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[Display omitted] • MOFs act as dual-functional adsorbents and electrocatalysts for the removal of PPCPs. • Real active sites of MOFs are pinpointed using in-situ electrochemical methods. • Fe-MOFs exhibit high efficacy and stability in practical wastewater treatment. Pharmaceuticals and personal care products (PPCPs) pose a significant wastewater pollution concern. While electrochemical oxidation is promising, it struggles with slow mass transfer. To address this, we propose a novel strategy utilizing bifunctional metal–organic frameworks (MOFs) that couple an adsorbent with an electrocatalyst. The real active sites within iron-based MOFs responsible for the adsorption of PPCPs are MIL-101(Fe) molecules, while the in-situ formed active sites, α -FeOOH, accelerate the charge transfer under bias, contributing to the electrooxidation of PPCPs. The rapid destruction of adsorbed organics on the dual-functional electrode surface enables to release adsorption sites. This, in turn, paves the way for fast and efficient re-adsorption of PPCPs molecules, consequently promoting mass transfer. Iron-based MOFs exhibit excellent adsorption capacity (∼60 mg g−1 for sulfosalicylic acid, ∼15 mg g−1 for acetaminophen) and electrooxidation ability (94 % removal in 2 h, 31.2 kWh kg−1 COD) with good stability in realistic pharmaceutical wastewater treatment. This study offers a novel strategy for removing PPCPs using molecular electrocatalysts and provides new insights for designing and constructing MOFs for refractory wastewater treatment. [ABSTRACT FROM AUTHOR]

Abstract: Hemp (Cannabis sativa L.) bast was used to prepare activated carbon fibers by phosphoric acid activation at 400–600°C. The pyrolysis process, textural and chemical properties for the samples were investigated by means of TG/DTA, SEM, cryogenic N2 adsorption, FTIR and XPS. Dye adsorption on the resultant sample was also measured. The textural properties of the activated carbon fibers were found to be strongly dependent on the activation temperature. Activated carbon fibers exhibited narrow pore size distributions with maxima in the micropore and small mesopore regions. BET surface area, total pore volume, micropore volume and mesopore volume increased with the increase of activation temperature up to 450°C and then decreased with further heating, and a sample with maximum surface area of 1142m2 g−1 and total pore volume of 0.67cm3 g−1 was obtained. Phosphoric acid facilitated the conservation of porous structure, led to the creation of tremendous porosity, and resulted in various P-containing functional structures on the surface and in the bulk phase of the resultant samples. The adsorption of acid blue 9 on the sample could be favorably described by Langmuir isotherm, and the adsorption kinetics was found to be well fitted by the intraparticle diffusion model. [ABSTRACT FROM AUTHOR]

This work aimed to develop a feasible technology to reuse dead pig biowaste for heavy metals removal, which was first carbonized into pig bone char (PBC) after pyrolysis and further functionalized with amino (NH 2) to improve its affinity with heavy metals. The application of PBC after NH 2 -functionalization for aqueous heavy metals removal was explored, including Pb2+, Cu2+, and different complex Cu(II) species. PBC@SiO 2 -NH 2 showed comparable performance with AC@SiO 2 -NH 2. The adsorption capacity of Pb2+ and Cu2+ by PBC@SiO 2 -NH 2 was 120 and 30 mg g−1, respectively. The NH 2 functionalization enhanced the adsorption of complex Cu(II) species, and PBC@SiO 2 -NH 2 exhibited good performance under a wide pH range and coexisting ions. The adsorption of Cu(II) EDTA species with an EDTA/Cu(II) molar ratio of 1.0 by PBC would be enhanced ~3 times and ~6 times after NH 2 functionalization and further addition of Fe3+, respectively. The results of EDX, elemental mapping, and XPS confirmed the adsorption of Cu(II) species. The adsorption kinetics, isotherm, and thermodynamics of different Cu(II) species by PBC@SiO 2 -NH 2 were investigated. The regeneration of PBC@SiO 2 -NH 2 was easily performed via acidic wash. These results suggested the application potential of the reuse of biowaste, which could be a promising adsorbent for aqueous heavy metals after specific functionalization. [ABSTRACT FROM AUTHOR]

