废水中聚丙烯酰胺在H-Beta分子筛上的吸附特性

Adsorption of polyacrylamide in wastewater on H-Beta molecular sieve

将H-Beta用于处理含聚丙烯酰胺（PAM）的驱油废水,研究了PAM在H-Beta上的吸附动力学和热力学特征,并考察了吸附条件对吸附效果的影响.结果表明,吸附过程遵循准二级动力学模型;在低PAM初始浓度（100 mg·L-1）时,吸附表观活化能〉40 k J·mol-1,说明H-Beta对PAM的吸附以化学吸附为主;在高PAM初始浓度（200和500 mg·L-1）时,吸附活化能降低,吸附向物理吸附转变.吸附等温线在低平衡浓度区符合Langmuir模型,25、40和50℃时的单层饱和吸附量分别达到70.2、76.9和90.9 mg·g-1;在高平衡浓度区符合Freundlich模型,表现为多层吸附.吸附主要来自氢键作用,为自发的吸热过程.p H为2～4,吸附剂用量为5 g·L-1时,具有更优的吸附效果.真实废水中油和盐类的存在对PAM在H-Beta上的吸附未产生不利影响。

H-Beta molecular sieve was used to adsorb polyacrylamide（ PAM） in oil field wastewater. The adsorption kinetics and thermodynamics of PAM on H-Beta and effects of different conditions on adsorption were investigated. The results showed that the adsorption kinetics can be well described by the pseudo-second-order kinetics model. At low initial PAM concentration（ 100 mg·L- 1）,the apparent adsorption activation energy（ Ea） was higher than40 k J·mol- 1,indicating chemical adsorption dominated. While Eadecreased at high PAM concentrations（ 200 and 500 mg·L- 1）,suggesting physical adsorption was dominant in these conditions. Under low PAM equilibrium concentrations,the adsorption isotherms could be well fitted by Langmuir equation. The monolayer saturation adsorption capacity was 70. 2 mg·g- 1at 25 ℃,76. 9 mg·g- 1at 40 ℃ and 90. 9 mg·g- 1at 50 ℃. Under high PAM equilibrium concentrations,the adsorption isotherms matched with Freundlich equation,indicating the multilayer adsorption. The adsorption was a spontaneous and endothermic process mainly caused by H-bonding. The optimal adsorption performance could be achieved under the conditions of p H value at 2 ～ 4 and adsorbent dosage at 5 g·L- 1. The adsorption performance of PAM on H-Beta was not affected by the oil and salts in the real PAMcontaining wastewater.