Written by Durga Nimmagadda, Four Green Steps

The application of low-cost adsorbents obtained from plant waste as a replacement for costly conventional methods of removing heavy metal ions from waste water has been effectively employed. Chemically, modified plant wastes exhibit higher adsorption capacities than unmodified forms.

Heavy metals have been excessively released into environment due to rapid industrialization and have created a major global concern. Cadmium, zinc, copper, nickel, lead, mercury and chromium are often detected in industrial waste waters. Heavy metals are non biodegradable and then can be accumulated in living tissues, causing various disorders; therefore they must be removed before discharge.

Adsorption is one of the best physico-chemical treatment processes found to be effective in removing heavy metals from aqueous solutions. Plant wastes are considered to be effective adsorbents as they have no or very low economic value. Plant wastes including rice husks, spent grain, saw dust, sugarcane bagasse, fruit wastes, weeds etc., are considered  to be as adsorbents.

Properties of Adsorbents for removal of heavy metals from the waste water

• Pretreatment of the Plant waste for ex (Rice Husk, Sugar cane bagasse/fly ash, wheat bran, corn cobs, plant fibers etc.,) can be done by using both acids and bases.

• Chemically modified plant wastes vary greatly in their ability to adsorb the heavy metal ions from solution.
• Chemical modification in general improved the adsorption capacity of adsorbents probably due to higher number of active binding sites after modifications.

• After modifications , Adsorbents can have Better Ion exchange properties and formation of new functional groups that favors metal uptake.

The Heavy metal ions obtained from various Industrial waste water can be effectively removed by chemically modified Plant wastes as adsorbents.

Image courtesy of Creative Commons.

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