Silica-Based Organic/Inorganic Hybrid Materials And Their Application In The Treatment Of Heavy Metal Wastewater

Heavy metal pollution is one of the most serious environmental problems, a lot of hybrid materials have been developed in order to adsorb or catalyze the toxic heavy metal ions from waste water. Silica as a class of porous materials, which have controllable morphology and surface easy to modify, can easily be modified by physical or chemical action. So the utilization of organic/inorganic hybrid materials based on silica to deal with heavy metal pollution problems have become more and more popular. But for most of the conventional silica-based hybrid materials, the function is relatively single. For overcome these conventional silica-based hybrid materials defects, a series of new nano organic/inorganic hybrid materials based on silica were prepared to remove heavy metal ions such as Cu（II） and Cr（VI）.（1） A core-shell structured magnetic nanocomposite（SDMA） modified by one kind of new organic fluorescent probe and selective chelating groups was prepared for simultaneous detection and removal of low concentration of Cu²⁺. Series of experiments were designed to detect and adsorb copper ions in aqueous solution by SDMA. The results showed that SDMA could detect Cu²⁺ from copper ion solution qualitatively and quantificationally with a certain degree of selectivity, and remove Cu²⁺ with a respectable removal efficiency of about 80%. Through the contrast adsorption experiments, the adsorption capacity of SDMA was significantly higher than that of other two common magnetic nano adsorbents（Fe₃O₄@mSiO₂-SH and Fe₃O₄@mSiO₂-NH2）. The adsorption behavior of SDMA was studied through equilibrium and kinetic experiments. The adsorption isotherm was well fitted by Freundlich model perfectly and the pseudo-second-order model could fit the kinetic adsorption. Moreover, SDMA could reach the adsorption equilibrium in only 20 min, which showed a fast kinetic adsorption to Cu²⁺. From the results of our completed work, it can be summarized that the prepared SDMA can be an effective and potential nano-adsorbent for detecting and removing copper ions from copper ions-containing wastewater.（2） Frequent industrial discharge of various contaminants such as heavy metals into water resources has caused severe environmental damage. In this study, a unique porous corallite-like microcomposite（SPNH-MOSF@SnS₂） was successfully fabricated via surface modification of visible-light-driven photocatalyst（SnS₂） and chelating ligand（spirobenzopyran derivative, SPNH） on macroporous siliceous foam（MOSF） and used for highly efficient reduction and removal of hexavalent chromium from water. SnS₂ was selected as the photocatalyst because of its high visible light induced photocatalytic activity. SPNH was modified due to it can selective chelate soluble Cr（III） by exposing to ultraviolet light. This new composite can efficiently and quickly reduce and remove hexavalent chromium ions from aqueous solution, especially under the condition of acid solution has higher catalytic efficiency.（3） Electrostatic spinning technique was used for preparing a functional carbon fiber membrane（FCNF/SnS₂） to remove low concentrations of hexavalent chromium from water. First, electrostatic spinning technology and high-temperature calcination were utilized to prepared silica-doped carbon fiber membrane. Second, the membrane surface was assembled by flower-like SnS₂ nanoparticles for photocatalytic reduction of Cr（VI）. Finally for chelating Cr（VI）, the fiber membrane surface was modified with amino by silane coupling agent due to the SiO₂ in the membrane, so the material FCNF/SnS₂ was prepared. FCNF/SnS₂ exhibited a superior performance for adsorption and photocatalytic reduction of Cr（VI）. Especially for the concentration of K₂Cr₂O₇ solution under 30mg/L, the removal efficiency was 100%. FCNF/SnS₂ solved the problem of some materials can not fulfill efficient removal of low concentration of Cr（VI）.