On the dominance of Pb during competitive biosorption from multi-metal systems: A review

Abstract Biosorption, despite being initially heralded as a technology offering great potential for detoxification, is still yet to be commercialized. One of the reasons given is the lack of universal understanding of the mechanisms involved. This review focused on the removal of heavy metals from solutions in which Pb(II) co-existed with other metals in binary, ternary and quaternary systems. Trends in sorption capacities were analysed using ratios of maximum adsorption capacities: , , and , where and represent the adsorption capacity in the presence and absence of the interfering metal ion, respectively, and is the metal ion co-existing with Pb(II). The data in literature were analysed for selected metal ions Pb(II), Cu(II), Zn(II), Cd(II), Ni(II) and Cr(III). It was shown that for all systems analysed, the ratio: < 1, thus confirming that the simultaneous presence of metal ions in solution reduced their adsorption capacities. For the selected Pb/Cu system it was shown that generally > , and , thus confirming antagonistic effects for the system. It was further shown that Pb(II) contributed to 70–77% of the total adsorption capacity, and the % change in adsorption capacity (ⵠ) was negative. In conclusion, these findings confirmed the superiority of Pb(II) adsorption across several metal-biosorbent systems, which has implications on the designing of model biotechnologies for possible practical applications.