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The as-grown CNTs and graphitized CNTs were used as adsorbents to remove 1,2-dichlorobenzene from water. The experiments demonstrate that it takes only 40 min for CNTs to attain equilibrium and the adsorption capacity of asgrown and graphitized CNTs is 30.8 and 28.7 mg/g, respectively, from a 20 mg/l solution. CNTs can be used as adsorbents in a wide pH range of 3-10. Thermodynamic calculations indicate that the adsorption reaction is spontaneous with a high affinity and the adsorption is an endothermic reaction.

Ceria nanoparticles supported on aligned carbon nanotubes (CeO 2 /ACNTs), a novel adsorbent for Cr(VI) from drinking water, were prepared by chemical reaction of CeCl 3 with NaOH in aligned carbon nanotube solution and subsequent heat treatment. The best Cr(VI) adsorption effect of CeO 2 /ACNTs occurs at a pH range of 3.0-7.4. The largest adsorption capacity of CeO 2 /ACNTs reaches 30.2 mg g À1 at an equilibrium Cr(VI) concentration of 35.3 mg l À1 at pH 7.0. The experiment results suggest that CeO 2 /ACNTs have great potential applications in environmental protection.

A novel adsorbent, ceria supported on carbon nanotubes (CeO 2 -CNTs), was developed for the removal of arsenate from water. The experiments show that CeO 2 -CNTs is an effective adsorbent for arsenate, and the adsorption is pH-dependent. Ca 2+ and Mg 2+ significantly enhanced its adsorption capacity, which suggests that it is a promising adsorbent for drinking water purification. Under natural pH conditions, an increase from 0 to 10 mg/L in the concentration of Ca 2+ and Mg 2+ results in an increase from 10 to 81.9 and 78.8 mg/g in the amount of As(V) adsorbed, respectively. The loaded adsorbent can be efficiently regenerated by diluted NaOH, and a regeneration efficiency of 94% was achieved using 0.1 mol/L NaOH. The adsorption mechanism was also suggested. D

Carbon nanotubes (CNTs), a novel kind of carbon, were first reported by Iijima in 1991 [1]. CNTs can be thought of as cylindrical hollow micro-crystals of graphite [2]. Because they have relatively large specific area, CNTs have attracted researchersÕ interest as a new type of adsorbent and offer an attractive option for the removal of organic and inorganic contaminants from water. Li et al. found that acid-refluxed CNTs can be good adsorbents for Pb 2+ and Cd 2+ [3,4]. Peng et al. reported that CNTs can also be used to remove organic pollutants from water [5].Because of their relatively large specific area, CNTs can also be used as supports for adsorption materials. Li et al. prepared amorphous Al 2 O 3 supported on carbon nanotubes (Al 2 O 3 /CNTs) and found that it has a much higher adsorption capacity of fluoride than c-Al 2 O 3 [6]. Our previous research has found that ceria nanoparticles supported on carbon nanotubes can be effective adsorbent for the removal of arsenate from water [7].In this work, a novel kind of magnetic composites based on CNTs was prepared and the obtained composites show good adsorption capacity for Pb(II) and Cu(II) from aqueous solution. CNTs-iron oxide magnetic composites can be used to adsorb contaminants from aqueous effluents and after the adsorption is carried out, the adsorbent can be separated from the medium by a magnetic process. The preparation of carbon-iron oxides magnetic adsorbent based on activated carbon has been reported in the literature [8]. But magnetic adsorbent based on CNTs has not been reported and is the topic of the present study.CNTs were prepared by catalytic pyrolysis of the propylene-hydrogen (C 3 H 6 :H 2 = 2:1) mixture at 750°C in a ceramic tube furnace using Ni particles as catalysts. The CNTs were then washed with deionized water and ground. The specific area of as-grown CNTs is 134.0 m 2 g À1 . For the preparation of CNTs-iron oxide magnetic composites, CNTs were first immersed in concentrated nitric acid and then hydrofluoric acid for 24 h each to dissolve the catalyst particles. Then they were oxidized by refluxing the as-prepared CNTs with 50% nitric acid at 140°C for 1 h. The magnetic composites were prepared from a suspension of 1.0 g oxidized CNTs in a 300 ml solution of 0.585 g FeCl 3 AE 6H 2 O and 0.390 g FeSO 4 AE 6H 2 O at 70°C under N 2 atmosphere. NaOH solution (18.7 ml, 0.5 mol l À1 ) was added dropwise to precipitate the iron oxides. After the addition of NaOH solution, the mixture was adjusted to pH 11.0 and stirred for 30 min. Then the mixture was aged at 70°C for 2 h and washed 3 times with deionized water. The obtained material were dried in an oven at 45°C and ground (particle size <0.075 mm).The magnetic composites were characterized by powder XRD using a D/max-RB X-ray diffractometer (CuKa, k = 1.540598 Å ) and SEM using a Hitachi model S-3000N scanning electron microscope. Magnetization measurements were carried out on a LDJ model 9600 vibrating sample magnetometer at room temperature.Batch adsorption experiments were perfor...

Carbon nanotubes (CNTs), a new type of carbon material, show exceptional adsorption capability and a high adsorption efficiency for the removal of chromium(VI) ions from water over a broad pH range extending from 4.0 to 7.5. The largest adsorption capacity for CNTs occurred at pH 7.5 and attained a value of 20.56 mg/g at an equilibrium Cr(VI) ion concentration of 33.28 mg/l. The adsorption rate of Cr(VI) ions was fast over the first 20 min with the adsorption capacity of the CNTs reaching 15 mg/g rapidly. The experimental results suggest that CNTs can be employed as good adsorbents for Cr(VI) ions and have great potential for applications in environmental protection.

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