In this study, the selective adsorption performance of different Fe-Mn binary oxides (FMBOs) towards Sb(V) in the textile wastewater under different concentrations of coexisting anions, surfactants and dyes were investigated. Results showed that the influences of different anions on the Sb(V) removal followed an order of phosphate > carbonate > sulfate > nitrate > chloride. The frequently-used organic acid of acetate was found to have insignificant effect. The coexisting surfactant with sulfonic groups could have adverse effect on the removal due to sulfonic groups could compete the adsorptive sites on Fe oxides with Sb(V). While the quaternary ammonium surfactant might have minor effect. The influences of the three widely used dyes on the Sb(V) adsorption decreased in the following order: reactive black-5 >acid orange-7> disperse blue-60, which confirmed that the dyes with sulfonic groups would have relatively higher effect. The selective adsorption capacities of Sb(V) by FMBOs followed an order of FMBO 3 > FMBO 5 >FMBO 10 > FMBO 20 >PFO. Fixed-bed column adsorption supplied useful parameters and evidently indicated that the cyclic utilization of FMBO 3 was cost-efficient for practical dynamic Sb(V) removal. The Sb(V) removal by FMBO 3 from real textile wastewater can simultaneously improve the removal efficiency, stabilize pH and prevent the increase of iron concentration as compared to the traditional coagulation, further demonstrating the high practical applicability of FMBO 3. Image 1 • Selective adsorption of Sb(V) by different FMBOs in textile wastewater was studied. • Effects of surfactants and dyes on Sb(V) removal was studied for the first time. • Surfactants and dyes with sulfonic group could have adverse effect on Sb(V) removal. • The cyclic regeneration and reuse of FMBO 3 was cost-efficient for Sb(V) removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adjustment of structure and interface of MFOC through soft-template is successful. • SMFO-B can achieve high removal rate and efficacy of Sb(V) and strong stability. • Direct tools with EXAFS and CD-MUSIC model showed specific inner-sphere complex. • E2 complex played the most important role in the Sb(V) adsorption onto SMFO-B. To achieve high removal rate and efficacy of Sb(V) from textile wastewater and simultaneously realize cyclic Sb(V) recovery, the structure and surface property of amorphous Mn-doped Fe oxide composite (MFOC) were regulated via the combination of facile soft-template synthesis and sintering treatment. Characterization and adsorption results indicated MFOC structure was greatly changed from aggregated large sphere to dispersive small sphere after adjusted by the optimal Brij-58 (SMFO-B). Because of the generated fasciculate micelle, long carbon chain feature and the lowest residual amount of Brij-58, abundant mesopores were generated and the aggregation of unit particles was apparently decreased for SMFO-B. Surface area and total pore volume of SMFO-B became 10 and 6 times of MFOC and more functional hydroxyl groups were generated and exposed on the interface between SMFO-B and water solution. Additionally, the surface positive potential of SMFO-B under neutral condition was also greatly increased. Thus, the maximum adsorption capacity and rate of SMFO-B towards Sb(V) reached to 147 mg/g and 0.1067 mg/(g·min), 2 and 5 times of MFOC. SMFO-B also possessed better selective adsorption ability, exhibited stronger static and dynamic adsorption performance in real textile wastewater and realized the cyclic desorption and enrichment of Sb(V) due to its better phase stability. X-ray absorption spectroscopy showed two main specific forms, such as bidentate edge-(E2) and corner-sharing (C2) complexes, for the inner-sphere complexation during Sb(V) adsorption and E2 complex was proved to play the most important role through the analysis of CD-MUSIC model. This study supplied an excellent adsorbent for Sb(V) removal from textile wastewater and a deeper insight about Sb(V) adsorption onto amorphous Fe oxide. [ABSTRACT FROM AUTHOR]

