Synthesis And Performance Study Of Hydrotalcite-based Porous Composites And Their Applications In Cr(?) Removal

Almost three decades, due to energy shortage and deteriorating ecological situation, how to break the critical situation of water pollution and supporting sustainable socio-economic development have become focus of attention of all sectors. As a new layered material, hydrotalcite?LDHs? have been applied in the field of environmental protection in growing demand because it is cheap,eco-friendly, strongly of plasticity and ideal pore structure. Nano-iron-based material is easy to act with materials in the system. It has properties such as magnetic separation, good compatibility, controllable absorber; especially generate a series of oxygen species through introduction of enhancement means such as ultraviolet and H2O2 to have synergistic degradation of water pollutants. It's rare to have hydrotalcite with magnetic and porous properties. The main research works of the paper are in the following aspects:1. Hydrothermal method was adopted to prepare hydrotalcite/carbon composite?LDH/C? under different thermal environment of water/glycol solvent, and examined impact of factors such as temperature and time of hydrothermal reaction as well as glucose content on the product. Then LDO material with porous structure was obtained through calcinations in an air atmospher. Some representations were applied to study structure, morphology and properties of the product. Optimization results were obtained: excellent MgAl-LDH/C could be obtained when reaction time is 8hour, reaction temperature is 170 degrees Celsius, n??Mg+Al?/ glucose?= 2: 1 and ethylene glycol solution. Methods such as thermodynamics and thermal analysis kinetics were adopted to study thermal stability of different hydrotalcites, focused on thermal decomposition behavior of MgAl-LDH/C, and obtained the integral formula of mechanism function, which was in line with AE-3 model, and kinetics was d?/dT=9.572×10⁹[-ln?1-??]³.2. Porous LDO was obtained by calcinations of precursor MgAl-LDH/C and MgFeAl-LDH/C under different conditions. Uniformly distributed magnetic nanomaterial could be obtained if ratio of doped iron is Fe:Al=3:2. After firing at 550 degrees Celsius, the iron-based hydrotalcite had larger surface area, more developed pore structure, i.e. uniform size and better dispersion. Then, adsorption characteristic of the calcined product was studied. The balance data of porous material to Cr???complied with Langmuir adsorption isotherm equation. The adsorption capacitieswere as high as 173.15 and 234.68 mg/g at 25oC,respectively. Temperature rising was conductive for restructuring memory adsorption of MgA1-LDO and MgFeA1-LDO to Cr???. They were mainly fast chemical adsorption.3. Fe₃O₄/C/LDH was synthesized by multi-step hydrothermal reactions. Then it was calculated at 500oC in order to get Fe₃O₄/C/LDO Magnetic Composites. The removal mechanism of Cr??? by Fe₃O₄/C/LDO was investigated.Both kinetics and thermodynamic data of the adsorption process were obtained. The kinetic data indicated that adsorption process could be described as Second-order kinetics model and apparent activation energy was 28.74 kJ·mol^-1. Equilibrium parameters were fitted well with Langmuir isotherms with the maximum adsorption capacity of194.68 mg/g for Cr????35oC?. The product after adsorption was used to degrade rhodamine B with ultraviolet source to avoid secondary contamination.