No abstract

The removal of highly toxic, ultra-dilute contaminants of concern has been a primary challenge for clean water technologies. Chromium and arsenic are among the most prevalent heavy metal pollutants in urban and agricultural waters, with current separation processes having severe limitations due to lack of molecular selectivity. Here, we report redox-active metallopolymer electrodes for the selective electrochemical removal of chromium and arsenic. An uptake greater than 100 mg Cr/g adsorbent can be achieved electrochemically, with a 99% reversible working capacity, with the bound chromium ions released in the less harmful trivalent form. Furthermore, we study the metallopolymer response during electrochemical modulation by in situ transmission electron microscopy. The underlying mechanisms for molecular selectivity are investigated through electronic structure calculations, indicating a strong charge transfer to the heavy metal oxyanions. Finally, chromium and arsenic are remediated efficiently at concentrations as low as 100 ppb, in the presence of over 200-fold excess competing salts.

Carbon capture, utilization, and storage technologies are needed to meet carbon emission reduction targets and prepare the energy industry for a carbon constrained world. Recent breakthroughs have identified the first liquid phase sorbents for CO2 capture at high temperatures. In this work, the material design space of the molten alkali metal borates (A x B1–x O1.5–x ) is explored finding sodium and sodium-rich lithium–sodium borates with a mixing ratio, x, of around 0.75 to be optimal. A mechanistic understanding of the material is developed through exploration of the sodium borate phase diagram, the development of a kinetic equilibrium model, and estimation of effective diffusion coefficients. Interesting features of the sorbents, such as the proposed formation of dicarbonate ions and counter-intuitive trends in the diffusion coefficient, are identified and explained with implications for the design of future high temperature carbon capture facilities discussed.

Molten ionic oxides based on sodium borate and mixed alkali-metal borates show remarkably fast sorption kinetics and intrinsic regenerability as liquid absorbents for CO2 capture at medium to high temperatures