Influence of modulus of alkaline activator on the removal of Pb²⁺ by mesoporous geopolymer adsorbent

ABSTRACT

In this study, we synthesised metakaolin-based mesoporous geopolymer adsorbent and investigated the effect of alkaline activator modulus (molar ratios of SiO₂/Na₂O) on Pb²⁺ adsorption. The geopolymer prepared using 1.2 M alkaline activator performs excellent Pb²⁺ removal with a maximum adsorption capacity of 172.71 mg g⁻¹. The pseudo-second-order model fit the adsorption kinetics satisfactorily, indicating that the adsorption process is dominated by chemical adsorption. The adsorption data appropriately fit the Langmuir isotherm model. The contributions of adsorption methods corresponding to the total quantity adsorbed declined in the following order: EDTA extraction (formation of Pb aluminium oxide and Pb-containing amorphous materials) > residual fraction (Pb stabilisation in the tetrahedral aluminosilicate network) > ion exchange. Overall, the alkaline activator modulus significantly influenced the Pb²⁺ adsorption characteristics of the geopolymer adsorbent.

GRAPHICAL ABSTRACT

KEYWORDS:

• Metakaolin
• geopolymerisation
• adsorption performance
• alkaline activator
• Pb²⁺

Data availability statement

All data, models, or code generated or used during the study are available from the corresponding author by request.

Acknowledgements

We thank Tingyu Bai from the Spice and Beverage Research Institute, Chinese Academy of Tropical Agricultural Sciences guidance on the operation of SEM-EDX.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC, No. 51978659).