The Adsorption Of Dyes And Fluoride In Water By Modified Magnetic Fe₃O₄/Chitosan

With the rapid development of modern industry, the pollutions ofwastewater containing dyes and high contents of fluorine become moreserious, causing great damage on ecological environment and human health.As a simple and efficient method, adsorption is used widely in the study andtreatment of environmental pollutions. Chitosan （CS）, which contains highcontents of amino and hydroxyl groups, is a natural polymer material withhigh adsorption capacity, however, its characters of easily dissolving in acidsolution and sensitivity to alkali limit its application as an adsorbent. Atpresent, magnetic Fe₃O₄particulates materials are widely used in thesynthesis of composite magnetic adsorbents, which combination withmodified chitosan is expected to develop a more economical and efficientnew type of water treatment agent.In this paper, the adsorption of C.I. Reactive Blue194（RB194）, C.I.Acid Red73（AR73） and fluoride ions by magnetic Fe₃O₄modified byhydrochloric acid and ultrasound, chitosan modified by AlCl₃and FeCl₃andchitosan modified by magnetic Fe₃O₄was mainly investigated. Meanwhile,several factors affecting the adsorption of RB194, AR73and fluoride ions bymodified adsorbents were studied, such as preparation conditions, adsorption time, pH value of the solution, initial concentrations of adsorbate, and so on.Furthermore, the kinetics and thermodynamics of the adsorption of RB194and AR73by modified magnetic Fe₃O₄and modified Al-chitosan-Fe werealso discussed, and subsequently we obtained the corresponding dynamic andthermodynamic models and their parameters. Finally, in order to increaseadsorbents regenerate capability, we selected appropriate desorption solventand regenerate method, and took sorption/desorption experiments on modifiedmagnetic Fe₃O₄and modified Al-chitosan-Fe.The results indicated that:1) Modification of magnetic Fe₃O₄by using10mmol/L HCl and ultrasonic treatment for90min could significantlyintensity its removal effect of RB194from water. The adsorption almostachieved balance after40min, and had a wilder applicable scope of pH thanthe original magnetic Fe₃O₄. What’s more, the pseudo-second-order kineticequation and Langmuir isotherm equation could suitably characterize theadsorption behavior of RB194by modified magnetic Fe₃O₄. After desorbedunder the ultrasonic treatment using0.1mol/L H2O2, the regenerate modifiedmagnetic Fe₃O₄’s adsorption ability of dyes almost remained unchanged.2)Prepared modified chitosan complex adsorbent, AlCl₃-CS-FeCl₃, couldobviously increase the adsorption ability of fluoride ions from water with aremoval rate of about90%for an initial concentration of10mg/L, and with aresidual content of fluoride ions less than1.0mg/L. When using a NaOHsolution to desorb and HCl to activate, the adsorbent regenerate adsorption capacity of fluoride ions had improved effectively. The adsorption of AR73by AlCl₃-CS-FeCl₃from water was rather swift, and its dynamic characterscould pretty conform to the pseudo-second-order equation.3) Various kindsof magnetic nano-particle adsorbents were prepared on the basis of severalcoating method. We also used some characterization methods such as SEM,TEM to observe the nano-particles’ surface structure properties, andcompared the adsorption effects of AR73and fluoride ions by diffidentnano-particle adsorbents.