Adsorption Of Bisphenol A From Aqueous Solutions Onto New Magnetic Composite Organic Sepiolite

Bisphenol A is a representative environmental endocrine distuping chemicals that wide-ranging existing in water. The adsorption of bisphenol A onto new modified sepiolite was studied, which had practical and guiding significance on treatment of endocrine distuping chemicals in water.Magnetic composite organic sepiolite(MCOS), which could be used as a novel wastewater purifying functional material, was prepared by modifying the natural sepiolite via magnetic and organic treatment. The removal rate reached 86.41% and the equilibrium adsorption capacity achieved 25.92mg/g at 25℃ when the initial concentration of bisphenol A was 30mg/L, p H was 10, oscillation rate was 180r/min, dosage was 1g/L, equilibrium time was 90 min. A concentration of 0.1mol/L Na OH was used in regeneration for 2h, and the decolorization rate was 57.94% after regeneration. The pseudo-second order model could correlate well with the results of adsorption kinetics analysis. The intraparticle diffusion model suggested that BPA was transferred to the MCOS by intraparticle diffusion at the beginning of adsorption. The activation energy of adsorption was 11.7k J.mol-1, which indicated that the adsorption process assigned to a chemisorption. Freundlich isotherm adsorption equation could describe MCOS adsorption behavior of bisphenol A better than Langmuir isotherm adsorption equation, which showed that adsorbent surface was not homogeneous. Thermodynamic study showed that, ΔH =-1.70 k J·mol-1<0,ΔG<0,ΔS=3.93 J·mol-1·K-1>0, the whole adsorption process was a spontaneous exothermic process and the degree of freedom increased.Surface area analysis showed that the surface area decreased from 49.67m2/g to 18.55m2/g after magnetic composite organic modification. And isoelectric point analysis showed that the isoelectric point decreased from 9.70 to 9.10. MCOS exhibited apparent superparamagnetism with saturation magnetization of 14.1emu.g-1 and coercivity of 39.1Oe.The SEM, FT-IR, XRD and XPS results showed that CTMAB and Fe3O4 magnetic particles had been attached to the edges of sepiolite after magnetic composite organic modification. The modification and adsorption are conducted on the surface of sepiolite. The adsorption of bisphenol A onto MCOS was mainly dominated by ion exchange. Electrostatic attraction and partition effects also had an effect on the adsorption of bisphenol A onto MCOS.