A modified batch reactor system to study equilibrium-reactive transport problems.

Area of Science:

• Environmental Science
• Geochemistry
• Chemical Engineering

Background:

• Studying slow geochemical reactions requiring long equilibrium times is experimentally difficult.
• Traditional column experiments have limitations in controlling reaction parameters.

Purpose of the Study:

• To introduce and validate a sequential equilibration reactor (SER) setup for studying equilibrium geochemical reactive transport.
• To assess the SER system's ability to mimic one-dimensional reactive transport models and provide precise control.

Main Methods:

• Developed a sequential equilibration reactor (SER) system comprising sequentially operated batch reactors.
• Conducted SER experiments investigating arsenic adsorption and transport on iron-oxide coated sand under varying conditions (pH, solid-solution ratio, concentration).
• Validated experimental data against predictions from the geochemical transport code PHREEQCI using established surface complexation models.

Main Results:

• The SER system successfully mimicked one-dimensional reactive transport processes.
• Experimental data on arsenic adsorption and transport closely matched model predictions.
• The SER setup demonstrated flexibility and superior control over reaction time, pH, and solid-solution ratio.

Conclusions:

• The sequential equilibration reactor (SER) is a viable and flexible alternative to column experiments for studying equilibrium geochemical reactive transport.
• The SER system offers enhanced control over critical experimental parameters, improving the study of slow geochemical reactions.
• The successful validation against PHREEQCI demonstrates the SER system's reliability for geochemical research.