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The objective of this research was to study the efficiency of Multi-Walled Carbon Nanotubes (MWCNTs) for the adsorption of hydrophobic natural organic matter (NOM) from aqueous solution under different operational conditions of contact time, pH, initial concentration of NOM and temperature. MWCNTs were synthesized via chemical vapor deposition (CVD) with average diameter of 10–50 nm. The results illustrated that both as-prepared and functionalized MWCNTs showed high adsorption capacity for the NOM studied. Functionalization of MWCNT affected the surface area and introduced oxygen-containing functional groups to the surface of MWCNT which depressed the adsorption of NOM onto MWCNTs-COOH. The obtained data were studied using Freundlich, Langmuir and BET isotherms; NOM adsorption data had the best conformity to the Freundlich isotherm. Kinetic studies were performed and the adsorption kinetics successfully followed the pseudo-second-order kinetic model. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were determined and evaluation of them showed that the adsorption process for NOM is general spontaneous, endothermic and thermodynamically favorable.

In the present study, continuous adsorption experiments were carried out in an adsorption column to survey the efficiency of the carbon nanotubes (CNTs) for removal of natural organic matters (NOMs) from aqueous solution. Parameters such as mass of CNTs, initial NOMs concentration were evaluated and also the breakthrough curves were obtained. Experiments performed with various initial NOMs concentration and various CNTs masses. The breakthrough period was longer at lower initial NOMs concentration. Increase of the initial NOMs concentration, expectedly, resulted in the faster saturation of the CNTs bed. The adsorption capacities for multi wall carbon nanotubes (MWCNT) and single wall carbon nanotubes (SWCNT) in highest initial NOMs concentration were 53.46 and 66.24 mg/g, respectively. The effect of amount of CNTs on breakthrough time and volume of treated water was investigated and resulted that with an increase in the mass of CNTs, breakthrough time occurs very late and the volume of treated water increased. These findings suggested that CNTs present a great potential in removal of NOMs from aqueous solutions.

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