Adsorption Of Cu(Ⅱ) And Methylene Blue By Synthesized Magnetic Multi-walled Carbon Nanotubes

In reality, the combined pollution of organic compounds and heavy metals is so widespread that it has become the most important source of environmental pollution. The composition of industrial wastewater is complex,Cu(Ⅱ) and methylene blue often coexist in wastewater and theco-pollutants are usually removed by adsorption method. Owing to large specific surface areas and unique structures, carbon nanotubes have attracted increasing attention of researchers for removal of both organic compounds and heavy metals. However, the conventional adsorbents were suffered from separation inconvenience after wastewater treatment. Not only a waste of resources but also the environmental risk of carbon nanotubes should also be concerned. In recent years, as a physical processing technology, magnetic separation technology, shows efficient, fast, economic and other advantages in water treatment.In this study, the carbon nano-materials was given the magnetism to form magnetic carbon nanomaterials. Magnetic multi-walled carbon nanotubes (MMWCNT) were synthesized by chemical co-precipitation method and were used as adsorbents for adsorption of Methylene (MB) and Cu(Ⅱ) in both single and binary system. The scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area, X-ray photoelectron spectroscopy (XPS) and zeta potential measurement were used to characterize the adsorbent. Adsorption kinetics, isotherms, and the effects of pH on adsorption were also discussed. In addition, the performance of MMWCNT to treat MB and Cu(Ⅱ) in real water samples (river water) of MMWCNT were studied. Furthermore, an intensive study was conducted to investigate the reusability and recovery of MMWCNT adsorbents and the competitive adsorption between MB and Cu(Ⅱ).The results indicated that iron oxides were successfully loaded on the surface of multi-walled carbon nanotubes to produce MMWCNT and it could be separated from aqueous solutions using a magnet easily; The specific surface area (SSA) of MMWCNT was 139.86 m2/g; The isoelectric point of MMWCNT was about 5.3; In single system,4 h was required to reach equilibrium for both MB and Cu(Ⅱ) adsorbed on MMWCNT and the sorption processes coincided with pseudo-second-order kinetic model. The sorption isotherm fitted with Langmuir model and the maximum adsorption was 46.03 mg/g and 27.74 mg/g for MB and Cu(Ⅱ), respectively. The pH value played an important role in adsorption efficiency. After five cycles,the adsorption capacities of MMWCNT was decreased from 23.5 to 17.6 mg/g and from 45.5 to 34.2mg/g for Cu(Ⅱ) and MB,respectively. Well adsorption behavior of MMWCNT remained after desorption cycles, indicating that MMWCNT has the potential in the application of wastewater treatment. Compared with Cu(Ⅱ), MB favored to be adsorbed onto MMWCNT in competitive adsorption process. In the simultaneous adsorption,MB had a strong suppression effect on Cu(Ⅱ) uptake. After the adsorption equilibrium for MB, the adsorption efficiency of Cu(Ⅱ) increased from 11 to 73% with the increase of MMWCNT dosage.