Micro-column testing of the dynamic adsorption of Pb by Fe-Mg clay-quartz beds

Clays have been used widely as sorbents of potentially toxic elements, especially Pb. However, their adsorption efficiency has been studied mostly under static experimental conditions, which are labour-intensive. In this study, dynamic adsorption experiments were established using micro-columns to assess the adsorption behaviour of natural Fe-Mg-rich clays for Pb ions by varying the inlet solution pH, Pb concentration and flow rate. The clays, consisting of varying amounts of palygorskite and Fe-smectite, were diluted with quartz (Qz) sand to enhance their permeability. Greater adsorption capacity was observed for the mixed palygorskite/Fe-smectite-rich clay beds (45.2 +/- 0.01 mg g(-1)) followed by the Fe-smectite-rich (35.7 +/- 0.07 mg g(-1)) and palygorskite-rich (20.0 +/- 0.03 mg g(-1)) clay beds. The results indicated that the greater adsorption efficiency of palygorskite/Fe-smectite-rich clays could be attributed to synergistic effects due to the coexistence of palygorskite and Fe-smectite clay phases, which have distinct physicochemical characteristics. Moreover, the results obtained showed good agreement with the static experiments, implying that the use of micro-columns could describe adsorption adequately over shorter experimental times.

Automated summary

In this study, dynamic adsorption experiments using micro-columns were conducted to assess the adsorption behavior of natural Fe-Mg-rich clays for Pb ions. The results showed that the mixed palygorskite/Fe-smectite-rich clay beds exhibited the highest adsorption capacity, followed by the Fe-smectite-rich and palygorskite-rich clay beds.