多乙烯多胺改性纤维素及其对水中砷、氟、铬吸附性能研究

Preparation of Polyethylene Polyamine-modified Cellulose and Its Adsorbability for As,F and Cr Anions

以木浆为原材料,采用高碘酸钠氧化法制备了醛基纤维素,并在温和的条件下以多乙烯多胺改性制备了氨基改性纤维素吸附剂.探究了氨基改性纤维素吸附剂对水中有害离子F-、Cr2O72-和AsO43-的吸附性能,结果发现该吸附剂对F-、Cr2O72-和AsO43-离子具有高的吸附能力,并可实现较快速的吸附平衡.其吸附过程受到pH值的影响,随着pH升高,对Cr2O72-和AsO43-的吸附能力增加,当pH接近中性时,F-离子吸附能力下降.在竞争离子的存在下,对Cr2O72-和AsO43-仍具有极强的选择吸附性,推测其吸附为络合吸附机理,而对F-则主要为静电力吸附机理,吸附选择性较差.

A novel wood-based adsorbent material was developed for removal of harmful anions from drinking water. First, wood pulp was partially oxidized by sodium periodate to form dialdehyde-modified cellulose; secondly, the aldehyde groups were coupled with polyethylene polyamine via Schiff base reaction to give amino- modified cellulose-based cationic adsorbent material. All reactions could be performed by mild and facile procedures. The adsorption performance of amino-modified cellulose-based cationic adsorbent against F-, Cr2O7^2- and AsO4^3- was studied in terms of adsorption capacity （isotherm） and rate of adsorption. The results showed that the amino-modified cellulose-based cationic adsorbent is effective for the harmful F- , Cr2O7^2- and AsO4^3- ions. High adsorption capacity for these species was displayed and rapid adsorption equilibrium could be achieved. The study of the adsorption isotherm has showed that,Langmuir monolayer adsorption isotherm is more favorable for description of the adsorption process within the studied concentration. The capacity was affected by the pH level：high pH gave increased adsorptivity for Cr2072- and AsO43- ,while neutral to low pH decreased the adsorption capacity of F-. This amino-modified cellulose-based cationic adsorbent showed selectivity for Cr2O7^2- and AsO4^3- , which were adsorbed under presence of other monovalent anions. This phenomenon is likely due to the chelating action of the cationic groups of polyamine in amino-modified cellulose-based cationic adsorbent. But for F- ,the electrostatic force is probably dominant in the adsorption mechanism, which did not show this high selectivity in the presence of competing anions.