed that these polymers had high Brunauer-Emmett-Teller (BET) surface area (404–521 m2/g) and hierarchical porosity with dominated micropores and mesopores. The equilibrium data for Hg2+ adsorption followed the Langmuir model with the maximum capacity of 229.9 mg/g. The Hg2+ concentration at the initial concentration of 6.0 ppm reduced to 6 ppb after 20 min, verifying its fast and deep treatment of Hg2+ wastewater. The adsorption was rapid and the pseudo-second-order rate model characterized the kinetic data perfectly. Moreover, the polymers exhibited excellent selectivity, easy regeneration, and superior reusability, indicative of their outstanding performance for Hg2+ removal. Analysis of the adsorption mechanism revealed that the embedded carboxyl, triazine ring, and amino groups played significant role due to the strong chelating coordination of the oxygen and nitrogen with Hg2+.

A novel three-dimensional (3D) adsorbent of reduced graphene oxide-β-cyclodextrin (r-GO-CD) aerogel was firstly synthesized through a one-step hydrothermal reaction. Various physicochemical characterization results demonstrated that the cross-linking of “soft” β-cyclodextrin among the “hard” graphene oxide nanosheets, simultaneously combining with self-assembly process of aerogel, contributed to the formation of superior structural and stable r-GO-CD aerogel. The adsorption of bisphenol A (BPA) onto r-GO-CD was chemisorption and endothermic, which fitted well with the pseudo-second-order kinetic and Langmuir isotherm. The saturated adsorption capacity of r-GO-CD towards BPA was 346.0 mg g−1 at 298 K, which was ∼11 times to that of conventional activated carbon. The r-GO-CD displayed a promising environmental application potential as revealed from the stable BPA adsorption efficiency in diverse interferences (H+/OH−, NaCl), presence of trace BPA and repeated cycling tests. The long-term dynamic filtration experiment conducted with raw surface water showed that the effective treated volume of r-GO-CD towards BPA (100 μg L−1) was 270 mL which was ∼30 times to that of r-GO due to the excellent selectivity and adsorptivity of β-cyclodextrin for BPA. The distinct adsorption mechanism of r-GO-CD aerogel was demonstrated as synergistic effects of graphene oxide nanosheets and β-cyclodextrin, along with π-π interaction and hydrogen bonding.

In this study, calcium carbide-derived carbon materials (CMs) were prepared by reacting CaC2 with chlorinated polymers via mechanochemical (CMs-M) and thermochemical (CMs-T) reaction in a planetary ball mill and tubular reactor, respectively. Their composition, structure, and adsorptive properties for dibenzothiophene (DBT) in oil and Hg2+ in water were studied, and the reaction mechanism was analyzed. In comparison with CMs-T, CMs-M possess higher specific area (600 ± 30 m2·g−1) and rich acetylenic and O-containing functional groups, and accordingly higher adsorptivity. Its saturated adsorbance is as high as 291.2 mg-Hg2+·g−1, and the adsorption isotherm can be well represented by Langmuir model, which manifests the chemisorption arising from the unique interaction between Hg2+ and the functional groups. CMs-M is one of the best carbonaceous sorbents for Hg2+ removal considering its high adsorption rate and capacity, high partition coefficient (21.8 mg·g−1·μM−1 at equilibrium concentration of 0.18 ppm), high selectivity w.r.t other heavy metal ions, and excellent recyclability. The mechanochemical method is more suitable for massive production of CMs in view of its mild operation condition and controllable reaction process. This study also sheds a light on the resource utilization of abundant highly chlorinated polymers, like polyvinylchloride (PVC) and chlorinated PVC (CPVC), for the manufacture of CMs-M.

In this study, an environmentally friendly struvite-loaded zeolite (S-NZ), prepared by nutrient recovery from swine biogas slurry, was used in the simultaneous removal of Cu (II) and tetracycline (TC) in solution for the first time. The adsorption behavior was systematically studied by accessing solution pH, kinetics, equilibriums in sole and binary systems. The results showed that the adsorption of Cu(II) and TC was fast and remarkably affected by solution pH due to pH-dependent speciation of adsorbates and the zeta potential of the S-NZ. Adsorption isotherms of TC and Cu(II) in binary system were well fitted by the Langmuir model and competitive Langmuir model, with the maximum adsorption capacities of 197.53 mmol TC/kg and 379.42 mmol Cu(II)/kg, respectively. The removal of TC could be significantly enhanced when Cu(II) coexisted, but not vice versa. Besides, the Coulombic interaction in the binary system at different pH was further supported by calculating relative charge distribution over the entire Cu(II)-TC complex and postulating the orientation of Cu-TC complex on the surface of S-NZ. Moreover, dissolved organic matter (DOM) impeded the adsorption of TC and Cu (II) onto S-NZ because of its formation of complex with Cu(II) and TC. This study shows new guidelines and useful methods for nitrogen and phosphorus recovery from livestock and poultry biogas slurry as well as its application in heavy metals and antibiotic pollution control.

Novel composite of immobilized layered K2xMnxSn3−xS6 (x = 0.5–0.95) (KMS-1) on the surface of reduced graphene oxide (r-GO), KMS-1/r-GO (KGO), has been fabricated by employing hydrothermal technique and used for the removal of radioactive Cs+ and Sr2+ ions from aqueous solutions. The KGO was characterized thoroughly with different characteristic techniques and found that the laminar KMS-1 nanoplate were immobilized on the surface of r-GO nanosheets, forming a highly porous stacked structure. Batch studies have been done for obtaining optimal experimental parameters and investigating the effect of adsorption time, initial concentration of pollutant, pH of solution, temperature, and competing anions on the removal properties. At room temperature, the maximum adsorption capacity of KGO was 338.18 mg·g−1 and 220.12 mg·g−1 for both Cs+ and Sr2+, respectively. Langmuir isotherm and pseudo-second-order kinetic models were fitted well with experimental data of removed Cs+ and Sr2+. Adsorption showed good selectivity of composite towards Cs+ and Sr2+ in the presence of co-existing ions (Ca2+ and Mg2+). The proposed adsorption mechanism involved ion exchange through the presence of K+ ions in KMS-1 and formation of surface ionic interactions between r-GO and ions through COO X or S X (X denoted Cs+ and Sr2+). This study highlighted the facile applicability of novel material KGO and could be used as a new adsorbent for the removal of radioactive ions.

Accurate prediction of gas transport in shale formations mainly consisting of micro- and nano-scale pores is a great challenge since most existing models only consider monolayer adsorption and the underlying multi-physics are either partially or completely overlooked. In this work, we have proposed a comprehensive single-component gas transport model integrating multilayer adsorption, surface diffusion, real gas effect, and pore confinement effect. The new analytical model is developed based on Bravo layer-sequence-model and then upscaled using an Effective Medium Approximation (EMA) method, where the generalized Brunauer-Emmett-Teller (BET) model, the modified Peng-Robinson equation of state (EoS) model, and the Sutton’s viscosity model are innovatively incorporated. The newly developed model has been successfully validated against simulation and experimental results with the assistance of an efficient iterative ensemble smoother (ES) algorithm. It is observed that the pore confinement effect is of importance when the pore size is smaller than 50 nm. The increase of gas viscosity due to the real gas effect is significant under reservoir conditions. The apparent permeability is found to increase greatly as the adsorption layer number increases, implying that the application of Langmuir model in existing gas transport models may substantially underestimate it. Given inorganic nanopores, the viscous flow is important at any pore sizes and the Knudsen diffusion plays a role in the pores that are less than 5 nm under reservoir conditions. As for organic nanopores, the contribution of surface diffusion is tangible when the pore size is below 150 nm and the Knudsen diffusion is negligible under high pressures.

