Heavy metals are a threat to human health and
ecosystem. These days, great deal of attention is being
given to green technologies for purification of water contaminated
with heavy metal ions. Biosorption is one among
such emerging technologies, which utilizes naturally
occurring waste materials to sequester heavy metals from
wastewater. Cadmium has hazardous impact on living
beings; therefore, its removal through green and economical
process is an important task. The aim of the present
study was to utilize the locally available
Portulaca oleracea
plant biomass as an adsorbent for cadmium removal
from aqueous solution. The biomass was obtained after
drying and grinding the portulaca leaves and stem. No
chemical treatment was done on the adsorbent so that it
remained green in a true sense. Batch experiments were
performed at room temperature. The critical parameters
studied were effects of pH, contact time, initial metal ion
concentration and adsorbent dose on the adsorption of
cadmium. The maximum adsorption was found to be 72 %.
The kinetic data were found to best fit the pseudo-secondorder
equation. High adsorption rates were obtained in the
initial 45 min, and adsorption equilibrium was then
gradually achieved in about 100 min. Adsorption increased
with increase in pH for a range 2 and 6. The equilibrium
adsorption results closely followed both the Langmuir and
Freundlich isotherms. The values of constants were calculated
from isotherms. Results indicated that portulaca
plant biomass could be developed as a potential material to
be used in green water treatment devices for removal of
metal ions.