Comparisons of Adsorbent Cost for the Removal of Zinc (II) from Aqueous Solution by Carbon Nanotubes and Activated Carbon

The reversibility of Zn²⁺ sorption onto single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and powdered activated carbon (PAC) was investigated to evaluate their repeated availability performance in water treatment. Under the same conditions, the Zn²⁺ sorption capacity of SWCNTs and MWCNTs was more than that of PAC and could be maintained after several cycles of water treatment and regeneration. A statistical analysis on the replacement cost of these adsorbents based on the best-fit regression of the measured equilibrium capacity of each water treatment cycle was also conducted. The results revealed that the SWCNTs and MWCNTs could be reused through a large number of water treatment cycles and thus appear cost-effective in spite of their high unit cost at the present time.