Investigation Of Sorption Of Contaminant From Aqueous Solutions On Mineral Materials

In this article, asbestos tailings, halloysite and illite were modified by physical and chemical treatments. These raw and modified materials were characterized detailedly by X-ray diffraction(XRD), infrared spectroscopy(FT-IR), vibrating sample magnetometer(VSM) and scanning electron microscopy(SEM). The sorption experiments were studied as function of adsorbent concentration, pH, ionic strength and temperature by using static experimental method. In addition, the kinetic model and the thermodynamics model were also studied. The results were as follows.(1) The sorption of Co(II), U(VI) and MB on acid leaching residue of asbestos tailings were strongly dependent on pH, ionic strength and temperature. When pH is low, the sorption mechanism of Co(II) were mainly ion exchange or surface complexation, and electrostatic sorption or surface complexation were the main sorption mechanism when pH is high. In the end, the sorption rate was in a larger and unchanged trend. At this stage, the main mechanism was probably the inner complexation. The sorption of U(VI) on acid leaching residue increased quickly with increasing pH when pH is less than 6 and the main sorption mechanism were ion exchange or outer complexation. However, the sorption of U(VI) decreased with increasing pH when pH is higher than 6.5, indicating that the main sorption mechanism was electrostatic interaction or outer complexation. Hydrogen bond between-OH on acid leaching residue surfaces and the nitrogen atom of the MB specie played the major role. When pH is less than 4.5, electrostatic interaction is weak. However, electrostatic interaction is higher in sorption performance when pH is higher than 4.5.(2) The sorption of Co(II), U(VI) and MB on acid leaching residue of asbestos tailings were better agreement with the Langmuir sorption isotherm model, indicating that the sorption process were monolayer sorption and spontaneous endothermic. In addition, high temperature was conductive to the sorption reaction.(3) The sorption of Co(II) on magnetic halloysite was mainly affected by pH.Under lower pH, the sorption mechanism was mainly ion exchange and surface complexation. At the same time, under higher pH, it could considered that the sorption mechanism was inner complexation reaction, because the sorption had nothing to dowith the pH value. All in all, the sorption of Co(II) on magnetic halloysite was a spontaneous endothermic process, and it conformed to the Langmuir sorption isotherm, indicating a monolayer sorption model.(4) The sorption of Co(II) on magnetic illite was mainly affected by pH. When pH is less than 8.8, the sorption rate of the Co(II) on magnetic illite increased gradually.And it reached the maximum when pH is 8.8, then a little lower. The possible mechanism of the sorption was as follows. When pH is between 3.5 and 6, the possible mechanism was ion exchange or surface complexation. When pH is between6 and 8, the possible sorption mechanism was electrostatic attraction or surface complexation. At the same time, the sorption of Co(II) on Fe3O4 was included. When pH is higher than 8.8, the sorption might still be depend on electrostatic attraction or surface complexation. However, the effects of the coprecipitation between compound particles and magnetic illite could result in the decrease of effective adsorbent.