Abstract
The potential of physic seed hull (PSH),
Jantropha curcas L. as an adsorbent for the removal of Cd
2+ and Zn
2+ metal ions from aqueous solution has been investigated. It has been found that the amount of adsorption for both Cd
2+ and Zn
2+ increased with the increase in initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic range), but decreased with the increase in the particle size of the adsorbent. The adsorption process for both metal ions on PSH consists of three stages—a rapid initial adsorption followed by a period of slower uptake of metal ions and virtually no uptake at the final stage. The kinetics of metal ions adsorption on PSH followed a pseudo-second-order model. The adsorption equilibrium data were fitted in the three adsorption isotherms—Freundlich, Langmuir and Dubinin–Radushkevich isotherms. The data best fit in the Langmuir isotherm indication monolayer chemisorption of the metal ions. The adsorption capacity of PSH for both Zn
2+ and Cd
2+ was found to be comparable with other available adsorbents. About 36–47% of the adsorbed metal could be leached out of the loaded PSH using 0.1
M HCl as the eluting medium.