Studies On The Adsorption Properties Of Heavy Metals By Eggshell And Orange Peel And Different Adsorption Processes

In view of heavy metal pollution and the secondary utilization of agricultural wastes,this paper prepared adsorbents from eggshells and orange peel,and used three adsorption processes to remove lead,cadmium and copper from wastewater.The maximum adsorption capacity of eggshell for lead,cadmium and copper were 149.3mg/g,31.79 mg/g and 17.90 mg/g,respectively.The adsorption process was in accordance with the pseudo second-order kinetic model and Langmuir isotherm.The maximum adsorption capacity of orange peel for lead,cadmium and copper were 139.5 mg/g,33.94mg/g and 33.11 mg/g,respectively.The adsorption process was in accordance with the pseudo second-order kinetic model and Freundlich isotherm.All adsorption reactions are spontaneous and endothermic.In the binary system composed of lead cadmium,lead copper and cadmium copper,the adsorption of each component on eggshell and orange peel conforms to the multicomponent E-Langmuir and E-Freundlich adsorption isotherm models respectively.The adsorption capacity decreased with the increase of the concentration of competing components.Cadmium and lead inhibited each other greatly.When eggshell was used as adsorbent,copper was more inhibited by lead,while orange peel was more susceptible to cadmium.In the ternary system of lead cadmium copper,multicomponent isothermal adsorption can not describe the adsorption process of each component.Lead and copper are greatly inhibited by cadmium.When the eggshell is used as the adsorbent,the inhibition of copper to cadmium is great,while the orange peel is used as the adsorbent,the inhibition of lead to cadmium is obvious.The effects of adsorbents on heavy metals treatment were studied by traditional adsorption,enhanced adsorption,and alternative staged adsorption processes.The theoretical models of enhanced adsorption process and alternative staged adsorption process were established and used to calculate the effluent concentration.At the same time,experiments were carried out to verify the accuracy of the model and the removal rate of heavy metals under different processes.The results showed that the removal rate of heavy metals by adsorbents increased in turn.Using eggshell and orange peel as adsorbents,the average removal rate of lead by traditional adsorption process is 89.7 % and 68.7 %,respectively;using enhanced adsorption process can increase 0.9 % and 4.8 %;and using alternative staged adsorption process can increase 3.1 % and 4.9 %.For cadmium,the average removal rate of the traditional adsorption process is 79.4 % and 61.8 % respectively;the enhanced adsorption process can increase the value by 5.2 % and 13.8 %;and the alternative staged adsorption process can increase the value by 5.3 % and 20.8 %.For copper,the average removal rate of traditional adsorption process is 82.3 % and 37.6 %;the value can be increased by 6.5 % and8.0 % by enhanced adsorption process;the value can be increased by 7.1 % and 19.0 % by alternative staged adsorption process.