木粉/壳聚糖接枝丙烯酸-丙烯酰胺吸附树脂对Pb^(2+)的吸附

Adsorption of Pb^(2+) on Wood Flour / Chitosan Graft Acrylic Acid-Acrylamide Adsorption Resins

以自制木粉/壳聚糖接枝丙烯酸-丙烯酰胺吸附树脂为研究对象,探讨不同吸附条件下其对金属Pb2+的吸附性能。在含Pb2+的溶液中,吸附树脂R的使用条件为:30℃,pH=6,树脂用量0.2g·L-1,初始浓度0.75mmol·L-1,吸附时间8h(静态)或6h(动态);此时树脂R对Pb2+的吸附量达2.52mmol·g-1,去除率为97.1%。溶液中加入NaCl、NaNO3、尿素后吸附量快速下降,且加入NaCl下降最快,加入尿素下降最慢。该吸附树脂R反复使用性能较好。从吸附树脂R等温吸附、吸附动力学及热力学、表面形态结构变化等方面对吸附机制进行了探讨。吸附Pb2+前树脂R表面起伏,凹凸不平,纹络结构分布不均匀;吸附Pb2+后,表面纹络结构被破坏;随吸附时间增加,"白色"斑点明显增加,且逐渐分布均匀。吸附树脂R吸附Pb2+的过程符合准一级动力学模型;Pb2+吸附过程的ΔG为负值,ΔS、ΔH均为正值,即吸附过程为自发过程,升温有利于吸附的进行。

The adsorption properties of self-made wood flour/chitosan graft acrylic acid-acrylamide copolymerization resin（ adsorbing resin R）are discussed under different adsorption conditions. The optimum using conditions of the adsorbing resin R in the Pb2＋ solutions are 30 ℃ , pH = 6.0, resin usage 0. 2 g. L-1, the initial concentration of Pb2＋ 0.75 mmol. L -1, the adsorbing time 8 h （static） or 6 h （dynamic）. Under the above-mentioned conditions, the adsorption capacity of Pb2＋ for the adsorbing resin R is 2.52 mmol.g-1 and its removing percent of Pb2＋ is 97. 1%. The adsorption capacities of the adsorbing resin R obviously reduced while NaC1, NaNO3 or urea is added in the Pb2＋ ion solutions, the decreasing rate is the fastest when NaNO3 is adding in the Pb2＋ solution and it is the slowest when urea is added in the Pb2 ＋ solution. The repeated using property of the adsorbing resin R is better. The adsorption mechanism is explored by the adsorption isotherm, the adsorption kinetics and thermodynamics, and the change of the surface morphology, etc. The surface morphology and the grain distribution of the adsorbing resin R before adsorbing Pb2＋ is uneven. And the grain structure of the surface before adsorbing Pb2＋ is disnlpted and the ＂ white＂ spots obviously increased and gradually changed uniform when the adsorbing time increased. The Pb2＋ adsorption process for the adsorbing resin R is fit for pseudo-first kinetic model, and AG is negative, and AS and AH is positive, that is, the adsorption process is spontaneous and the increasing temperature is favorable for the Pb2＋ adsorption onto the adsorbing resin R.