Competitive biosorption of Pb(II) and Cd(II) ions from aqueous solutions using chemically modified moss biomass (Barbula lambarenensis)

Treatment of biosorbents to add functional groups that increase toxic metal biosorption is an important way to improve its effective application. Hence, different portions of pristine Barbula lambarenensis (RBL) were treated separately with sodium tripolyphosphate (TPP) and ethylene glycol. The pristine and treated RBL biomasses were used to evaluate the simultaneous removal of Pb(II) and Cd(II) from aqueous solutions. Equilibrium, kinetics and adsorption isotherms were studied. Results revealed that biosorption of Pb(II) and Cd(II) metal ions were spontaneous and described by the pseudo-second-order kinetics. TPP-treated RBL showed higher biosorption capacity for Pb(II), while the ethylene glycol-treated adsorbent was more efficient for Cd(II) biosorption. The simultaneous presence of Pb(II) and Cd(II) in solution did not affect Pb(II) biosorption. However, Cd(II) biosorption dropped 44, 42 and 19% for the pristine, ethylene glycol and TPP-treated adsorbents, respectively, in the competitive adsorption. Both treatments enhanced Pb(II) and Cd(II) biosorption by RBL.