Metal biosorption by algae Gelidium derived materials from binary solutions in a continuous stirred adsorber

Continuous metal biosorption from Pb(II)/Cu(II) and Pb(II)/Cd(II) solutions onto algae Gelidium and granulated algal waste was performed in a continuous stirred tank adsorber (CSTA). Biosorption was simulated by a mass transfer model including intraparticle and film resistances and equilibrium described by the Langmuir binary equation. The breakthrough curves present an initial “knee” suggesting a film resistance to mass transfer. Biosorption of Pb(II) is significantly reduced by the presence of Cu(II), which indicates that competition exists for the same binding sites. In the binary system Pb(II)/Cd(II), an “overshoot” region was observed, for the cadmium concentration profile, due to the higher affinity of lead ions to the binding sites. A fast and efficient desorption of Cu(II) and Pb(II) was obtained using a 0.1M HNO3 solution, as eluent. Results suggest that desorption is based on ion exchange between the metal ions, loaded in the biomass, and H+ in solution. Desorption was adequately predicted by a mass transfer model considering intraparticle diffusion resistance and equilibrium given by the mass action law.