In the present work, we synthesized CuO-ZnO (CZ) nanocomposites using a bio-templated method from biowaste-eggshell membranes (ESM). Results showed that CZ-ESM nanocomposites of morphology and structure preserved the original structural characteristics of ESM with interlaced network coated by small inorganic nanoparticles. In addition, the samples exhibit excellent adsorption, catalysis and antibacterial activities. Experimental results showed the adsorption kinetics and isotherm were well described by pseudo-second order kinetics and Langmuir isotherm model for Congo red dye, the maximum adsorption capacity was determined to be 775 mg•g−1. The catalysis reduction efficiency of CZ-ESM nanocomposites for 4-nitrophenol (4-NP) reached 98% after 12 min at room temperature. CZ-ESM could be recycled several times without any significant activity loss. Furthermore, the results of antibacterial experiments indicated that CZ-ESM nanocomposites exhibited a strong inhibition activity against E. coli and S. aureus. The maximum diameter of the inhibition zone was 27.5 mm for S. aureus and 20.3 mm for E. coli.

Traditional wastewater treatment plants cannot completely remove trace pharmaceutical and personal care products. In particular, quinolone antibiotics are mainly adsorbed on microbial cell surfaces in excess sludge and are released into the water environment during agricultural supplementation, mainly due to the exfoliation of extracellular polymeric substances (EPS) caused by changes in environmental conditions. Here, the occurrence of seven typical quinolone antibiotics from three generations in excess sludge was investigated at trace concentrations using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). EPS facilitated adsorption independent of pH and quinolone antibiotic type, and the solid-liquid distribution coefficient decreased markedly as pH increased (pH 5–9, range of municipal wastewater). Metal ions bound in EPS were predominantly responsible for the adsorption of antibiotics in sludge, rather than the macroscopic size of the sludge floc. pH affected patterns of quinolone antibiotics, the zeta potential of sludge floc, and the contents of metal ions contained in sludge. The adsorption capacity of antibiotics first increased and then decreased with increasing pH in the range of pH 3–11, reaching a maximum (20,506, 14,458, 10,689, 22,854, 20,302, 8494, and 29,547 L/kg for CIP, ENR, LOM, MOX, NOR, OFL, and SAR, respectively) near pH 5, at which the cationic bridging of Ca2+ and Mg2+ bound in EPS played a major role owing to their larger ion radius and higher contents in excess sludge. Due to high surface heterogeneity of sludge, the Freundlich model was more suitable than the Langmuir model for describing the adsorption behavior of quinolone antibiotics. These results provide further insight into the release of quinolone antibiotics adsorbed in excess sludge, with potential implications for the agricultural use of sludge.

Copper ferrite modified carbon nanotubes (CuFe2O4/CNTs) were synthesized and employed as adsorbents/catalysts to assist electro-peroxone treatment of aqueous emerging pollutant fluconazole (FLC). Results suggest that the synthetic CuFe2O4/CNTs integrated the CNTs adsorption and ferrite magnetic abilities, showing a fast FLC removal and an excellent recyclability. The pseudo-second-order equation and the Langmuir isotherm model could well elaborate the adsorption of FLC on prepared catalysts. Compared to individual processes, electro-peroxone treatment exhibited a synergetic degradation of FLC. Approximately 89% FLC transformation was observed in the CuFe2O4/CNTs catalytic electro-peroxone process, 10% higher than that without catalysts, implying that CuFe2O4/CNTs could enhance the peroxone oxidation. Increasing of inlet gasphase ozone concentration (7.2–29.7 mg/L), catalysts dose (0.1–0.8 g/L), initial solution pH (3–11), and reaction temperature (10–30 °C) could improve the treatment efficiency, while initial FLC concentration (5–40 mg/L) and natural organic matter contents (humic acid, 0–20 mg/L) have opposite effects. The role of cathodic current density (10–60 mA/cm2) was complex, 40 mA/cm2 was observed as the optimal value. Furthermore, the degradation of FLC followed the hydroxyl radicals (HO ) oxidation mechanism. The production of HO was mainly via peroxone reactions, and the presence of CuFe2O4/CNTs could catalytic ozone and H2O2 decomposition, thereby promoting HO generation. Although the magnetic CuFe2O4/CNTs had not shown obvious microelectrode characteristics, it combined adsorption and catalytic peroxone oxidation, may serve as the catalyst for electro-peroxone process.

Increasing evidence has shown that plastic pollution and water contamination are serious environmental issues. Herein, by utilizing cheap, abundant waste expanded polystyrene (EPS) as the raw material, high-value-added porous organic polymers (POPs) were prepared through a Friedel–Crafts alkylation reaction using two types of cross-linkers and applied to the removal of antibiotics and chlorophenols. The structural characterization indicated that the pore structure of the two types of POPs (EPS-FDA and EPS-CC) can be successfully tuned by stepwise crosslinking with dimethyl acetal (FDA) and introducing different doses of cyanuric chloride (CC) as a cross-linker. Notably, EPS-FDA and EPS-CC have high specific surface areas with abundant micro/mesoporous structures. The maximum adsorption capacity of EPS-FDA-2 for TC removal (calculated by the Langmuir model) can reach 621.12 mg·g−1, and the amount of 2,4-DCP on EPS-CC-3 is up to 680.27 mg·g−1. Moreover, possible adsorption mechanisms including pore filling and π–π electron interactions are discussed. Hydrogen bonding also plays a role in the removal process of 2,4-DCP by EPS-CC-3. This study developed a novel and green synthetic method for the efficient recycling of waste plastics and demonstrated an industrialized approach for conversion of waste plastics into high-value-added adsorbing material, which could be a promising candidate for the removal of organic contaminants.

In this study, hydroxyapatite/biochar nanocomposites (HAP/BC-NCs) were synthesized through a simple one-pot hydrothermal process and utilized as an adsorbent for the removal of copper(II) from aqueous media. Characterization results revealed that rod-shaped HAP nanoparticles were successfully incorporated on the surfaces of synthesized HAP/BC-NCs. A set of systematically designed batch experiments were carried out to determine the influences of adsorbent dosage, solution pH, ionic strength, and temperature on the adsorption behavior of the HAP/BC-NCs. Overall findings from batch experiments and extended X-ray absorption fine structure analysis demonstrated that the potential mechanisms responsible for the removal of Cu(II) from aqueous media are cation exchange between Cu2+ in solution and Ca2+ in the HAP on the surfaces of the as-synthesized nanocomposites and the formation of inner-sphere surface complexes on the surfaces of the HAP/BC-NCs. Kinetic studies revealed that the adsorption process follows the pseudo-second-order model and that the overall adsorption rate is controlled by film diffusion as the dominant mechanism and intraparticle diffusion as a secondary mechanism. Adsorption isotherms were accurately represented by a Langmuir isotherm model and the maximum adsorption capacity was determined to be 99.01 mg/g at 298 K, which represents a higher efficiency for Cu(II) adsorption compared to previously reported composite materials. Thermodynamic analysis indicated that the process is thermodynamically spontaneous and endothermic process. Overall, the findings presented in this paper suggest that HAP/BC-NCs have promising applicability for the removal of heavy metals from aqueous media as an alternative, low-cost, and eco-friendly adsorbent for environmental remediation.

In this paper, a facile immobilization method was applied to load alginate, ferric oxide and dopamine onto fungal mycelium to prepare a series of spherical composites as potential adsorbents for the separation and removal of thorium from aqueous solution. The structure and chemical properties of the as-prepared adsorbents were characterized in detail via scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), pH value at the point of zero charge (pHPZC) and thermogravimetric (TG) analysis. Based on the adsorption studies, the magnetic gamma-ferric oxide (γ-Fe2O3) and polydopamine (PDA) cofunctionalized fungal microspheres (FPFMs) exhibited excellent adsorption performance for thorium and could represent convenient agents for the removal and recovery of thorium. The equilibrium adsorption data for the FPFMs were well fitted by the Langmuir model, and a high maximum thorium adsorption capacity of 326.346 mg·g−1 was obtained. The thermodynamic parameter values (ΔH0 > 0, ΔS0 > 0, ΔG0

Upgrading coal mine methane (CMM) with adsorption method is an effective way to enhance the energy utilizing efficiency and reduce greenhouse gas emissions. In this work, adsorption equilibrium and kinetics of CH4, N2 and O2, as typical components in CMM, on three carbon molecular sieves (CMSs) and the corresponding separation performances were studied. The equilibrium and kinetic selectivity were obtained from adsorption isotherms fitted with the Langmuir model and uptake curves fitted with the micropore-diffusion model, respectively. O2 with the highest diffusion time constant among three gases suggests the advantage of CMS-based kinetic separation in deoxygenation of CMM and the critical role that N2/CH4 kinetic separation plays in CH4 enrichment. CMS-1 with the highest microporosity has the largest adsorption capacities, and CMS-3 with a proper average pore size has the greatest N2/CH4 kinetic selectivity. The actual separation performances shown by CH4/N2/O2 breakthrough curves according to the principle for practical CMM upgrading processes exhibit the order of CMS-1 > CMS-3 > CMS-2 which is inconsistent with that of the conventional N2/CH4 selectivity highly due to the underestimation of effects of N2 equilibrium adsorption relative to N2 kinetic selection without covering specific adsorption range corresponding to practical working capacity region. A modified selectivity with consideration of actual N2 amount adsorbed was therefore developed, showing the correct performance order and the potential to be used as a practical adsorbent selection parameter. An advanced CMS materials design with proper existence of microporosity would benefit practical CMM upgrading in terms of reaching an optimal balance between adsorption equilibrium and kinetics.

