Agave salmiana as biosorbent of cobalt and cobalt-nickel ionic species from aqueous solutions

The Agave salmiana biosorption behavior for cobalt ions (Co2+) and cobalt-nickel ions (Co2+-Ni2+) from aqueous solutions have been investigated in this study. The removal of Co(II) and Co(II)-Ni(II) was evaluated in a batch system as a function of contact time, pH, and the initial concentra-tion of each metal in the solutions. It was observed that the biosorption equilibrium was reached after 60 min in all cases: Co(II) from a monocomponent solution and Co(II) and Ni(II) from a bicomponent solution. Pseudo-first-order and pseudo-second-order models were applied to the kinetic sorption process. The experimental data were well described by the pseudo-second -or-der model in all cases. The pH range observed for the maximum biosorption by Agave salmiana for the removal of Co2+ and Co2+-Ni2+ from aqueous solutions was between 6 and 10. The maxi-mum biosorption capacity (qmax) of the Agave salmiana for Co(II) with the base on the Langmuir model was 6.69 mg Co/g Agave. However, the uptake data for Co(II) and Ni(II) from bicomponent solution was described well by a linear model, and the sorption capacities were 50.02 mg Co(Co-Ni)/g Agave and 57.7 mg Ni(Co-Ni)/g Agave. The Kd value was higher for Ni(II)(Co-Ni) than for Co(II)(Co-Ni). These results showed that Agave salmiana exhibits a notable difference in the sorp-tion capacity of the biosorbent when Co was presented in the bicomponent solution compared to that of monocomponent solution. The adsorption capacity for Ni(II) is higher for Co(II) in a bicomponent solution. The metals' co-precipitation could play a role in the biosorption processes.