Study of Cu2+, Zn2+ and Mn2+ ions adsorption using asphaltenes-chitosan composite beads

Algerian petroleum asphaltenes deposits were extracted, treated and modified in order to valorize it as adsorbent material. The treated asphaltenes deposit with chitosan biomaterial were used to prepare asphaltenes/chitosan composite beads with the aim of reducing the toxic Cu (II), Zn (II) and Mn (II) metals ions from aqueous solution. The adsorption studies of both asphaltenes and asphaltenes/chitosan composite beads were performed in a batch system, and the effects of various process parameters such as pH, adsorbent dosage, contact time, initial concentration of metal ions and temperature were considered. The results revealed that the novel composite had higher selectivity and uptake for adsorption of the metal ions than asphaltene. The maximal adsorption capacity of asphaltenes/chitosan composite beads regarding all metal ions was determined to be 60–80 mg.g−1 comparing to that of asphaltenes material (52–61 mg.g−1). It was also showed that the optimal adsorption pH values of Zn(II) and Mn(II) was 6.0 and that of Cu(II) was 5.0. The adsorption equilibrium data was well fitted with the Sips isotherm for both samples with all metal ions. The kinetic studies indicated that the adsorption process was best described by pseudo-second-order kinetics. The preliminary study of removal selectivity and competitive adsorption in multi-metal systems (binary and ternary mixtures) shows a weak antagonistic effect between ions and the adsorption capacity follows the order Cu (II) > Mn (II) > Zn (II). The temperature effect on the adsorption revealed an exothermic process and a decrease in adsorption capacity when the temperature of aqueous solution was increased. Characterization of chitosan, asphaltenes and composite asphaltenes/chitosan beads were carried out using Fourier Transform Infrared (FTIR), Thermogravimetric analysis (TGA) and Transmission Electron Microscope (TEM). Concentration of metal ions was determined using Atomic Absorption Spectroscopy (AAS). [Display omitted]