Amine containing polymers (ACPs) were synthesized by heating glyoxal and melamine under argon conditions. The batch characterization, including SEM, FTIR, XRD and XPS techniques, indicated that ACPs had various nitrogen-containing functional groups. The batch experiments indicated that ACPs presented the high removal performances (Qmax = 250 mg/g, calculated by Langmuir model), well stability, strong salt tolerance and great regeneration cycle toward U(VI). XPS analysis confirmed the coordination of U(VI) with nitrogen- or oxygen-containing groups via covalent bonding. The theoretical calculations revealed that the binding energies of U-N, U-O and U-C were −27.49, −16.94 and −11.81 kcal/mol, respectively, indicating that U(VI) was tended to combine with nitrogen-containing groups. These observations suggested that ACPs can be regarded as a promising adsorbent for immobilization and pre-concentration of U(VI)-containing wastewater in environmental cleanup.

Extraction of Eu(III) from wastewater has recently received extensive attention in environmental water pollution improvement because Eu(III) is the chemical analogue of trivalent lanthanides [Ln(III)] and actinides [An(III)]. In this work, UiO-66-AO with remarkable physicochemical properties was designed through introducing amidoxime groups (C(NOH)NH2) on the surface of UiO-66-CN which was derived from UiO-66-Br through introducing cyano groups (C N). SEM, TEM, BET, FT-IR, XRD, and TGA techniques demonstrated the effective synthesis and excellent structural performances of target materials. The outstanding sorption efficiency of UiO-66-AO (∼253.8 mg/g within 2 h) was verified through kinetic and thermodynamic analyses, showing that the kinetics data were well fitted by pseudo-second-order kinetic model, and the sorption isotherms were effectively fitted by Langmuir model. Based on macroscopic experiments and spectroscopic analyses (FT-IR and XPS), the removal mechanisms of Eu(III) onto UiO-66-AO were electrostatic interaction and inner-sphere surface complexation. In addition, the environmental application assessment had proved that UiO-66-AO owned excellent stability, outstanding selectivity, and remarkable Eu(III) removal percentage in simulated wastewater systems, demonstrating the great potential of UiO-66-AO to remove radionuclides from the actual wastewater.

A novel adsorbent, chitosan/cellulose biocomposite sponge (CCS) for removing Hg(II) ions rapidly and selectively from aqueous solution is successfully fabricated via a facile glutaraldehyde cross-linking reaction and lyophilization. The CCS can be rapidly separated and easily regenerated by simple extrusion compared with most particulate or powder absorbent. In the adsorption tests, the experimental data follows the pseudo-second-order kinetic model and Langmuir isotherm. The CCS uptakes more than 97% of the ultimate adsorption capacity in aqueous solution within 2 min, and the adsorption capacity is derived to be 495 mg/g. Furthermore, the CCS shows good selectivity for removing Hg(II) ions, and the coefficient of selectivity to Hg(II) ions is 461, 227, and 35 times higher than that to Cu(II), Pb(II), and Cd(II) ions, respectively. The mechanism for selective adsorption is elucidated via Fourier transform infrared spectrum (FTIR) and X-ray photoelectron spectroscopy (XPS) spectral analysis before and after adsorption. Density functional theory (DFT) calculations are also performed. Notably, the adsorption capacity retains 85% of its initial value (495 mg/g) after five cycles, indicating excellent reusability of the CCS. Significantly, the applicability of the CCS is evaluated in simulated Hg(II) effluent (PVC production). The results indicate that the removal efficiency of the CCS exceeds 84% of the initial value (11.45 ppm) within just 2 min. The sponge is a portable and eco-friendly composite, thereby has a great potential to decontaminate Hg(II) ions in water treatment.

A coral-like hierarchical micro/nano-structural polyaniline consisting of short nanowires (CL-PANI) was synthesized via a simple chemical oxidation method and firstly used as an adsorbent for removal toxic Cr(VI) ions. Two types of magnetic CL-PANI nanocomposites, i.e., CL-PANI shell coated by Fe3O4 nanoparticles (CL-PANI@Fe3O4) and Fe3O4 nanoparticles protected by CL-PANI (Fe3O4@CL-PANI), were further prepared for the easy separation purpose in the practical application. As-prepared adsorbents were well characterized and their performance for the removal of Cr(VI) were systemically investigated and compared. Adsorption results showed that the adsorption of Cr(VI) ions was dependent on solution pH and temperature for all three adsorbents. The fitted data revealed that the adsorption process followed the pseudo-second-order kinetic model and Langmuir isotherm model. CL-PANI exhibited an enhanced adsorption performance due to its well-defined and accessible mesoporous and plenty surface active sites compared with common synthesized irregular nanorod PANI. Moreover, modified with Fe3O4 nanoparticles endowed CL-PANI with a slight decreased adsorption capacity, but provided more active sites for immobilizing the reduced Cr(III) ions. Besides, compared with CL-PANI@Fe3O4, Fe3O4@CL-PANI was found to be more promising in the practical treatment of Cr(VI)-containing wastewater.

The bioaccumulation and transformation of U(VI) by sporangiospores of Mucor circinelloides under different environmental conditions (e.g., reaction time, pH, carbonate, sporangiospores concentration, and temperature) was investigated by batch, XPS and EXAFS techniques. The bioaccumulation kinetics and isotherms can be fitted by the pseudo-second-order kinetic mode and Langmuir model, respectively, due to the high correlation coefficient. The maximum bioaccumulation capacity of sporangiospores for U(VI) was 166.13 mg/g at pH 6.0, which was significantly higher than that of other mycelia or spores. The intracellular and extracellular morphology of sporangiospores were significantly changed after U(VI) bioaccumulation, and levels of intracellular H2O2, O3−, GPx and SOD compounds in sporangiospores increased significantly. XANES analysis confirmed that the intracellular U(VI) was reduced to U(IV) by sporangiospores, and U(IV) might be stably associated with oxygen-bearing functional groups by EXAFS analysis. These results show that the sporangiospores can be used a promising adsorbent for the bioaccumulation and transformation of U(VI) from aqueous solutions, which has important scientific significance for the immobilization of U(VI) in environmental remediation.

Excellent column packing is a precondition for efficient separation of radioactive 90Sr from high level liquid waste (HLLW). α-ZrP particles are traditionally used as column packing for capturing radioactive nuclides from HLLW due to their excellent stability and adsorption ability. However, there remains room for improvement in terms of capacity and selectivity. Here, the traditional α-ZrP column packing was exfoliated and further modified by anchoring sulfonic groups on its surface to improve its adsorption capacity for 90Sr. The resulting ZrP-SO3H not only retained the excellent properties of α-ZrP but also possessed a larger surface area and much more adsorption sites. Adsorption experiments indicated that ZrP-SO3H exhibited excellent adsorption ability for separating of Sr2+ from acidic condition, and the maximum adsorption capacity of Sr2+ fitted by a Langmuir model is 183.21 mg g−1, which is higher than that of traditional α-ZrP and other similar column packings. In addition, kinetic studies indicated that Sr2+ adsorption on ZrP-SO3H is fast, and surface chemical adsorption is the main interaction between Sr2+ and ZrP-SO3H. Remarkably, radioactive experiment proved that ZrP-SO3H is an excellent adsorbent, and shows good stability for high efficiency for selective removal of 90Sr under complicate radioactive environment. Our present results implied that the novel ZrP-SO3H is potential column packing and could be suggested as promising column packing for separation of 90Sr from HLLW.

