Removal of Organic Pollutants from Water by Improved Carbon Nanotubes

Organic pollutants soluble in water such as chlorine compounds, biphenyls and aldrins caused by dyes, detergents, herbicides and toxins cannot be removed in conventional purification processes such as filtration. Carbon nanotubes have a high ability to separate organic pollutants, but its slurry application is not desirable due to the need to remove them at the end of purification. In the present study, upgraded carbon nanotubes attached to particles of sand filters (CNTsand) were synthesized and used to remove organic pollutants. The capacity and efficiency of these nanotubes and the variables affecting it including pH, temperature, contact time and concentration were investigated. Also, reaction kinetics and adsorption isotherms were analyzed. The results showed that CNTsand has a high capacity to remove organic compounds. The data processing showed the pseudo-second order kinetic model for the elimination reaction and the Langmuir isotherm was the most consistent. The reaction enthalpy change equal to ΔH=11.02 kJ/mol and the free energy change from ΔG=-7.32 to -9.20 kJ/mol both indicate an endothermic and thermodynamically spontaneous reaction. Therefore, the adequacy and efficiency of the upgraded nanotube coating on sand grains in removing organic pollutants was confirmed.