STUDIES ON THE ADSORPTION OF HEAVY METAL IONS AND DYE FROM AQUEOUS SOLUTION USING PHYSIC SEED HULL (Jatropha curcas L.)

In this work, the adsorption potential of physic seed hull (PSH), Jantropha
curcas L. as an adsorbent for the removal of metal ions (Zn2+ and Cd2+) and
malachite green dye (MG) from aqueous solution has been investigated. The study
also has been extended to investigate the effect of anionic surfactant (tetra sodium
N-(1, 2dicarboxy ethyl)-Noctadecyl sulfosuccinamate), known as Aerosol 22, on
these adsorption processes. The performance of the adsorbent PSH has also been
compared with granular activated carbon (GAC) adsorbent. The adsorbent, PSH was
thoroughly characterized by SEM-EDX, BET, CHNS, Zeta potential measurement
and FTIR studies. It has been observed that the adsorption of metal ions and dye
increased with the increase in initial metal ions/dye concentration, contact time of
adsorbent and adsorbate, temperature of adsorption, dosage of adsorbent and pH of
the solution in an acidic range, but decreased with the increase in the particle size of
PSH. Both PSH and GAC adsorbent exhibited better adsorption ability towards Zn2+
than Cd2+ from aqueous solution. But the adsorption capacity of PSH was found to
the higher than that of GAC for both the metal ions and MG dye. Aerosol 22 was
used during the adsorption process to provide the anionic functional group on the
surface of PSH for supplying further adsorption site for metal ions. Addition of
Aerosol 22 improved the adsorbing capacity of PSH for both the metal ions, but the
effect was observed to be more for Zn2+. Again, it was further observed that at
higher concentration of the surfactant there was a decrease in the adsorption of metal
ions. It might be related to the formation of micelles that prevented the adsorption of
metal ions. The adsorption process for both the metal ions and dye on PSH was
found to be consists of three-staged process - a rapid initial adsorption of the metal
ions initially, followed by a period of slower uptake of the metal ions and finally no
significant uptake of the metal ions. The kinetics of metal ions adsorption process was therefore described by a pseudo-second order model. The adsorption
equilibrium data were fitted in the three adsorption isotherms, e.g. Freundlich
isotherm, Langmuir isotherm and Dubinin-Radushkevich isotherm. The adsorption
data fitted best to the Langmuir isotherm indicating the adsorption of metal ions and
dye on PSH could be described as a monolayer chemisorption proces. The activating
energy for the adsorption of metal ions and dye as calculated using from D-R
Isotherm was found to be more than 16kJ/mol which is particle diffusion. The
adsorption capacity of PSH was found to be comparable to that for other available
adsorbents as cited in literatures. From the study it is evident that as an adsorbent,
PSH has significant potential for usage in the separation of metal ions and dye from
waste water.