Adsorption of copper (II) onto cameroonian clay modified by non-thermal plasma: Characterization, chemical equilibrium and thermodynamic studies

A cameroonian clay from Konhontsa'a (West Cameroon) has been treated in aqueous suspension by Non-thermal plasma (NTP) in order to modify its surface properties for a possible enhancement of effectiveness of heavy metals control in water by clays. FTIR spectroscopy, SEM-FEG analyses, X-ray diffraction and N2 physisorption analyses were used to evaluate the physico-chemical, textural and crystalline properties changes in clay before and after plasma exposure. Copper (II) ions were used as heavy metal model for adsorption studies. XRD, elementary and FTIR analyses indicated that the clay is a disordered Kaolinite. XRD analysis also showed that, plasma treatment improved the crystallinity of the clay as a result of elimination of impurities by plasma actives species. However, the sheet structure remains unchanged. Furthermore, FTIR analysis reports that, none new functional group except oxygen was bonded to the clay after plasma exposure. SEM-FEG and N2 physisorption analyses show that, the specific surface area and the volume of micropores decreased respectively from 98.40 to 35.43 m2·g− 1 and from 0.23 to 0.079 cm3·g− 1 by exposition to NTP. The adsorption capacity of Cu2 + by the clay decreased with plasma treatment but not significantly. The adsorption equilibrium was analyzed by Langmuir, Freundlich and Temkin models. Langmuir and Temkin models fit well the Cu2 + adsorption onto both samples. Adsorption of Cu2 + onto untreated and plasma treated clays was an exothermic process.