K Ramakrishnan Rohith, Padil Vinod V T, Wacławek Stanisław, Černík Miroslav, Varma Rajender S
Institute for Nanomaterials, Advanced Technologies and Innovation (CXI), Technical University of Liberec (TUL), Studentská 1402/2, 461 17 Liberec, Czech Republic.
Regional Centre of Advanced Technologies and Materials, Palacký University in Olomouc, Šlechtitelů 27, 783 71 Olomouc, Czech Republic.
Polymers (Basel). 2021 Jan 13;13(2):251. doi: 10.3390/polym13020251.
A novel, lightweight (8 mg/cm), conjugate sponge of karaya gum (Kg) and chitosan (Ch) has been synthesized with very high porosity (~98%) and chemical stability, as a pH-responsive adsorbent material for the removal of anionic and cationic dyes from aqueous solutions. Experimental results showed that Kg-Ch conjugate sponge has good adsorption capacity for anionic dye methyl orange (MO: 32.81 mg/g) and cationic dye methylene blue (MB: 32.62 mg/g). The optimized Kg:Ch composition grants access to the free and pH-dependent ionizable functional groups on the surface of the sponge for the adsorption of dyes. The studies on the adsorption process as a function of pH, adsorbate concentration, adsorbent dose, and contact time indicated that the adsorption capacity of MB was decreased with increasing pH from 5 to 10 and external mass transfer together with intra-particle diffusion. The adsorption isotherm of the anionic dye MO was found to correlate with the Langmuir model (R = 0.99) while the adsorption of the cationic MB onto the sponge was better described by the Freundlich model (R = 0.99). Kinetic regression results specified that the adsorption kinetics were well represented by the pseudo-second-order model. The H-bonding, as well as electrostatic interaction between the polymers and the adsorption interactions of dyes onto Kg-Ch sponge from aqueous solutions, were investigated using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and the highly wrinkled porous morphology was visualized in depth by field-emission scanning electron microscopy (FE-SEM) analysis. Moreover, the samples could be reused without loss of contaminant removal capacity over six successive adsorption-desorption cycles. The hierarchical three-dimensional sponge-like structure of Kg has not been reported yet and this novel Kg-Ch sponge functions as a promising candidate for the uninterrupted application of organic pollutant removal from water.
一种新型的、轻质的（8毫克/立方厘米）卡拉亚胶（Kg）和壳聚糖（Ch）共轭海绵已被合成，其具有非常高的孔隙率（约98%）和化学稳定性，作为一种pH响应型吸附材料用于从水溶液中去除阴离子和阳离子染料。实验结果表明，Kg-Ch共轭海绵对阴离子染料甲基橙（MO：32.81毫克/克）和阳离子染料亚甲基蓝（MB：32.62毫克/克）具有良好的吸附能力。优化后的Kg:Ch组成使得海绵表面的游离和pH依赖的可电离官能团能够用于染料吸附。对吸附过程随pH、吸附质浓度、吸附剂剂量和接触时间变化的研究表明，随着pH从5增加到10，MB的吸附容量降低，同时存在外部传质和颗粒内扩散。发现阴离子染料MO的吸附等温线与朗缪尔模型相关（R = 0.99），而阳离子MB在海绵上的吸附用弗伦德里希模型描述得更好（R = 0.99）。动力学回归结果表明，吸附动力学可用准二级模型很好地表示。使用衰减全反射-傅里叶变换红外（ATR-FTIR）光谱研究了聚合物之间的氢键以及静电相互作用以及染料从水溶液到Kg-Ch海绵上的吸附相互作用，并通过场发射扫描电子显微镜（FE-SEM）分析深入观察了高度褶皱的多孔形态。此外，样品可以在连续六个吸附-解吸循环中重复使用而不损失污染物去除能力。尚未报道过Kg的分级三维海绵状结构，这种新型的Kg-Ch海绵是从水中不间断去除有机污染物的有前途的候选材料。
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