Highly efficient removal of geosmin and 2-methylisoborneol by carboxylated multi-walled carbon nanotubes

Geosmin (GSM) and 2-methylisoborneol (2-MIB) have been identified as the major taste and odor-causing compounds in drinking water obtained from surface water. Carboxylated multi-walled carbon nanotubes (C-MWCNs) were developed for the highly efficient removal of GSM and 2-MIB from water owing to their unique large surface area, well-defined pore size, and high pore volume. Besides, the carboxyl group on the surface of C-MWCNs can improve the adsorption capacity of GSM and 2-MIB which each contain one hydroxyl group. Each adsorption of 200 cm(3) 1 mu g/dm(3) of GSM (or 2-MIB) onto 40 mg/dm(3) of C-MWCNs reached equilibrium within 120 min. This agreed well with the Langmuir adsorption model with maximum adsorption capacities of 23.56 and 23.52 mu g/g for GSM and 2-MIB. The adsorption rates of GSM and 2-MIB on C-MWCNs fit pseudo-second-order kinetic models (R (2) > 0.99), which suggest that the adsorption process could be a rate-limiting step. Thermodynamic studies illustrated that the adsorption process was endothermic and spontaneous. C-MWCNs are able to remove over 90 % of GSM and 2-MIB in 200 cm(3) of solution containing 1 mu g/dm(3) GSM (or 2-MIB) under optimized conditions.