Electrodeposited Self-Assembled Bromide-Trapping Ion Sieve Based on Conductive Polyaniline for Rapid and High-Capacity Bromide Adsorption Under Electric Field

In oilfield brine, the bromide ion (Br–) concentration ranges from 100 to 300 mg/L, accompanied by high concentrations of coexisting anions, especially chloride (Cl–) at 100–300 g/L. The selective separation of Br– remains extremely challenging due to the similar structural and charge properties of halide ions. This study developed an electrodeposited self-assembled bromide ion-trap polyaniline (Br-trap PANI) film, leveraging the synergistic enhancement between the highly selective Br– capture capability of the Br-trap structure and the electrical conductivity of PANI. Under optimized conditions (voltage: 0.7–1.0 V, pH: 1–14), the composite film demonstrated a maximum Br– adsorption capacity of 68.05 mg/g with excellent cyclic stability, retaining over 50 mg/g upon repeated use. At an anion concentration ratio of 1:1, the selectivity coefficients for Cl–, SO42–, and NO3– were 1.17, 1.44, and 1.59, respectively. It was found that these coefficients increased with the increase of the concentration difference between Br– and competing anions. Furthermore, the film exhibits rapid adsorption kinetics, acid resistance, and electrochemical stability. The composite material also features low production costs, benefiting from the low cost and wide availability of aniline monomer, combined with the scalable nature of the electrodeposition synthesis method. This technology provides an effective approach for the sustainable extraction of Br– from complex brines. It is clear that the effective utilization of oilfield brine represents a valuable resource, with significant implications for the goals of critical mineral security and resource recycling.