Vahidhabanu Shappur, Adeogun Abideen Idowu, Babu B Ramesh
Pollution Control Division, CSIR-Central Electro Chemical Research Institute, Karaikudi 630003, Tamil Nadu, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
ACS Omega. 2019 Jan 31;4(1):2425-2436. doi: 10.1021/acsomega.8b02960.
The quest for sustainable development and green chemistry had led to the design and synthesis of advanced adsorbent materials for efficient removal of pollutants in industrial effluents. Magnetic halloysite nanotubes with chitosan nanocomposite sponges were prepared by combining solution-mixing and freeze-drying. Magnetic@chitosan/halloysite (FeO-HNT/CS) and spongelike chitosan/halloysite (HNT/CS) were used as adsorbents for the removal of Congo red dye in aqueous solution in a batch process. The as-prepared composites were characterized using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, vibrating-sample magnetometry, thermal gravimetry-differential scanning calorimetry, and Fourier transform infrared spectroscopy. Data from kinetic study were analyzed with pseudo-first-order and pseudo-second-order models, whereas the mechanism was analyzed using Bangham's, Elovich's, intraparticle, and double-exponential diffusion models. The equilibrium data were evaluated using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The adsorption kinetics of dye removal followed the pseudo-first-order model with average rate constants of 0.260 and 0.196 min for FeO-HNT/CS and HNT/CS, respectively. The Langmuir adsorption isotherm best fitted the equilibrium data with > 0.9 with maximum adsorption capacities of 41.54 and 54.49 mg g obtained for HNT/CS and FeO-HNT/CS, respectively. Negative values of Δ° obtained from thermodynamic studies revealed that the adsorption process was spontaneous. The values of Δ° and Δ° obtained for Congo red dye removal were 69.46 and 39.54 kJ mol and 240.5 and 145.1 J mol K for HNT/CS and FeO-HNT/CS, respectively. The results indicated that CS-HNT is an excellent adsorbent; however, its magnetic modification further improved its recyclability and enhanced the performance for the removal of Congo red dye from aqueous solution.
对可持续发展和绿色化学的追求促使人们设计并合成先进的吸附材料，以有效去除工业废水中的污染物。通过溶液混合和冷冻干燥相结合的方法制备了具有壳聚糖纳米复合海绵的磁性埃洛石纳米管。磁性@壳聚糖/埃洛石（FeO-HNT/CS）和海绵状壳聚糖/埃洛石（HNT/CS）被用作吸附剂，以分批处理的方式去除水溶液中的刚果红染料。使用扫描电子显微镜、能量色散X射线分析、X射线衍射、振动样品磁强计、热重-差示扫描量热法和傅里叶变换红外光谱对所制备的复合材料进行了表征。动力学研究数据用拟一级和拟二级模型进行分析，而机理则使用班汉姆模型、埃洛维奇模型、颗粒内扩散模型和双指数扩散模型进行分析。平衡数据用朗缪尔、弗伦德利希、特姆金和杜宾宁-拉杜舍维奇等温线模型进行评估。染料去除的吸附动力学遵循拟一级模型，FeO-HNT/CS和HNT/CS的平均速率常数分别为0.260和0.196 min⁻¹。朗缪尔吸附等温线最适合平衡数据，相关系数>0.9，HNT/CS和FeO-HNT/CS的最大吸附容量分别为41.54和54.49 mg g⁻¹。热力学研究得到的ΔG°负值表明吸附过程是自发的。HNT/CS和FeO-HNT/CS去除刚果红染料的ΔH°和ΔS°值分别为69.46和39.54 kJ mol⁻¹以及240.5和145.1 J mol⁻¹ K⁻¹。结果表明CS-HNT是一种优良的吸附剂；然而，其磁性改性进一步提高了其可回收性，并增强了从水溶液中去除刚果红染料的性能。
