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Adsorptive removal of fluoride from aqueous solution using orange waste loaded with multi-valent metal ions

2011; Elsevier BV; Volume: 192; Issue: 2 Linguagem: Inglês

10.1016/j.jhazmat.2011.05.070

1873-3336

Hari Paudyal, Bimala Pangeni, Katsutoshi Inoue, Hidetaka Kawakita, Keisuke Ohto, Hiroyuki Harada, Shafiq Alam,

Geochemistry and Elemental Analysis

Adsorption gels for fluoride ion were prepared from orange waste by saponification followed by metal loading. The pectin compounds contained in orange waste creates ligand exchange sites once it is loaded with multi-valent metal ions such as Al3+, La3+, Ce3+, Ti4+, Sn4+, and V4+ to be used for fluoride removal from aqueous solution. The optimum pH for fluoride removal depends on the type of loaded metal ions. The isotherm experiments showed the Langmuir type monolayer adsorption. Among all kinds of metal loaded gels tested, Al loaded gel appeared to exhibit the most favorable adsorption behavior. The adsorption kinetics of fluoride on loaded gel demonstrated fast adsorption process. The presence of NO3−, Cl− and Na+ ions has negligible effect on fluoride removal whereas SO42− and HCO3− retarded the fluoride removal capacity in some extent. Fluoride removal at different adsorbent doses showed that fluoride concentration can be successfully lowered down to the acceptable level of environmental standard. The fluoride adsorption mechanism was interpreted in terms of ligand exchange mechanism. The complete elution of adsorbed fluoride from the gel was successfully achieved using NaOH solution.