| Natural organic matter (NOM) and metal oxides both exist widely in nature water. NOM is the main source of color, smell and taste in water and also the main cause of water contamination. Metal oxides generally exist in the form of minerals in water and act as a carrier of NOM. In nature, most NOM adsorb on the surfaces of mineral particles through a variety of interactions and this adsorption are affected by the environment of solution such as pH and ionic strength, and the characteristic of NOM and metal oxides. After the adsorption of NOM, the stability of colloidal particles, the difficulty of water treatment and the coagulant dosage increase. Micro-pollutants in water, like heavy metal ions, can mingle with NOM, which extends the residence time of pollutants in water, increases the difficulty of dealing with pollutants such as heavy metal ions and affects the form, migration, transformation, bioavailability and toxicity of pollutants in environment. In addition, NOM can also bring about the membrane fouling, disinfection by-products and the secondary pollution of pipe network. Because a series of impacts of NOM on water and water treatment processes, the effectively remove of NOM becomes an important issue in the water chemistry field. So studying clearly on the adsorption and interaction of NOM and metal oxides not only conducives to the removal of NOM in water, but also effectively improves the efficiency of water treatment processes.On the basis of the previous studies by our research group, aimming to the adsorption behavior of humic acid andα-Fe2O3 nanoparticles, with TOC test, FTIR and thermogravimetric analysis methods, this paper was focused on the impact of pHs and ionic strengths in solution on three aspects of the adsorption of NOM on metal oxide/ water interface, which were the changing of adsorption density, hydrophilicity and hydrophobicity ofα-Fe2O3-HA complex and type and content of functional groups of HA molecular. According to the adsorption density curves, TG curves and FTIR spectrum, the law about how these three aspects changed with the solution environments and their mutual influence was studied in this paper. Therefore the impact of varius solution enviroments on the hydrophobic effect of humic acid molecules in the adsorption process ofα-Fe2O3 nanoparticles was discussed.With the thermogravimetric analysis, the results showed that, when the ionic strength was kept at 0,0.005,0.01 and 0.05mol/kg and pH value was changed from 7 to 12, the hydrophilicity ofα-Fe2O3-HA complex decreased at first and then increased as the pH value increased while the hydrophobicity enhanced at first and then decreased. When the ionic strength was O.OOlmol/kg, and pH value was changed from 7 to 12, the the hydrophilicity ofα-Fe2O3-HA complex decreased as the pH value increased while the hydrophobicity enhanced. When the pH was constant and ionic strenth was increased, the hydrophilicity and hydrophobicity of complex changed alternately.The FTIR spectrum results indicated that the functional groups of HA molecular, which played a significant role in the hydrophilicity and hydrophobicity of the complex after adsorption process of nanoα-Fe2O3 and the dissolved humic acid molecules, might be hydrophilic hydroxyl-OH, carbonyl C=O and the hydrophobic alkane CH3.This paper also evaluated the impact of solution environments on adsorption behavior of humic acid onα-Fe2O3 nanoparticles through the adsorption density experiment. The results indicated that the changing of adsorption density was related closely to the hydrophilicity and hydrophobicity ofα-Fe2O3-HA complex which meant the changing of solution environments would have an important impact on the adsorption behavior. |
