【摘要】 用水热法合成δ-MnO2,研究其对重金属Pb2+的吸附性能,以及溶液的pH值、盐浓度对吸附效果的影响,并与无定型二氧化锰对比。研究结果表明水热法可以成功合成δ-MnO2,且具有颗粒微小,无杂质等优点。δ-MnO2对Pb2+的等温吸附结果用多种等温吸附式拟合,结果显示Temkin方程的拟合效果最好。相同条件下,δ-MnO2对Pb2+的吸附量远大于无定型二氧化锰。同一种吸附剂,对Pb2+吸附率随着溶液pH值的增大而增大,随着盐浓度的增加先增加后稳定再减少。更多还原

【Abstract】 The present article takes as its aim the introduction to our renovated hydrothermal method in preparing δ-MnO2 along with its study on the adsorption of Pb2+.At the same time,the paper has also discussed the effect of pH and salty concentration on the adsorption in comparison with the non-crystal manganese.Our experimental results have shown that the given method can be made highly successful in synthesizing crystal δ-manganese dioxide free from impurities.When samples produced with our method were tested by way of X-ray diffraction and infrared spectrum,it is found that the δ-MnO2 crystal measurement is worse with small grain diameters.The samples δ-MnO2 produced in our innovated method display a lot of surface hydroxyl functional groups(Mn—OH),which prove to adsorb heavy metal Pb2+ of different initial densities at the temperature of 25 ℃.The experimental results of ours also indicate that the Pb2+ adsorption is likely to increase with initial density comparatively increased.To be exact,when the initial density<150 mg/L,the Pb2+ adsorption would increase sharply.And,then,when the initial density >210 mg/L and the Pb2+ adsorptiongets to saturation,the experimental data proves to agree with Langmuir equation,Freundlich equation and Temkin equation,with the best model in correspondence with the isothermal adsorption data of Pb2+ as in the Temkin-equation.Under the same experimental conditions,the adsorptive capacities of the δ-MnO2 pair of Pb2+ prove to be stronger than the non-crystal manganese dioxide.Last of all,compared with non-crystal manganese under the same condition,the variation of the two adsorbents in absorption efficiency trends to be slight.To the same adsorbent,the increase of pH may result in a corresponding increase of the adsorption efficiency.To the δ-MnO2,on the condition of 1< pH<4.5,the adsorption efficiency may increase with the increase of pH when pH >5.22,and the Pb2+ totally adsorbed.On the other hand,when 0.05<salty concentration<0.15,the adsorption efficiency would increase with the increase of salty concentration,and then would stand still at 0.15.However,when the salty concentration>0.15,the adsorption efficiency would decrease as the salty concentration increases.更多还原