Magnetic biochar is increasingly known as a multi-functional material and the appropriate synthesis method further increase its efficient applications. In this study, the effects of synthesis methods on the fabrication of Kans grass straw/biochar (KGS/KGB) with Fe 3+ /Fe 2+ by chemical co-precipitation and subsequently pyrolyzing at 500 °C for 2 and 4 h were studied in details, and compared their As(III, V) adsorption potentials under different operating conditions. Magnetic biochars (MKGB3 and MKGB4) prepared from KGS revealed of superior Fe 3 O 4 loading, higher As(III, V) adsorption efficiency and saturation magnetization (45.7 Am 2 kg −1 ) than that of KGB (MKGB1 and MKGB2). Moreover, Thermogravimetric analysis (TGA) demonstrated three stages of decomposition and the MKGB3 and MKGB4 generated higher residual mass (>60%) at stage 3 (1000 °C) due to greater Fe 3 O 4 composite in biochar matrix and turned to be thermally more stable. As(III) and As(V) adsorption equilibrium data well fitted in Langmuir model and followed the order: MKGB4 > MKGB3 > MKGB2 > MKGB1. The maximum As(III) and As(V) adsorption capacities were about 2.0 mg g −1 and 3.1 mg g −1 , respectively. The data best fitted in pseudo-second-order ( R 2 > 0.99) rather than pseudo-first-order kinetics model indicating of more complex mechanism. The adsorption of As(III) and As(V) was found to decrease with increasing in ionic strength of competing ions and PO 4 3− was found to strongly inhibit arsenic adsorption. Highest desorption was achieved at pH 13.5 using NaOH. This study suggests that selective adsorbent synthesis method could be useful to prepare effective adsorbent for toxic metals immobilization. [ABSTRACT FROM AUTHOR]

Highlights: [•] Arsenic removal performance of SSFs containing HBC and Fe-HBC (50% w/w) is studied. [•] Over 99% and 98% arsenic removals were achieved in SSF(a) and SSF(b) under oxic-environment. [•] Two steps in situ mechanism is proposed to convert As(III) into As(V) and subsequent adsorption. [•] Low levels of influent co-occurring ions did not significantly interfered arsenic removal. [•] Filter with low-cost adsorbents could be proposed as feasible and efficient method for arsenic removal. [ABSTRACT FROM AUTHOR]

Abstract: In this study a systematic investigation of two specified MWCNTs-Pd/Fe nanocomposites to remove 2,4-dichlorophenol (2,4-DCP) is presented. Two specified Multi-Walled Carbon Nanotubes (MWCNTs), i.e., 60–100nm and 10–20nm were introduced in nZVI synthesis in order to improve its adsorption–dechlorination efficiency. Both MWCNTs-Pd/Fe nanocomposites showed excellent adsorption efficiencies for phenols and followed the sequential order; 2,4-DCP>p-CP>o-CP>P. Batch sorption experiments including kinetics and isotherm were also intensively investigated. Significantly high 2,4-DCP removal was observed after 1min when it reached to 49.7% and 53.2%, then continuously increased up to 95.2% and 77.7% after 5h at 0.20wt.% Pd loading by 60–100nm and 10–20nm MWCNTs-Pd/Fe nanocomposites, respectively. However, stronger dechlorination and weaker adsorption was found in 60–100nm MWCNTs-Pd/Fe nanocomposites. Moreover, an integrated approach of physical adsorption by 60–100nm MWCNTs and chemical reduction by Pd/Fe nanoparticles to remove 2,4-DCP was successfully achieved. The property of quick adsorption of targeted pollutants and steady release of dechlorination products enhance the applicability of this process for an in situ pollution remediation measures. [Copyright &y& Elsevier]

Abstract: Water pollution caused by ammonia nitrogen has attracted a great attention as its toxicity affects both the environment and human health. The objective of this paper was to investigate the adsorption behavior of NH4 +-N from aqueous solution by activated carbons prepared from rice husk. The physico-chemical properties of the activated carbon were characterized by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was found that the NH4 +-N adsorption on the rice husk derived carbons was dependent on adsorbent dosage and solution pH. The adsorption kinetics and isotherms of NH4 +-N by rice husk carbon were also investigated, and good correlation coefficients were obtained for the pseudo-second order kinetic equation. Dubinin-Radushkevitch (D-R) adsorption isotherm model could better describe the adsorption behavior of NH4 +-N on the rice husk carbon. Calculated by D-R model, the adsorption course of NH4 +-N on the rice husk carbon was favored chemical ion-exchange mechanism. Moreover, the activated carbon adsorbed NH4 +-N was highly fertilizer conservation especially for the nitrogen element. It was proposed that the amount of removed NH4 +-N from aqueous solutions would increase evidently treated by rice husk carbon if combined with biological method. [Copyright &y& Elsevier]

