CO$_2$ plumes dissolved in brine or localized fluids with viscosities different from the surrounding fluid, may not always exhibit a planar interface. In cases such as pollutant contamination in soils, can take on an arbitrary initial shape and are subsequently carried and deformed by groundwater flows. These non-planar interfaces significantly influence the dynamics of fluid movement and can complicate predictions of the plume`s behaviour and spread in subsurface environments. We have considered a blob in rectilinear porous media. Since the adsorption plays a vital role in pollutant contaminant in groundwater, we have considered a non-linear type adsorption known as Langmuir adsorption isotherm in a convection-diffusion equation along with Darcy law, continuity equation and Arrhenius relation of viscosity and concentration. The above mentioned coupled system of partial differential equations is solved using Fourier pseudo spectral method and the time derivative is solved using a predator corrector method. We have observed a non-monotonic behaviour in the blob shape as the adsorption parameter increases. Initially, the blob transitions from an unstable regime to a comet-shaped regime. However, beyond a certain value of the adsorption parameter, the system re-enters the unstable regime. Additionally, we identified a competition between the retention parameter and the adsorption parameter. While the retention parameter slows down the movement of the blob, the adsorption parameter has the opposite effect, accelerating the blob`s progression.