Regulating interlayer and surface properties of montmorillonite by dodecyl dimethyl betaine for enhanced lead ion capture

Abstract

Developing low-cost and high-performance adsorbents is of great significance for the treatment of wastewater containing heavy metal ions. Herein, dodecyl dimethyl betaine modified Na-based montmorillonite (BS-MMT) is successfully prepared by a facile wet method for enhanced lead ion (Pb2+) adsorption. The interlamellar spacing of Na-MMT is effectively regulated ranges from 1.25 to 1.79 nm by changing the ratio of BS-12 content from 5% to 150% (vs. MMT). The Pb2+ capacity adsorption of BS-MMT could reach up to 255.36 mg/g when the usage of BS-12 is 15%. Pb2+ adsorption process on BS-MMT follows the Langmuir model and is endothermic. Mechanism analysis suggests that the main Pb2+ adsorption pathways on BS-MMT include ion exchange, functional group complexation, electrostatic attraction and precipitation by CO32−. Moreover, the modification of BS-12 could not only brings carboxyl and amine functional groups to trap of Pb2+ on the surface and interlayer of MMT, but also optimize the layer spacing of MMT since its long carbon chain. This work provides a feasible strategy to optimize the adsorption capacity of organic modified MMT for heavy metals.