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Elevated Sb(V) concentration in textile wastewater is a growing environmental concern worldwide and has received wider attention in recent years. Iron oxides possess appealing characteristics as efficient and cost-effective adsorbents in large-scale applications. In the present study, Sb(V) adsorption capacity of α-Fe2O3, γ-Fe2O3, and Fe3O4 was compared under experimental conditions close to the practical textile wastewater treatment. Results demonstrated that α-Fe2O3 performed better under different pH values, reaction times, dye compounds, and co-existing ions as compared to γ-Fe2O3 and Fe3O4, and the adsorption equilibrium was achieved within 8 h. Sb(V) adsorption is found to be highly pH dependent, and higher removal was achieved in lower pH, indicating the involvement of electrostatic interactions. The pHpzc value of α-Fe2O3 was 7.15, which favored Sb(V) adsorption in practical wastewater having neutral pH value (pH ~ 7). Pseudo-first- and pseudo-second-order described the data and the simulated values of qe fitted well with the experimental values, indicating that pseudo-second-order model described the adsorption kinetics better with R2 (> 0.95) higher than of pseudo-first-order plots. The Langmuir and Freundlich models both described well the sorption data of all the adsorbents, where the R2 values were > 0.90 with a better fit in the Freundlich model for α-Fe2O3, suggesting that the adsorbent has heterogeneous surface characteristics. Similarly, characterizations revealed that the specific surface area, pore volume, and hydroxyl group content in α-Fe2O3 were higher than others, making it easier for contaminants to bind on to the active sites. Furthermore, the effect of dyes and co-existing anions on Sb(V) adsorption was negligible, except for SO42−, CO32−, and PO43− by the formation of inner-sphere complexes with iron oxides through competitive adsorption with [Sb(OH)6]−. Findings from the present study suggested that α-Fe2O3 effectively reduced Sb(V) in textile wastewater and could be a promising alternative for practical textile wastewater treatment. [ABSTRACT FROM AUTHOR]

Black carbon (BC) is considered to be a promising novel material for controlling organic contaminants due to its strong adsorption property, low production cost, and less secondary pollution. However, seldom systemic research was conducted to investigate adsorption-desorption characteristics and interaction mechanism between BC and nonylphenol (NP), one kind of endocrine-disrupting contaminants (EDCs) and persistent organic pollutants (POPs). Therefore, in the present study, adsorption characteristics of NP on two BCs (rice straw black carbon (RC) and fly ash carbon (FC)) involving adsorption isotherm, kinetics, effect of pH, as well as desorption kinetics, were investigated to explore the feasibility of BC for remediation of NP pollution in a water environment. Adsorption isotherm data showed that Q was 61,889.21 ± 2777.68 and 6538.99 ± 606.72 mg/kg and n was 0.39 ± 0.037 and 0.55 ± 0.043 for RC and FC, respectively, suggesting the sorption capacity and nonlinearity of RC to NP is far higher than FC and indicating BC was an effective sorbent for NP pollution control, especially RC. The pH affected BC sorption capacity to NP by influencing the surface properties of BC and the NP speciation together. Desorption kinetics data indicated that more than 80% NP could not be released from both BCs, suggesting that BC could reduce NP releasing risk in a water environment evidently when BC is applied for NP pollution remediation. [ABSTRACT FROM AUTHOR]

[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]

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]

Carbon-based nanomaterials, especially carbon nanotubes and graphene, have drawn wide attention in recent years as novel materials for environmental applications. Notably, the functionalized derivatives of carbon nanotubes and graphene with high surface area and adsorption sites are proposed to remove heavy metals via adsorption, addressing the pressing pollution of heavy metal. This critical revies assesses the recent development of various functionalized carbon nanotubes and graphene that are used to remove heavy metals from contaminated water, including the preparation and characterization methods of functionalized carbon nanotubes and graphene, their applications for heavy metal adsorption, effects of water chemistry on the adsorption capacity, and decontamination mechanism. Future research directions have also been proposed with the goal of further improving their adsorption performance, the feasibility of industrial applications, and better simulating adsorption mechanisms. [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]

[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]

In this work, the surface properties, functional groups and stability of Fe–Mn bimetal composite (FMBC) was modified through sintering to improve the weaknesses of pristine FMBC, such as poor separation performance, high amount of dissolved Fe and Mn, and easy phase transformation. Characterization analysis indicated that 2-line ferrihydrite in sintered FMBC (SFMC) gradually transformed into hematite with the phase-transition temperature of 450 °C. With the increasing sintering temperature and time, the dehydroxylation reaction enhanced and gradually became irreversible, while the BET surface area and porosity of SFMC firstly increased and then decreased, resulting in the initial increase and then sharp decrease of the amount of exposed hydroxyl groups on SFMC. The sintering treatment greatly improved the separation performance and stability of SFMC. 350 °C and 2 h were determined as the optimal sintering conditions of SFMC in this study and the calculated maximum adsorption capacity of optimal SFMC reached up to 95 mg/g. Freundlich model and pseudo-second-order kinetics model can describe the Sb(V) adsorption data well. As compared to pristine FMBC, optimal SFMC presented larger BET surface area and porosity, better separation performance and stability, lower dissolved Fe and Mn amount, larger cyclic adsorption efficiency and enough ability for Sb(V) removal in real textile wastewater. Furthermore, the inner sphere complexation between Sb(OH) 6 - and exposed hydroxyl groups played a key role in adsorption. Additionally, the NaCl + NaOH elution exhibited greater Sb(V) desorption performance and effectively retarded the phase transformation of SFMC than NaOH solution. Image 1 • Calcining process facilitate transformation of ferrihydrite in SFMC to hematite. • The surface area and porosity of optimal SFMC was higher than pristine FMBC. • Regeneration of SFMC by NaCl + NaOH effectively retarded the phase transformation. • Optimal SFMC after sintering had better cyclic Sb(V) adsorption performance. [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]