Hi
I have done the removal of heavy metals from the aqueous solutions through batch experiments. I observed that with increasing the concentration adsorbent (g) the % removal of heavy metal has increased almost 100% but the adsorption capacity (mg/g) has decreased. Are these two entities are inversely related to each other? While optimizing the experiments which factor should be considered more important % removal or adsorption capacity w.r.t. manuscript as well?
Thanks for your response in advance.
Hello,
when you want to see the adsorption capacity you must keep the same quantity of adsorbent, the same volume of solution and increase the adsorbate concentration (and not the adsorbent one).
Adsorption capacity more important than removal(%). Because adsorption capacity value is used for treatment system design.
Neşe Öztürk thanks for your kind response. But does that mean if increasing the adsorbent dose the decreases the adsorption capacity so contact time required or more adsorbate needs to be added to reach the equilibrium?
Gabriela Dima Thanks for the guidance. Which adsorbent dose should be picked then the one showed highest % removal of the heavy metal? and check it with increasing concentration of metal?
Usually (but this was 20 years ago), some 1-2 grams of adsorbent per 100-200mL of solution. So, at equilibrium, you'll have the adsorption capacity. Then, for the same concentration (which should be near to your study interest), you can increase the amount of adsorbent, in order to see the variation of the removal; with these results you can optimize the dose of adsorbent.
Noor Ul Ain Optimal conditions is determined and then it should be applied. There is no need to add additional adsorbent or increase contact time during application.
I think It depends on the aim of your study, economic considerations (adsorbent capacity, regeneration cycle...)or environmental ones (maximizing the removal).
Gabriela Dima I have done batch adsorption studies with adsorbent doses 0.01-0.1 g and total volume 10 mL. Is it fine or do I need to increase to 1 g and 100 mL volume?
Maybe you could increase if enough solution and adsorbent. I don't know if sampling is difficult and relevant for the 10mL...
Gabriela Dima one more question while performing batch adsorption studies. Should the adsorbent dose selected as optimal be based on the adsorption capacity or % removal? Some researchers suggest that select the adsorbent dose at which 50% of the contaminant is removed.
Adsorption capacity is more important.
For your second part, it really depends on what you want to achieve. Batch, or continuous, regeneration or disposal, what is the desired treated fluid composition? How to achieve that continuously. Your batch volumes are tiny and that itself may result in problems in reproducibility. Are your experiments conducted in triplicate? How wide is the variance?
Shyam Lakshmanan I am carrying out experiments in the lab and I have been using 10 mL volume for batch studies to optimize the parameters like pH, adsorbent dose, concentration of heavy metal and time. Should I increase the volume of heavy metal solution and also the adsorbent dose as I am using 0.01 g-0.1 g?
I'm not sure about the aim of your study but think that you could increase the volume for your batch test (100mL/200mL) and, consequently, the optimal adsorption dose. You can perform, with same conditions, 4-5 test and confirm the capacity you obtained with 10 mL. Such a small volume (10 mL) may give important error.
Gabriela Dima the aim of my study is to check the heavy metal removal efficiency of a newly developed system. So I am checking it for the parameters like adsorbent dose, pH, time and concentration of the heavy metal through batch adsorption studies. So for lab scale studies I kept the volume of adsorbate 10 mL. So when I increase the adsorbent dose the % removal increases of my material but adsorption capacity decreases. So for my next experiment should I select the adsorbent dose based on % removal or adsorption capacity? Later, I want to use it for industrial purpose.
Hello,
you should use adsorption capacity for your scale-up experiments.
Only you should be quite sure that the adsorption capacity obtained in your 10 mL test is the good one.
Adsorption capacity is inversely proportional to the adsorbent dose added. so when you add more doses the adsorption capacity will decrease. percentage removal only dependent on the change in initial and final concentrations of the adsorbate.
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