In this study, we performed modeling analysis based on isothermal experimental data to develop linear free energy relationship (LFER) model, which is a very useful concept for predicting the molecular interaction of an adsorbate in a certain system. Thirty compounds containing cationic, anionic, and neutral were used, and the effect of diverse intermolecular interactions was captured by isotherm fitting of the Langmuir model. The predicted equation of distribution coefficient (Kd), adsorption capacity (qm), and adsorption affinity (Kad) of activated charcoal (AC) for compounds was developed. For the Kd values, an activity-dependent LFER model was developed, and could predict log Kd within R2 of 0.85. The determined system parameters and their statistical results revealed that the molecular volume (V) of compounds encouraged the adsorption from water to AC, whereas the hydrogen basicity (B) discouraged such adsorption. In the cases of qm and Kad, AC had relatively good capacities for neutrals, which were higher than those for cations and anions. Whereas, AC had stronger adsorption affinities with anions, compared to those for neutrals and cations. The phenomena were explained by the developed LFER models, in which the p−/n− electron interaction (E) made a great positive contribution to increase the adsorption capacity and affinity, while Coulombic interactions (J+ and J−) demonstrated a negative trend. Finally, the developed models can predict the qm and Kad in R2 of 0.86 and 0.76, respectively.

Natural gums, mainly composed of polysaccharides, are green feedstock to synthesize a variety of functional materials. Herein we report Moringa oleifera gum (MOG) to synthesize new bio-based polyurethane foam (MOG-PUF), wherein MOG acts as polyol for reaction with 4,4′−diphenylmethanediisocyanate via urethane linkages. MOG-PUF was used for the adsorption of malachite green (MG) dye from its aqueous solution and also tested for antibacterial activity. Synthesis of MOG-PUF and malachite green-loaded MOG-PUF (MG-loaded MOG-PUF) were successfully characterized using various analytical techniques. Batch experiment studies revealed almost 100% removal of MG using MOG-PUF within 30 min. Dye adsorption followed pseudo-second order kinetics and conformed Langmuir isotherm with maximum adsorption capacity (qm) of 125.945 mg/g. Moreover, MOG-PUF showed noticeable reusability having adsorption efficiency of ∼61% after 15th repeat cycle. Results of antibacterial study showed prominent zones of inhibition against four strains of bacteria, S. aureus, Enterococcus, P. aeruginosa and E. coli, thus revealing its strong antibacterial nature.

Reduction of sulfur-containing compounds from fossil fuel is vital. This work reports on the adsorptive removal of benzothiophene (BT) from liquid fuel using a highly porous metal-organic framework based on a bicomponent zirconium(IV) benzene-tricarboxylate Zr(BTC), and its post-synthetically modified hybrid form with dodeca-tungstophosphoric acid (HPW/Zr(BTC). The HPW loading for the high-performing hybrid adsorbents was 0.5–2.0 wt/wt of W/Zr. Temperature and concentration dependent BT adsorption data were in good agreement with the non-linear Langmuir model combined with a van’t Hoff description of the heat of adsorption. The maximum predicted adsorption capacities were estimated to be 290 and 238 mg.g−1 for HPW(1.5)/Zr(BTC) and Zr(BTC) comparable to the contemporary reported adsorbents. The adsorption kinetics followed a pseudo-second order model, which was related to the low concentration of BT used for these studies. Although the highly porous Zr(BTC) had good adsorptive sites, its adsorption capacity was enhanced by incorporation of HPW, this was attributed to availability of added acid sites for adherence of basic BT. The adsorption findings were further corroborated with DFT calculations, which showed favorable BT adsorption with calculated binding energies of −140.2 and −47.3 kJ.mol−1 for HPW(1.5)/Zr(BTC) and Zr(BTC), respectively. Much of adsorption sites were retained after regeneration of adsorbents.

Discharging coloring products in the natural streams has degraded water quality irreversibly over the past several decades. Order mesoporous carbon (OMC) was modified by embedding neodymium(III) chloride for the first time onto the surface of OMC to enhance the adsorption capacity for these contaminants. The modified OMCs were characterized using Nitrogen Adsorption-Desorption Isotherm, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FT-IR) spectra, and X-ray Photoelectron Spectroscopy (XPS). TEM images of neodymium modified OMCs revealed ordered structure. Analysis of FT-IR and XPS spectra revealed the formation of hydroxides coordinated with neodymium(III). In the lower pH region, the modified OMCs have increased positively charged sites for adsorption of anionic sunset yellow. Adsorption kinetics revealed that the adsorption of sunset yellow was better fitted with the Pseudo-Second-Order Kinetic model than the Pseudo-First-Order Kinetic Model. The adsorption isotherms were well fitted with Langmuir Model depicting the formation of monolayer adsorbates onto the surface of OMC-Nd. The maximum monolayer adsorption capacity of 285.7 mg g−1 was observed for OMC-2Nd. The overall adsorption capacity was increased by 40% compared to the virgin OMC. The interaction mechanism involved ligand exchange between Nd-modified OMC and sunset yellow.

Developing a facile and rapid method to prepare adsorbents for an efficient and selective removal of dyes is of great importance for human health and environment. In this work, a silsesquioxane-based disulfide-linked polymer (DLP) was rapidly synthesized by a simple oxidative coupling reaction of octa(3-mercaptopropyl)silsesquioxane within 2 min at room temperature. The synthesized DLP demonstrated selective and efficient adsorption of cationic dyes over anionic dyes with the maximum capacities of 12.94 mg g−1 for methylene blue, 18.47 mg g−1 for rhodamine B and 26.69 mg g−1 for crystal violet. The high uptake and selectivity for cationic dyes was attributed to the electrostatic interactions between the anionic charges from sulfur and oxygen anions formed by the deprotonation of thiols and hydroxyls in the DLP and the cationic charges from the dyes, and the swelling behavior of the DLP. To investigate the adsorption process, the effect of various factors such as contact time, initial concentration, temperature, and pH on the adsorption activity of cationic dyes was studied. The adsorption equilibrium data showed a better fitting to the Langmuir isotherm model than the Freundlich model and the adsorption kinetics fitted well with the pseudo-second-order kinetic model, indicating that the adsorption process is mostly governed by the chemisorption behavior. Additionally, the absorbent was recyclable with the adsorption capacity being >95% after five times recycle adsorption. These results indicated that the present disulfide-linked polymer could be promisingly applied as an efficient adsorbent for the selective removal of cationic dyes from industrial wastewater.

A magnetic nanocomposite (NC), Fe3O4@PPy-MAA, was synthesised via in situ oxidative polymerisation of the pyrrole monomer in a thioglycolic acid (mercaptoacetic acid) solution (as a dopant), in the presence of iron oxide (Fe3O4). The newly developed NC was characterised using ATR-FTIR, FE-SEM, HR-TEM, XRD, TGA, BET and VSM. The performance of the NC for silver ion (Ag+) adsorption was carried out through batch studies as a function of pH, adsorbent dose, temperature and initial Ag+ concentration. The maximum adsorption capacity of Ag+ was determined to be 806.4 mg/g at 25 °C using Langmuir adsorption isotherm at a solution pH of 5.6. The kinetics studies indicated that the Ag+ adsorption onto the Fe3O4@PPy-MAA NC surface was rapid and was well described by the pseudo-second-order kinetics equation. Also, the present study emphasised the reusability of Ag+-adsorbed waste material for the disinfection of microorganisms, which was demonstrated through the excellent antimicrobial activity of the NC against Escherichia coli in both synthetic and natural water samples. Therefore, the as-prepared Fe3O4@PPy-MAA NC has an excellent ability to successfully remove Ag+ ions from aqueous solutions and subsequently, the Ag-loaded waste material could be used as a potential candidate disinfectant.

