| In recent years,with China's economic and social development and the acceleration of the process of industrialization,heavy metal pollution has become a global environmental pollution problem that can not be ignored.Because heavy metals are toxic,they are not easy to be chemically or biodegradable degraded,and the pollution is hidden,irreversible and lacks of treatment for its persistence,which will eventually lead to the accumulation of heavy metals in soil and sediment.The research used sediment and surrounding soil in Changhcun Xinlicheng Reservoir as the research samples,which selected three kinds of mental: Pb?Cr and Ni,and used the OECD guideline 106 of batch equilibrium adsorption desorption test method,studying the effects of adsorption and desorption characteristics and the influence of different influencing factors on the adsorption and desorption characteristics of Pb?Cr and Ni in sediment and soil.The results were summarized as follows:The adsorption of Pb,Cr and Ni in sediment and soil can be divided into fast adsorption and slow equilibrium stages.The adsorption equilibrium time was 24 h,When the adsorption equilibrium was reached,the maximum adsorption capacity of Pb were 3977.60 and 3889.98mg·kg-1,and the maximum adsorption capacity of Cr were 1665.02 and 1079.04mg·kg-1.the maximum adsorption capacity of Ni were 1881.60 and 1804.58mg·kg-1,The Elovich equation can be welled with Pb,Cr and Ni adsorption kinetics,and the correlation coefficient was 0.9710~0.9895,which showed significant difference.The desorption equilibrium time was 24 h for Pb?Cr?Ni,When the desorption equilibrium was reached,the desorption capacity of Pb were 49.16 and81.58mg·kg-1,and the desorption capacity of Cr were 38.64 and 137.06mg·kg-1.the desorption capacity of Ni were 24.04 and 31.62mg·kg-1,The Elovich equation can be welled with Pb,Cr and Ni desorption kinetics,and the correlation coefficient was 0.9792~0.9926,which showed significant difference.The adsorption isotherm of Pb in sediment and soil belonged to the "L" type curve,which belonged to the monolayer adsorption and accorded with the Temkin model,the correlation coefficient r were 0.9615 and 0.9778,which showed significant difference..The isotherms of Cr and Ni belonged to the "S" curve,and the Freundlich equation was used to fit the effect,and the correlation coefficient was 0.9834~0.9963,which showed significant difference..The desorption amount for 0.74% and 0.87% of the adsorption for Pb in sediment and soil.The desorption amount for 2.28% and 4.60% of the adsorption for Cr.The desorption amount for 1.26% and 1.35% of the adsorption for Ni.And the adsorption capacity of Pb,Cr,Ni was strong in sediment and soil,and after adsorption was not easy to be desorbed.With the increase of temperature,the adsorption capacity of Pb,Cr and Ni increased gradually,the adsorption thermodynamics parameter ?G<0,the adsorption process was spontaneous,and ?H<0 which reflected the adsorption process was endothermic reaction.The desorption of Pb,Cr and Ni decreased with the increase of temperature,and the ?G was decreased with the increase of temperature,that we can knew the temperature was favorable for its spontaneousity.The adsorption capacity of Pb was increased and then tended flat with the increase of p H value,and p H=5 was the inflection point,after the p H was greater than 5,the adsorption capacity did not change much,the maximum adsorption capacity were 3979.32 and 3923.34mg·kg-1;The adsorption capacity of Cr and Ni increased first and then decreased with the increase of p H value,and the inflection points were 7 and 9,the maximum adsorption capacity were 3140.02,2406.84mg·kg-1 and 3763.48,3716.5mg·kg-1.And the desorption rate tends to be gentle after the decrease of p H value.And the desorption capacity was gradually reduced and then tended to be gentle.The desorption capacity decreased and the tended flat with the increase of p H value,when the p H changes from 3 to 5,the desorption capacity decreased fastest,,the desorption capacity of Pb,Cr and Ni decreased by 96.16% and 94.94%,18.94% and 14.75%,62.97% and 68.21% respectively.When the contents of N were 1,5,10 mg·L-1,the adsorption capacity of Pb,Cr and Ni decreased with the addition of N,and the growth rate was between 0.072% and 14.12%.When the contents of P were 0.5,3 and 5 mg·L-1,the adsorption capacity of Pb,Cr and Ni in the sediment and soil was lower than that in the untreated P,and the growth rate was between 0.46% and 8.41%.And with the increase of N and P concentration,the degree of inhibition of the adsorption process is stronger.The presence of N and P will inhibit the desorption process,and the higher the concentration of N and P,the weaker the degree of inhibition. |
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