两性聚电解质P(DMDAAC-AM-AA)处理造纸白水中Ca^(2+)的研究

Removal of Ca^(2+) from Papermaking Whitewater by Polyampholyte P( DMDAAC-AM-AA)

以实验室自制聚二甲基二烯丙基氯化铵-丙烯酰胺-丙烯酸(P(DMDAAC-AM-AA))为吸附剂、造纸白水中Ca2+为吸附质,研究了pH值、Ca2+初始浓度及聚合物重均相对分子质量(MW)对吸附过程的影响,采用Freundlich、Langmuir等温吸附模型绘制了吸附等温线,并通过Lagrange动力学方程对实验数据进行了拟合。结果表明,碱性环境下有利于吸附过程的进行,且最佳pH值范围为9~11;随着Ca2+初始浓度的增加,吸附量先增加后趋于平稳;对吸附最有利的MW范围为600 000~800 000。聚合物对Ca2+的吸附动力学曲线符合Lagrange准二级动力学模型,属于化学吸附过程;其等温吸附曲线符合Langmuir模型,属于单分子层吸附;无量纲平衡参数(RL)值在不同温度下均小于0.5,表明吸附性能良好。同时,还探讨了纸浆纤维对聚合物的吸附性能和影响因素,采用傅立叶红外差谱进行了表征。结果表明,温度20~30℃、搅拌速度120 r/min的条件下,吸附在60 min时达到平衡,平衡吸附量为2.4 mg/g(以绝干浆计)左右;红外差谱证实了纤维表面吸附有一定量的聚合物,且氢键结合是纤维与聚合物吸附的主要机理之一。

A polyamoholyte, P（DMDAAC-AM-AA） which was composed of acrylamide （AM）, acrylic acid （AA） and dimethyl diallyl ammonium chloride （DMDAAC） was prepared in the lab. Its property, mechanism and affecting factors for Ca2＋ adsorption from papermaking whitewater were studied. The results indicated that, alkaline environment was beneficial to the adsorption process under the optimum pH range 9 to 11. Besides, along with the increasing of the initial concentration of Ca2＋ , the adsorption increased firstly and then leveled off, and the optimum molecular weight range was 600 000 to 800 000. Moreover, the adsorption kinetic curve of Ca2＋ was represented as a chemisorption process and was quite fit for Lagrange pseudo-secondorder model. The adsorption isotherm was accordance with a Langmuir model. It was a monomolecular layer and easy adsorption process. The values of RL at different temperatures were below 0.5. Besides, the adsorption of P（DMDAAC-AM-AA） onto fibers was characterized by FT-IR. The adsorption equilibrium was achieved at 60min as the whitewater was stirred at 120 r/min and 20 - 30 ℃ , and the equilibrium absorption capacity was ca. 2.4 mg/g oven dry fiber. The adsorption of the polymers on the fiber surface was confirmed by the FT-IR analysis.