Is Silica help to adsorp heavy metal from aqueous solution?

[lpy2000]

Hi all,
My biomaterial contains high percentage of Silica and Calcium element in its biomass. I am now utilizing this biomass for the heavy metal removal from aqueous solution and the result was very satisfactory. My question is that does silica or calcium have any function to the removal of heavy metal from aqueous solution? what are their mechanism? As i know Silica and calcium are one of the metal, so i guess that those silica in the biomass should be present in a complex form not a single element like SiO4, Ca(OH)2, or something similar to this.
Anyone know if there are any relation between these elements with the adsorption capacity of my biomass?

Best regards all,
LPY2000

 

[aspearin1]

There are a number of silica structures that will adsorb heavy metals via cation exchange. Zeolites are a naturally occuring porous silicates. Clinoptilolite and laumontite are two naturally occuring zeolites that are comprised of a silica skeleton and have exchange ions like Ca, Na, K, as well as some other trace metals. Kaolinite is a natural clay which also has this capability, many silica structures do. From your post I visualize a biomass consisting of some humic soil that probably includes a given amount of clay, and you are finding that in your liquid form you have dissolved Si and Ca (ICP readings?). This could very well mean that your heavy metals are replacing Ca ions on the silica backbone of a zeolite or kaolinite pore or surface. From my experience, I would wager that adsorption plays a major role in your heavy metals reduction. You'll need to conduct more experiments to find out whether your metals reduction is biological or abiotic adsorption (or a combination of both).

If you are taking readings at time intervals, you may be able to use Ca, Na, and K as your indicators. If they increase over time, you can assume ion exchange is occuring, until your exchange capacity is exhausted.

ChemE, M.E. EIT
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