Study Of Adsorption Behavior Of Pb²⁺ By Iron And Zinc Activated Carbon

With the rapid development of industrialization,lead-containing batteries,metal smelting,electroplating and other industries will produce a large amount of lead-containing wastewater,which will pollute the environment and cause great harm to human health directly or indirectly.Activated carbon adsorption is widely used in the treatment of heavy metal wastewater,but activated carbon prepared by conventional methods are not suitable for Pb²⁺removal from wastewater.In this paper,activated carbon were prepared using shaddock peel as raw material and Fe（NO₃）₃,Zn Cl₂and Fe Cl₃as activation agents,and a series of characterization were used to study the surface structure and surface chemical properties of activated carbon.The influence of each single factor on the removal rate of Pb²⁺was studied by changing the experimental conditions.The removal mechanism was preliminarily explored by adsorption isotherm model and kinetic model.The adsorption of Pb²⁺by different desorbents was investigated,and the cyclic adsorption performance of activated carbon was evaluated by adsorption-desorption experiments.The main results are concluded as follows:（1）The yield results show that when the total amount of activator is kept unchanged,the yield of activated carbon from high to low is:T-Z>AC>T-F>T-11>T-12.As the content increases,the yield of activated carbon gradually decreases,that is,the order of the yield is:Fe-F>Fe-F-11>Fe-F-12.However,when the zinc content is kept unchanged,as the iron content increases increased,the yield of activated carbon remained basically unchanged,indicating that the yield of activated carbon was mainly affected by the zinc content.（2）All activated carbon samples have strong thermal stability by thermogravimetric spectrum.N₂adsorption and SEM showed that the specific surface area and micropore volume become larger,and the average pore diameter becomes smaller.Through EDX,XRD and FTIR analysis,show that the surface of activated carbon samples contains oxides,resulting in the reduction of pore structure.According to Boehm titration and FTIR,the surface of iron loaded activated carbon contains a large number of acidic oxygen-containing functional groups,which is conducive to the adsorption of heavy metals.（3）The adsorption behavior of Pb²⁺was studied by changing the experimental conditions including dose,time,temperature and concentration,etc.The results showed that the equilibrium time of adsorption Pb²⁺by activated carbon was about 320 min,and the optimal adsorbent dose and initial concentration of Pb-containing solution were 25 mg and 10 mg/L,respectively.When the p H is neutral,the removal of Pb²⁺by all activated carbons reaches the maximum.The adsorption of Pb²⁺by activated carbon samples belongs to an endothermic process.With the increase of adsorption temperature,the removal efficiency of Pb²⁺gradually increases,which is conducive to the adsorption of Pb²⁺by activated carbon.（4）The adsorption isotherm modeling indicat that the adsorption process of Pb²⁺onto all activated carbon samples was well fitted with Freundlich model.The kinetic study of Pb²⁺adsorption by activated carbon shows that the pseudo-second-order model can better describe the kinetic process of Pb²⁺adsorption by activated carbon,whereas Elovich model can better describe the experimental data of Pb²⁺adsorption by AC,T-Z and T-12.（5）Through the adsorption-desorption cycle experiments,it is shown that as for three desorbents selected in experiment,the removal efficiency is in the order of:distilled water>Na Cl>HCl.With the increase of the number of adsorption desorption cycles,the content of iron loaded on the adsorbent decreases gradually,and the removal efficiency of Pb²⁺by the adsorbent also decreases gradually.Using distilled water as desorbing agent and Fe（NO₃）₃as activation agents,the removal efficiency of Pb²⁺by activated carbon sample at the third cycle can still more than 80%,indicating that iron loaded activated carbon had good adsorption ability.