酸和热处理对海泡石结构及吸附Pb^(2+)、Cd^(2+)性能的影响

Effects of Acid and Heating Treatments on the Structure of Sepiolite and Its Adsorption of Lead and Cadmium

通过X射线衍射、傅里叶变换红外光谱及比表面积分析等研究了酸和热处理对天然海泡石结构的影响,并考察不同处理后的海泡石样品吸附重金属Pb2+、Cd2+性能.结果表明,海泡石比表面积均随盐酸浓度、处理时间的增加而略有增大,而结构无明显变化,0.5mol·L-1HCl处理时,天然海泡石中的CaCO3未能被完全去除,6.0mol·L-1HCl处理72h时,海泡石比表面积达到最大301.47m2·g-1.盐酸热处理并不能提高海泡石的比表面积,也不会使海泡石结构产生明显变化.不同类型酸处理对海泡石比表面积提高顺序依次为:HCl>HNO3>H2SO4;海泡石经焙烧后比表面积迅速下降,由100℃的21.44m2·g-1下降到900℃的0.17m2·g-1.重金属吸附实验表明,盐酸处理浓度和时间对海泡石吸附Pb2+、Cd2+离子性能无明显影响;不同酸处理对海泡石吸附Pb2+、Cd2+离子性能存在一定影响,H2SO4处理后海泡石对Pb2+、Cd2+离子吸附量明显高于HCl和HNO3处理.海泡石焙烧处理后对Pb2+离子吸附量无明显影响,但对Cd2+离子吸附量在焙烧700℃以上时增加明显.

The effects of acid and heating treatment on the structure of sepiolite and its adsorption capacities for Pb2 ＋ and Cd2 ＋ were investigated using X-ray powder diffraction,infrared spectroscopy,surface area analyses and batch sorption experiments in this paper.The results showed that the BET surface area of the sepiolite samples grew with increase concentrations of HCl and prolong treatment time and no obvious structural changes were observed.CaCO3 as the impurity in the natural sepiolite can not be removed completely in the treatment process with 0.5 mol·L-1 HCl.The surface area of sepiolite treated with 6 mol·L-1 HCl and continuous stirring 72 h reached the maximum 301.47 m2 ·g-1.A decrease in the BET surface area was observed for the samples treated with acid at higher temperature.The BET surface area of samples treated with different acid species arranged in the order HCl HNO3 H2 SO4.The calcinations process decreased the BET surface area from 21.44 m2 ·g-1 at 100℃ to 0.17 m2 ·g-1 at 900℃.The adsorption results indicated that despite increases in the surface areas upon acid activation,improvements in the adsorption were not observed for heavy metal Pb2 ＋ and Cd2 ＋ ions.Pb2 ＋ ions have higher affinity for specific adsorption onto the sepiolite samples than Cd2 ＋ ions.H2 SO4 treatment was found to be more effective for the removal of Pb2 ＋ and Cd2 ＋ ions than HCl and HNO3 treatments.It is apparent that PbSO4 and CdSO4 were formed during the sorption process.The calcinations treatment exhibited no significant effects on the adsorption of Pb2 ＋ ions onto sepiolite,but the adsorption of Cd2 ＋ ions obviously increased above 700℃.