Preparation of stable nickel nanosuspensions and evaluation of their efficiency in enhancing carbondioxide solubility in brine

Abstract

In recent years, there is a surge of interest in harnessing nanoparticles for enhancing mass transfer of CO₂ in water. Utilizing Nickel nanoparticles for enhancing CO₂ solubility in brine and preparing carbonated water for the purpose of addition oil recovery and CO₂ storage, has not been reported to date.

Nickel nanoparticles settle down easily when dispersed in brine containing monovalent and/or divalent ions. In this study, prior to absorbing CO₂ in brine, stable nickel-nanosuspensions in brine have been prepared, by adding a bio-polymer, Xanthan Gum as a stabilizer. Addition of Xanthan gum (XG) escalates brine viscosity, thereby reducing the sedimentation rate of Nickel nanoparticle decreases. It has been observed that, at room temperature, stable NiNP-XG-brine nanosuspension can be prepared at XG concentration greater than or equal to 0.2 wt%. Various factors such as temperature, concentration of Xanthan Gum and Nickel nanoparticles, that effect the viscosity and stability of Nickel nanosuspensions prepared in XG-brine mixture have been studied. Characterization techniques such as zeta potential analysis, turbiscan stability analysis, measuring dynamic viscosity and visual observations have been used for this purpose.

In this study, pressure-decay-based method is proposed to calculate molal solubility, Henry’s constant, and diffusivity of CO₂ in deionized water, synthetic brine, and the prepared nickel nanofluids at initial pressure of 50 bar and temperature of 32 ℃. Thereafter, the pressure–time data collected after each experiment and an analytical-graphical approach suggested by Pacheo-Roman and Hejazi is used to solve Fick’s second law equation of diffusion that governs the diffusion process. The results provide new insight into the mechanisms of CO₂ mass transfer in the nickel nanofluids. It is found that molal solubility of CO₂ in NiNP-XG-brine nanosuspension containing 0.2 wt% XG is greater than brine. Moreover, solubility of CO₂ in NiNP-XG-brine nanosuspension containing 0.02 wt% NiNP and 0.2 wt% XG is 15 % more than pure brine. The observed increase might be attributed to enhanced hydration of CO₂ in presence of Nickel nanoparticles. However, it is observed that diffusivity of CO₂ in deionized water and brine are greater than all the NiNP-XG-brine nanosuspension studied here.