Recombinant Fusion Protein PbrD Cross-Linked to Calcium Alginate Nanoparticles for Pb Remediation

Lead (Pb) pollution arising from industrial and mining activities has led to widespread environmental toxicity, particularly in South Africa. Humans exposed to Pb are reported to suffer from detrimental health impacts that can lead to fatalities. As such, there is an urgent need to remediate Pb from the environment. In this study, we propose the use of a Pb-specific recombinant fusion metalloprotein, rPbrD surface-cross-linked onto calcium alginate nanoparticles (CANPs) for the biosorption of Pb(II) from aqueous solution. The prepared biosorbents were characterized using scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. Their ability to biosorb soluble Pb(II) was determined by inductively coupled plasma mass spectroscopy and their adsorption mechanism was described according to the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherms. The rate of Pb uptake for bare CANPs and rPbrD-CANPs at a concentration of 100 mg/L metal was 3.34 and 8.82 mg/g, respectively, within 30 min. The adsorption data for the bare CANPs best fit the Langmuir isotherm, whereas the adsorption data for rPbrD-CANPs best fitted the Freundlich isotherm. Based on the sorption intensity (n) and the separation factor (R_L), both biosorbents represent a favorable adsorption system. These findings suggest that the proposed nanobiosorbent is a promising candidate for the recovery of Pb ions present in high concentrations such as acid mine drainage or industrial effluent.