Adsorption of lead and mercury by rice husk ash.

An attempt at the use of rice husk ash, an agricultural waste, as an adsorbent for the adsorption of lead and mercury from aqueous water is studied. Studies are carried out as a function of contact times, ionic strength, particle size, and pH. Rice husk ash is found to be a suitable adsorbent for the adsorption of lead and mercury ions. The Bangham equation can be used to express the mechanism for adsorption of lead and mercury ions by rice husk ash. Its adsorption capability and adsorption rate are considerably higher and faster for lead ions than for mercury ions. The finer the rice husk ash particles used, the higher the pH of the solution and the lower the concentration of the supporting electrolyte, potassium nitrate solution, the more lead and mercury ions absorbed on rice husk ash. Equilibrium data obtained have been found to fit both the Langmuir and Freundlich adsorption isotherms.