Adsorptive remediation of aqueous inorganic mercury with surfactant enhanced bismuth sulfide nanoparticles

Abstract

Heavy metal contamination in water is a growing threat, endangering the environmental stability. Mercury (Hg) is one of the most lethal heavy metals damaging the immune and nervous system irreversibly. A novel synthetic route to prepare bismuth sulfide (Bi₂S₃) nanoparticles in presence of the surfactant Pluronic (P123) was illustrated in this work. The sorption of Hg (II) by the nanoparticles was investigated. The surfactant assisted nanoparticles showed enhanced surface area and potential compared to the unmodified ones. The effects of adsorbent dose, pH, initial concentration, and temperature were investigated. The maximum Hg (II) adsorption capacity for the surfactant enhanced Bi₂S₃ was 832 mg/g at 303 K and pH 5. The distribution coefficient (K_d) of the order ∼10⁶ ml/g indicated high selectivity of the synthesized adsorbent toward mercury ions. Chemisorption was identified to be the dominant mechanism of adsorption. The adsorbent also showed excellent reusability (>95%) after 5 cycles. The transport parameters involved in the adsorption, the effective pore diffusivity (D_p: 7.36 × 10^-12 m²/s) and the mass transfer coefficient (k_ƒ: 1.52 × 10^-6 m/s) were estimated from a first principle-based model.