Kinetic And Thermodynamic Studies On The Adsorption Of Heavy Metal Ions Onto Chitosan-aluminium Oxide Composite Material

With the development of modern industry, the emissions of waste water containing heavy metals is more and more bigger and is also more complex, which environmental protection workers get more attention about the treatment of waste water containing heavy metals. In the study of treatment of this kind of waste water, we reached a consensus:characteristics of effective treatment should be highly efficient, convenient, without secondary pollution. The ways to removal of heavy metal ions in industrial water which have chemical precipitation, electrolysis-coagulation, adsorption and so on, especially adsorption is more interesting.Chitosan is a crude macromolecular compound, the active functional groups(-NH2,-OH) in chitosan's molecular formula can chelated heavy metal ions, so, chitosan can used as a macromolecular sorbent to remove heavy ions. Furthermore, chitosan is avirulent and it would not bring secondary contamination, moreover, chitosan can disassemble by biologic catabolism. However, chitosan dissolve into water causing the loss of adsorbent because of-NH2 becoming into-NH3+when chitosan adsorbed metal ions in the acidic environment; secondly, the presence of hydrogen bonds by chitosan molecular chain and molecular chain between the internals will affect the adsorption capacity; again, mechanical strength, thermal stability and chemical stability of chitosan also need to be improved. To improve the performance of chitosan, the means of modification are often crosslinking, derivatization, blending with other polymers or inorganic. However, these methods are or only one aspect of the performance of local improvement, or the existence of mixed uneven, or the existence of defects of strictoperation and costly price, which affect their practical application.AI2O3 and other inorganic compounds are rich in hydroxyl on their surface, which can also be used as adsorbent for heavy metal ions in wastewater treatment, but they are brittleness, easy inactivation in aqueous solution, not easy to settlement, difficult recovery and reuse, so their application is limited.Organic polymer/inorganic composite material has advantages of both polymers and inorganic substances. In this paper, we used aluminum compounds with nature of Lewis acid, the hydroxyl and amino of chitosan with the nature of Lewis base, used aluminum isopropoxide as the raw material, which the metal oxide were introduced in the chitosan molecular chain units using chemical bonding method and prepared chitosan-aluminum oxide composite materials. It was found that it was good at adsorption of the metal ions. This paper studied the adsorption of Ni2+, Co2+, Zn2+in aqueous solution onto chitosan-aluminium oxide composite material and the influence of physical and chemical parameters such as pH value, reaction time and temperature and initial concentration on the adsorption process. It determined the optimal adsorption conditions. Kinetics and thermodynamics of the adsorption of Ni2+, Co2+, Zn2+onto chitosan-aluminium oxide composite material was studied and we got the kinetics and thermodynamics equation, Ea and the thermodynamics constant.