Studies of Chitosan at Different pH’s in the Removal of Common Chlorinated Organics from Wastewater

This work explores the use of chitosan as an adsorbent of common chlorinated organics in waste water, namely 4-chlorophenol and tetrachloroethylene. We use both isothermal adsorption equilibrium and dynamic adsorption experiments to describe the phenomena of adsorption at pH 4, 5, 6, 7 and 9. Results show that 4-chlorophenol is adsorbed the greatest at pH 6 while tetrachloroethylene is adsorbed the greatest at pH 4. The Langmuir constant b values range from 0.00003 to 0.00012 and 0.00001 to 0.00007 for 4-chlorophenol and tetrachloroethylene, respectively, and overall it appeared that the binding energy of 4-chlorophenol to chitosan is higher than that of tetrachloroethylene. Dynamic adsorption experiments show that the adsorption of 4-chlorophenol on chitosan follows a second order process while tetrachloroethylene follows a first order process, where the external mass transport coefficient of 4-chlorophenol and tetrachloroethylene ranged from 0.081 - 0.755 and 0.009 - 0.285, respectively. Additionally, the internal pore diffusion rate of 4-chlorophenol inside the micropores of chitosan is shown to be approximately 2.5 times that of tetrachloroethylene.