Calcium ions electrochemical detection by Cu-Fe LDH/cysteine-based nanocomposite for water softening applications

Water softening is a treatment process required to manage calcium and magnesium cations in water streams. Moreover, detection of such cations in water samples using simple portable techniques is required for monitoring and inspection of water quality. Nanocomposites can provide solutions for such multiple challenges while showing high performance and cost-effectiveness. In this work, the Cu-Fe layered double hydroxides (LDH)/cysteine-based electrodes were synthesized and are used as active materials for the electrochemical detection of calcium ions. The electrode materials were characterized using XRD, FTIR, and SEM. The synthesized electrode showed a limit of detection and a limit of quantification of 0.21 µM and 0.73 µM, respectively. The concentration range of detection was 5–30 µM. The intermolecular interactions of Ca ions with cysteine-free LDH and cysteine-LDH were investigated by Monte Carlo and molecular dynamics simulations. Monte Carlo simulations revealed that the (001) surface is favored for Ca(II) adsorption within the LDH structure with an energy of adsorption equals to 372.46 kcal/mol. This work paves the road towards developing cost-effective disposable electrode based on portable electrochemical detection of Ca ions for on-site water softening applications.