Udoetok Inimfon A, Wilson Lee D, Headley John V
Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SK S7N 5C9, Canada.
Water Science and Technology Directorate, Environment and Climate Change Canada, 11 Innovation Boulevard, Saskatoon, SK S7N 3H5, Canada.
Materials (Basel). 2016 Jul 30;9(8):645. doi: 10.3390/ma9080645.
Quaternized (QC) and cross-linked/quaternized (CQC) cellulose hydrogels were prepared by cross-linking native cellulose with epichlorohydrin (ECH), with subsequent grafting of glycidyl trimethyl ammonium chloride (GTMAC). Materials characterization via carbon, hydrogen and nitrogen (CHN) analysis, thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR)/C solid state NMR spectroscopy provided supportive evidence of the hydrogel synthesis. Enhanced thermal stability of the hydrogels was observed relative to native cellulose. Colloidal stability of octanol and water mixtures revealed that QC induces greater stabilization over CQC, as evidenced by the formation of a hexane-water Pickering emulsion system. Equilibrium sorption studies with naphthenates from oil sands process water (OSPW) and 2-naphthoxy acetic acid (NAA) in aqueous solution revealed that CQC possess higher affinity relative to QC with the naphthenates. According to the Langmuir isotherm model, the sorption capacity of CQC for OSPW naphthenates was 33.0 mg/g and NAA was 69.5 mg/g. CQC displays similar affinity for the various OSPW naphthenate component species in aqueous solution. Kinetic uptake of NAA at variable temperature, pH and adsorbent dosage showed that increased temperature favoured the uptake process at 303 K, where Q = 76.7 mg/g. Solution conditions at pH 3 or 9 had a minor effect on the sorption process, while equilibrium was achieved in a shorter time at lower dosage (ca. three-fold lower) of hydrogel (100 mg vs. 30 mg). The estimated activation parameters are based on temperature dependent rate constants, k₁, which reveal contributions from enthalpy-driven electrostatic interactions. The kinetic results indicate an ion-based associative sorption mechanism. This study contributes to a greater understanding of the adsorption and physicochemical properties of cellulose-based hydrogels.
通过将天然纤维素与环氧氯丙烷（ECH）交联，随后接枝缩水甘油基三甲基氯化铵（GTMAC），制备了季铵化（QC）和交联/季铵化（CQC）纤维素水凝胶。通过碳、氢和氮（CHN）分析、热重分析（TGA）以及傅里叶变换红外（FTIR）/C固态核磁共振光谱对材料进行表征，为水凝胶的合成提供了支持性证据。相对于天然纤维素，观察到水凝胶的热稳定性有所增强。辛醇和水混合物的胶体稳定性表明，QC比CQC具有更高的稳定性，己烷 - 水皮克林乳液体系的形成证明了这一点。对油砂工艺水（OSPW）中的环烷酸盐和水溶液中的2 - 萘氧基乙酸（NAA）进行的平衡吸附研究表明，CQC对环烷酸盐的亲和力相对于QC更高。根据朗缪尔等温线模型，CQC对OSPW环烷酸盐的吸附容量为33.0 mg/g，对NAA的吸附容量为69.5 mg/g。CQC对水溶液中各种OSPW环烷酸盐组分具有相似的亲和力。在不同温度、pH值和吸附剂用量下对NAA的动力学吸附表明，温度升高有利于在303 K时的吸附过程，此时Q = 76.7 mg/g。pH值为3或9的溶液条件对吸附过程影响较小，而在较低用量（约低三倍）的水凝胶（100 mg对30 mg）下能在更短时间内达到平衡。估计的活化参数基于温度依赖性速率常数k₁，其揭示了焓驱动的静电相互作用的贡献。动力学结果表明存在基于离子的缔合吸附机制。本研究有助于更深入了解纤维素基水凝胶的吸附和物理化学性质。