Biochars pyrolyzed at different temperatures were thiol-modified using 3-mercaptopropyltrimethoxysilane (3-MPTS) and applied on aqueous Hg2+ and CH3Hg+ removal with high efficiencies. The structure and physicochemical properties of biochar before and after thiol-modification were characterized. The biochar pyrolyzed at low temperature had more active sites ( OH, C O, C O C, and π bond) for surface modification with 3-MPTS. Pseudo-second-order kinetic model and Langmuir isotherm model fitted well with the sorption data. Among all the raw and thiol-modified biochars, 3BS (thiol-modified biochar from pyrolysis at 300 °C) had the largest Langmuir adsorption capacities of Hg2+ (126.62 mg/g) and CH3Hg+ (60.76 mg/g). The introduction of SH enhanced the selectivity of biochar for mercury sorption (especially CH3Hg+). Ligand exchange and complexation between surface active sites ( SH, OH, COOH, and NH2) and mercury were the dominant removal mechanisms. Among them, SH played a major role. With the increase of 3-MPTS content in the preparation of 3BS, the adsorption capacity of Hg2+ and CH3Hg+ increased first and then decreased (the optimal content of 3-MPTS was 2%). Natural organic matter (NOM), glucose and humic acid (0–24 mg/L) had little effect on the adsorption of Hg2+ and CH3Hg+ by 3BS (the mercury removal rate only changed by 1.2–9.4%). This study demonstrates potential of thiol-modified biochar for mercury (especially CH3Hg+) removal from water.

Few studies have focused on the effects of biomass feedstocks on the structure–reactivity of magnetic biochar. In this study, four types of magnetic biochar were first prepared using steel pickling waste liquor (serving as iron salt) and sugarcane bagasse (SMBC), rice straw (RMBC), peanut shells (PMBC) and herb residue (HMBC). According to the Langmuir model, the maximum adsorption capacity of Cr(VI) by SMBC was 43.122 mg/g, which was approximately 1.298 times, 3.175 times and 3.677 times higher than that of RMBC, PMBC and HMBC, respectively. The mass balance of chromium indicated that Cr(VI) was removed mainly via reduction. However, the reduction capacity of Cr(VI) differed among the four types of magnetic biochar. The results of characterisations of those magnetic composites before and after reaction demonstrated that the Cr(VI) was electrostatically attracted to the surface of the materials. Consequently, most of the adsorbed Cr(VI) was reduced and the remainder of the Cr(VI) was complexed with C O groups in magnetic biochar. Further, the total iron in magnetic biochar, especially Fe(II), played a dominant role in the removal and reduction of Cr(VI). Finally, correlation analysis showed that the cellulose and ash in the biomass were the main factors that induced the differences in the magnetic biochar’s total iron content. Therefore, this study may provide a reference for the use of magnetic biochar to remove Cr(VI) from aqueous solutions.

Designing and fabricating environmental friendly adsorbents with more accessible active sites and higher specific surface area for achieving rapid kinetics and high efficiency have become an impending challenge in radionuclides’ pollution remediation. To overcome these issues, we rationally designed the hierarchical structured layered double hydroxides with mesoporous carbon template (CMK-3@LDHs) by in situ hydrothermal method. The adsorption data could be well simulated with pseudo-second-order and Langmuir model, and the results indicated that the CMK-3@LDHs exhibited higher adsorption capacities (171 mg·g−1 for CMK-3@Mg-Al LDHs and 301 mg·g−1 for CMK-3@Ni-Al LDHs at pH = 5.0) and more rapid kinetics (achieved equilibrium within 30 min) than SBA-15@LDHs towards U(VI). The kinetic model simulation demonstrated that the adsorption rate was dominated by intra-particle and film diffusion models simultaneously. In addition, the interaction between U(VI) and LDHs was pH-dependent and weakly related with ionic strength at pH

This paper reports the efficient removal of Pb2 + ions from water by modified alkaline lignin (MAL), in which alkaline lignin was used as the raw material and ornamented with amine/imine (–NH2/–NH) and dithiocarbamate (–CSS−) groups by using polyethyleneimine (PEI) and carbon disulfide (CS2) as the modifier. The pseudo-second-order model and Langmuir model expressed the adsorption kinetics and isotherm well, indicating the adsorption of Pb2 + ions on MAL was a chemisorption and monolayer. The maximum adsorption amount (qm) of MAL towards Pb2 + ions was 79.9 mg/g, significantly higher than that of other reported biomass-based-sorbents such as Hamimelon peels (7.9 mg/g), dairy manure-derived biochar (37.8 mg/g), and acid-treated avocado kernel seeds (21.8 mg/g). Even after six continuous adsorption–desorption cycles, the values of qm for the regenerated MAL at each cycle were still obviously higher than those aforementioned sorbents. The binding affinity of different groups of MAL towards Pb2 + ions followed the sequence: C–N > –NH2 > N–H/O–H > C–S > C S. This work not only gave a comprehensive picture of the adsorption/desorption mechanism of Pb2 + ions on MAL but also evaluated the reusing ability of MAL. These results may provide insights for the further studies on the subsequent construction of devices to be used in bench- and pilot-scale experiments.

The hollow-structured porous aromatic polymers (H-PAP) with cavity diameter from 228 ± 11 to 464 ± 15 nm were controllably prepared through surface coating and template-etching method under scalable synthesis conditions from standard scale to 20-fold scale-up. It is found that the fill factor (f) of reactor is an important parameter for determining the scalability of synthesis. Benefiting from the favorable textural properties, chemical and thermal stability, surface hydrophobicity and π electrons, the well-developed H-PAP as adsorbent was investigated in selective adsorption of 5-hydroxymethylfurfural (HMF) under static batch mode from the single-component and multi-component aqueous solutions. The H-PAP shows an exclusive adsorption for HMF, without adsorption of fructose, levulinic acid (LA) and formic acid (FA), and can be recycled three times without significant decrease in adsorption capacity. Structure-performance relationship points out that the apparent amount of HMF adsorbed on H-PAP is related to micropore surface area, micropore volume and cavity diameter, while HMF selectivity depends on surface hydrophobicity. In the case of HMF adsorption from the real reaction mixture of acid-catalyzed fructose dehydration, the HMF constituent with high purity (ca.94.4%) can be recovered. Combining the adsorption isotherms with DFT calculation reveals adsorption mechanism that HMF adsorption on H-PAP proceeds initially via π–π stacking interaction, and then assembles into regular array around spherical surface to form monolayer coverage following modified Langmuir model, and finally diffuses into interior cavity until adsorption saturation.

A novel multi-templates molecularly imprinted polymer (MIP) was prepared on the surface of mesoporous silica coated magnetic graphene oxide (MGO@mSiO2), and applied for the rapid and selective detection of alkylphenol compounds including bisphenol A (BPA), 4-tert-octylphenol (4-tert-OP) and 4-nonylphenol (4-NP) in water. The synthesized composite was characterized by Fourier transform infrared spectrometer, vibrating sample magnetometer, transmission electron microscopy and Brunauer-Emett-Teller surface area analyzer. The MIP showed high adsorption capacity, good selectivity and fast kinetic for these alkylphenols. The maximum adsorption capacities of the MIP for BPA, 4-tert-OP and 4-NP were 16.81, 35.97 and 61.73 mg g−1, respectively, which were significantly higher than those of the non-molecularly imprinted polymer (NIP) due to the imprinting effect. The adsorption of alkylphenols reached equilibrium within 30 min, and followed pseudo-second-order kinetic model and Langmuir model well. The MIP exhibited good sorption selectivity towards BPA, 4-tert-OP and 4-NP, and could be reused 5 times. Furthermore, a new method for ultrasensitive determination of BPA, 4-tert-OP and 4-NP in water by high performance liquid chromatography was developed, using MIP-based magnetic solid-phase extraction coupled with dispersive liquid-liquid microextraction. Under the optimum conditions, the limits of detection (LODs) for BPA, 4-tert-OP and 4-NP were 0.013, 0.010 and 0.010 μg L−1, respectively. The proposed method was used to the detection of BPA, 4-tert-OP and 4-NP in real water samples, with spiked recoveries of 81.5–104.1% and relative standard deviations (RSDs) of 1.0–7.6%, indicating the multi-templates MIP could be a promising adsorbent for separation and analysis of alkylphenols.

