Electrocatalytic effects during redox reactions of arsenic at platinum nanoparticles in acid medium: Possibility of preconcentration, electroactive film formation, and detection of As(III) and As(V)

Electrochemical Leaching of Cobalt from Cobaltite: Box-Behnken Design and Optimization with Response Surface Methodology

Cobalt, a critical metal, is anticipated to increase in market demand in the next couple of decades, particularly as a battery material used in electric vehicle application. To boost the domestic production of cobalt in the United States, an electrochemical process has been developed to recover cobalt from a cobaltite-rich concentrate and produce cobalt- and arsenic-rich leachate. The leaching efficiency of cobalt was optimized with a response surface methodology by modifying the electrochemical parameters. A series of experiments based on the Box-Behnken design of experiments were carried out using ferric iron as an electrochemically generated oxidant to leach metals from the concentrate. Operating parameters, such as electrochemical cell current, iron/arsenic molar ratio, and anolyte acidity, were optimized for maximum cobalt recovery. A predicted 73% cobalt extraction efficiency can be achieved with the electrochemically assisted leaching method within 24 h. Compared to other leaching methods, such as bioleaching, electrochemically assisted leaching shows a promising alternative for extracting metals from mining concentrates, showing higher efficiency in less time and under mild conditions.

High sensitivity atomic fluorescence spectroscopy for the detection of AsIII by selective electrolysis of arsenic on nanoflowers-like Fe/NFE

Modified electrosynthetic sample introduction technique is a reliable means of solving the problem of high sensitivity analysis of trace arsenite. This article attempts to achieve selective electroreduction of AsIII through the construction of electrode surfaces with different structures and materials from the perspective of interface reactions. Among the four transition metal modifiers, the iron modified nickel foam electrode with nano-flower structure documented higher efficiency in inducing arsenic reduction and better species selectivity. Systematic electrochemical and spectroscopic tests suggest that strong adsorption effect between Fe and AsIII, appropriate hydrogen evolution potential, and catalytic activity jointly promote efficient electroreduction of AsIII. Optimization based on electrode materials and electrolysis conditions, with high sensitivity, wide linear range (0.1-50 μg L-1), and excellent species selectivity, this paper offers an efficient and economic sample introduction method for trace AsIII/V selective atomic spectroscopy direct determination.

Discrete, Cationic Palladium(II)-Oxo Clusters via f-Metal Ion Incorporation and their Macrocyclic Host-Guest Interactions with Sulfonatocalixarenes

We report on the discovery of the first two examples of cationic palladium(II)-oxo clusters (POCs) containing f-metal ions, [PdII6 O12 M8 {(CH3 )2 AsO2 }16 (H2 O)8 ]4+ (M=CeIV , ThIV ), and their physicochemical characterization in the solid state, in solution and in the gas phase. The molecular structure of the two novel POCs comprises an octahedral {Pd6 O12 }12- core that is capped by eight MIV ions, resulting in a cationic, cubic assembly {Pd6 O12 MIV8 }20+ , which is coordinated by a total of 16 terminal dimethylarsinate and eight water ligands, resulting in the mixed PdII -CeIV /ThIV oxo-clusters [PdII6 O12 M8 {(CH3 )2 AsO2 }16 (H2 O)8 ]4+ (M=Ce, Pd6 Ce8 ; Th, Pd6 Th8 ). We have also studied the formation of host-guest inclusion complexes of Pd6 Ce8 and Pd6 Th8 with anionic 4-sulfocalix[n]arenes (n=4, 6, 8), resulting in the first examples of discrete, enthalpically-driven supramolecular assemblies between large metal-oxo clusters and calixarene-based macrocycles. The POCs were also found to be useful as pre-catalysts for electrocatalytic CO2 -reduction and HCOOH-oxidation.

Highly Sensitive and Stable Determination of As(III) under Near-Neutral Conditions: Benefit from the Synergetic Catalysis of Pt Single Atoms and Active S Atoms over Pt1/MoS2

Designing new catalysts with high activity and stability is crucial for the effective analysis of environmental pollutants under mild conditions. Here, we developed a superior catalyst of Pt single atoms anchored on MoS₂ (Pt₁/MoS₂) to catalyze the determination of As(III). A detection sensitivity of 3.31 μA ppb^-1 was obtained in acetate buffer solution at pH 6.0, which is the highest compared with those obtained by other Pt-based nanomaterials currently reported. Pt₁/MoS₂ exhibited excellent electrochemical stability during the detection process of As(III), even in the coexistence of Cu(II), Pb(II), and Hg(II). X-ray absorption fine structure spectroscopy and theoretical calculations revealed that Pt single atoms were stably fixed by four S atoms and activated the adjacent S atoms. Then, Pt and S atoms synergistically interacted with O and As atoms, respectively, and transferred some electrons to H₃AsO₃, which change the rate-determining step of H₃AsO₃ reduction and reduce reaction energy barriers, thereby promoting rapid and efficient accumulation for As(0). Compared with Pt nanoparticles, the weaker interaction between arsenic species and Pt₁/MoS₂ enabled the effortless regeneration and cyclic utilization of active centers, which is more favorable for the oxidation of As(0). This work provides inspiration for developing highly efficient sensing platforms from the perspective of atomic-level catalysis and affords references to explore the detection mechanism of such contaminants.