Department of Biotechnology, Karunya Institute of Technology & Sciences, Coimbatore, 641114, India.
Environ Sci Pollut Res Int. 2019 Oct;26(29):30044-30054. doi: 10.1007/s11356-019-06164-0. Epub 2019 Aug 14.
Presence of carcinogenic chromium, i.e., Cr(VI), in different industrial effluents necessitates design and development of effective abatement technologies. Nanosorbent consisting of iron oxide nanoparticles functionalized with soil-derived humic acid was employed for removal of Cr(VI). The point of zero charge for both humic acid and nanoparticles as estimated from pH shift experiments was between pH 8 and 9. Adsorption isotherm from batch experiments at neutral pH followed Langmuir model with projected maximum adsorption capacities for humic acid coated nanoparticles (24.13 mg/g) much higher than its uncoated counterpart (2.82 mg/g). Adsorption was process very fast and kinetics could be described with pseudo-second-order model (R > 0.98), for both nanoparticles. High E4/E6 ratio of extracted humic acid and Fourier transform infrared spectroscopy of coated nanoparticles (20-100 nm) indicated enrichment of hydroxyl, carboxylic, and aliphatic groups on surface leading for the better adsorption. Humic acid coated and uncoated nanoparticles regenerated with EDTA, NaOH, urea, NaCO, and NaCl treatments retained 35.90-59.67 and 26.37-36.28% of their initial adsorption capacities, respectively, in 2nd cycle. Experimental controls (virgin nanoparticles subjected to an identical regenerating environment) revealed irreversible surface modification as the cause for loss of their adsorption capacities.
存在致癌铬，即六价铬，在不同的工业废水中，需要设计和开发有效的减排技术。由氧化铁纳米粒子与土壤衍生的腐殖酸功能化组成的纳米吸附剂用于去除六价铬。从 pH 值移位实验估计的腐殖酸和纳米粒子的零电荷点在 pH 8 到 9 之间。在中性 pH 下进行的批量实验的吸附等温线遵循朗缪尔模型，预计腐殖酸包覆纳米粒子的最大吸附容量（24.13 mg/g）远高于未包覆的纳米粒子（2.82 mg/g）。吸附过程非常快，动力学可以用拟二级模型（R > 0.98）来描述，对于两种纳米粒子都是如此。提取腐殖酸的高 E4/E6 比和涂覆纳米粒子的傅里叶变换红外光谱（20-100nm）表明表面羟基、羧酸和脂肪族基团的富集，从而导致更好的吸附。用 EDTA、NaOH、尿素、NaCO 和 NaCl 处理再生的腐殖酸包覆和未包覆的纳米粒子在第 2 周期分别保留了 35.90-59.67%和 26.37-36.28%的初始吸附容量。实验对照（未经处理的纳米粒子受到相同的再生环境）表明，不可逆的表面修饰是导致其吸附容量损失的原因。
