Sir I have calculated the delta G value in chromium adsorption using lignocellulosic biomass as per the suggestion given in the following link:

https://www.researchgate.net/post/How_can_I_calculate_correctly_the_Gibbs_free_energy_change_of_adsorption_DG

Biosorbent dose: 0.5 g/L or 0.025 g in 50 mL, Volume of solution: 50 mL, Initial metal concentration: 100 ppm or mg/L, qe: 30 mg/g, Ce: 85 mg/L

This process was carried out at 30 degree Celsius and 100 rpm which I think can be considered as room temperature and hence this process should be cosidered as spontaneous. However,

I want to ask you first one thing: Do you think that this process can be considered as spontaneous from the theoretical or thinking point of view.

When I did the calculations as one of the person suggested to use the formula for Kc:

(qe*Wt of biosorbent)/(Ce*Volume of solution in mL)

I am getting the Kc between 0 and 1 and consequently I am getting the delta G value to be positive which means that the biosorption process is not spontaneous.

I further want to ask you that the the term lnKc suggest that for process to be spontaneous, the qe should be more than Ce if Kc = qe/Ce or the number of chromium ions adsorbed should be more than present in the solution after biosorption. How much this agrees in case of biosorption as it happens that sometime the number of chromium ions adsorbed be not more than the residual number of chromium ions in the solution as in my case. I think that the expression for Gibbs free energy does not validate in the biosorption process.

Please someone suggest some modification so that as per my calculation the biosorption process comes out to be spontaneous in case if you think the biosorption process is truly spontaneous under the conditions which I have used.