Preparation Of Layered Double Hydroxides From Simulated Titanium Slag Wastewater And Their Dye Adsorption Performanc

Layered double hydroxides are unique layered host-guest two-dimensional structures appropriate for building organic-inorganic composite structures,and thus can be widely used to treat organic printing and dyeing wastewater due to their interlayer anion exchange properties.In this thesis,mimetic highly acidic wastewater containing Mg²⁺,Al³⁺and SO₄^2-left after the extraction of titanium from titanium-bearing blast furnace slag was used as the raw material,and the valuable metals were extracted by precipitation method to prepare the LDHs with good performance.The as-obtained LDHs were employed for treatment the wastewater containing organic dyes such as Congo Red（CR）and Rhodamine B（Rh B）,with the effect of"Using waste to treat waste".This work consists of the following two parts:Firstly,Na OH was used to precipitate the valuable metals Mg²⁺and Al³⁺in the acidic wastewater originated from titanium slag,leading to a low Mg-Al ratio precipitate.The precipitate was then dispersed in water,resulting in a turbid liquid.Mg salt was added to the system,so as to balance the Mg-Al ratio and promote the formation of LDHs nanosheets.After that,Na OH and Na₂CO₃solutions were introduced as the precipitating agents.Na OH could precipitate Mg²⁺and provide alkaline environment for the formation of Mg/Al-LDHs nanosheets,and Na₂CO₃ could supply CO₃^2-as the intercalating anions,and as a result LDHs nanosheets were obtained after aging at a constant temperature within an oil bath.Effect of the aging time and precipitant dropping rate on the product were investigated,and the optimal experimental conditions were determined under the rapid dropping rate condition（oil bath,80°C,8h）.Secondly,sodium dodecyl sulfate（SDS）was added to the reaction system,so as to provide a soft template for the growth and organic intercalation layer for LDHs.Porous LDHs-SDS nanospheres were obtained when the molar ratio of SDS to Mg²⁺was 0.22,89.0%of which had a diameter of 60-100 nm.The specific surface area of LDHs-SDS nanospheres was 95.95 mg g^-1,and the adsorption performance of the anionic dye CR was significantly enhanced,with the highest adsorption capacity up to 2438.67 mg g^-1.And also,the adsorption capacity of the cationic dye Rh B was up to 111.85 mg g^-1.In addition,the adsorption mechanisms of Rh B and CR on the LDHs-SDS nanospheres were studied.It is found that adsorption of CR fits in with the pseudo-second-order model and Langmuir isotherm model,the adsorption process is spontaneous and the chaos on the adsorbent surface increases during adsorption,and the hydrogen bonding and electrostatic forces are confirmed to have contributed to the adsorption.For the adsorption of Rh B,in contrast,it fit in with the pseudo-secondary model and the Freundlich adsorption isotherm model,the adsorption process is also spontaneous and the chaos on the adsorbate surface goes up,and the adsorption is affected by the van der Waals forces and hydrogen bonding.In brief,SDS modified spherical LDHs-SDS were produced by the valuable elements extracted from the simulated titanium slag wastewater.The LDHs-SDS nanospheres were further used for the treatment of organic dye containing wastewater with remarkably promoted adsorption performances,and thus providing useful references for the resource utilization of the real titanium slag wastewater as well as the efficient treatment of organic dye wastewater.