Efficiency of oil separation and demulsification following sonication gel degradation: Influence of Cr(III) ions, NaCl concentrations, and sodium-based retarders

•Investigation of the impact of chromium (III), salinity, and retarders on demulsification efficiency and of oil–water emulsions.•Chromium (III) ions significantly increase emulsion stability, while their removal markedly reduces demulsification duration.•The influence of salinity on demulsification is dependent on the type of retarder used, showing diverse behaviors.•Oil separation rates are higher for samples treated with resin and are notably influenced by the choice of retarder. This study investigates the impact of chromium (III) ions, salinity, and retarders on demulsification efficiency and oil separation in oil–water emulsions stabilized by hydrolyzed polyacrylamide (HPAM) aqueous solutions. Two different concentrations of HPAM (1000 and 2000 ppm) and NaCl (0–200,000 ppm), along with two distinct retarders (sodium lactate and sodium malonate), were employed to prepare the emulsion samples. A comprehensive analysis of emulsion stability and demulsification duration was conducted under varying treatment conditions, such as the presence or absence of chromium (III) ions and resin application for chromium removal. Results demonstrate that the presence of chromium (III) ions significantly increases emulsion stability, while their removal leads to a marked reduction in demulsification duration. Notably, the impact of salinity was found to depend on the specific retarder used, with sodium lactate and sodium malonate exhibiting differing demulsification durations. As the HPAM concentration was raised from 1000 to 2000 ppm, the demulsification duration also, regardless of the presence or absence of chromium (III) ions. Additionally, the oil separation rates were higher in samples treated with a resin for chromium removal and are notably influenced by the choice of retarder. In particular, using sodium malonate as a retarder resulted in a significant improvement in the oil separation rate compared to sodium lactate under various salinity conditions. The findings of this study provide valuable insights into the optimization of oil–water separation processes, offering the potential for improved oil recovery and environmental sustainability. This study is particularly novel in its comprehensive investigation of the interplay between different factors (chromium, salinity, and retarders) in oil–water separation processes.