Removal of chlorophenols from groundwater by chitosan sorption.

The equilibrium and kinetics of chlorophenol (CP) sorption by chitosan, poly D-glucosamine, were studied under simulated groundwater conditions. Lower temperature, from 25 degrees C to 15 degrees C and then 5 degrees C, markedly decreased the adsorption rates by a factor of 30-53% and 7-22%. Comparison between two types of chitosan, flakes and highly swollen beads, demonstrated that the maximum pentachlorophenol (PCP) uptake capacities in Langmuir and Freundlich models depend on the specific surface area of the particle. Low temperature (5 degrees C) significantly increased the PCP uptake capacity in comparison to higher temperatures (15 degrees C and 25 degrees C). PCP uptake capacity was halved at pH levels higher than 6.5, and NaCl concentrations greater than 1% blocked PCP sorption almost completely. Of five kinds of chlorophenols, i.e. 2,4,6-trichlorophenol (2,4,6-TCP), 3,4-dichlorophenol (3,4-DCP), 2,3-dichlorophenol (2,3-DCP), 2,6-dichlorophenol (2,6-DCP), 3-monochlorophenol (3-MCP), TCP had the maximum sorption efficiency on flake-type chitosan, followed by DCPs, and finally MCP (the three kinds of DCP, with the same elemental compositions, achieved similar sorption performances).