Lead And Cadmium Adsorption And Dissociation From Water Using Modified Chestnut Endothelium

In order to eliminate adverse effects of pigment in the process of adsorption of heavy metals by chestnut endothelium, this paper made the following treatments:(1) Finding the right extraction solvent to removal chestnut endothelium pigment and examine the factors affecting the removal of pigment and optimal process;(2) By means of a modified(such as:acidic formaldehyde, maleic acid, irradiation, modifier- radiation double modification method) to make removal of pigment chestnut endothelium,it can be achieved effectively remove Pb2+ and Cd2+ purpose;(3)It applied adsorption thermodynamics and kinetics model fit;(4)it studied the factors that affect endothelium chestnut modified adsorption of Pb2+ and Cd2+ adsorption rate, such as temperature, p H, adsorption time, initial concentration of metal ions, adsorbents vote dosage, etc.,and response surface experiments, looking chestnut modified endothelium adsorption of Pb2+ and Cd2+in optimal conditions;(5) It digestied test verification modified endothelium chestnut actual adsorption capacity of Pb2+ and Cd2+;(6) It used different inorganic acid to treat chestnut endothelia that adsorpted Pb2+ and Cd2+,which can find a suitable agent for enriching heavy metal ions to recycling. Specific results are as follows:Pigment extraction solvent: Na OH is better than ethanol solution and Na2CO3 to extract the chestnut endothelium pigment out. By orthogonal experiment: solid-liquid ratio>Temperature>extraction times> extraction time, the optimal combination was solid-liquid ratio 1:80, temperature 70 ℃, extraction time 5h, extraction times 2.Follow this result, chestnut endothelium pigment extraction rate can reach 14.07%.Chestnut endothelium decolorization compared with natural chestnut endothelium of Pb2+ and Cd2+ adsorption rate lower 12.62 percent and 22.79 percent, respectively.Modified by maleic acid, acid formaldehyde, radiation, radiation- maleic acid, irradiation-acid modified formaldehyde adsorption results showed that after maleic acid modified,0.5mol/L Na OH decolorization of endothelium chestnut can effectively improve the adsorption rate than other modification methods for heavy metal Pb2+ and Cd2+.After bleaching and modified, chestnut endothelium for Pb2+ and Cd2+ adsorption could be fit with thermodynamic model of Langmuir model better,and the maximum adsorption capacity for Pb2+ and Cd2+ were 52.91mg/g and 51.28mg/g. Elevated temperature also conducive to the adsorption of conduct, indicating that this process is endothermic chemical process; thermodynamic parameters indicated that the process of modified chestnut endothelium adsorption of Pb2+ and Cd2+ is spontaneous, endothermic,and system increased disorder. Adsorption process adsorption enthalpy indicates mechanism for hydrogen bonding force and the dipole force. Modified chestnut endothelium adsorption of Pb2+ and Cd2+ fitted more in line with the second order kinetic model, 0.9999 and 0.9997 respectively.Single factor test showed that: modified chestnut endothelial adsorption of p H on Pb2+and Cd2+ range is wide, with the increase of p H adsorption rate increased significantly; in0.5~1h range of Pb2+ and Cd2+ adsorption rate was more than 90%, for the rapid adsorption stage; the adsorption rate of Pb2+ increased after 5h flatten,Cd2+ on 5h highest adsorption rate, decreased after 6h; at the same concentration, the adsorption rate increased with increasing dosage,but capacity with increasing dosage has declined significantly.As possible as to efficient use of adsorbents, under ambient conditions of Pb2+ 40mg/L, Cd2 +30mg/L of simulated water,it select dosage of 4g/L; when low initial concentration, Pb2+and Cd2+ can fully with the modified adsorbent, so the higher adsorption efficiency,adsorption capacity increaseds; but with the increase of initial concentration saturation adsorption sites is also increased, the adsorption rate is low, the adsorption capacity increased slowly, gradually become saturated.Response surface of endothelium been modified chestnut Pb2+ adsorption optimal conditions: adsorption temperature 59.23 ℃, adsorption time is 5.72 h, the p H was 6.16, the optimal conditions for adsorption of Cd2+: adsorption temperature was 55.99℃, adsorption time is 4.43 h, solution at p H 6.06. The highest adsorption rate of Cd2+ and Pb2+ was99.76% and 98.90%.Digestion tests proved that the modified decolorization chestnut endothelium comparing natural chestnut can effectively adsorb Pb2+ and Cd2+ in aqueous.Selecting HCL as the adsorption of Pb2+ chestnut endothelium dissociation agents,dissociation conditions was 0.2 mol/L HCL, dissociation temperature 30℃, time 2h,dissociation twice, dissociation rate up to 94.3924%, concentration of 23.51mg/L; selecting H3PO4 as the adsorption of Cd2+chestnut endothelium dissociation agents, dissociation condition was 0.2mol/L H3PO4, dissociation temperature 30℃, time 3h, dissociation twice the rate of up to 84.5880% concentration of 15.68mg/L.