Assessment of De-fluoridation in Waste Water Using Activated Biochar: Thermodynamic and Kinetic Study

Thermally treated domestic food waste is utilized to prepare biochar, followed by chemical activation to obtain activated bio-char (Biochar-act) which is used as de-fluoridating agent in contaminated water. The structural property of the synthesized activated bio-char is studied in detail. From continuous batch process , it is shown that efficiency of bio-char with lower degree of carbonization has remarkable properties of de-fluoridation. Here temperature, contact time and adsorbent dose , used as process parameters, have strong influence on fluoride uptake process. The adsorption equilibrium data are well fitted to the Langmuir isotherm model. Comparatively the data provided by pseudo-second-order kinetic model correlated better experimentally than pseudo-first-order kinetic model. From thermodynamic point of view, it is experimentally proved that de-fluoridation onto activated bio-char is spontaneous and endothermic in nature. Here, a low-cost process is suggested using low-cost starting materials to convert bio-char upon heat treatment at 350ËšC and then activated chemically by acid. The prepared adsorbent has higher de-fluoridation efficiency such as 91.24%. So it may be concluded that activated bio-char is economically and environmentally safe for de-fluoridation in waste water.