ADSORBENTS FOR CD REMOVAL FROM WATER WASTE: A SHORT REVIEW OF THE RECENT DEVELOPMENT - Management of Hazardous Residues Containing Cd - page 6

The olive tree leaves (Olea europaea) are proposed as a new and low-cost
non-conventional sorbents for the removal of cadmium from aqueous
solutions. The olive tree leaves were processed with and without ultrasound
under stirring [35]. The sorption was significantly increased in the presence of
ultrasound. Langmuir simulation showed that the monolayer sorption
capacities of olive leaves for the conventional, ultrasound-assisted and
combined method were 42.19, 55.87 and 64.94 mg g -1 , respectively.
Chemically modified olive stones were investigated for the Cd 2+ removal
by Aziz et al. [36]. The olive stones were prepared with concentrated sulfuric
acid at room temperature, with a posterior neutralization with a 0.1M NaOH
aqueous solution. The maximum adsorption capacity was found to be 128.2
mg g -1 and the equilibrium was reached in less than 15 min. It was found that
the cadmium adsorption mechanism is described by an ion exchange process.
Later, Aziz et al. reported that the chemical functionality of olive stone with
succinate linkers can improve the performance of wastewater treatment
stations. This improvement is related to the high affinity of the covalently
attached succinate groups for heavy metals [37].
Kaikake et al. [38] examined the feasibility of using dripped and
degreased coffee beans (DCB) as adsorbent for Cd 2+ . The DBC contains sulfur
and small amounts of cadmium in this macroporous structure. They obtained a
Cd 2+ adsorption capacity of 7 mg g -1 and a Cd 2+ desorbability of about 90%
using HCl or HNO 3 treatments.
Çay et al. [39] evaluated the Cd 2+ adsorption using tea-industry waste. The
decolorized and sieved tea waste exhibits very good adsorption for Cd 2+ in
synthetic wastewater at pH 5.5 and room temperature. The maximum
adsorption capacity of Cd 2+ per gram of tea waste was 11 . 29 mg.
The biosorption behavior of a solid waste from the manufacture of
Chinese herb Pang Da Hai was studied as an adsorbent of cadmium traces by
Liu at al. [40]. The maximum adsorption capacity was 17.5 mg g -1 .
Petiolar felt-sheath of palm (PFP) is a waste material from palm trees.
Iqbal et al. investigated PFP as a new adsorbent material for removing heavy
metals from the contaminated water [41]. PFP efficiently removed the metallic
ions, in which the selectivity increased in the following order:
Pb(II)>Cd(II)>Cu(II)>Zn(II)>Ni(II)>Cr(III). The uptake was fast and it took
about 15 min to uptake more than 70%. Among other advantages, the most
significant ones are the heavy metal desorption ability from the metal-laden
biosorbent and the reuse in repeated cycles of adsorption-desorption process.
A typical lignocellulosic agricultural residue is the tobacco dust. Qi and
Aldrich investigated the tobacco dust efficiency on the heavy metal removal