Synthesis of red mud/metakaolin based geopolymer for adsorption of methylene blue and tetracycline hydrochloride from water

For reusing red mud (RM) and treating wastewater, a green granular potassium-activated RM/metakaolin (MK) -based geopolymer (RMG) adsorbent was produced using RM and MK as raw materials. The effects of RM/MK ratio on the phase evolution and pore structure of the RMG adsorbents were evaluated. The removal mechanism of methylene blue (MB) and tetracycline hydrochloride (TCH) in wastewater by these adsorbents was studied. The removal efficiencies of MB and TCH were improved with the reduced RM/MK ratio of adsorbents. With the increase of dosage, the removal efficiencies of MB and TCH by RMG adsorbent increased, culminating at 98.28 % and approximately 100.00 % at 8000 mg/L and 16,000 mg/L, respectively. The adsorption mechanism was thought to include physical and chemical adsorption, as well as electrostatic attraction. After three adsorptiondesorption cycles, removal efficiencies remained at 99.66 % (MB) and 62.79 % (TCH). The green RMG adsorbents have exceptional adsorption properties and can be employed as a long-term adsorbent for dyeing and antibacterial wastewater treatment.