Removal of metal ions from aqueous solution by adsorption onto low-cost biosorbent

Abstract

Removal of heavy metals (Cu(II), Pb(II) and Zn(II)) from aqueous solution was investigated using native or saponified chicory pulp biomass. Firstly, carbohydrates constituted about 70% of pulp dried matter. The pectic fraction represented 12-14% of dried matter and about 51% of these pectic units were esterified by methanol. The pH of the zero net proton charge of the pulp ranged from 4.5 to 5. Native pulp contained numerous surface functional groups and their cation exchange capacity is 0.566 meq g(-1). After saponification of chicory pulp, the cation exchange capacity reached 0.959 meq g(-1) due to the demethylation of carboxylic groups from pectic polymers. Then, the kinetics and equilibrium of sorption were examined. A pseudo second-order kinetic model was used to correlate experimental data and to determine the kinetic parameters. The equilibrium sorption data fitted well with the Langmuir model and showed the following affinity order of the materials: Pb2+ > Cu2+ > Zn2+. The maximum adsorption capacities ranged from 0.215 to 0.315 mmol g(-1) for native pulp and from 0.341 to 0.507 mmol g(-1) for saponified pulp. Finally, competitive effects were observed in multi-metallic solution adsorption experiments.