Hierarchical N-Doped Carbon as CO2 Adsorbent with High CO2 Selectivity from Rationally Designed Polypyrrole Precursor.

Carbon capture and sequestration from point sources is an important component in the CO2 emission mitigation portfolio. In particular, sorbents with both high capacity and selectivity are required for reducing the cost of carbon capture. Although physisorbents have the advantage of low energy consumption for regeneration, it remains a challenge to obtain both high capacity and sufficient CO2/N2 selectivity at the same time. Here, we report the controlled synthesis of a novel N-doped hierarchical carbon that exhibits record-high Henry's law CO2/N2 selectivity among physisorptive carbons while having a high CO2 adsorption capacity. Specifically, our synthesis involves the rational design of a modified pyrrole molecule that can co-assemble with the soft Pluronic template via hydrogen bonding and electrostatic interactions to give rise to mesopores followed by carbonization. The low-temperature carbonization and activation processes allow for the development of ultrasmall pores (d < 0.5 nm) and preservation of nitrogen moieties, essential for enhanced CO2 affinity. Furthermore, our described work provides a strategy to initiate developments of rationally designed porous conjugated polymer structures and carbon-based materials for various potential applications.

Predictors of excessive renal displacement during access in percutaneous nephrolithotomy: a randomized clinical trial.

To determine the magnitude of renal displacement (a major cause of access failure or loss) during the renal access steps in percutaneous nephrolithotomy (PCNL), investigate predictors of excessive renal displacement, and compare the effect of one-stage versus gradual dilation on renal displacement during access. Sixty-six adult patients undergoing PCNL were randomized into two groups containing 33 patients each: Group 1 underwent gradual tract dilation with Alken metal dilators, and Group 2 received one-stage tract dilation. In each patient, maximum renal displacement was measured in three planes (cephalocaudal, anteroposterior, and mediolateral) during the three access steps (needle puncture, Alken guide insertion, and dilator advancement). The patients' demographic data and intraoperative parameters were compared. In both groups, net renal displacement during the three access steps was in the cephalad, medial, and anterior directions. There were no significant differences in the magnitude of renal displacement in patients with gradual versus one-stage tract dilation. Renal displacement was significantly more pronounced in all planes and in all access steps in female patients and in those with no previous history of open stone surgery on the ipsilateral kidney. High body mass index (BMI) showed a significant negative correlation with cephalad and anterior renal displacement, but not with medial displacement. Three-dimensional movement of the kidney during percutaneous access in PCNL is similar when gradual versus one-stage tract dilation is used. Inherent patient characteristics, such as female sex, BMI, and a previous ipsilateral flank scar are major determinants of the magnitude of renal displacement during the PCNL access steps.

Advancing adsorption and membrane separation processes for the gigaton carbon capture challenge.

Reducing CO2 in the atmosphere and preventing its release from point-source emitters, such as coal and natural gas-fired power plants, is a global challenge measured in gigatons. Capturing CO2 at this scale will require a portfolio of gas-separation technologies to be applied over a range of applications in which the gas mixtures and operating conditions will vary. Chemical scrubbing using absorption is the current state-of-the-art technology. Considerably less attention has been given to other gas-separation technologies, including adsorption and membranes. It will take a range of creative solutions to reduce CO2 at scale, thereby slowing global warming and minimizing its potential negative environmental impacts. This review focuses on the current challenges of adsorption and membrane-separation processes. Technological advancement of these processes will lead to reduced cost, which will enable subsequent adoption for practical scaled-up application.

Optimization of isocratic supercritical fluid chromatography for enantiomer separation.

This paper presents multi-objective optimization analysis and experimental implementation of a single column isocratic supercritical fluid chromatography process for the enantioseparation of flurbiprofen. The single column process is simulated using a detailed model with equilibrium description by a competitive Langmuir isotherm. The optimization problem has been formulated with the objectives of maximizing productivity and minimizing solvent consumption under different product purity and recovery constraints. The solubility of the solute in the mobile phase is explicitly accounted in the problem formulation. The results showed a maximum productivity of 5 kg racemate/kg stationary phase/day with a corresponding organic solvent consumption of 80 L kg⁻¹ racemate for a required purity and recovery of 95%. The optimal operating conditions have been experimentally implemented in an analytical scale laboratory set-up which support the optimization results.