Removal of metallic trace elements (Pb2+, Cd2+, Cu2+, and Ni2+) from aqueous solution by adsorption onto cerium oxide modified activated carbon.

The equilibrium and kinetic studies of removal of Pb2+, Cd2+, Ni2+, and Cu2+ metal ions were carried out using activated carbon prepared from palm kernel shell and doped with CeO2 (Ce/AC). The obtained material carbon was characterized by XRD which showed some crystalline traces of CeO2, SEM displaying the porous texture with spherical pores and the determination of pH of point of zero charge (pHPZC) which was found to be equal to 6. The contact time and adsorbate were thoroughly investigated. The maximum adsorption depends inversely on the hydrated metal radius. This observation was confirmed by calculating the formation energies (ΔH(M(OH)2)) of M(OH)2. The metal ionic radii were acting on calculated sorption capacity and that sorption efficiency related to ionic radii of metal was as follows: R(Ni2+) ≤ R(Cd2+) < R(Cu2+) < R(Pb2+). The texture and morphology of the material after sorption were affected by the metallic ion nature as observed by SEM. The kinetic studies showed that the rate constant (k2) of pseudo-second-order model decreased with the increase of the hydrated cations radii, while the rate constant of intraparticle diffusion increased with the increase of the ionic radii. The Freundlich isotherm model best fit the experimental sorption data for all the metallic ions.

Characterization of Akilbenza clay from Cameroon and its performance for the removal of copper(II) ions from aqueous solution.

Akilbenza clay (Akil) was characterized by XRD, FT-TIR, XRF, EDX, SEM, and N2 gas adsorption. The adsorption performance for Cu(II) ions by this clay was also studied. Akil is composed mainly of kaolinite with mica illite and quartz as minor minerals. The ATR-FTIR analysis shows Si-O-Al, Si-O, Al-O, Si-OH, and Al-OH as the main functional groups. SEM indicates that the clay particles are irregular in shape and size by supported BJH. Akil has a specific surface area of 45.62 m2/g with the presence of both mesopores and micropores. The average pore diameter is 19.4196 nm. XRF and EDX reveal that the clay is mainly composed of silica, aluminum, and iron with a Si/Al ratio of 1.41. For the adsorption performance of Cu(II) ions, a maximum quantity of 76 mg/g was recorded. Freundlich isotherm models best describe the adsorption processes at equilibrium. Kinetic studies revealed that the adsorption process was well explained with pseudo-second-order kinetic model. The value of the mean energy of adsorption from Temkin isotherm and the values from Elovich kinetic model suggest that the adsorption of Copper(II) ions on Akil is a combination between ion exchange and electrostatic attraction. The results obtained can be introduced into the database of knowledge on clay minerals with emphasis on their use for the removal of Cu(II) ions.