Defluorination of water using aluminium – loaded lemon peelings carbon as modified natural adsorbents

Abstract

The contamination of groundwater and high concentrations of fluoride ions are major problems worldwide, causing diseases like dental and skeletal fluorosis; in the population that uses this water for their consumption and therefore, its removal from groundwater is a very important issue. This study was aimed at developing an inexpensive and effective adsorbent for removing fluoride ions from drinking water to the safety limit, 1.5 mg/L set by World Health Organization and Uganda National Bureau of Standards. Lemon peelings obtained from Nagongera market, Tororo district were impregnated with aluminium by subsequent carbonization, alkalinizing and treatment with aluminium chloride and effectiveness in adsorbing fluoride ions was confirmed by batch adsorption studies. The adsorption data were analyzed by Freundlich and Langmuir isotherms. The adsorption on the aluminium-loaded lemon peelings carbon (ALLPC) obeyed the pseudo second order kinetic model. The adsorption capacity ALLPC was studied with variation in size of adsorbent dose, size particles, pH, adsorbent dose and initial fluoride concentration. The extent of adsorption of fluoride ions by ALLPC adsorbent increased with increase in adsorbent dose, contact time and pH until an optimum value but decreased with the increase in particle size and initial fluoride concentration. In future, the potential ALLPC adsorbent can be used to design a household defluorination unit for effective and economical fluoride removal.