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The adsorption capacities of new humic acids isolated from Yakouren forest (YHA) and Sahara (Tamenrasset:THA) soils (Algeria) and commercial humic acid (PFHA) on polyaniline emeraldine base (PEB) were studied at pH 6.6.Also the adsorption of heavy metals such as Cd2+,Zn2+ and Ni2+ on humic acid-polyaniline systems (HA-PEB) was investigated at the same conditions.HA-PEB compounds were characterized by scanning electron microscopy (SEM),infrared spectrometry and cavity microelectrode.In addition,batch adsorption and cavity microelectrode were used in the adsorption study of Cd2+,Zn2+ and Ni2+ on HA-PEB.To develop biocaptors of polluting metals using a cavity microelectrode modified by HA-PEB systems,the adsorption kinetic and adsorption capacity were investigated.The SEM analysis showed that the presence of humic acid affected the PEB surface and caused the formation of a granular morphology.The maximum adsorption capacities (qmax) of PFHA,THA and YHA determined by adsorption isotherms were 91.31,132.1 and 151.0 mg/g,respectively.Batch adsorption results showed that qmax of Cd2+,Zn2+ and Ni2+ on HA-PEB followed the order:THA-PEB 〉 YHA-PEB 〉 PFHA-PEB.The voltammograms obtained with HA-PEB modified cavity microelectrode showed the appearance of new redox couples reflecting the adsorption of HA on PEB.Metal-humic acid-polyaniline voltammograms were characterized by appearance of oxidation-reduction couples or reduction wave corresponding to metal.Finally,the result may be exploited to develop a biocaptor based on the cavity microelectrode amended by THA-PEB and YHA-PEB.