Removal Of Cadmium From Soil By Adsorption

The heavy metal pollution in China's soil is very serious,and the current status of cadmium pollution is not optimistic.At present,there are certain limitations in the methods of soil heavy metal pollution restoration.Adsorption is a common and effective way to treat heavy metal cadmium.There are many researches on cadmium adsorption materials,but most of them are in powder state,which is difficult to recycle in practical applications.Therefore,it is necessary to prepare a soil adsorbent with good adsorption performance and high mechanical strength.In this paper,two kinds of adsorbents,coagulated adsorbent and sintered adsorbent,were prepared from natural zeolite powder and their surface modification was carried out.Zeolite concrete and zeolite charcoal were selected as the research objects according to the removal effect and mechanical strength of different adsorbents in solution.In order to explore the removal mechanism of adsorbents,and considering the uncontrollability of soil experiments,static adsorption experiments were carried out in solution.The effects of different time,pH,temperature,initial cadmium concentration and metal ions on the removal efficiency were studied.Finally,the prepared materials were applied in soil to explore the actual removal effect of cadmium.The existing materials cannot simultaneously ensure the removal efficiency and mechanical strength,and the total removal effect of the prepared solidified material and the fired type material is relatively good,and the removal effect of the fired adsorbent under the anaerobic condition is above 80%.The effect of removal after amino functionalization has not been greatly enhanced.Static adsorption experiments show that?1?the solidification adsorbent is stable around 9 d,and the total removal rate is basically unchanged with the increase of pH,while the adsorption removal rate is reduced.The adsorption process is more in line with the quasi-secondary kinetic equation.The initial concentration and temperature together affect the entire removal process.Common metal cations have different effects on the removal efficiency of the adsorbent,while high concentration metal ions will greatly reduce the removal rate of cadmium,but the removal rate.is still 18%The adsorbent still has a high removal effect after 3 cycles of using.According to the relevant experimental analysis,it is known that the removal of cadmium by the solidified adsorbent during the adsorption process is related to Ca²⁺and Mg²⁺.?2?The optimal pH value of the removal process of Cd²⁺from zeolite charcoal is 5.5⁶.8,which is stable around 10 d,and the adsorption process satisfies the quasi-second-order kinetic equation.With the increase of the initial concentration,the total removal rate of cadmium first increased and then decreased,and the change of precipitation removal rate was not significant.When the initial concentration is lower,the total removal rate and adsorption removal rate increase slightly with increasing temperature;when the initial concentration is higher,the removal rate is maximum at 30°C.In addition,Ca²⁺and Mg²⁺in the solution will affect the removal effect,and high concentration of metal ions will greatly reduce the removal ability of the zeolite charcoal.After 3 cycles of use,the removal rate is still above 80%.In a dry environment,the adsorbents H2-Z₈₆C₄A₁₀,H1-Z₇₆C₄A₂₀ and A-H1-Z₇₆C₄A₂₀ can reduce the cadmium concentration in the soil;The flooding conditions can promote the removal of cadmium by the adsorbent,and the adsorption effects of charcoal H6-Z₄₀C₄₀A₂₀,H6-Z₄₀C'₄₀A₂₀ and H6-Z₄₀C''₄₀A₂₀0 and zeolite concrete C1-Z₂₀C₈₀/CN_0.5 are the best.