Abstract: Nanoscale Pd/Fe particles were combined with multi-walled carbon nanotubes (MWNTs) to prepare supported particles (MWNT-stabilized Pd/Fe), which were used to remove 2,4-dichlorophenol (2,4-DCP). The adsorption capacity of MWNTs was found to be increased with the increasing amount of chlorine atoms, and the removal rates of phenol (P), 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-DCP reached 19.7%, 60.5%, 72.0% and 95.1% respectively, in 1min by MWNTs due to π–π interaction. The adsorption kinetics and adsorption isotherm were also discussed. MWNTs as a supporter, was effective for avoiding the agglomeration of nZVI. Furthermore, the speedy removal efficiency of the initial substances (2,4-DCP) reached about 50% in 1min, and over the time continued to rise to 100%, remaining low concentrations (<1mgL−1) of the intermediate substances (o-CP, p-CP), and gradual release of the final substance (P) from MWNT-stabilized Pd/Fe composites during the whole process, proposed a novel method for in situ remediation technology. [Copyright &y& Elsevier]

Abstract: Acid treatment is a routine demineralization process to obtain black carbon (BC), but there has been little systematic research about its influence on BC’s characteristics. In this study, elemental analysis, SEM, FTIR, and Boehm titration were used to investigate that effect. Our results showed that the acid treatment had little influence on the sorption of fly ash and soot to pentachlorophenol (PCP), but it greatly increased the sorption of rice chars to PCP. There were two competing effects of acid demineralization on the adsorption capacity of BC. On one hand, it increased the amount of the acidic functional groups, which decreased the adsorption capacity. On the other hand, it increased the surface and pore volume of BC and caused the emergence of hidden carbon enclosed by minerals, which in turn increased the sorptivity significantly. Especially for rice chars (600°C), after acid treatment, their surface area increased from 3.52 to 235m2 g−1 and the sorption capacity coefficient increased from 2.12 to 4.10. [Copyright &y& Elsevier]

Abstract: To investigate the feasibility of using biochar to control organic pollutants in sediments, we extracted biochar from rice-straw combustion residues (RBC) and studied its adsorption ability and effect on seed germination ecotoxicity of pentachlorophenol (PCP). The results showed that the Freundlich and dual-mode models could describe all the sorption isotherm data well, and the log KOC values increased with increasing RBC content. With 50mgkg−1 PCP in the sediment, a significant seed growth inhibition (P <0.01) was observed. The addition of 2.0% RBC lowered the PCP concentration in the extraction liquid from 4.53 to 0.17mgL−1 and increased the germination rate and root length significantly. Furthermore, it was found that the addition of RBC had no toxic but stimulative effect on root elongation. Consequently, RBC could serve as a potential supersorbent for the remediation of organic pollution in situ. [Copyright &y& Elsevier]

Abstract: The adsorption of Cu(II) from aqueous solution by carbons prepared from rice husk through pyrolysis and steam activation was studied. The rice husk carbon was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and its pore structure was also examined. After comparing different characteristics of the carbons prepared under different conditions and their adsorption abilities of Cu(II), the optimum temperature for pyrolysis and steam activation was chosen as 700 and 750°C, respectively, using 3% (V/V) steam as the best activation gas. It was found that the Cu(II) adsorption on the rice husk derived carbons was pH and temperature dependent with an optimum pH value of 5.0, and an equilibrium time of 24h. The adsorption kinetics and isotherms of Cu(II) by the rice husk derived carbons were also investigated under four different temperatures, and good correlation coefficients were obtained for the pseudo-second-order kinetic models, and the Langmuir isotherm model fitted very well with the experimental data. The mean free energy E (kJmol−1) obtained in the Dubinin-Radushkevitch (D-R) adsorption isortherm equation indicated a chemical ion-exchange mechanism. Several thermodynamic parameters were also caculated to predict the nature of adsorption process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A functionalized material (CTAB-Pd/GAC) was synthesized as the catalyst. • CTAB could reduce the consumption of Pd for the catalyst. • Adsorption performance of catalyst was controlled by the amount of CTAB load. • Selective adsorption performance of the catalysts to 2,4-DCBA was enhanced. • The adsorption-desorption for 2,4-DCBA and BA was a dynamic process. The CTAB-Pd/GAC catalyst was obtained by functionalizing palladium/granular activated carbon (Pd/GAC) with cetyltrimethylammonium bromide (CTAB), which was used for the electrocatalytic reductive dechlorination of 2,4-dichlorobenzoic acid (2,4-DCBA). The degradation rate of 2,4-DCBA by 40 mg g−1 CTAB-Pd/GAC was 9.8 × 10−3 (min−1 g−1 Pd), which was 11 folds than that by Pd/GAC (0.9 × 10−3 min−1 g−1 Pd), and the value of q e, 2,4-DCBA / q e, BA was 2.33 as compared to 0.67 for Pd/GAC. The combined result of dechlorination and adsorption experiments suggested that the functionalization by CTAB would enhance the 2,4-DCBA concentration on the surface of CTAB-Pd/GAC, and accelerate the degradation rate. However, the removal efficiency of 2,4-DCBA would decrease when the CTAB load reached 80 mg g−1, due to the excessive adsorption capacity for dechlorinated product. Density functional theory (DFT) calculations also proved that CTAB would increase adsorption capacity of catalyst and selective adsorption behavior of 2,4-DCBA, which accelerated the degradation rate of 2,4-DCBA. [ABSTRACT FROM AUTHOR]

