改性蒙脱石对正态磷酸盐和非正态磷酸盐混合体系的吸附特性

Adsorption behavior of mixture of orthophosphate and unortho phosphate by modified smectite

为研究吸附剂对正态磷酸盐、非正态磷酸盐的吸附特征,以及正态磷酸盐和非正态磷酸盐混合体系下的竞争吸附行为,制备出3种改性蒙脱石SWy-焙烧、SWy-Al、SWy-Fe,将其分别用于对不同形态的磷酸盐吸附实验中。结果表明,制备的3种改性蒙脱石对磷的吸附效果均有所提升。SWy-Fe的吸附效果最佳,对正态磷酸盐和非正态磷酸盐4 h吸附去除率分别提高了56.1%和55.3%,实验结果符合Ho拟二级吸附动力学方程。根据Langmuir吸附热力学方程,对正态磷酸盐和非正态磷酸盐的饱和吸附量分别为21.9 mg·g-1和18.8 mg·g-1。此外,在初始总磷浓度高于3.0 mg·L-1的条件下,正态磷酸盐和非正态磷酸盐混合体系中的非正态磷酸盐吸附量显著高于正态磷酸盐,二者单位平衡吸附量之比为2.9∶1.0。改性蒙脱石对正态磷酸盐和非正态磷酸盐的吸附结果均表现为吸附外部液膜扩散、表面吸附、颗粒内扩散等多种过程的综合作用,可交换阳离子Ca2+/Fe3+/Al3+的引入通过吸附络合作用提高了蒙脱石对磷酸盐的吸附能力。在初始总磷浓度高于3.0 mg·L-1的条件下,正态磷酸盐和非正态磷酸盐混合体系存在吸附竞争现象,这为实际处理含磷废水吸附技术的发展和应用提供了理论依据。

In order to study the adsorption characteristics of orthophosphate and unortho phosphate, and the competitive adsorption behavior under the mixture of orthophosphate and unortho phosphate, three kinds of modified smectite SWy-roasted, SWy-Al and SWy-Fe were prepared and were used to adsorb the different morphological phosphates. The experimental results showed that the phosphorus adsorption was improved by all the three kinds of modified smectite. SWy-Fe had the best performance on phosphorus adsorption, the removal rates of orthophosphate and unortho phosphate increased by 56.1% and 55.3% within 4 hours adsorption,respectively, which accords with the pseudo-second-order kinetic model. According to Langmuir adsorption thermodynamic equation, the saturated adsorption capacities toward orthophosphate and unorthophosphate by SWy-Fe were 21.9 mg·g-1 and 18.8 mg·g-1, respectively. In addition, when the initial total phosphorus concentration was higher than 3.0 mg·L-1 in the hybrid system of orthophosphate and unorthophosphate, the adsorption amount of unorthophosphate was significantly higher than that of orthophosphate, the ratio of their equilibrium adsorption amounts was 2.9∶1.0. The adsorption process of modified smectite on orthophosphate and unorthophosphate was determined as the comphrehesive functions of external liquid membrane diffusion,surface adsorption, and intraparticle diffusion. The introduction of adsorption and complexation by exchangeable cation Ca2+/Fe3+/Al3+ improved the adsorption capacity of smectite on phosphate. Under the condition of high initial total phosphorus concentration, the adsorption competition phenomenon existed in the hybrid system of orthophosphate and unorthophosphate, which can provide a theoretical basis for the development and application of adsorption technology treating the actual phosphorus-containing wastewater.