Investigation of Crystal Growth in Enzymatically Induced Calcite Precipitation by Micro-Fluidic Experimental Methods and Comparison with Mathematical Modeling

Lars Von Wolff,Felix Weinhardt,Holger Class,Christian Rohde,Johannes Hommel

doi:10.1007/s11242-021-01560-y

Lars Von Wolff, Felix Weinhardt + Show 3 more

Open Access

https://doi.org/10.1007/s11242-021-01560-y

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Abstract

Enzymatically induced calcite precipitation (EICP) is an engineering technology that allows for targeted reduction of porosity in a porous medium by precipitation of calcium carbonates. This might be employed for reducing permeability in order to seal flow paths or for soil stabilization. This study investigates the growth of calcium-carbonate crystals in a micro-fluidic EICP setup and relies on experimental results of precipitation observed over time and under flow-through conditions in a setup of four pore bodies connected by pore throats. A phase-field approach to model the growth of crystal aggregates is presented, and the corresponding simulation results are compared to the available experimental observations. We discuss the model’s capability to reproduce the direction and volume of crystal growth. The mechanisms that dominate crystal growth are complex depending on the local flow field as well as on concentrations of solutes. We have good agreement between experimental data and model results. In particular, we observe that crystal aggregates prefer to grow in upstream flow direction and toward the center of the flow channels, where the volume growth rate is also higher due to better supply.

Highlights

Induced calcium carbonate precipitation (EICP) is an engineering technology that employs enzymatic activity for altering geochemistry, resulting in precipitation of calcium carbonate
This study, we focus on Enzymatically induced calcium carbonate precipitation (EICP) via ureolysis by the enzyme urease extracted from ground seeds of the Jack Bean Canavalia ensiformis, which are known for their high urease content
We have developed a phase-field approach for modeling crystal growth in enzymatically induced calcite precipitation and compared it to micro-fluidic experiments

Summary

Introduction

Induced calcium carbonate precipitation (EICP) is an engineering technology that employs enzymatic activity for altering geochemistry, resulting in precipitation of calcium carbonate. This is mostly due to hydrolysis of urea and catalyzed by ureases, which are widespread enzymes in soil bacteria and plants (Kappaun et al 2018). In. this study, we focus on EICP via ureolysis by the enzyme urease extracted from ground seeds of the Jack Bean Canavalia ensiformis, which are known for their high urease content. Urease catalyzes the hydrolysis reaction of urea (( NH2)2CO ), resulting at typical environmental conditions in the products bicarbonate (HCO−3 ) and ammonium (NH+4 ) , i.e., (NH2)2CO + urease → NH+4 H2NCOO− ⟶ HCO−3

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