A series of MXene materials with high specific surface areas was obtained by HF treatment of MAX materials at 25 °C, 35 °C and 45 °C, named MXene-25, MXene-35 and MXene-45, respectively. These materials exhibited excellent ability to remove Pd2+ from HNO3 aqueous solution due to their large specific surface area and wide layer spacing, especially for the materials prepared at higher temperature. Adsorption experiments indicated that these adsorption behavior better fitted the Langmuir model, with the maximum adsorption capacity of Pd2+ being 184.56 mg g−1, 163.82 mg g−1, and 118.86 mg g−1 for MXene-45, MXene-35 and MXene-25, respectively; this is higher than for most other inorganic adsorbents, and is attributed to the wide layer d-spacing and large surface area. Moreover, these materials can retain high selectivity for Pd2+ in simulated nuclear wastewater, and thermodynamic analysis revealed that low temperatures benefit adsorption of Pd2+. Remarkably, MXene-45 exhibits excellent regeneration performance and reusability, with no obvious loss after five cycles of adsorption. The present results suggest that 2D MXene materials are promising adsorbents for removing radioactive palladium from radioactive wastewater.

Combined water pollution with the coexistence of heavy metals and organic contaminants is of great concern for practical wastewater treatment. In this study, a jaboticaba-like nanocomposite, titanate nanotubes supported TiO2 (TiO2/TiNTs), was synthesized by a two-step hydrothermal treatment. TiO2/TiNTs had large surface area, abundant of –ONa/H groups and fine crystal anatase phase, thus exhibited both good adsorptive performance for Cu(II) and high photocatalytic activity for phenanthrene degradation. The maximum Cu(II) adsorption capacity on TiO2/TiNTs was 115.0 mg/g at pH 5 according to Langmuir isotherm model, and >95% of phenanthrene was degraded within 4 h under UV light. TiO2/TiNTs showed about 10 times higher observed rate constant (kobs) for phenanthrene degradation compared to the unmodified TiNTs. More importantly, the coexistence of Cu(II) promoted photocatalytic degradation of phenanthrene, because the incorporated Cu(II) in the lattice of TiNTs could trap photo-excited electron and thus inhibited the electron-hole recombination. Density functional theory (DFT) calculation indicated that the sites of phenanthrene with high Fukui index (f0) preferred to be attacked by OH radicals. The quantitative structure–activity relationship (QSAR) analysis revealed that the degradation intermediates had lower acute toxicity and mutagenicity than phenanthrene. TiO2/TiNTs also owned high stability, as only slight loss of Cu(II) and phenanthrene removal efficiency was observed even after four reuse cycles. The developed material in this study is of great application potential for water or wastewater treatment with multi-contaminants, and this work can help us to better understand the mechanisms on reaction between Ti-based nanomaterials and different kinds of contaminants.

A large number of mechanism were anticipated for copper since 1988 in NaCl medium. The detail electrochemical behavior leading to the anodic dissolution of copper, however, still remains uncertain. Herein, an Imidazopyrimidine Dye, named, 4-amino-3-(phenyldiazenyl)benzo[4,5]imidazo[1,2-a]pyrimidin-2(1H)-one, (APIP) has been used as a copper corrosion inhibitor in 3.5 wt.% (by weight) NaCl solution. The present investigation provides a brief mechanistic overview of the electrochemical mechanism of copper in aerated NaCl solution, simulating a static marine environment, with and without addition of APIP inhibitor. Potentiodynamic polarization (PDP) results confirmed that the APIP can suppress copper corrosion effectively at low concentration in 3.5 wt.% NaCl solution with an inhibition efficiency of 92.79% due to adsorption, along with the prediction of electrochemical mechanism. Electrochemical impedance spectroscopy (EIS) measurements showed that the corrosion inhibition of Cu proceeds via both diffusion and kinetic controlled processes. Adsorption of APIP on copper surface is well fit with the Langmuir isotherm model and mode of adsorption is proposed. Antimicrobial activity was also studied and the result obtained showed ‘‘eco-friendly’’ nature of APIP. Field Emission Scanning Electron Microscope (FE-SEM), Energy dispersion X-ray (EDX) and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) observations of the copper surfaces confirmed the existence of adsorption of APIP thus can be potentially used in industries in which seawater is implied are numerous such as cooling water systems, desalination plants, power plants, and oil production units. Results obtained from theoretical calculations including quantum chemical density functional theory (DFT) method and molecular dynamics (MD) simulations confirms the experimental findings and provide further insight into the mode of adsorption on the copper surface.

Struvite crystallization is one of the most promising routes for phosphorus recovery from phosphorus-rich sludge. However, the adsorption of alginic acid, a surrogate of extracellular polymeric substances in phosphorus-rich sludge, on struvite crystals has been proved to significantly inhibit struvite crystallization. To comprehensively understand the inhibitory mechanism, the adsorption behavior was evaluated at various adsorption time, the concentration of alginic acid, pH and ionic strength in the present study. Subsequently, adsorption equilibrium isotherm, kinetic and thermodynamics models were employed to fit the adsorption data. Interestingly, the adsorption mechanism was explored by X-ray photoelectron spectra (XPS) and Fourier transform infrared spectroscopy analysis (FTIR), which was further elucidated by triple-layer model (TLM). The results indicated that the adsorption capacity of struvite crystals almost reached a plateau value within the first 30 min. Meanwhile, the adsorption capacity was significantly reduced with increasing pH, but slightly increased with increasing ionic strength. Moreover, the adsorption process obeyed pseudo-second order kinetic model and Langmuir adsorption isotherm model, whereas intra-particle diffusion was a main rate-limited step. Furthermore, hydrogen bonding and surface complexation between alginic acid and struvite crystals dominated the adsorption mechanism. Additionally, alginic acid underwent surface reactions by virtue of two outer-sphere surface complexes and one inner-sphere surface complex. The findings presented herein will facilitate understanding of the inhibitory mechanism of organic matters on struvite crystallization from phosphorus-rich sludge.

The leakage of radionuclides poses a great threat to the global ecosystem, which has aroused world-wide continuous attention. Since sorption plays the most important role in their environmental fate and humic acid (HA) is a key factor to their migration behavior, it is necessary to develop highly-efficient adsorbents that can remove radionuclides from the contaminated water in the presence of HA. Herein, we reported a novel multi-shelled Fe3O4@MnOx, which showed considerable sorption capacities towards uranium (U(VI)) and europium (Eu(III)). From the systemic batch experiments, the sorption kinetics follows the pseudo-second-order model, and sorption thermodynamics are endothermic processes. The sorption edges are pH-dependent but independent of ionic strength. Furthermore, the sorption isotherms are well described by the Langmuir model, giving maximum sorption capacities of 106.72 mg·g−1 for U(VI) and 138.13 mg·g−1 for Eu(III) at 298 K. Based on the spectroscopic studies, U(VI) is mainly adsorbed on the MnIII-O-H site while Eu(III) shows higher affinity to the MnIV-O-H site. In the presence of humic acid (HA), the HAUO2+ and (HA)2Eu+ species can accelerate the sorption kinetics and enhance the sorption capacities. This work can not only boost the exploration of adsorbent systems in the field of materials, but also promote the investigations of the interface reaction mechanism in the field of radiochemistry.

