TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method further comprises centrifugation after removing the complex. The centrifugation is carried out at a speed of 5000-30000 revolutions per minute for 1-20 hours. In the method, the promoter is employed. The coordinating step includes: converting the metal elements present in the catalyst and/or optional promoter into ions; and coordinating the ions with substance capable of forming a complex with the metal elements present in the catalyst and/or optional promoter to produce a complex. The converting of the metal elements includes oxidizing the catalyst and/or optional promoter to produce their oxides. The corresponding metal ions are obtained from the oxide by using the substance capable of forming a complex with the metal elements present in the catalyst and/or optionally promoter, and are coordinated with the substance to produce a complex. The step of removing the complex includes converting the complex into a salt form and removing the complex in the salt form. The converting of the metal elements further comprises reacting the oxides with an acid to produce ions of the metal elements present in the catalyst and/or the optional promoter. The oxidizing of the catalyst comprises oxidizing the catalyst and/or optionally the promoter with an oxygen containing gas. The oxidation time and the oxidation temperature of the oxygen containing gas are sufficient to convert the catalyst and/or the optional promoter into oxides. The oxidation temperature is 80-300 degrees C. The oxidation time is 1-20 hours. Preferred Components: The promoter is iron(II) sulfide. The catalyst is lanthanum metal oxide, transition metal, the mixture of nickel or a rare earth element. The catalyst is yttrium-nickel alloy, iron-nickel alloy, iron-cobalt alloy, cobalt-nickel alloy, rhodium-platinum alloy, or cerium-nickel alloy. The oxygen containing gas is air.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The substance capable of forming a complex with the metal elements present in the catalyst and/or optionally promoter is aminopolycarboxylic acids. The aminopolycarboxylic acid is triethylenetetraaminehexaacetic acid (preferred), EDTA, trans-1,2-diaminocyclohexane-N,N,N',N'-tetracetic acid hydrate (CYDTA) or diethylenetriaminepentaacetic acid (DTPA). The substance capable of forming a complex with the metal elements present in the catalyst and/or optionally the promoter comprising tetrahydrofuran, trialkyl phosphine, epsilon -caprolactone, epsilon -caprolactam, dimethyl formamide and dimethyl sulfoxide. The complex is of formula ((M((NC)2CC(OCH2CH2OH)C(CN)2)2(4,4'-bpy)(H2O)2)), (dinuclear ((M1(phenyl)2)2V4O12)C6H12O.H2O) or ((Ni(L)(H2O)3)2H2O).M = Ni, Fe or Co;M1 = Ni or Co;bpy = bipyridine; andL = (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl)-acetic acid. EXAMPLE - A hole 4 mm in diameter and 80 mm in length was drilled in one end of an anode graphite rod, which was filled with a powder mixture of high purity graphite powders, yttrium-nickel alloy powder as metal catalyst and iron sulfide powder as promoter in which the mole ratio of carbon and the catalyst was 15:1, the weight ratio of the catalyst and the promoter was 10:1. Then the powders filled in the hole were compacted. The cathode was fixed on a water-cooled copper base. The arc furnace was vacuumized to 3 Pa, then the vacuum valve was closed, and helium gas was filled to reach 0.07 MPa. After the power supply was connected, the current and the voltage were controlled at 80-120 Angstrom and 20-25V, respectively, and the distance between two electrodes was maintained 3 mm by manually adjusting the cathode, so that a stably arc-discharge was provided. The three parts of the samples were collected: cloth-like soot, which adhere on the wall of chamber, web-like soot, which hang between the wall of the chamber and cathode, and collar-like soot, which adhere on one end of the cathode. Among those three parts, the purity of the web-like soot is highest, that of the cloth-like soot is lowest, and that of the collar-like soot is between them. Firstly, the pristine samples (each 10 mg) were annealed at 200 degrees C using an air flow of 20 ml/minute for 10 hours. The samples as annealed were dispersed in deionized water and ultrasonic treatment for 30 minutes 0.5M EDTA aqueous solution was prepared and then added into the carbon nanotube dispersion. After the mixture was refluxed in 110 degrees C for 18 hours, pH value was adjusted to 8 by using 1M sodium hydroxide solution. Subsequently the dispersion was filtrated with porous polytetrafluoroethylene filter (0.5 mu m) and rinsed by hot water for many times. Then the samples were dispersed in o-dichlorobenzene and centrifuged at 15000 revolutions per minute for 3 hours. The supernatant was decanted and collected via filtration with a mixed cellulose ester (MCE) membrane filter. Finally the obtained product was purified carbon nanotubes.