Effectiveness of the engineered pinecone-derived biochar for the removal of fluoride from water

Drinking fluoride (F -)-contaminated water (> 1.5 mg L-1) causes severe dental and skeletal disorders. In the central province of Pakistan, ~20 times higher levels of F- in the drinking groundwater (compared with the 1.5 mg L-1 permissible limit of the World Health Organization) are triggering bone abnormalities in teenagers. In this study, we demonstrated the potential of pinecone-derived biochar (pristine) impregnated with Fe-and Al salts (engineered) to defluoridate water. Batch mode adsorption experiments were carried out under variable conditions of solution pH, F- initial concentration, adsorbent dose, and contact time. The engineered biochars resulted in greater adsorption than that of pristine biochar. Specifically, the AlCl3-modified biochar exhibited a maximum adsorption capacity of 14.07 mg g(-1) in spiked water and 13.07 mg g(-1) in in-situ groundwater. The equilibrium isothermal and kinetic models predicted monolayer, cooperative, and chemisorption types of the adsorption process. The chemical interaction and outer-sphere complexation of F- with Al, Na, and H elements were further confirmed by the post-adsorption analysis of the AlCl3-modified biochar by FTIR and XRD. The AlCl3-modified biochar resulted in 87.13% removal of F- from the in-situ F --contaminated groundwater, even in the presence of naturally occurring competing ions (such as Cl-, HCO3-, SO42-, and NO3-). We conclude that the AlCl3-modified biochar derived from pinecone could be a promising cost-effective adsorbent for the defluoridation of water.

Automated summary

The study demonstrates the potential of engineered biochar derived from pinecone, impregnated with iron and aluminum salts, to effectively remove fluoride ions from water. The AlCl3-modified biochar exhibits enhanced adsorption capacity and can remove fluoride ions even in the presence of competing ions.