Particulate contaminant transport in rivers—Modelling of near bed exchange processes

Sequestration of CO2 within stable mineral carbonates (e.g., CaCO3) represents an attractive emission reduction strategy because it offers a leakage-free alternative to geological storage of CO2 in an environmentally benign form. However, the pH of aqueous streams equilibrated with gaseous streams containing CO2 (pH < 4) are typically lower than that which is required for carbonate precipitation (pH > 8). Traditionally, alkalinity is provided by a stoichiometric reagent (e.g., NaOH) which renders these processes environmentally hazardous and economically unfeasible. This work investigates the use of regenerable ion-exchange materials to induce alkalinity in CO2-saturated aqueous solutions such that the pH shift required for mineralization occurs without the need for stoichiometric reagents. Na+-H+ exchange isotherms (at [H+] = 10−8–10−1 M) and rates were measured for 13X and 4A zeolites and TP-207 and TP-260 organic exchange resins in batch equilibrium and fixed-bed exchange experiments, respectively. At solutions equilibrated with CO2 at 1.0 atm (pH = 3.9), H+ exchange capacities for the materials were similar (1.7–2.4 mmol H+/g material) and resulted in pH increases from 3.9 to greater than 8.0. Multi-component mixtures using Ca2+ and Mg2+ cations (at 10−3–10−1 M) in CO2-saturated water were used to probe competitive ion exchange. The presence of divalent cations in solution inhibited H+ exchange, reducing capacities to as low as 0.2 mmol H+/g for both resins and zeolites. Dynamic H+ exchange capacities in fixed-bed ion exchange columns were similar to equilibrium values for resins (∼1.5 mmol/g) and zeolites (∼0.8 mmol/g) using inlet solutions that were equilibrated with gaseous streams of CO2 at 1.0 atm. However, exchange kinetics were limited by intraparticle diffusion as indicated by the increased rate parameters with increasing inlet flow rates (20–160 cm3 min−1). Experimental calcite precipitation from mixing the alkaline CO32−-rich water solution obtained from the ion-exchange column with a simulated liquid waste stream solution achieved thermodynamic maximum yields. The results from these studies indicate that ion exchange processes can be used as an alternative to the addition of stoichiometric bases to induce alkalinity for the precipitation of CaCO3, thereby opening a pathway toward sustainable and economic mineralization processes.

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Formation of the Zeebrugge coastal turbidity maximum: The role of uncertainty in near-bed exchange processes

Marine Geology ◽

10.1016/j.margeo.2020.106186 ◽

2020 ◽

Vol 425 ◽

pp. 106186

Author(s):

D.S. van Maren ◽

J. Vroom ◽

M. Fettweis ◽

J. Vanlede

Keyword(s):

Turbidity Maximum ◽

Exchange Processes ◽

Bed Exchange

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Numerical investigation of indoor particulate contaminant transport using the Eulerian-Eulerian and Eulerian-Lagrangian two-phase flow models

Experimental and Computational Multiphase Flow ◽

10.1007/s42757-019-0016-z ◽

2019 ◽

Vol 2 (1) ◽

pp. 31-40 ◽

Cited By ~ 1

Author(s):

Yihuan Yan ◽

Xiangdong Li ◽

Kazuhide Ito

Keyword(s):

Numerical Investigation ◽

Contaminant Transport ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Flow Models ◽

Particulate Contaminant

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Social exchange processes, health behaviour, and health behaviour change

Zeitschrift für Gesundheitspsychologie ◽

10.1026/0943-8149.16.3.131 ◽

2008 ◽

Vol 16 (3) ◽

pp. 131-134

Author(s):

Urte Scholz ◽

Rainer Hornung

Keyword(s):

Social Exchange ◽

Health Behaviour ◽

Psychological Research ◽

Smoking Behaviour ◽

Self Report ◽

Long Term Effects ◽

Main Research ◽

Research Areas ◽

Exchange Processes ◽

Multi Method Approach

Abstract. The main research areas of the Social and Health Psychology group at the Department of Psychology at the University of Zurich, Switzerland, are introduced. Exemplarily, three currently ongoing projects are described. The project ”Dyadic exchange processes in couples facing dementia” examines social exchanges in couples with the husband suffering from dementia and is based on Equity Theory. This project applies a multi-method approach by combining self-report with observational data. The ”Swiss Tobacco Monitoring System” (TMS) is a representative survey on smoking behaviour in Switzerland. Besides its survey character, the Swiss TMS also allows for testing psychological research questions on smoking with a representative sample. The project, ”Theory-based planning interventions for changing nutrition behaviour in overweight individuals”, elaborates on the concept of planning. More specifically, it is tested whether there is a critical amount of repetitions of a planning intervention (e.g., three or nine times) in order to ensure long-term effects.

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