Adsorption Properties Of Perchlorate Onto Typical Carbonaceous And Mineral Materials And Their Molecular Interaction Mechanisms

Perchlorate (ClO4-), as an emerging persistent and trace pollutant, has become one of the research hotspots in environmental field, because it can inhibit the secretion of thyroid hormone in organism and then cause various metabolic or developmental diseases, especially for the women of childbearing age and infant. Due to its broad anthropogenic source and universal natural origin, ClO4-contamination has been very serious, however, the current investigation was mainly limited in America, and the survey data about ClO4-level was extremely deficient in other countries. With the properties of high solubility, strong stability and fast mobility, ClO4-not only poses a great risk for human health and ecological safety, but also makes it hard for the control and remediation of ClO4-polluted environments. On the basis of brief introduction about the contamination status, health risk, and control technologies of ClO4-, the progresses of ClO4-adsorption onto different type of materials were particularly reviewed, including their removal capacities and adsorption mechanisms. In view of the tough conditions and unsystematic design in the preparation of ClO4-adsorption materials, and the unclear recognition of the adsorption mechanisms and regulation factors of ClO4-onto the interface of materials, this dissertation firstly carried out the concentration levels and sources survey of ClO4-in water (surface water and tap water) and air. Then, typical carbonaceous materials (biochar, carbon nanotubes, and graphene) and mineral materials (organobentonites modified with different types and loading-amount of surfactants) were synthesized. Their structural properties were characterized via XPS, XRD, FTIR, Raman spectra, SEM, Zeta potential, elemental analysis, the specific surface area and organic carbon content. In addition to the systematic test of the adsorption capacity and influential factors of the obtained materials for ClO4-, the molecular interaction mechanisms of ClO4-on different material interfaces were deeply investigated according to the structural evolvement before and after ClO4adsorption. The quantitative relationships between the adsorption capacities and material structures (including matrix and surface properties) were established, which provide a theoretical basis and an engineering reference for designing novel and high-efficient adsorption materials for ClO4-removal. The main original conclusions of this work are drawn as follows:(1) The effect of disinfection process on ClO4-concentrations in the tap water was first discovered through the field survey. Results showed that disinfection using ozone and liquid chlorine did not affect the C1O4-concentrations in drinking water, while disinfection using ClO2and NaClO would significantly increase the ClO4-concentration in water, which was mainly resulted from that both of them can act as the active precursor of C1O4-formation. This observation usually ignored in previous studies should be paid attention for drinking water safety management. Meanwhile, the pollution contribution of human fireworks was also elucidated, which not only brought high C1O4-pollution to the air, but also significantly increased the ClO4-contamination in surface water via the dry and wet depositions.(2) Hydrogen bonding and its regulating factors contributed to C1O4-adsorption onto carbonaceous materials were proposed, and the dominant roles of the matrix and surface properties of the carbonaceous materials for ClO4-binding were clearly illustrated. A series of biochars with different structures and properties were prepared from the waste biomass via pyrolysis under different temperatures. It was found that high-temperature derived biochars not only had a broad scope of application, but also behaved superior adsorption capacity for ClO4-and can be easily regenerated. The hydrophobic surface and aromatic matrix of high-temperature biochars can further enhance the hydrogen bonding derived from the surface oxygen-containing groups for ClO4-binding. Carbon nanomaterials of carbon nanotubes and graphene were controllably modified and used for ClO4-adsorption, which demonstrated that the interface property of carbonaceous materials determined the availability of their adsorption sites and a hydrophobic interface will help to expose the sites for ClO4-binding. Furthermore, surface oxygen-containing functional groups (hydroxyl and carboxyl) were the main adsorption sites, whose forms were largely dependent on the solution pH and dominated the contribution of electrostatic attraction and hydrogen bonding for ClO4-adsorption. Thus, the carbonaceous materials can be designed through the regulation of matrix (aromatic/aliphatic) and surface (functional groups/hydrophobic) of materials as well as the solution conditions (pH and co-existing ions), achieving the optimal removal of ClO4-(3) The non-conventional blue-shift hydrogen bonding (BSHB) involved in ClO4-binding and its influential factors were first verified, and a quantitative relationship between the loading amount of cationic surfactant and adsorption capacity of organobentonites was established. The modification using cationic surfactant with long chain (cetyltrimethylammonium bromide, CTMAB) made the obtained organoclay behave high adsorption capacity for ClO4-, and the adsorption capacity will be improved with the increase of the loading amount of CTMAB, which presented good linear relationship between them and reached the controllable preparation of adsorption materials. In the nano-interlayer of organobentonite, besides the ion-exchange and electrostatic attraction, non-conventional BSHB formed between ClO4-and C-H from [(CH3)3N+-] on CTMAB was demonstrated through spectral information and quantum chemical calculations, and the BSHB were bonded in configuration of triple forms. It can be quantitatively controlled of the adsorption contribution of BSHB via the adjustment of the hydrophilic or hydrophobic degree of nano-interlayer, and the contribution of BSHB for ClO4-adsorption in hydrophobic micro-environment was5.6time of that in hydrophilic micro-environment.