Metal ion biosorption potential of lignocellulosic biomasses and marine algae for wastewater treatment

The metal ion-binding abilities of six lignocellulosic biomasses obtained from agro-industrial products and sustainable plantations, as well as of two red and one green marine algal species, were examined in a comparative manner to ascertain their potential as biosorbents of heavy metals from low concentration wastewater. Dilute single-solute solutions of cadmium and nickel ions (<= 1 mM) were used as models. All the biontaterials showed appreciable Cd(II) ion biosorption which was strongly dependent on the dosage used. The maximum Cd(II) ion biosorption capacities (X-mL), as estimated from the experimental isotherms using the Langmuir model, indicated that the red algae (X-mL= 0.26-0.52 mmol/g) and the lignocellulosic biomasses with larger lignin contents (X-mL= 0.17-0.20 mmol/g) possessed the greatest potential. This behaviour also applied to Ni(II) ion biosorption, although the bioniaterials proved to be less effective in this case, especially towards low dosage. Comparison of the Cd(II) ion equilibrium sorption by one of the lowest performing biomasses (sawdust from Arundo donax stems) with that for activated carbons developed from the same biomass under different atmospheres revealed that the biomass behaviour was similar to that of carbons activated by heating in inert or mildly oxidative atmospheres.