糖用脱色树脂吸附己糖碱性降解色素传质机理解析

Mass Transfer Mechanisms for Decolorizing Resin Adsorption of Alkaline Degradation Products of Hexose

以回溶糖浆代表性色素——己糖碱性降解色素为吸附模型底物,考察糖用脱色树脂对其吸附性能,并采用4种新型吸附传质现象学模型,即外部传质阻力(external mass transfer resistance,EMTR)、内部传质阻力(internal mass transfer resistance,IMTR)、活性位点吸附(adsorption on active sites,AAS)及EMTR-IMTR组合模型,解析树脂吸附色素传质机理。在色素初始质量浓度为60、90 mg/L及120 mg/L条件下,树脂对色素平衡吸附量分别为190、270 mg/g及326 mg/g,对应脱色率分别为95%、90%及82%。树脂吸附色素限速步骤由EMTR和IMTR共同决定,但AAS步骤不可忽略。EMTR-IMTR组合模型可准确求解吸附体系任意时刻树脂周围液膜及其内部孔道对色素吸附量,AAS模型可准确计算吸附过程任意时刻物理及化学吸附速率大小,可为阐明吸附传质机理提供新视角。

Alkaline degradation products of hexose(HADP)were prepared as a representative colorant in remelt syrup to evaluate their adsorption performance onto a decolorizing resin.Four novel phenomenological adsorption mass transfer models,namely,external mass transfer resistance(EMTR),internal mass transfer resistance(IMTR),combined EMTRIMTR,and adsorption on active sites(AAS),were used to decipher the mass transfer mechanisms for the resin adsorption of HADP.At the initial colorant concentrations of 60,90,and 120 mg/L,the equilibrium adsorption capacities of the resin for HADP were 190,270,and 326 mg/g,and the corresponding decolorization rates were 95%,90%,and 82%,respectively.EMTR combined with IMTR was the rate-limiting step for HADP adsorption onto the resin,and AAS could not be neglected.The dynamic characteristics of HADP adsorption through the liquid film around the resin and the pores inside the resin could be described well using the combined EMTR-IMTR model.The AAS model could accurately calculate the physisorption and chemisorption rates during the whole adsorption process.These models can help provide new insights into the mass transfer behaviors of the adsorption system.