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Graphical abstract Highlights • TiC doped palladium/nickel foam cathode was synthesized via electroless deposition. • Pd/TiC/Ni foam show superior activity for 2,4-DCBA dechlorination to Pd/Ni foam. • Optimized conditions on 2,4-DCBA dechlorination were investigated. • Possible promotion mechanism by doped TiC over Pd/Ni foam cathode was proposed. Abstract Titanium carbide (TiC) with excellent electrical conductivity, chemical and thermal stabilities has been recognized as one of the most promising electrocatalysts. A novel cathode, titanium carbide doped palladium/nickel foam (TiC-Pd/Ni foam), was synthesized via electroless deposition to improve the performance of Pd/Ni foam in electrocatlytic hydrodechlorination (ECH). TiC can be co-precipitated onto the surface of cathode during galvanic replacement reaction between Pd(II) solution and Ni foam. Both constant potential and constant current tests proved that TiC-Pd/Ni foam cathode performed remarkably higher activity for 2,4-dichlorobenzoic acid (2,4-DCBA) than Pd/Ni foam cathode, owing to the excellent conductivity of TiC and enhanced water dissociation over TiC-Pd/Ni foam cathode. Under the optimized reaction conditions of –0.85 V (vs Ag/AgCl), electrolyte of 10 mM and initial pH of 4, 99.8% of aqueous 2,4-DCBA (0.2 mM) was removed within 90 min. The removal process of the aqueous 2,4-DCBA obeyed first-order decay kinetic model. Over 86.3% of 2,4-DCBA can still be removed by TiC-Pd/Ni foam cathode in the fifth consecutive run within 120 min, which was much higher than that of Pd/Ni foam cathode (37.5%). Consequently, TiC-Pd/Ni foam cathode was a promising design for enhanced ECH activity and reduced operation cost. [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzo- p -dioxins (PCDDs), as a group of notorious anthropogenic environmental toxicants, are arguably ubiquitous in nature. In this study, we investigated the photocatalytic reductive dechlorination of 2-chlorodibenzo- p -dioxin (2-CDD) over Pd/g-C 3 N 4 catalysts under UV–vis irradiation. The g-C 3 N 4 and a series of Pd/g-C 3 N 4 catalysts were prepared by thermal polymerization and mechanical mixing-illumination method and characterized by XRD, TEM, BET, SEM and UV–vis DRS analyses. Among all the samples, the Pd/g-C 3 N 4 (5 wt%) yielded the optimal dechlorination activity with a total 2-CDD conversion of 54% within 4 h, and 76% of those converted 2-CDD were evolved to dibenzo- p -dioxin (DD). The kinetics of dechlorination could be described as pseudo-first-order decay model (R 2  > 0.84). Corresponding rate constants (k) increased from 0.052 to 0.17 h −1 with Pd contents up to 5 wt% and decreased to 0.13 h −1 with a 10 wt% of Pd. The enhanced activities originated from the surface plasmonic resonance (SPR) effect of Pd nanoparticles and the formation of Schottky barrier between Pd and g-C 3 N 4 , which extend the spectrum responsive range and suppress the charge recombination of g-C 3 N 4 . This is the first report on the photocatalytic reductive removal of PCDDs and may provide a new approach for PCDDs pollution control. [ABSTRACT FROM AUTHOR]

Magnetic multi-walled carbon nanotubes (MWCNTs) were prepared to support Pd/Fe nanoparticles, inhibit the aggregation and passivation, and achieve magnetic separation to avoid the environmental risk of nanoparticles. Rapid adsorption of initial contaminant, steady dechlorination, and gradual desorption of final product was observed. The micromorphology, chemical structure, and components of the nanohybrids were comprehensively characterized by a series of analysis technologies, such as EDX, XRD, SEM, TEM, and XPS. The interactions between the nanohybrids compositions were discussed according to the characterization and experimental data. The whole insight of 2,4-dichlorophenol (2,4-DCP) adsorption- dechlorination-desorption was studied in detail, including the pathways, influence factors, dechlorination kinetics and selectivity. Weak acidity (pH = 5.0 and 6.5) favored the 2,4-DCP removal. Satisfactory reactivity of the Pd/Fe-Fe 3 O 4 @MWCNTs nanohybrids was observed in five consecutive runs, and 99.2%, 89.6%, 92.1%, 99.8%, and 99.9% of 2,4-DCP was removed, respectively. Most of the final product (phenol) was steadily desorbed to the liquid phase, resulted in the re-exposure of active sites on the nanohybrids and maintained a longer activity. [ABSTRACT FROM AUTHOR]

In this study, a novel composite adsorbent (HBC–Fe 3 O 4 –MnO 2 ) was synthesized by combining honeycomb briquette cinders (HBC) with Fe 3 O 4 and MnO 2 through a co-precipitation process. The purpose was to make the best use of the oxidative property of MnO 2 and the adsorptive ability of magnetic Fe 3 O 4 for enhanced As(III) and As(V) removal from aqueous solutions. Experimental results showed that the adsorption capacity of As(III) was observed to be much higher than As(V). The maximum adsorption capacity (2.16 mg/g) was achieved for As(III) by using HBC–Fe 3 O 4 –MnO 2 (3:2) as compared to HBC–Fe 3 O 4 –MnO 2 (2:1) and HBC–Fe 3 O 4 –MnO 2 (1:1). The experimental data of As(V) adsorption fitted well with the Langmuir isotherm model, whereas As(III) data was described perfectly by Freundlich model. The pseudo-second-order kinetic model was fitted well for the entire adsorption process of As(III) and As(V) suggesting that the adsorption is a rate-controlling step. Aqueous solution pH was found to greatly affect the adsorption behavior. Furthermore, co-ions including HCO 3 − and PO 4 3− exhibited greater influence on arsenic removal efficiency, whereas Cl − , NO 3 − , SO 4 2− were found to have negligible effects on arsenic removal. Five consecutive adsorption-regeneration cycles confirmed that the adsorbent could be reusable for successive arsenic treatment and can be used in real treatment applications. [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]