重金属水处理

1、Heavy metal removal from aqueous solution by advanced carbon nanotubes(CNTs)Introduction1Mechanism2Factors3Carbon nanotube toxicity4Challenges and further research5Main ContentsIntroduction The main sources of heavy metals are the wastewaters from modern chemical industries such as metal plating fac

2、ilities, battery manufacturing, fertilizer, mining, paper and pesticides, metallurgical, fossil fuel, tannery and production of different plastics such as polyvinyl chloride.Introduction The possible symptoms of the toxic metals includes high blood pressure, speech disorders, fatigue, sleep disabili

3、ties, aggressive behavior, poor concentration, irritability, mood swings, depression, increased allergic reactions, autoimmune diseases, vascular occlusion, and memory lossIntroduction Available techniques for the removal of heavy metals from water : oxidation reduction, bioremediation, reverse osmo

4、sis, electrochemical treatment, coagulation, lime softening, precipitation, membrane filtration, ion exchange and adsorptionIntroduction All these methods have their own capabilities and limitations. Adsorption is proven to be economical and effective method for the removal of a number of contaminat

5、es from water. In recent years, CNTs have been employed extensively as a new adsorbent for the removal of a number of heavy metals from waterIntroduction Advantage: large surface area, light mass density, high porous and hallow structure, and strong interaction between the pollutant molecules and CN

6、Ts Adsorption properties of CNTs depend on their purity，porosity, surface functional groups, surface area, site density and type of CNTs (open ended or closed ended).MechanismSchematic diagram of the major mechanism for sorption of divalent metal ions onto CNT surfaceFactors affecting the adsorption

7、 of heavy metal ions on CNTs The main factors affecting adsorption of heavy metal ions on CNTs surface include the initial metal ion concentration, pH, contact time, CNT dosage, agitation speed, temperature, surface charge, ionic strength, isoelectric point and foreign ions.Factors affecting the ads

8、orption of heavy metal ions on CNTs 1、PHpH plays a vital role in the adsorption of heavy metal ions onto the CNTs surface. At pH value higher than point of zero charge (pHPZC), the adsorption of cations is higher due to electrostatic interactions between the cation ions and negative surface charge.

9、On the other hand, the adsorption of cation ions is lower at low pH due to neutralization of surface chargeFactors affecting the adsorption of heavy metal ions on CNTs 1、PHFactors affecting the adsorption of heavy metal ions on CNTs 2、Ionic strengthGenerally, increasing the ionic strength has an adv

10、erse effect on the sorption of heavy metals.：The ionic strength affects the activity coefficients of metal ions and hence the transfer of ions to CNTs surface is limited. : The formation of electrical double layer complexes between the cations and the CNTs limit the adsorption at high concentration

11、of ions Factors affecting the adsorption of heavy metal ions on CNTs 3、Dosage of CNTsIncreasing in CNTs dosage can either increase or decrease the sorption of heavy metals.Effect of adsorbent dose on Cd(II) ion removal capacityFactors affecting the adsorption of heavy metal ions on CNTs 4、Contact ti

12、meGenerally, with increase in contact time, the removal percentage of heavy metals increases until equilibrium is established. The effect of contact time on the adsorption of Pb2+ ions by different types of MWCNTsFactors affecting the adsorption of heavy metal ions on CNTs 5、TemperatureThe most comm

13、on observation is the increase in sorption capacity with rise in temperature. For example, sorption of Pb2+ and Zn2+and is endothermic process and increases with rise in temperature. This might be due to faster diffusion of metal ions through the solution due to decrease in solution viscosity at hig

14、h temperature. Factors affecting the adsorption of heavy metal ions on CNTs 5、Temperature.Effect of temperature on the sorption rate of Zn2+ by CNTsCarbon nanotube toxicity Release of CNTs into the environment can lead to serious environmental problems： ：The nano sized carbon particles pose an occup

15、ational inhalation exposure hazard if entered in the working environment as suspended particulate matter (PM) ：In water treatment plant, there is a risk that the CNTs might leach after certain cycles and can harm the treatment plant Carbon nanotube toxicity ：CNTs, not only, can disrupt the metabolic

16、 functions of microbes in the treatment plant but can also affect the aquatic life if enters to the environment ： CNTs have been observed to induce lung cellular proliferation and pulmonary inflammation in rats Challenges and Need for further research ： The researchers should focus on the large scale e