Synthesis Of Core-shell Micro/nano Structured Adsorbents And Their Application In Removing Micro-pollutants From Water

Water pollution has become the most challenging problem which we have to fight against in twenty-first century. Adsorption technique is an attractive method for water pollution control in terms of cost-effectiveness and simplicity of design and operation. Various conventional adsorbents such as zeolite and iron oxides suffer from the limited adsorption, low adsorption rate, poor separation ability and undesirable regeneration. Therefore it is still desirable to design and fabricate highly efficient adsorbents to meet the requirements of water treatment.The novel core shell structures have extraordinary textural and component characteristics, such as high surface area, abundant pores, thermal stability and easy to be functional. They show many good advantages in adsorptive removal of toxic pollutants in water, such as possessing abundant active adsorption sites by inheriting their parent nano building unit; providing multiple accessible channels for mass transport through new assemble of the parent building unit; having good mechanical property through the support of the core; and exhibiting unique functionality through functional components grafting. In this dissertation, we focus on the synthesis of novel core shell micro/nanostructures with unique properties and systematically investigate their performance towards adsorptive removal of micro-pollutants in water.The main contents can be summarized as follows:1) Synthesis of core shell hierarchical CAN zeolite microspheres for efficient removal of fluoride.Novel hierarchical core shell and hollow nitrate cancrinite （CAN） zeolite microspheres with micro-plate crystals act as sphere shell and wrapped with large number of nanorods crystal in the center of the microspheres as core were synthesized by a simple one step organic-free hydrothermal synthesis methods, and the growth progress of the CAN zeolite was investigated to be a potassium cation induced surface to core Ostwald ripening. The batch adsorption of fluoride results indicated that the adsorption can be finished at about 30 min, the maximum adsorption capacity was 38.46 mg g^-1. The kinetics of fluoride were well fitted to pseudo-second order model, and isotherms could be described with the Langmuir isotherms.2) Synthesis of core shell micro/nanostructured C@Fe₃O₄ for removal of chromium.Core shell micro/nano structured C@Fe₃O₄ was successfully synthesized by decoration of magnetic with sizes less than 10 nm with in situ high-temperature decomposition of the precursor. The obtained core shell particles are powerful to reduce and immobilize Cr（VI） with maximum capacity of 93.458 mg/g. According to the XPS analysis, most of Cr（VI） was reduced to Cr（III）, which indicated that the core shell materials can decrease the toxicity of Cr（VI）. Magnetic measurements showed that the core shell micro/nano materials are superparamagnetic with magnetic remanence of 14.169 emu g’1 at room temperature. The resulting micro/nano materials can be easily dispersed in water and can be manipulated by an external magnetic field.3) Synthesis of rattle-type C@Fe2O3 micro/nanostructured microspheres for arsenic removal.Novel rattle type carbon-maghemite core-shell spheres was prepared by calcination of the C@ Fe₃O₄ precursor. The synthesized rattle type structure have magnetic remanence of 25.389 emu g^-1 at room temperature. The kinetics and isotherms could be described with the pseudo-second order and Langmuir model. The maximum adsorption capacity for As（Ⅴ） and As（Ⅲ） was 54.993 and 48.179 mg g^-1,respectively. We discovered the inner spheres coordination complexation reaction of iron oxide and arsenite, and the partial oxidation of arsenite.There are two novel points of this thesis:1) Synthesis core shell hierarchical CAN zeolite microspheres from natural minerals by a facile and cheap hydrothermal treatment, and revealed the potasium cation induced surface to core Ostwald ripening growth progress; 2) preparation of of highly efficient arsnnic adsorbent rattle type C@Fe2O3, and understanding of its interaction with As（Ⅲ）.