Tailored functionalized polymer nanoparticles using gamma radiation for selected adsorption of barium and strontium in oilfield wastewater

Abstract

To improve oil recovery from oilfield wells mineral scales derived by insoluble BaSO4 and SrSO4 salts during oil extraction should be diminished. In this work, adsorption selectivity of Barium (Ba2+) and Strontium (Sr2+) ions associated with saline formation waters was examined for the first time using nano-sized bi-functional polymer blend synthesized by Cobalt-60 (60Co) γ-rays, as green technology. A bifunctional polymer formed from poly(acrylonitrile)/(styrene-butadiene rubber) homogenous blend is functionalized by -SO3H and -COOH terminal groups (termed as SASB). Those functional groups were selected based on systematic calcium (Ca2+) ions adsorption studies of carboxylate containing molecules. Main and binary interactive effects of solution pH (3–9), adsorbents dose (1-3 g/L), total dissolved salts (TDS, up to 30 g/L), initial Ba2+ and Sr2+ concentrations (10-500 mg/L) and temperature (20–50 oC) on the adsorption selectivity were examined and optimized using Plackett-Burman factorial design (PBD) combined with multiple regression analysis. The regression statistics revealed the significance of quadratic polynomial model to optimize interactive sorption conditions from salty waters with high accuracy level (R2≈ 0.99) rather than linear and two-way interactive models at 95% confidence level. Interestingly finding, the regression and experimental data proved that the presence of up to 10 g/L TDS from alkali metal ions had a significant effect on the enhancement sorption capacity of Ba2+ and Sr2+ when using the prepared sorbent. The SASB adsorbent showed higher sorption selectivity with maximum equilibrium capacity (qmg/g) of 175.3 mg Ba+2 and 210.5 mg Sr+2 per each gram sorbent used in kinetic study. Adsorption kinetics of Ba2+ and Sr2+ sorption by both adsorbents obey pseudo-first and pseudo-second order kinetics, respectively. In sum, the adsorptive power of SASB sorbent is found to be in reverse order of the electronegativity and the hydration radii of the metal ions. Keywords: γ-radiation, Acrylonitrile/styrene-butadiene copolymer, Oilfield scale, Adsorption kinetics, Plackett-Burman factorial design (PBD) optimization