Simultaneous removal of methylene blue and Pb2+ from aqueous solution by adsorption on facile modified lignosulfonate.

In this paper, simultaneous removal of methylene blue (MB) and Pb2+ from the binary component system by an easily prepared cross-linked lignosulfonate bio-adsorbent (CLLS) was described. CLLS was characterized by FTIR, SEM/EDS and TGA. The influences of pH, temperature, contact time and initial MB and Pb2+ concentrations on the adsorption performance were investigated. The results demonstrated a good ability of CLLS to remove MB and Pb2+ simultaneously. Using of 1.0 g L-1 loading, removal efficiency of MB and Pb2+ reached 98.0% and 97.8%, respectively, in the MB (100 mg.L-1)-Pb2+ (50 mg.L-1) system. Moreover, the adsorption isotherms and adsorption kinetics indicated that the results were fitting well with the Langmuir and pseudo-second-order model, respectively, for both MB and Pb2+. Based on the Langmuir model, the maximum adsorption capacity of MB and Pb2+ reached 132.6 and 64.9 mg g-1, respectively, in the MB-Pb2+ system, which was much lower than that in the single component system (358.4 mg g-1 100.9 mg g-1 for MB and Pb2+, respectively). Hence, simultaneous adsorption of MB and Pb2+ onto CLLS was an antagonistic adsorption. In addition, an apart-sequential adsorption method was used to study the action of adsorption sites on CLLS for MB and/or Pb2+ with the help of an efficient self-made apparatus. Rudimental results showed that there would be three different kinds of adsorption sites on CLLS: MB-site, Pb2+-site and MB/Pb2+- shared sites. Furthermore, in the MB (100 mg.L-1)-Pb2+(50.0 mg.L-1) system, the simultaneous removal efficiency of MB and Pb2+ still maintained 91.8% and 85.0%, respectively, after 6 cycles.