胺型腰果酚醛树脂对Ag^+的吸附

Adsorption of Ag^+ onto cardanol aldehyde-amine resins

制备了3种胺型腰果酚醛树脂(二乙撑三胺型腰果酚醛树脂(PCD)、己二胺型腰果酚醛树脂(PCE)、己二胺型腰果酚醛树脂(PCH)),采用XPS(X-射线光电子能谱仪)、EA(元素分析仪)、FTIR(傅利叶变换红外光谱分析仪)等手段研究了其结构特征,并考察了其对水溶液中Ag+的吸附行为和机理.结果表明,3种树脂对Ag+有较高的吸附量和吸附作用;在pH值为5.5的条件下,树脂对Ag+的吸附效果最佳;2h内吸附达到平衡;吸附行为均符合Lagergren准二级速率方程;树脂对Ag+的吸附均符合Langmuir等温吸附方程;吸附反应为自发吸热和熵增的过程;可溶性无机盐对树脂吸附Ag+的影响不大;推测其吸附机理是树脂上胺基、羟基与Ag+发生较强的配位作用和较弱的离子交换作用的化学吸附为主.吸附Ag+后的树脂可用硝酸脱附再生;树脂循环使用4次后,吸附率和脱附率仍大于90%.

Three types of cardanol aldehyde-amine resins,cardanol aldehyde-diethylenetriamine（ PCD）,cardanol aldehyde-1,2-ethanediamine（ PCE）,and cardanol aldehyde-1,6-hexanediamine（ PCH）,were prepared by the condensation of cardanol aldehyde resin with diethylenetriamine,1,2-ethanediamine,and 1,6-hexanediamine,respectively. Their surface structure was characterized by X-ray photoelectron spectroscopy（ XPS）,Elemental analysis（ EA）,and Fourier-transformed infrared spectroscopy（ FTIR）. In addition,adsorption mechanism of Ag＋in water was also studied by using these cardanol aldehyde-amine resins as adsorbents. Results indicated that the three cardanol aldehyde-amine resins had high adsorption capacity for Ag＋. Specifically,the adsorption capacity of Ag＋reached maxmum at p H 5. 5,and adsorption equilibrium was reached within 2hours. Additionally,the adsorption behavior of the cardanol aldehyde-amine resins was well fitted with the Langmuir isotherm. Further results showed that the adsorption kinetics could be well described with the pseudo-second-order kinetic model. And thermodynamic studies revealed that the adsorption process of Ag＋was endothermic（ ΔH 〉0,entropy favored（ ΔS〉 0）,and spontaneous（ ΔG 〈0）. Inorganic salts in the solution had little effect on the adsorpty capacities of Ag＋. The adsorption mechanism of Ag＋was mainly attributed to chemical adsorption,that is,Ag＋would coordinate strongly with amino group or hydroxyl group,and exchanged weakly with amino group in resins. Moreover,the desorption and regeneration processes were easy to carry out using a nitric acid solution. The adsorption-desorption efficiency of the resin was over 90% after four recycle.