Rapid removal of methylene blue and nickel ions and adsorption/desorption mechanism based on geopolymer adsorbent

Abstract

Ongoing researches about adsorption removal of heavy metal ions and dyes are targeted to improve adsorption efficiency and recycle to solve environmental problems. Geopolymer as an adsorbent for wastewater treatment exhibits a good application potential. Here, a rapid removal strategy for methylene blue (MB) and nickel ions based on metakaolin-based geopolymer (MG) is provided. The adjustment of pH allows the MG to expose more negative charge adsorption sites, resulting in rapid removal of MB and Ni2+. The adsorption data fitted well by the pseudo-second-order model and Langmuir model, indicating the chemisorption of MG for MB and Ni2+. The decrease of pH of wash solution is conducive to the desorption of Ni2+. However, the desorption of MB-loading MG proved to be very difficult. This study provides a universal reference and possibility for rapid removal of cationic dyes and heavy metal ions under relatively mild conditions.