Uptake of lead, cadmium and copper by heavy metal-resistant Pseudomonas aeruginosa strain DR7 isolated from soil

This study highlights the biosorption capacity for Cd (II), Cu (II) and Pb (II) by a locally isolated Pseudomonas aeruginosa DR7. At initial concentrations of 150 mg L-1 and 240 min of contact time, P. aeruginosa DR7 showed a 62.56 mg/g removal capacity for Cd (II) at an optimum pH of 6.0, 72.49 mg/g for Cu (II) at an optimum pH of 6.0, and 94.2 mg/g for Pb (II) at an optimum pH of 7.0. The experimental data of Cd (II), Cu (II), and Pb (II) adsorbed by the pseudo-second-order kinetic model correlates well with P. aeruginosa DR7, with R2 all above 0.99, showing that the fitting effect was satisfactory. The isothermal adsorption processes of Cd (II) (0.980) and Cu (II) (0.986) were more consistent with the Freundlich model, whereas Pb (II) was more consistent with the Langmuir model (0.978). FTIR analysis suggested the involvement of hydroxyl, carbonyl, carboxyl, and amine groups present in the inner regions of P. aeruginosa cells during the biosorption process. SEM-EDS analysis revealed that after contact with metals, there were slight changes in the surface appearance of the cells, which confirmed the deposition of metals on the bacterial surface. There was also the possibility of the metals being translocated into the bacterial inner regions by the appearance of electron-dense particles, as observed using TEM. As a conclusion, the removal of metals from solutions using P. aeruginosa DR7 was a plausible alternative as a safe, cheap, and easily used biosorbent.