Sorption experiments as efficient as possible: Mini-column experiments (MCE) using HPLC-ICP-MS coupling with a new data analysis approach to determine sorption parameters

Abstract

To quantify retention and sorption parameters, diffusion-, batch- or column experiments are common practice. However, these are either not close to nature, extremely time-consuming or material intensive. A promising approach to eliminate these problems is the performance of mini-column experiments (MCE). Due to dynamic retention and realistic solid–liquid ratios, these are close to nature and resource-efficient. The aim of this work is to perform highly controllable MCE using a HPLC (high-performance liquid chromatography) system and HPLCICP-MS (inductively coupled plasma mass spectrometry) coupling. With this approach, ultra-fast sorption experiments are possible only using 100–150 mg adsorbent and 160 mL eluent. That means, sorption experiments are even more time- and cost-efficient and also more controllable than with conventional methods. The presented method is based on a newly developed MCE-HPLC-ICP-MS coupling, which was applied to investigate the sorption of Eu(III) on kaolinite and sand in 10 mM NaCl. With that it was possible to carry out dynamic sorption experiments in just 5–15 h and thus determine e.g. maximum loading capacity (qmax) in a very short amount of time. Furthermore, a quantification method for eluates of high ionic strength is presented. Here, the sorption of Cs(I) on calcium silicate hydrate (C-S-H) phases in 10 mM and 100 mM NaCl was investigated. For validation, the sorption distribution ratios (Rd) obtained were compared with those from batch experiments. These agreed very well with each other and with those from the literature. Overall, with MCE more sorption parameters can be determined much faster, more accurately and more efficient than with the conventional methods.