Ionic Liquid Modification Of Sepiolite And Its Adsorption On Cu²⁺

The natural sepiolite,produced from Xiangtan,Hunan Province is purified and modified to evaluate its ability and mechanism of absorbing Cu²⁺.It was processed through the reaction with ethanolamine-acetic acid ionic liquid to obtain ethanolamine-acetic acid modified sepiolite,and we also investigated the impact of varied experimental conditions such as modification time,temperature and ratios of ionic liquid on the absorption ability.After that the modified sepiolite was utilized to absorb Cu²⁺in different conditions such as pH,the amount of modified sepiolite,adsorption time and initial concentration of Cu²⁺,and then its mechanism was discussed.The main conclusions are as follows:1.The sepiolite was calcinated at 400°C and the optimal ionic was made under the condition that the molar ratio of ethanolamine to acetic acid is 2:1,the reaction temperature is 25°C,and the reaction time is 24h.The specific surface area of the heat-modified sepiolite is 155.27 m²/g,the pore volume is 0.18 cm²/g and the pore size is 11.23 nm;while the ionic liquid-modified sepiolite increases its specific surface area from 110.43 m²/g to 130.75 m²/g,the pore volume decreases from 0.29cm³/g to 0.14 cm³/g,and the pore size increases from 7.25 nm to 14.73 nm.The increase of the micro-surface area and micro-volume of the modified sepiolites facilitate the enhancement of its adsorption.2.The pH has a great influence on the ability of heat-modified and the ionic liquid-modified sepiolite to adsorb Cu²⁺ions.The greater the pH,the stronger the adsorption ability of the sepiolite.When the pH value of the solution was 4-6,the heat-modified modified sepiolite has an absorption capacity of 7.36 mg/g Cu²⁺.When the solution pH value was 6,the capacity of the ionic liquid modified sepiolite for absorbing the Cu²⁺of was 8.41 mg/g.3.The heat-modified sepiolite reaches the adsorption equilibrium point at about 6h,and the adsorption amount is 9.56 mg/g.The ionic liquid-modified sepiolite reaches the adsorption equilibrium point at about 8 h,and the adsorption amount is 10.58mg/g.The adsorption process of the two modified sepiolites can be simulated by the pseudo-second-order kinetic model.4.Two kinds of modified sepiolites in this paper enhance their absorption of Cu²⁺along with the increasement of the initial concentration of Cu²⁺.When the concentration of Cu²⁺reaches 80mg/L,the adsorption of Cu²⁺ions by the heat-modified sepiolite is saturated,and the maximum adsorption amount reaches10.62mg/g.When the concentration of Cu²⁺reaches 80 mg/L,the ionic liquid modified sepiolite is saturated,and the maximum adsorption amount is as large as11.68 mg/g.Both the modified sepiolites fit the Langmuir model and belong to single layer chemical adsorption.5.The process of ionic liquid modified sepiolite is surface modification and does not change its internal structure.The adsorption process of ionic liquid modified sepiolite is a relatively complicated,including chemical and physical adsorption.