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Keywords:

  • biosorption;
  • cadmium;
  • Hydrilla verticillata;
  • pH;
  • low-cost sorbent

Abstract

The kinetics and equilibrium of cadmium biosorption from aqueous solutions were investigated using fresh tissues of Hydrilla verticillata. The biosorptive characteristics of cadmium ions were studied with respect to well-established effective parameters, including pH, temperature and contact time. The biosorptive capacity of H. verticillata for cadmium increased with increasing pH. In addition, the resulting isotherms were well-described by Langmuir and extended Langmuir models (R2 = 0.9794–0.9957 and 0.9880, respectively). The comparison between calculated and experimental qe values showed that the extended Langmuir model had a better simulation for the cadmium biosorption by H. verticillata than the Langmuir isotherm model. The equilibrium biosorption data at a constant temperature were well-interpreted by the Langmuir model. The maximum biosorptive capacity increased from 33.54 to 37.46 mg/g when the solution temperature was increased from 278 to 298 K. Other various thermodynamic parameters were also estimated. Biosorptive equilibrium was established within approximately 20 min. Moreover, the pseudo-second-order equation was more appropriate in predicting biosorptive capacity than the pseudo-first-order equation. In practical viewpoints, the abundant and inexpensive plant biomass H. verticillata can be used as an effective and environmentally friendly biosorbent for the detoxification of cadmium from aqueous solutions. © 2012 Canadian Society for Chemical Engineering