Ascribing to their significant differences in physicochemical properties, it is extremely challenging to treat complex wastewater containing more than one class of pollutants via one-step treatment. Here, we focused on disposal of complex wastewater bearing organic dye and heavy metal by using adsorptive method. Thus, we successfully fabricated a novel and versatile EDTA functionalized magnetic chitosan composite adsorbent (Fe3O4-CS/EDTA) for simultaneous removal of methyl blue(MB) and heavy metal (Pb(II) and Cu(II)) from complex wastewater. In this setting, EDTA chelating groups are mainly responsible for the binding of heavy metals, while the protonated amino groups of CS adsorb anionic dyes through electrostatic interaction, thus enabling the simultaneous capture of these two classes of pollutants. In mono-pollutant system, the resulting material showed prominent uptake ability toward MB, Pb(II), and Cu(II) with uptake characteristics of pseudo-second-order model and Langmuir isotherm equation. The maximum monolayer uptake capacities were determined to be 225.0 mg g−1 of Cu(II), 220.0 mg g−1 of Pb(II), and 459.9 mg g−1 of MB at 303 K, respectively. More interestingly, in metal-MB binary system, uptake of MB was almost not affected by coexisting metal. While the uptake capacity of Cu(II) or Pb(II) was enhanced with increasing of MB concentration. These results demonstrated the synergetic removal performance of as-designed adsorbent toward cationic metal ions and anionic dye. Moreover, as-resulting adsorbent showed no significant adsorption capacity loss even after 8 runs of sorption-desorption cycle, manifesting that it is of great stability and could be regarded as a promising candidate adsorbent for treating complex wastewater. This study provides some insights into the design of highly efficient adsorbents with spatially separated sorption sites for disposing complex wastewater bearing organic and metallic contaminants.

We introduced (MoS4)2− moiety into the lamellar layers of Ca0.66Al0.34(OH)2(NO3)0.34⋅yH2O to fabricate Ca0.66Al0.34(OH)2(MoS4)0.17⋅yH2O (CA-MoS4⋅LDH), a stable and efficient adsorbent for removal of two envoy Fluoroquinolones (FQs), Ciprofloxacin (CIP) and Ofloxacin (OFL), from contaminated aquatic sources. Various characterization tools, such as X-ray diffraction (XRD), Scanning electron microscopy, Energy dispersive X-ray spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and Thermogravimetric analyses etc. were applied to confirm structural and compositional changes during the synthesis and adsorption properties of CA-MoS4⋅LDH. The efficiency of adsorbent was investigated by evaluating different parameters including contact time, pH of solution, initial concentration of pollutant, and effect of temperature. By using CA-MoS4⋅LDH as adsorbent, we found more efficient removal of CIP than that of OFL due to the steric hindrance. The highest uptake of 707.20 mg/g and 476.74 mg/g of CIP and OFL, respectively, was found at pH of 6 with improved kinetics and easily reusability for these representative antibiotics models so far. Removal kinetics of both FQs were found to better follow the pseudo-second-order kinetic model than the pseudo-first-order. The Langmuir adsorption isotherm was employed to understand the removal process, suggesting monolayer chemisorption mechanism. The adsorbate-adsorbent interaction revealed remarkable features originate from the combination of weak hydrogen bond interaction between thio group and NH2+ group of antibiotic and electrostatic interaction between positive LDH layer and COO− group of antibiotic as well, and anion exchange mechanisms, which were also confirmed by XRD, FTIR, XPS and Raman spectrum etc. obtained after adsorption. It is proposed that all (MoS4)2− moiety offers stability to the CA-MoS4⋅LDH structure to avoid its solubility under ambient environments.

Although thermodynamically feasible, reduction of U(VI), Re(VII), Se(VI) and Se(IV) in homogeneous Fe(II) solution could be hardly observed. Whereas, surface-mediated reduction by Fe(II) has been generally regarded as a major pathway for the immobilization of these radionuclides. In this paper, graphene oxide (GO) was firstly revealed to mediate the reduction of U(VI), Re(VII), Se(VI) and Se(IV) by aqueous Fe(II) via a combined batch, DFT calculation and spectroscopic investigation. The kinetics for all adsorption systems could be fitted by the pseudo-second-order model, which was indicative of a chemical interaction. The isotherms for all reaction systems could be described by the Freundlich model better than that by the Langmuir model. Spectroscopic studies indicated that the enhancement effects of GO were attributable to the facilitated electron transfer by the graphitic surfaces and particularly to the decreased Fe(III)-Fe(II) redox potential by surface adsorption of Fe(II) with O-bearing functional groups on GO. Additionally, the presence of coexisting dissolved fulvic acid (FA) could significantly promoted GO-mediated reduction, by enhancing the electron shuttle ability of GO. Therefore, owning to the combined strong mediation efficiency and excellent adsorption affinity, GO exhibited an important role in mediating the reductive immobilization of radionuclides in a wide range of redox-stratified environments.

The complete, high-efficiency removal of cationic dyes in industrial wastewater before discharge becomes particularly urgent due to their biological toxicity. The membranes have emerged for removal of dyes benefiting from free separation, cheap component and easy operation, and thus aroused increasing research interest. Herein, the negatively charged hollow crosslinked aromatic polystyrene (PS) fiber (HPF-C) membrane has been successfully synthesized by a rapid room-temperature crosslinking of linear PS in HPF membrane, followed by deep sulfonation. The sulfonated HPF-C (HPF-C-S) membrane showed high experimental equilibrium adsorption capacity of 443.6 mg·g-1 for basic red 46 (BR46) with initial concentration of 50 mg·L-1. Its maximum adsorption capacity (346.0 mg·g-1) of methylene blue (MB) calculated by Langmuir model was about 5 times that of carboxylated cellulose fabrics (CCFs) membrane and higher than that of the most reported or commercially available nanofiber/nanoparticle adsorbents. Without external driven pressure, a flow rate of cationic dye solution through HPF-C-S membrane was up to 530 L·m-2·h-1 which was about 90 times that (6 L·m-2·h-1) of the CCFs membrane. The solution concentration through the HPF-C-S membrane always remained 0 mg L-1 (lower than the LODs of UV) before the permeation volume reached 4000 mL for 2 mg L-1 BR46 solution (In other words, 20 L of clean water could be obtained through per gram of membrane) and 1500 mL for 2 mg L-1 MB solution, respectively. The rejection ratio of 100% fully met the environmental criterion for wastewater disposal, indicating absolute superiority to the reported CCFs membrane that could not completely purify dyes. Moreover, the HPF-C-S membranes indicated excellent sustainability and stability. Besides, the kinetics, thermodynamics and mechanism behind these phenomena were studied.

Adsorptive desulfurization of transportation fuels can be affected by high diffusion limitations in porous sorbents due to the existence of larger kinetic dimensions of sulfur compounds and aromatics. In this contribution, we explored that metal based hierarchically ZSM-5-based micro-/mesostructures (MMZ) can overcome such scarcities without compromising the desulfurization activity. The mesopores of MMZ reduces path length for diffusion to the zeolite internal sites, and the metals (here, Ni) not only establish strong interactions but also enhances the adsorption configurations. The MMZ was synthesized by subjecting commercial H form ZSM-5 (SiO2/Al2O3 = 28) via sequential dissolution-self-assembly and doped with Ni via ultrasound-assisted impregnation. The samples were characterized by N2 sorption, NH3-TPD, XRD, H2-TPR TEM, SEM, FT-IR, elemental distribution mapping, and XPS techniques. The results revealed that high surface area up to 831 m2.g−1 and well-ordered mesostructures obtained when ZSM-5 was subjected to dissolution in 1.0 mol.L−1 NaOH solution and re-assembly of Al- or Si-containing species using cetyltrimethylammonium bromide (CTAB) as a template. The sulfur adsorption capacity was improved from 4.8 to 14.1 mg/g after Ni species and up to 10 wt% are highly dispersed over MMZ. The adsorption capacities of samples decrease in the following order 10Ni/MMZ > 5Ni/MMZ > 15Ni/MMZ > MMZ > 10Ni/ZSM-5 and the increased performance may be ascribed to increased surface acidity, well distributed Ni NPs and texture of MMZ. The isotherm data of thiophene adsorption were fitted well by Langmuir isotherm while kinetic study described that the adsorption data followed pseudo-second order model.

