Defluoridation of aqueous solution using raw and surface modified biosorbents prepared from adansonia digitata fruit pericarp

Abstract

In some parts of Tanzania, there are higher fluoride concentrations in water bodies that affect public health. This work reports on water defluoridation using bio-sorbents prepared from Adansonia digitata fruit pericarp which is an agricultural waste. The raw and surface modified Adansonia digitata fruit pericarps were prepared, characterized, and used for defluoridation of the aqueous solution. The surface-modified adsorbent has better physical and chemical characteristics for bio-sorption. FT-IR spectra of adsorbents revealed that carboxyl, hydroxyls, carbonyls, and halogen groups are present on the adsorbent. The maximum removal efficiencies of raw and surface-modified bio-sorbents were 67.61 and 91.91% respectively which means surface modified bio-sorbent is effective for the removal of fluoride. Maximum adsorption efficiency was achieved with an initial concentration of 27.50 mg/L, the final concentrations of fluoride after adsorption were 8.907 and 2.225 mg/L for RADFP and SMADFP respectively. The adsorption capacity, q0 of RADFP and SMADFP are 0.2475 and 0.3173 mg/g, respectively. The values adsorption intensity, n is 1.3988 for RADFP and 1.1714 for SMADFP which lies between 1 and 10 indicating a favorable adsorption process. The adsorption data fitted well with the Freundlich adsorption model and Pseudo second order kinetics. Therefore, the surface-modified Adansonia digitata fruit pericarp is a potential bio-sorbent for the removal of fluoride ions from water.