Investigation of bio-based chelating agents to prevent and remove mineral scales caused by mixing of incompatible brine water: An insight into molecular characterization and active forces

Scaling is one of the problems that challenge smart water injection due to damage to reservoir porous media and causing wellbore skin. To alleviate this problem, six bio-based chelating agents were extracted from the waste of Glycyrrhiza glabra, Maple, Morus nigra, Eucalypt, Zyziphus spina Christi, and Platanus leaves to be used as scale inhibitors and removal for CaSO₄ and SrSO₄ salts. After characterizing the chelating agents via FTIR technique, HNMR spectroscopy, zeta potential, and CMC calculation, they were used in static inhibition and removal tests. According to the static tests, the chelating agents inhibited 85.7–95.8 % of the scale formation, and 29.7–85.9 % of the precipitated scales were removed by using them. Ion chromatography of filtrated water was investigated to cation (Sr²⁺ and Ca²⁺) concentrations. The higher removal/inhibition efficiency was explained by the higher concentration of potential precipitating cations. The highest strontium and calcium concentration was observed in the sample inhibited by the chelating agent extracted by Glycyrrhiza glabra leaf waste, and on the next level, the agent extracted by maple waste. A comparison of static tests and characteristic indexes, which were given by the FTIR and HNMR techniques, showed that two mechanisms of electrostatic attraction and cation–π interaction are responsible for scale inhibition and removal. In other words, agents with more polar functional groups (such as O-H bonds) and electron-rich π compounds (such as alkenes and aromatic rings) are more feasible for inhibition and removal of scales. The adsorption of chelating agents was also studied to see their retention on reservoir rock. The adsorption of chelating agents on CaCO₃ powders was in the range of 11.2–19.2 mg/g, while their ultimate adsorption on SiO₂ was in the range of 7–10.3 mg/g. The higher adsorption potential of chelating agents was consistent with polar indexes, such as the alcoholic index of the FTIR technique, representing the fact that electrostatic interaction is the main intermolecular interaction for adsorbing chelating agents on the rock. Regarding the feasibility of economic waste-derived chelating agents for both scale inhibition and removal, a promising future is anticipated for using them in water injection projects.