In this work, novel composite nanofibers which exhibited ‘core–shell’-like structure were fabricated through the deposition of polypyrrole (PPy) particles on the electrospun poly(vinylidene fluoride) (PVDF) nanofibers with the aid of polydopamine (PDA). First, the PVDF/DA electrospun nanofibers were prepared. Then, the self-polymerization of PDA was triggered in a Tris–HCl buffer solution. After that, the pyrrole monomer was added into the distilled water containing the PVDF/PDA fibrous membrane and the chemical oxidation polymerization of PPy was triggered by adding FeCl3. Morphological characterization confirmed that the electrospun PVDF/PDA nanofibers were homogenously coated by PPy particles. Largely enhanced hydrophilicity of the fibrous membrane surface was achieved due to the presence of many nitrogen-containing groups and the increased surface roughness of nanofibers. The adsorption abilities of the composite nanofibers were investigated using Methylene Blue (MB) and Congo Red (CR) as the probe dyes. The results showed that the composite nanofibers exhibited excellent adsorption abilities toward cation and anion dyes simultaneously, and the maximum adsorption capacities were 370.4 and 384.6 mg/g for MB and CR adsorption, respectively. The adsorption behaviors toward the two dyes could be well described by the pseudo second-order adsorption model and the Langmuir adsorption model. Further results showed that the adsorption abilities of the composite nanofibers were greatly dependent upon the pH values of the solution. Furthermore, the composite nanofibers exhibited good regeneration ability. The removal ability toward Cr(VI) was also measured and the experimental adsorption capacity was 126.7 mg/g. The excellent adsorption abilities toward cation/anion dyes and heavy metal ions endow the composite nanofibers with great potential application in wastewater treatment.

The development of highly selective, effective, and regenerable adsorbents with good separability for thallium (Tl) removal remains a challenge. In this study, a hierarchical composite containing MnO2 and magnetic pyrite cinder was fabricated to remove Tl(I) from wastewater. SEM, TEM, XRD, BET, and VSM analyses indicate that the hierarchical composite was composed of amorphous, flower-like MnO2 as outer coating and magnetite-dominated pyrite cinder as inner core, with a specific surface area of 29.1 m2/g and saturation magnetization of 15.4 emu/g. Good Tl(I) adsorption was achieved over a wide pH range from 2 to 12. A maximum Tl(I) adsorption capacity of 320 mg/g was attained at pH 12. The presence of Na+, Mg2+, and humic acid had little effect on Tl(I) removal, indicating the high selectivity of this adsorbent. The adsorption isotherm data were better fitted by the Langmuir model, while the pseudo-second order model was more suitable for describing the kinetic data. The composite was effectively regenerated using 1 mol/L HCl solution in only 5 min, and the Tl(I) adsorption capacity of the composite did not change significantly even after the fifth regeneration. Tl(I) removal was mainly achieved via surface complexation, followed by oxidation and electrostatic attraction. This flower-shaped MnO2 coated pyrite cinder composite shows promise for Tl(I) removal due to its excellent efficiency, selectivity, separability, and reusability.

Fe3O4 nanoparticles have attracted extensive attention in the field of environmental remediation owing to magnetism, large specific surface, size and ease of recycling. However, the removal efficiency and mechanisms of doxorubicin hydrochloride (DOX) with as-prepared Fe3O4 nanoparticles are still not well understood. In this study, Fe3O4 magnetite nanoparticles were prepared by euphorbia cochinchinensis extract via the green synthetic route and used to remove DOX, an anti-cancer drug. The green synthesized Fe3O4 nanoparticles were characterized using TEM, XRD, BET, FTIR and magnetism techniques. Results revealed that green synthesized nanomaterials consisted of magnetite Fe3O4 having 10–30 nm particle size and exhibiting high specific surface area of 95.8 m2/g. These Fe3O4 nanoparticles were employed to adsorb DOX from aqueous solution and the influences of initial pH, initial concentration of DOX and temperature were investigated. The results showed that 80.2% of DOX was removed using 20 mg/L of Fe3O4 nanoparticles at 303 K. Adsorption isotherms and kinetics data revealed that the removal of DOX fitted well to the pseudo second-order model and that the Freundlich adsorption model was a better fit than the Langmuir model. The probable removal mechanism of DOX on Fe3O4 was electrostatic interaction. Moreover, the application of Fe3O4 to remove DOX from real wastewater was evaluated.

A simple, scalable, novel polymer was synthesized by the aminolysis of poly(styrene-co-maleic anhydride) cumene terminated (PSMAC) using p-aminohippuric acid. The main objective was to perceive the effect of blend ratio of polysulfone (PSF) and poly[styrene-alt-(N-4-benzoylglycine-maleamic acid)] cumene terminated (PAH) on morphology and permeation properties of the membranes. The PSF/PAH blend membranes unveiled enriched hydrophilicity, porosity, zeta potential, water uptake and permeability owing to the existence of the hydrophilic PAH. However, the contact angle was not diminished over 20% of PAH ratio as there was an increase of hydrophobic alkyl group density. Differential scanning calorimetry (DSC) was employed for the determination of the glass transition temperature of the blends and the results revealed that the polymer blend is miscible in nature. Moreover, the M-3 membrane was screened for the heavy metal ion removal and achieved removal of 91.5% of Pb2+ and 72.3% of Cd2+ ions, respectively. The adsorption parameters indicated that the Langmuir isotherm model fits well for both Pb2+ and Cd2+ ions adsorption on M-3 membrane. The adsorption capacity attained from Langmuir isotherm model was 19.35 and 9.88 mg/g for Pb2+ and Cd2+ ions correspondingly.

A novel metal sulfide (KZTS) adsorbent has been synthesized using a simple one-step hydrothermal method for radioactive Sr2+ removal from aqueous solutions. XRD and TG analyses indicated that KZTS was chemically and thermally stable. SEM-EDS and TEM images showed that KZTS possessed both flake-like and polyhedral structure with the formula of K1.67Zn0.67Sn2.17S6.00 and K5.84Zn3.47Sn5.04S16.99, respectively. The average formula was determined to be K1.87ZnSn1.68S5.30 using ICP-OES. The adsorption ability of KZTS for Sr2+ was evaluated in detail by batch experiments. The kinetics studies showed that Sr2+ was rapidly removed from the aqueous solution within the equilibrium time of 10 min. According to Langmuir isotherm, the maximum adsorption capacity of KZTS was 19.3 mg/g at 298 K and the high value of the Langmuir constant indicated the high affinity of KZTS for Sr2+. The adsorption mechanisms involved ion exchange and surface Sr–S bonding interactions, with the former dominating. High adsorption performance was observed over a broad pH range of 3–11, although it could be inhibited by co-existing ions, especially Ca2+ and Mg2+. The adsorbent showed a high distribution coefficient (Kd = 1.26 × 106 mL/g) and negligible adsorbate leaching at low Sr2+ concentrations, indicating the strong and irreversible adsorption of Sr2+ on KZTS. Further, KZTS exhibited high selectivity for Sr2+ in alkaline and tap water. These remarkable features suggest that KZTS is a highly desirable adsorbent to remove radioactive strontium from radioactive wastewater.

The application of conventional DC electrocoagulation for remedying the anoxic As(III)-contaminated groundwater normally suffers from the external introduction of O2 and the vulnerability of the ohmic contact between iron electrode and conductive wire. To address these limitations, a novel full-wave rectified alternating current wireless electrocoagulation (FWAC-WEC) technology for the oxidative immobilization of As(III) from anoxic groundwater was developed in this study. The FWAC-WEC process produced Fe(II) and O2 simultaneously when utilizing iron bipolar electrodes (Fe-BPEs) and two Ti plate coated mixed IrO2/Ta2O5 (MMO) driving electrodes. The increase in Fe-BPEs number (1–3) and outage time (0–6 s) and the decrease in the angle for Fe-BPEs to electric field line separately benefited As(tot) removal. Besides, As(tot) removal was enhanced with increasing pH value but deteriorated by the presence of HCO3− and PO43−. In the FWAC-WEC process, As(III) was initially oxidized to ionic As(V) by intermediate Fe(IV) species. Thus, As(tot) removal was significantly promoted by adsorption and/or co-precipitation of As(V) with the fresh Fe(III) (oxyhydr)oxides, which appreciably obeyed the Langmuir isotherm and the second-order kinetics. Notably, the FWAC-WEC technology can effectively eliminate the passivation of Fe-BPEs and thereby increase the utilization of Fe-BPEs due to the periodic exchange of driving electrodes polarity. This strategy could remarkably reduce the energy consumption to 0.101 kW·h/m3 for As(III) removal, which was much less than 0.167 KW·h/m3 in the DC counterpart. Generally, the FWAC-WEC technology is energy-efficient and has the potential of being a sustainable treatment option to improve access to safe groundwater for millions of people.