Details

Autor(en) / Beteiligte

• Xie, Lei
• Lu, Qiuyi
• Mao, Xiaohui
• Wang, Jingyi
• Han, Linbo
• Hu, Junqing
• Lu, Qingye
• Wang, Yixiang
• Zeng, Hongbo

Titel

Probing the intermolecular interaction mechanisms between humic acid and different substrates with implications for its adsorption and removal in water treatment

Ist Teil von

• Water research (Oxford), 2020-06, Vol.176, p.115766-115766, Article 115766

Ort / Verlag

England: Elsevier Ltd

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• Humic substance is a ubiquitous class of natural organic matter (NOM) in soil and aquatic ecosystems, which severely affects the terrestrial and aquatic environments as well as water-based engineering systems by adsorption on solids (e.g., soil minerals, nanoparticles, membranes) via different interaction mechanisms. Herein, the chemical force microscopy (CFM) technique was employed to quantitatively probe the intermolecular forces of humic acid (HA, a representative humic substance) interacting with self-assembled monolayers (SAMs, i.e., OH-SAMs, CH3-SAMs, NH2-SAMs and COOH-SAMs) in various aqueous environments at the nanoscale. The interaction forces measured during approach could be well fitted by the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory by incorporating the hydrophobic interaction. The average adhesion energy followed the trend as: NH2-SAMs (∼3.11 mJ/m2) > CH3-SAMs (∼2.03 mJ/m2) > OH-SAMs (∼1.38 mJ/m2) > COOH-SAMs (∼0.52 mJ/m2) in 100 mM NaCl at pH 5.8, indicating the significant role of electrostatic attraction in contributing to the HA adhesion, followed by hydrophobic interaction and hydrogen bonding. The adhesion energy was found to be dependent on NaCl concentration, Ca2+ addition and pH. For the interaction between NH2-SAMs and HA, their electrostatic attraction at pH 5.8 turned to repulsion under alkaline condition which led to the sudden drop of adhesion energy. Such results promised the adsorption and release of HA using the recyclable magnetic Fe3O4 nanoparticles coated with (3-aminopropyl)tiethoxysilane (APTES). This work provides quantitative information on the molecular interaction mechanism underlying the adsorption of HA on solids of varying surface chemistry at the nanoscale, with useful implications for developing effective chemical additives to remove HA in water treatment and many other engineering processes. [Display omitted] •Intermolecular forces of humic acid (HA) with self-assembled monolayers (SAMs) are quantified.•HA-SAMs adhesion energy is dependent on ionic strength, ion type and pH.•Electrostatic attraction plays the dominant role, followed by hydrophobic force and H-bonding.•PH responsive adhesion energy of NH2-SAMs facilitates the adsorption and release of HA.•Recyclable APTES/Fe3O4 nanoparticles with –NH2 groups promise excellent HA removal.