Studies on defluoridation of water using magnesium titanate

Abstract

Batch sorption system using magnesium titanate as an adsorbent was investigated to remove fluoride ions from the aqueous solution. The amount of fluoride adsorbed from 4 mg L^-1 of fluoride solution at 30^oC was found to be 0.029 mg g^-1. The system variables studied include initial concentration of the sorbate (2-10 mg L^-1), adsorbent dose (0.5-5 g/50 mL), agitation time (5-60 min), <i style="">p</i>H (3-11), co-ions (Cl^-, SO₄^2-, NO₃^-, and HCO₃^-) and temperature (30-50^oC). The experimental data fitted satisfactorily (r>0.97) to the Langmuir isotherms. Thermodynamic parameters such as <img src='/image/spc_char/delta.gif' border=0><i style="">H</i>^o, <img src='/image/spc_char/delta.gif' border=0><i style="">S</i>^o and <img src='/image/spc_char/delta.gif' border=0><i style="">G</i>^o concluded the adsorption is endothermic. The magnitude of the enthalpy change (20-45 kJ mol^-1) indicated that the mechanism of adsorption process involves physisorption.