Xiong Huixin, Liu Yang, Wang Shuyue, Zhu Shibei
College of Environmental Science and Engineering, Yangzhou University, Yangzhou Jiangsu, 225127, People's Republic of China.
Environ Sci Pollut Res Int. 2023 May;30(22):62295-62311. doi: 10.1007/s11356-023-26348-z. Epub 2023 Mar 20.
Iron hydroxides have received high attention in the treatment of chromium (Cr) polluted wastewater. In this study, the obtained chemical (or biological) pincushion-schwertmannite spheres had a diameter of 2 - 5 μm (0.5-1 μm), and akaganéite rods had a length of 300-500 nm (100-150 nm) at an axial ratio of about 3. The average diameters (μm) of their agglomerated particles in solutions were 20.6-32.5 (only 0.480 for Aka-Chem). Schwertmannites and akaganéites were used to investigate Cr(VI) adsorption behaviors in aqueous solutions by batch experiments, under various reaction times, initial Cr(VI) and adsorbent levels, pH values, temperature and anions of NO, Cl, CO, SO, and HPO. Adsorption data well fitted to pseudo-second-order rate model (R = 0.999), and Langmuir (R = 0.954-0.988) and Freundlich (R = 0.984-0.996) isothermal models at pH 7.0. Maximum Cr(VI) adsorption capacities were 119/133 for Sch-Chem/Sch-Bio, and 14.6/83.6 for Aka-Chem/Aka-Bio. The HPO than SO/CO had a stronger effect on Cr(VI) adsorption. Adsorbents with pH of near to 4.0 still had a good Cr(VI) removal ability at pH 3.0-8.0. The possible Cr(VI) adsorption mechanisms by FTIR and XPS results for schwertmannite and akaganéite were electrostatic attractions and ion exchanges between hydroxyl (or sulfate) and chromate ions. The Cr(VI) adsorption of optimal schwertmannite and bioakaganéite was a spontaneous, endothermic and random process at the temperatures of 288-318 K. They had a good regeneration ability for Cr(VI) adsorption, and removal ratios could reach to about 80% of original values (60-70% in aqueous solution with 60 mg/L Cr(VI) and pH7.0, and 35-50% in wastewater with 120 mg/L Cr(VI) and about pH4.0), after three cycles. Herein, schwertmannite/bioakaganéite have a promising application in treatment of acidic/neutral wastewater with chromate.
氢氧化铁在铬（Cr）污染废水的处理中受到了高度关注。在本研究中，所制备的化学（或生物）针垫状施氏铁矿球直径为2 - 5μm（0.5 - 1μm），而四方纤铁矿棒长度为300 - 500nm（100 - 150nm），轴比约为3。它们在溶液中团聚颗粒的平均直径（μm）为20.6 - 32.5（对于Aka - Chem仅为0.480）。通过批量实验，在不同反应时间、初始Cr（VI）和吸附剂用量、pH值、温度以及NO、Cl、CO、SO和HPO等阴离子存在的条件下，研究了施氏铁矿和四方纤铁矿对水溶液中Cr（VI）的吸附行为。吸附数据很好地拟合了准二级速率模型（R = 0.999），以及在pH 7.0时的朗缪尔（R = 0.954 - 0.988）和弗伦德利希（R = 0.984 - 0.996）等温模型。施氏铁矿化学法/生物法对Cr（VI）的最大吸附容量为119/133，而四方纤铁矿化学法/生物法为14.6/83.6。HPO比SO/CO对Cr（VI）吸附的影响更强。pH接近4.0的吸附剂在pH 3.0 - 8.0时仍具有良好的Cr（VI）去除能力。通过傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）结果得出，施氏铁矿和四方纤铁矿对Cr（VI）可能的吸附机制是羟基（或硫酸根）与铬酸根离子之间的静电吸引和离子交换。在288 - 318K的温度下，最佳施氏铁矿和生物四方纤铁矿对Cr（VI）吸附是一个自发、吸热且随机的过程。它们对Cr（VI）吸附具有良好的再生能力，经过三个循环后，去除率可达到原始值的约80%（在含60mg/L Cr（VI）和pH7.0的水溶液中为60 - 70%，在含120mg/L Cr（VI）和约pH4.0的废水中为35 - 50%）。在此，施氏铁矿/生物四方纤铁矿在处理含铬酸盐的酸性/中性废水方面具有广阔的应用前景。
