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Transition metals such as cobalt are necessary for various clean-energy technologies, notably electric-vehicle batteries. Global demand for these metals is therefore projected to increase exponentially in coming decades. Metal-ion adsorption from water offers many advantages over mining, as adsorption processes are energy-efficient and compatible with diverse water sources. Porous organic polymers are promising adsorbents: Their covalent nature provides thermal and chemical stability, while their porosity leads to high adsorption capacity. Here, we synthesized a series of amide-linked porous organic polymers denoted TMC-TAPM through the polymerization of a tri-functional acyl chloride monomer with a tetra-functional amine monomer, and we studied the resulting materials for cobalt capture from aqueous solution. By controlling monomer stoichiometry during synthesis, we obtained materials with varying amounts of carbonyl or amino groups. The materials with increasing carbonyl content showed increasing cobalt adsorption capacities, with measured adsorption capacities up to 50 mg Co g−1. Cobalt adsorption capacity was observed to plateau past a certain stoichiometric ratio, indicating an optimal monomer stoichiometry of 1.5-fold excess acyl chlorides relative to amines. The captured cobalt could be desorbed to yield a re-activated adsorbent capable of repeated adsorption cycles, without loss in performance. These results provide design rules for the synthesis of robust, high-capacity transition metal adsorbents. [ABSTRACT FROM AUTHOR]

We report a new assay for breakdown of high molecular weight, insoluble lignin based on lignin films. In this method, decrease in film thickness is detected upon solubilization of mass through either chemical alteration of the lignin or molecular weight reduction. The assay was performed with organosolv lignin, the only chemical modification being an oxidative pretreatment to provide film stability with respect to dissolution. The assay is sensitive to release of as little as 20 Å of material from the film. A multiplexed format was developed using a silicone block in the form of a standard 96-well plate, allowing simultaneous assaying of a large number of reaction conditions. The assay was demonstrated using the Fenton reaction, revealing new insights into the physicochemical aspects of this reaction system with insoluble lignin. In particular, mass solubilized from the film was found to pass through a maximum as a function of the initial concentration of FeCl2 ([FeCl2]o), with the maximum occurring at [FeCl2]o = 1 mM for [H2O2]o = 5%. At that condition, solubilization of mass occurs in two stages. The reaction produces mostly ring-opened products of mass greater than 700 g mol−1, along with a minority of low molecular weight aromatics. The new insight from this work is an important step toward optimizing this complex reaction system for effective lignin breakdown. [ABSTRACT FROM AUTHOR]

To investigate the influence of manganese substitution on the saturation magnetization of manganese ferrite nanoparticles, samples with various compositions (Mn x Fe 3- x O 4 , x = 0, 0.25, 0.5, 0.75, and 1) were synthesized and characterized. The saturation magnetization of such materials was both calculated using density functional theory and measured via vibrating sample magnetometry. A discrepancy was found; the computational data demonstrated a positive correlation between manganese content and saturation magnetization, while the experimental data exhibited an inverse correlation. X-ray diffraction (XRD) and magnetometry results indicated that the crystallite diameter and the magnetic diameter decrease when adding more manganese, which could explain the loss of magnetization of the particles. For 20 nm nanoparticles, with increasing manganese substitution level, the crystallite size decreases from 10.9 nm to 6.3 nm and the magnetic diameter decreases from 15.1 nm to 3.5 nm. Further high resolution transmission electron microscopy (HRTEM) analysis confirmed the manganese substitution induced defects in the crystal lattice, which encourages us to find ways of eliminating crystalline defects to make more reliable ferrite nanoparticles., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)