Kinetics of Hydrochloric Acid Leaching Al3+ from Montmorillonites

The components of purified samples were examined by means of X ray diffraction (XRD) and FTIR. XRD was performed on unorientated samples with an Ultima IV diffractometer, operating at 40 kV and 40mA, using Ni-filtered CuK α radiation, at a scanning speed of 8°2θ/min. FT-IR spectra were obtained using a Nicolet 380 FTIR Spectrometer. 3 mg of each sample previously dried at 110°C for 3 hours were mixed with 160 mg of KBr and pressed on disks. The particle-size distribution of the purified sample was determined by Bettersize BT-9300Z laser particle analyzer. A complete chemical analysis of the purified samples was performed by use of China's Nation Standard GB/T 16399-1996 and GB/T 14506.28-2010. Select Al3+ as the structure cations leaching objective to learn the cationic leaching kinetics on acid leaching montmorillonite. Acid leaching were carried out in a 250 mL three-neck flask which was soaked in a constant temperature oil bath to heat. A mechanical stirring rod, a thermometer and a condensing tube were inserted in the flask through the three necks, respectively. For each run, the solution was freshly mixed by 100 mL distilled water and 20 mL 37% analytical grade hydrochloric acid in the three-neck flask and stirred at a fixed rate of 300 r/min. When the temperature was reached, put 4 g sample into the flask through one neck and start to clock. The liquid-solid mixture was heated at 47, 67, 87 and 97℃ respectively, for different period time between 1 hour and 45 hour. After the designed leaching time, the mixtures were centrifuged immediately. Precipitation was washed by deionized water repeatedly until without Cl- tested by AgNO3 liquid drop. After drying, grinding solid product to -200 mesh (-75μm). The constant volume of filtrate and lotion were used to determine the leaching amount of Al3+ from montmorillonite by China's mechanical industry Standard B/T9225 - 1999. According to the total chemical analysis of Al3+ and the content of Al3+ in the leaching solution, the leaching ratio of Al3+ XB at different time was calculated, and a variety of dynamic model of liquid-solid reaction was fitted. There are two type models commonly used in literature for liquid-solid reaction: Shrinking-Core Model (SCM), also called interfacial reaction models, and Progressive-Conversion Model (PCM), also called capacity model. All fitting figures are drawn with ORIGIN software.采用X射线衍射（X-ray Diffraction, XRD）与傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FTIR）对纯化样品的组分进行表征。XRD测试采用Ultima IV型X射线衍射仪，针对无取向样品开展测试，测试参数为：管电压40 kV、管电流40 mA，使用镍滤光片过滤的Cu Kα辐射，扫描速率为8°(2θ)/min。傅里叶变换红外光谱测试采用Nicolet 380型傅里叶变换红外光谱仪：将每份样品预先置于110℃下干燥3小时，称取3 mg样品与160 mg溴化钾（Potassium Bromide, KBr）混合后压制成片。采用Bettersize BT-9300Z型激光粒度分析仪测定纯化样品的粒度分布。采用中国国家标准GB/T 16399-1996与GB/T 14506.28-2010对纯化样品进行全化学组分分析。 选取Al³+作为结构阳离子浸出目标，开展酸浸蒙脱石过程中的阳离子浸出动力学研究。酸浸实验在250 mL三口烧瓶中进行，将烧瓶置于恒温油浴中加热。分别通过三个瓶口安装机械搅拌棒、温度计与冷凝管。每次实验前，在三口烧瓶中现配制100 mL蒸馏水与20 mL 37%分析纯盐酸的混合溶液，并以300 r/min的固定转速搅拌。待体系升温至设定温度后，通过其中一个瓶口加入4 g样品并启动计时。将液固混合物分别在47、67、87与97℃下加热，反应时长介于1小时至45小时之间。达到预设浸出时长后，立即对混合体系进行离心分离。将离心得到的沉淀用去离子水反复洗涤，直至采用硝酸银（Silver Nitrate, AgNO₃）液滴检测无Cl⁻存在为止。干燥后将固体产物研磨至-200目（即粒径小于75 μm）。将滤液与洗涤液定容后，采用中国机械行业标准B/T 9225-1999测定蒙脱石中Al³+的浸出量。根据Al³+的全化学组分分析结果与浸出液中Al³+的含量，计算不同时刻下Al³+的浸出率X_B，并拟合多种液固反应动力学模型。液固反应领域的文献中常用两类模型：缩芯模型（Shrinking-Core Model, SCM，又称界面反应模型）与渐进转化模型（Progressive-Conversion Model, PCM，又称容量模型）。所有拟合图表均采用ORIGIN软件绘制。