Role of solution chemistry in the attachment of graphene oxide nanoparticles onto iron oxide minerals with different cha
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RESEARCH ARTICLE
Role of solution chemistry in the attachment of graphene oxide nanoparticles onto iron oxide minerals with different characteristics Ruixia Jin 1 & Taotao Lu 2,3 & Haojing Zhang 1 & Mengjie Wang 1 & Mengli Wang 4 & Wei Qi 1 & Zhichong Qi 1
&
Deliang Li 4
Received: 10 June 2020 / Accepted: 15 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Given the ubiquity and abundance of the iron oxide minerals and their important roles in affecting the environmental fate of graphene oxide (GO) nanoparticles, the attachment of GO onto three iron oxide minerals (i.e., hematite, goethite, and ferrihydrite) under different solution chemistry conditions was investigated in this study. The main mechanism of the attachment of GO was electrostatic interaction. Calculations based on the DLVO theory showed that the attachment was a favorable process. Interestingly, the affinity of GO towards three iron oxide minerals was in the order of ferrihydrite > goethite > hematite. This result indicates that different characteristics of various iron oxides (e.g., specific surface area, crystal structure, and surface charge, and surface hydroxyl densities) can influence their attachment capacities for GO. The attachment of GO depended on the solution pH and ionic strength. Electrostatic attraction and hydrogen bonding were the important retention mechanisms for GO attachment when pH < pHPZC (the point of zero charge) and pH > pHPZC, respectively. The attachment capacities of iron oxides decreased with increasing ionic strength at lower pH because of the decrease of the electrostatic attraction. Meanwhile, the presence of divalent cations (i.e., Ca2+ and Cu2+) could significantly promote GO attachment mainly by the surface-bridging mechanism. Meanwhile, the enhancement effect of Cu2+ was greater than Ca2+ due to the greater complexation affinity of Cu2+. Furthermore, attachment isotherms showed that the presence of phosphate could inhibit the attachment of GO onto minerals obviously. Because phosphate could form inner-sphere surface complex on the iron oxide surface, and consequently decreased the electrostatic attraction between nanoparticles and minerals. Our study has important implications for predicting the fate of GO in natural environment where amounts of iron oxide minerals are present. Keyword Graphene oxide . Iron oxide . Attachment . Solution chemistry . Phosphate Ruixia Jin and Taotao Lu contributed equally to this work.
Introduction
Responsible Editor: Santiago V. Luis Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-10886-x) contains supplementary material, which is available to authorized users. * Zhichong Qi [email protected] * Deliang Li [email protected] 1
Henan Joint International Research Laboratory of Environmental Pollution Control Materials, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China
2
Ministry of Education Key Laboratory of Pollution Processes and Environm
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