Adsorption Of Heavy Metal Ions On Modified Bagasse Fixed-bed Column

Adsorption method has been widely used in heavy metal adsorption studies for itsreadily available, low processing cost, non-toxic, small secondary pollution and easilybiodegradable. However, unmodified adsorbents were poor in adsorption capacity ofheavy metal ions and wastewater treatment. In order to improve the adsorption efficiency,scholars have done a lot of research and some modified adsorbents were prepared.Research on the static adsorption of heavy metal ions were much more than dynamicadsorption. Few studies on the behavior and mechanism of competitive adsorption ofheavy metal ions in multicomponent system was done. Based on the above, thepyromellitic dianhydride modified bagasses were successfully prepared through a simplemethod. The bagasses before and after modification were characterized by infraredspectrophotometric and scanning electron microscope(SEM). The modified bagasseswere successfully used as adsorbents for heavy metal ions removal in a fixed bed toinvestigate the behavior and mechanism of dynamic adsorption. The effect of the initialconcentration, filler particle size and flow rate on the adsorption of heavy metal ionsunder continuous model in one component system was investigated. Adsorption modelswere used to fitted the breakthrough curves. Furthermore, the reuse ability of the fixedbed was studied. Dynamic competitive adsorption behavior of Pb（II）、Cd（II）、Cu（II）、Zn（II） was also investigated, and the adsorption mechanism was discussed. The resultsare as follows.(1) SEM results showed that the morphology of the modified bagasse basicallyunchanged. Infrared spectrum analysis showed that a number of carboxyl wasintroduced to the surface of modified bagasses. The surface-active functional groupsof the bagasse were significantly increased after modified.(2) The dynamic adsorption of heavy metal ions in a single system showed that theadsorption capacity of Cd（II） on modified bagasse fixed-bed column was121mg/g,which was53.2mg/g on unmodified bagasse fixed-bed column. The adsorptioncapacity was significantly enhanced after modified. The dynamic adsorption capacity of heavy metal ions at different flow rates was121mg/g~113.8mg/g forCd(II) and121.2mg/g~127.6mg/g for Pb(II). The dynamic adsorption capacity atdifferent particle size was124mg/g~142mg/g for Cd(II) and127.6mg/g~148.6mg/g for Pb(II). The dynamic adsorption capacity at different initial concentrationwas103.2mg/g~125mg/g for Cd(II) and115mg/g~139.8mg/g for Pb(II). Theadsorption capacity was still good after repeated for3times. Results showed thatparticle size, initial concentration and flow rate had little effects on the adsorption ofheavy metal ions, and the fixed bed could used repeatedly under wide experimentalconditions.(3) Competitive adsorption results in the binary system showed that the acidity had greatimpact on the adsorption. The greater acidity, the smaller the adsorption capacity.The acidity had adverse effect on the adsorption of heavy metal ions. The pHexperiment demonstrated that adsorption of the metal ions was accompanied by therelease of H+.Competitive replacement existed in the adsorption process. Themodified bagasse had higher affinity toward Pb(II) than Cu(II) and Zn(II). Pb/Cu，Pb/Zn and Cu/Cd can be selectively separated from binary system. The researchprovided a new method for the separation and concentration of heavy metal ions.