Enhanced fluoride removal with sequentially modified alginate biopolymer: Insights from mathematical and column...

This study investigates the use of brown algae-derived alginate biopolymer to improve fluoride (F^-) removal in water treatment. It compares two modified alginate-based adsorbents: zirconium-crosslinked alginate (AZ) and a newly developed material created by combining ferric aluminosilicate laterite (FASL), a mining by-product, with alginate and crosslinking it with zirconium, called ALZ. Both AZ and ALZ were synthesized and characterized using SEM-EDX, FT-IR, TGA-DTA, XRD, XRF, and BET. Their ability to remove fluoride from aqueous solutions was tested, achieving over 70 % removal efficiency through process optimization with response surface methodology (RSM). The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetics. Increasing temperature improved fluoride adsorption for both materials, with maximum capacities at 30 °C and 50 °C: 70.27 mg g^-1 and 117.64 mg g^-1 for AZ, and 170.14 mg g^-1 and 410.81 mg g^-1 for ALZ, respectively. Thermodynamic analysis confirmed the process was spontaneous across all temperatures. Mathematical modelling was also used to predict fluoride breakthrough. This research provides valuable insights for developing efficient methods to address fluoride contamination, with both industrial and drinking water samples tested. The synthesis process demonstrated environmental sustainability, with a low environmental-factor (E-factor) of 0.023, highlighting its eco-friendly nature.