• Doping of suitable Si oxide greatly decrease the aggregation of SFOC. • Coordination interaction between Si-OH and Fe-OH led to property change of SFOC. • More functional Fe-OH groups (adsorption sites) were exposed after Si doping. • Almost no phase transformation of SFOC 10 happened during long cycle use. The development of amorphous iron oxide-based composites for the Sb(V) removal is limited by their easy phase transformation, aggregation, and unstable nature. Herein, novel modified Si-doped Fe oxide composites (SFOC) were prepared to break through the current obstacle. Characterization results of SFOC with a suitable amount of doped Si indicated that the coordination interaction between Si-OH and Fe-OH blocked the crystal growth sites in both Si and Fe oxide, and the crystal unit cells of same element were difficult to contact with each other. Hence, the crystal growth of Si and Fe oxide was retarded and their unit particle size became smaller. Meanwhile, the crystal phase transformation of amorphous ferrihydrite was prevented and the aggregation extent of Fe oxide was greatly decreased after Si doping. These changes caused that more Fe vacancies were generated on the surface of amorphous Fe oxide unit and the surface area of SFOCs also increased, resulting in the great increasement of exposed Fe hydroxyl groups in SFOC. As compared to pristine Fe oxide, the optimal SFOC 10 with Fe/Si molar ratio of 10:1 exhibited the highest surface area of 363.9 m2/g, the maximum Sb(V) removal capacity of 176.1 mg/g, and higher selective Sb(V) adsorption performance. The introduction of Si oxide also endowed SFOC 10 with much better phase stability and Sb(V) removal capacity during the long cyclic adsorption-desorption process. Moreover, the inner-sphere complexation of Fe-OH and Sb(OH) 6 − played a key role in adsorption. Furthermore, optimal SFOC 10 was sufficient for the Sb(V) removal from real textile wastewater in both the batch and dynamic column adsorption processes. [ABSTRACT FROM AUTHOR]

• A novel adsorbent (FeMnO x /SBA-15) was successfully synthesized. • SBA-15 functioned as a supporting matrix to disperse Fe-Mn binary oxide. • Calcination treatment could enhance the adsorption capacity of FeMnO x /SBA-15. • FeMnO x /SBA-15 with 45% loading ratio possessed larger specific surface area. • The uptake of arsenic on adsorbents was controlled by surface complexation. Iron-manganese binary oxides (FeMnO x) can remove contaminants from aqueous solutions with high efficiency, and mesoporous silica (SBA-15) is widely used as a supporting material due to its large specific surface area and good stability. In this study, SBA-15 was used to support FeMnO x in the synthesis of a novel arsenic (As) adsorbent (FeMnO x /SBA-15), and its characteristics under different reaction conditions, such as pH, temperature, presence of competing ions, and humic acid, were tested. The results showed that the contaminant adsorption efficiency of the novel adsorbent was better than that of bare FeMnO x , as the addition of SBA-15 decreased the agglomeration effect of FeMnO x. Additionally, FeMnO x /SBA-15 underwent calcination to further enhance its performance. The state of iron and manganese in FeMnO x /SBA-15 and the corresponding arsenic removal efficiency were improved by calcination at 350 °C with an FeMnO x /SBA-15 mass fraction of approximately 45%. Almost 90% of As (50 mL, 5.0 mg L−1) could be removed by 0.2 g L−1 of FeMnO x /SBA-15 (mass ratio of 45% and calcination temperature of 350 °C). The FeMnO x /SBA-15 could regenerate and still be used after four consecutive cycles. The high As sorption capacity, ability to regenerate, and reusability of FeMnO x /SBA-15 confirmed that this adsorbent is promising for treating As-contaminated drinking water. [ABSTRACT FROM AUTHOR]