Method to remove a plurality of heavy metals from wastewater using activated partially charred rice husks

A method to remove a plurality of heavy metals from wastewater comprising:

• a method of making activated partially charred rice husks consisting essentially of:
• providing rice husks,
• exposing the rice husks to a heat source to heat the rice husks to a temperature of between about 250° C. and about 550° C. for a period of between about 1 to about 10 minutes in at atmosphere having less than 2 percent oxygen in order to at least partially char the rice husks;
• removing the partially charred rice husks from the heat source,
• cooling the partially charred rice husks to an ambient temperature, and
• treating the partially charred rice husks to provide a filtration media having ion exchange capacity;
• drying the filtration media;
• wherein the activated partially charred rice husks have a silicon content of not greater than 40 percent, range from between about 0.1-2 mm in length, have a specific surface area of between 400-500 m2/g, and have a porosity between 0.4 to 0.55;
• passing the wastewater through said filtration media to remove the heavy metals from the wastewater;
• and
• regenerating the filtration media by washing the partially charred rice husks with an aqueous acid solution.