Dear Anuj,

Normally the first thing you would want to know is the typical concentration range of that metal in the waste.

Then, I would take the highest or median concentration (this is up to your application). With that concentration, we will typically use 1g of adsorbent and vary the time of contact. You can plot the graph of concentration adsorbed vs time. When the line of your graph is stable and flat at a particular time, we would call it an optimum adsorption time. This is the kinetic experiment.

Then we will do the batch experiment. With that optimum time from the kinetic ex., we will try to vary different concentrations and use Langmuir or Freundlich to fit your results. Regularly your adsorption curve will start to reverse at the point of maximum absorption concentration. 

If your waste concentration is so small like those of radioactive substance then those models cannot be applied. Normally they will just show the % removed. 

Then you can start to vary different things, pH, temperature, etc. The point is to keep other factors constant when 1 of the factors are being varied. For instance, you can try different pH but temperature, initial waste concentration and weight of adsorbent must be kept constant. 

If there are more than 1 target metal ions then we can use the mixed model.

I believe this is for you to start with. I am still not a pro in adsorption experiment but at least, this method produced me my Master's thesis. 

Following articles are..may be helpful.....................

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3209935/

http://pubs.sciepub.com/ajmr/3/3/1/

http://download.springer.com/static/pdf/51/art%253A10.1007%252Fs13738-016-0908-9.pdf?originUrl=http%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2Fs13738-016-0908-9&token2=exp=1487707165~acl=%2Fstatic%2Fpdf%2F51%2Fart%25253A10.1007%25252Fs13738-016-0908-9.pdf%3ForiginUrl%3Dhttp%253A%252F%252Flink.springer.com%252Farticle%252F10.1007%252Fs13738-016-0908-9*~hmac=f61a49c395ebc2efcb87cde34405ef3d35dde7b6dcd68b348a3e36f9df66e1d7

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I agree with Jakkapon, but would like to add that it is possible to test various factors with less experiments by using statistical design of experiments. I would then select adsorbent dose, contact time, initial pH, initial metal (or other adsorbate) concentration and temperature as factors and the removal percentage or adsorption amount (mg/g) as the response.

Thanks everyone for your reply and valuable suggestions