Aluminium fumarate-based polymer matrix composite for selective removal of fluoride from groundwater

Aluminium fumarate (AlFu) metal–organic framework (MOF) shows high fluoride adsorption from water, compared to other MOFs (Zr-MOFs, fumaric acid based MOFs), alumina-based porous materials, hydrated cement, waste mud etc. However, the nano-sized AlFu MOF tends to agglomerate in water. Thus, it reduces the fluoride removal efficiency of the MOF. Further, the exhausted MOF is difficult to regenerate and reuse. The present study prepared polymer matrix composite (PMC) to resolve it using an integrated chitosan mix coated on top of nanofiber (polyvinyl alcohol) support. Some of the PMC studied includes Ca-Zr @ polyvinyl alcohol (PVA), Fe-Al-Mn nanoparticles @ chitosan, and monetite bundles @ chitosan. AlFu MOF based PMC (9 g) was packed in a pouch-like tea bag and dipped in groundwater (1 L) with 10–30 mg fluoride/L. After 100 ± 10 min, the fluoride concentration was reduced to 1–1.5 mg/L. The exhausted PMC pouch could be regenerated by dipping it in 100 mL of treated water, tap water or deionized water for 5 h respectively. The same process was repeated ten times in fresh groundwater. Thus, PMC pouch could be used in our daily life.