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首页> 外文期刊>RSC Advances >Hematite decorated multi-walled carbon nanotubes (α-Fe2O3/MWCNTs) as sorbents for Cu(ii) and Cr(vi): comparison of hybrid sorbent performance to its nanomaterial building blocks
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Hematite decorated multi-walled carbon nanotubes (α-Fe2O3/MWCNTs) as sorbents for Cu(ii) and Cr(vi): comparison of hybrid sorbent performance to its nanomaterial building blocks

机译：赤铁矿装饰了多壁碳纳米管（α-Fe2O3 / mwcnts）作为Cu（II）和Cr（VI）的吸附剂：杂交吸附剂性能与其纳米材料构建块的比较

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Major hurdles in the application of engineered nanomaterials for water treatment include loss of reactive surface area arising from particle aggregation and the development of application platforms that limit their potential release into the treated water supply. Here, we develop hybrid nanostructures through the growth of hematite (α-Fe _(2) O _(3) ) nanoparticles, which are recognized sorbents for various heavy metals, on multi-walled carbon nanotubes (MWCNTs). The hybrid nanostructures were synthesized via hydrolysis of ferric nitrate in the presence of carboxylated MWCNTs, and their activity as sorbents toward Cu( II ) and chromate (CrO _(4) ~(2?) ) was examined as a function of pH ( i.e. , pH-edge experiments) and initial metal concentration ( i.e. , adsorption isotherms). Characterization of α-Fe _(2) O _(3) /MWCNT nanostructures via Raman spectroscopy and transmission electron microscopy (TEM) with selected area electron diffraction (SAED) confirmed the deposited iron phase as α-Fe _(2) O _(3) . Further, complementary acid digestions and TEM imaging revealed that the amount (0.1 and 0.5 g g ~(?1) α-Fe _(2) O _(3) /MWCNT) and size [5.9 (±1.1) and 8.9 (±1.5) nm, respectively] of α-Fe _(2) O _(3) nanoparticles immobilized on MWCNTs were tunable during synthesis. Generally, mass-normalized concentrations of adsorbed Cu( II ) and CrO _(4) ~(2?) were greatest for α-Fe _(2) O _(3) /MWCNT hybrids relative to adsorption on either carboxylated MWCNTs or freely suspended α-Fe _(2) O _(3) nanoparticles, with evidence implicating α-Fe _(2) O _(3) as the active sorbent phase in hybrid materials. Indeed, per unit mass of available α-Fe _(2) O _(3) , hybrid sorbents exhibited capacities comparable to or exceeding most other iron-based sorbents for Cu( II ) and CrO _(4) ~(2?) (from 220 to 470 mg Cu( II ) per g α-Fe _(2) O _(3) and 60 mg CrO _(4) ~(2?) per g α-Fe _(2) O _(3) , respectively, at pH 6 and 20 °C). The enhanced sorption capacity of the hybrid nanostructures is due, at least in part, to the greater available surface area of α-Fe _(2) O _(3) nanoparticles immobilized on MWCNTs when compared to their more extensively aggregated state in suspension. Notable differences in the pH-dependent trends of Cu( II ) and CrO _(4) ~(2?) uptake on α-Fe _(2) O _(3) /MWCNT hybrids, along with differences in zeta potential measurements across pH, also suggest that the immobilized α-Fe _(2) O _(3) nanoparticles may exhibit unique surface reactivity relative to their freely suspended analogs as a result of their association with the negatively charged MWCNT surface.
机译：用于水处理的工程纳米材料应用的主要障碍包括颗粒聚集产生的反应性表面积和应用平台的开发，限制其潜在释放到处理过的供水中。在此，我们通过赤铁矿的生长（α-Fe _（2）O _（3））纳米颗粒进行杂化纳米结构，其在多壁碳纳米管（MWCNT）上被识别出各种重金属的吸附剂。通过在羧化的MwCnts存在下通过硝酸铁的水解合成杂化纳米结构，并将其作为Cu（II）的吸附剂的活性和铬酸盐（CRO _（4）〜（2→））作为pH的函数（即，pH-边缘实验）和初始金属浓度（即吸附等温线）。通过拉曼光谱和透射电子显微镜（TEM）具有选定区域电子衍射（SAED）的α-Fe _（2）o _（3）/ mWCNT纳米结构的表征证实了沉积的铁阶段作为α-Fe _（2）O _ （3）。此外，互补的酸消化和TEM成像显示出量（0.1和0.5gg〜（α1）α-Fe _（2）O _（3）/ mwCNT）和尺寸[5.9（±1.1）和8.9（±1.5 ）在合成期间可调谐固定在MWCNT上的α-Fe _（2）o _（3）纳米颗粒。通常，具有相对于羧化MWNT或自由的吸附，对α-Fe _（2）O _（3）/ MWCNT杂种的α-Fe _（2）O _（3）/ MWCNT杂种的质量归一化浓度最大。悬浮α-Fe _（2）O _（3）纳米颗粒，证据显示α-Fe _（2）o _（3）作为杂交材料中的活性吸附相。实际上，每单位质量可用α-Fe _（2）O _（3），杂交吸附剂表现出与Cu（II）和CRO _（4）〜（2？）相当或超过大多数其他铁基吸附剂的能力（从220至470mg Cu（II）每Gα-Fe _（2）O _（3）和60mg CRO _（4）〜（2？）每Gα-Fe _（2）O _（3 ）分别在pH6和20℃下）。杂交纳米结构的增强吸附能力至少部分地到达α-Fe _（2）Oα（3）纳米颗粒的α-Fe _（3）纳米颗粒的纳米颗粒，与其在悬浮液中更广泛的聚集状态相比时在MWCNT上固定在MWCN上。 Cu（II）的pH依赖性趋势和CRO _（4）〜（2？）对α-Fe _（2）o _（3）/ mWCNT杂种的摄取的显着差异，以及Zeta电位测量的差异pH，还表明，由于它们与带负电的MWCNT表面的关系，固定的α-Fe _（2）O _（3）纳米颗粒可以表现出独特的表面反应性，其相对于其可自由悬浮的类似物。

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